| Author |
Thread: Archive through January 08, 2007 |
    
New member Username: Bill_c
Post Number: 10
Registered: Jun-06
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| Posted on Wednesday, December 13, 2006 - 09:20 pm: |
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Nuck,
McIntosh just released an upgraded MC275...... |
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Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9461
Registered: May-04
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| Posted on Wednesday, December 13, 2006 - 10:05 pm: |
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.
"Item Features and Specification
THIS AMPLIFIER CAN BRING YOU TO A PROFESSIONAL LEVEL OF MUSIC-FIELD!!! THE QUALITY DEFINITELY CAN COMPARE TO 845!! WHAT CAN I SAY MORE??? I THINK NONE OF ANY ADJECTIVE IS GOOD ENOUGH TO DESCRIBE IT!!! YOU WANT IT?? YOU WANT THIS WONDERFUL shining thing put it in you house to show your friends how the music is????"
'Nuff said. You already have one of these. |
Gold Member Username: John_a
London
U.K.
Post Number: 4598
Registered: Dec-03
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| Posted on Thursday, December 14, 2006 - 03:08 am: |
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And that was "The item specifics in the original language". |
Gold Member Username: Nuck
Post Number: 4864
Registered: Dec-04
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| Posted on Thursday, December 14, 2006 - 06:52 pm: |
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I know. It's hilarious. But the cheap little one is ok by me. |
Gold Member Username: Joe_c
Atlanta,
GA
Post Number: 1096
Registered: Mar-05
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| Posted on Friday, December 15, 2006 - 02:35 pm: |
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Good day folks |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9473
Registered: May-04
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| Posted on Friday, December 15, 2006 - 02:51 pm: |
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.
Hello, JC. |
Silver Member Username: My_rantz
Australia
Post Number: 978
Registered: Nov-05
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| Posted on Friday, December 15, 2006 - 08:27 pm: |
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It must be getting close to Christmas. |
Gold Member Username: Joe_c
Atlanta,
GA
Post Number: 1098
Registered: Mar-05
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| Posted on Friday, December 15, 2006 - 10:45 pm: |
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How are you Jan? Still around these parts spreading knowledge I see. |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9476
Registered: May-04
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| Posted on Friday, December 15, 2006 - 11:44 pm: |
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.
Still around at least. |
Gold Member Username: Joe_c
Atlanta,
GA
Post Number: 1099
Registered: Mar-05
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| Posted on Saturday, December 16, 2006 - 04:09 pm: |
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Has anyone tried the diamond bottom Telefunken? If so , worth 79 bucks a pop (12ax7)?? |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9480
Registered: May-04
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| Posted on Saturday, December 16, 2006 - 09:21 pm: |
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I've never found a tube that was worth $79 @. |
Gold Member Username: Joe_c
Atlanta,
GA
Post Number: 1101
Registered: Mar-05
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| Posted on Sunday, December 17, 2006 - 12:39 am: |
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I bought some used US tubes for pretty cheap (no specific name brand) and they sound better than any new Russian or other new tube. Just wondering if you guys have any recommendations on a 12ax7 tube for less than $100 each (preferably much less) that is a good all round tube. By that I mean great soundstage, good with most "calm" music and doesn't really have any hot spots. Tall order I know, but I have been through ALL current production tubes and still have not found a pair up to the used no name domestic pair. |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2747
Registered: Dec-03
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| Posted on Sunday, December 17, 2006 - 03:35 am: |
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Try pretty much any 5751 and you just may be very very happy with the results.
(nos of'course, some are better then others like RCA triple mica BP)
Otherwise the RCA's will give you the best bang for the buck in 12ax7 territory.
My favorite 12ax7's are amperex but in most circuits the 5751 is still a better tube. |
Gold Member Username: Nuck
Post Number: 4888
Registered: Dec-04
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| Posted on Sunday, December 17, 2006 - 08:32 am: |
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Without trying to break up the theme, how do I know if my tube amp can support various other types of tubes?
Are there specific voltage measurements to be taken?
The small 18w is great so far with the Chinese E84's and 6N3's, but I want to know which tubes to watch for if I see them cheap. |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9481
Registered: May-04
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| Posted on Sunday, December 17, 2006 - 01:00 pm: |
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Kegger may have more input here but his suggestion to move from a 12AX7 to a 5751 is moving from a consumer tube to a military spec tube. Such substituions are covered in any tube substituion manual which will also give you numbers for the comparable European tube types. Tube manuals are available from multiple sources though most are literally too comprehensive for the average consumer. What you can find on the internet will normally suffice for the needs of most audiophiles who deal with a limited number of audio tubes. Cruise through this often cited reference to find substitution manuals and guides; http://www.worldtubeaudio.com/
Not to disagree with Kegger, we all hear what we hear, but I have stated several times I don't really share the joy of tube rolling that others seem to appreciate. Buying 5751's rather than AX7's is as much a crap shoot as buying any other tube as far as I am concerned. Many buyers like the idea of military tubes, thinking they were manufactured to a higher or tighter specification than consumer tubes of the same era. While that may be true in many cases, you would have to know what the spec for the tube was before you decided it was a good choice. If the tube was meant for harsh conditions, it might have sacrificed some sound quality over reliability. If the tube was meant for low microphonics, it might have sacrificed some sound quality over the ability to remain quiet while artillery shells were fired at close range to the transmitter. Vice versa, if the tube was intended for optimum sonics, it might prove to be very microphonic as its intended installation point was sunk in several tons of cement. One military spec tube might have gold plated pins. But your amp has tinned socket receptacles. The two metals don't mate properly and the discontinuity of materials can possibly have adverse effects on the sound quality you achieve with that combination. In short, know what you are buying instead of just buying a number on a glass (or metal in some cases) enclosure.
JC - Just out of curiosity, if you've tried every current production tube (and I assume you've purchased multiples and not relied on the sound of one tube), how much money have you sunk into this experiment? Do you suppose you might have gained more by using that same amount of money to buy a better piece of gear to start with?
Nuck - You seem determined to put some other tube in your amp. Any particular reason?
I am a curmudgeon on this topic but all this tube chasing reminds me of a dog chasing its own tail.
. |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2749
Registered: Dec-03
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| Posted on Sunday, December 17, 2006 - 01:13 pm: |
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Actually Jan a 5751 is a completly different animal then a 12ax7 is.
Not just a militiry spec 12ax7.
There a lower gain, lower noise tube and made slightly different.
Trust me when I say this, allmosy any circuit will benefit from using ANY 5751 over ANY 12ax7.
That's the research conclusion I have come to. Just want to share the info.
Yes I am a tube roller, sometimes the differences are very subtle and sometimes they aint. |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9486
Registered: May-04
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| Posted on Sunday, December 17, 2006 - 02:39 pm: |
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Yes, Kegger, I understand a 5751 and a 12AX7 are not the same tube and I don't want to argue over semantics or numerics. But 5751 is a number given to designate a military spec tube and was based on the essential parameters of a 12 series consumer tube. And a 7025 and an ECC83 are different tubes that a 12AX7. They all can swap fairly easily with each other. If you want to, you can use a 12AU7 in place of the AX7 and then look at all the variants of that tube also. https://www.tubeworld.com/index_low.htm
Keeping in mind different tubes have different requirements for bias and plate voltage/current, putting a tube that should run a lower bias in a higher bias circuit, or vice versa, might not be the trade you really want. That so many audio components have enough slack in their operation to accept an easy substitution of all these tubes gives tube rollers plenty of latitude in what sound they can get out of their gear. But to what end? My point was just buying a number doesn't ensure success. Your experience tells you it will. My point was buying a 5751 still might not get the tube that benefits the circuit you have and sound you want. Along with the lower noise of the 5751 you will get lower gain. So, you run the circuit noise up to get sufficient gain from the lower noise tube. That may not be quite the tradeoff you want in some instances. Then again it might be as the tube is the active part of the circuit and will contribute more noise than a dozen resistors. Kind of depends on where the tube is in the circuit. Add a cathode follower and now that tube isn't seeing the voltage it expects. Without thinking about what you're doing to the circuit as a whole, I think you can get into a world of trying tubes just for the sake of trying tubes. If you're buying tubes at typical NOS prices, I still think you are better off upgrading the basic circuit by using the money for better gear.
There are plenty of options as far as tube construction and build within the 12AX7 alone to keep someone busy comparing tubes for many a long night's listening. Throwing in too may vairables is more than I want to deal with. For the most part, I find that subtle differences come from tubes that are close in their basic operational specs. Generally more distinct differences come from a tube that has wandered farther from the spec of the circuit you're running. And everything I know of in audio has a tradeoff for something else. And every tube has some distinct sound and one Telefunken or RCA isn't the same as another similarly branded tube. Debating black plates vs. diamond points is more than I care about. As I've said before, I'll give you one thing while I take away two others. But, that's me and others are free to spend their time and money as they choose.
I'm not discounting your knowledge, Kegger. You've had the opportunity to roll more tubes in more circuits than I will ever care to. And anyone interested in experimenting with tubes would be wise to listen to anyone who has bought out stocks of NOS tubes for the purpose of rolling tubes. JC sounds like he could benefit from your experience. I think you and I just differ philosophically about all this.
. |
Gold Member Username: Nuck
Post Number: 4899
Registered: Dec-04
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| Posted on Sunday, December 17, 2006 - 02:48 pm: |
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If y'all don't mind, I am gonna grab a beer and re-read the last series' of posts.
And maybe sommore.
Cheers! |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2750
Registered: Dec-03
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| Posted on Sunday, December 17, 2006 - 03:13 pm: |
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I was just commenting on the fact it sounded as if you were saying that
a 5751 was just a military spec version of a 12ax7 when it really isn't. 
That's all my point was. And I'm not a big fan of 12AX7's but like 5751's.
So if someone is into rolling and wants the best 12AX7 they can find I'm
going to suggest a 5751 everytime, may not allways be the best choice but
your chances for success are on a very high level so it's worth seeking them out.
There not a truly expensive tube either like a 12AX7 can be, not really a gamble. IMHO
That's all I meant by my post.
Cheers! |
Gold Member Username: Joe_c
Atlanta,
GA
Post Number: 1109
Registered: Mar-05
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| Posted on Sunday, December 17, 2006 - 09:39 pm: |
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Wow, took a year off for bad behaviour and look what happens!!
Seriously though, I have got a pair of all the russian brand 12ax7 types except for EI, one pair of each only though. Never really gave too much though into spending money on two pair when I was mainly trying to see which ones I liked. As far as sinking more money into gear instead of tubes, I have spent maybe $20 bucks on all the tubes. Cannot see what type of upgrade can be made from the Jolida (significantly) without spending thousands. Seeme the higher up you go with this stuff(Moneywise) the less of a jump(qualitywise) is made each time. I will try those tubes (5751) because I do enjoy rolling. Even with the amateur setup and collection of tubes I have I really do notice subtle but rewarding nuances with most of the tubes I have. Just like moving speakers around for better soundstage/imaging, those differences add up. I can definitely see how upgrading the internals would make a difference, but the last time I checked the basic upgrade package (done by others) for my amp was $700. That's a heck of alot more than a pair of really good NOS tubes and all the tubes I currently have. Thank you for the advice (both of you). |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9490
Registered: May-04
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| Posted on Sunday, December 17, 2006 - 10:12 pm: |
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.
My comments were more generic about military spec tubes rather than speaking to any one particular tube. I've seen several people get involved in tube rolling and they began buying NOS mil spec tubes thinking they were getting better sounding tubes due to the tighter tolerances required for military use. In some cases they ended up with good tubes and in some cases they got something that wasn't what they were expecting. I had a friend send me some mil spec 6DJ8's to audition in my pre amp and they were one of the best sounding tubes I've used but they were so microphonic they drove me nuts trying to isloate the pre amp well enough to actually use them. As I said above, they were meant to be used in a very large, very heavy and very inert installation nowhere near any source of mechanical or airborne feedback, not in a little bitty pre amp a few feet from a speaker playing Lou Reed. Everyone should read my comments to mean I suggest you know what you are buying rather than just buying a number.
OK, now you've got me interested. Just what is it you hear in a 5751? How much less expensive are they than a 12AX7 (I've seen what I consider outrageous prices on NOS 12AX7's)? And, do you have six to loan out for an audition? The phase splitter and input tubes on my Mac's are so old I don't remember the last time I swapped them out.
. |
Gold Member Username: Joe_c
Atlanta,
GA
Post Number: 1115
Registered: Mar-05
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| Posted on Sunday, December 17, 2006 - 10:42 pm: |
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Looks like at www.tubeworld.com I can get a pair of circa 1970-80's GE grey plate double mica (whatever the heck that means) for $55 a pair! Might have to give myself a christmas prezzie!! |
Gold Member Username: Nuck
Post Number: 4919
Registered: Dec-04
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| Posted on Sunday, December 17, 2006 - 10:45 pm: |
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JC, aren't NOS kind of dicey for the vintage?
I mean, have they been sitting beside the Layfayette and cared for as well?
Just kinda wondered. For the price, I might get them too if I were you! |
Gold Member Username: Joe_c
Atlanta,
GA
Post Number: 1116
Registered: Mar-05
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| Posted on Sunday, December 17, 2006 - 11:22 pm: |
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Don't know much about how a tube needs to be stored. I suppose it's "cool dry place" like most other things. I do know that most of these retailers who sell NOS tubes have a reputation for selling good stuff and I feel confident buying product like that (non returnable as is kinda stuff). |
Gold Member Username: Nuck
Post Number: 4925
Registered: Dec-04
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| Posted on Sunday, December 17, 2006 - 11:29 pm: |
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A dealer friend suggested that NOS tubes are like old Dodge's. 'They don't go far, but they sure go fast' |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2751
Registered: Dec-03
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| Posted on Monday, December 18, 2006 - 02:04 am: |
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"OK, now you've got me interested. Just what is it you hear in a 5751? How much less expensive are they than a 12AX7 (I've seen what I consider outrageous prices on NOS 12AX7's)? And, do you have six to loan out for an audition? The phase splitter and input tubes on my Mac's are so old I don't remember the last time I swapped them out."
(This isn't just a response to Jans question above but to the subject as a whole)
And yes I did ramble on a bit,
I'll check and see what I have left. Quite a few of my better 12ax7 tubes and a few
5751's got sold to a local audio acquaintance for his phono stage plus his preamp
that runs 6dj8's and 12ax7's. I don't use many 12ax7's except in my own phono.
(I've since modded my phono to where it uses 1 12ax7 instead of 3)
I took over a bunch of tubes like the usual tellies, mullards, amperexes and whatnot
for him to tryout on his own, he was reluctant to try the 5751's in his preamp as he'd
been using some pretty expensive tellie 12ax7's he'd found very satisfying, so he tried
all the 12ax7's for a few month's and found combos that he found improved his system.
Seeing as though the 5751 is a little different then a 12ax7 he really didn't think they
should be used in a phono stage where gain and or riaa may be set by the tubes, so
he didn't give a lot of thought to the 5751, but after me suggesting "nicely" to at least
try them in the pre he did on his own then probably a few days later called to tell me
he wanted whatever 5751's I could spare and he was on the hunt for more.
He finally tried them in the phono stage with less then stellar performance, he had said
they sounded ok, and in some areas he thought there may have been an improvement
but also something not quite right. His phono stage uses I believe 10 tubes total with 2
of them being 6dj8's.
I have heard his system quite a bit and it is better sounding now by a wide margin with
the tube rolls he's done and what he's settled on. Not all his rolls or choices went the
way I have experienced on my systems and or gear I've tested out, but still within the
scope of what I have come to hear as being better sounding "to me".
As some people will tell you not every tube will sound the same on every system, not to
mention not everyone will agree what is best, so it is trial and "error" but the more time
you spend experimenting the better feel you get what things usually do. Also when you
look at the schematic for a certain piece may lend it'self to educated substitutions.
-------------------------------------------------
It's not so much what I find great in the 5751 as what I find not so great in most circuits
that use the 12ax7 and what I find is a grainy/haziness while at the same time lacking
detail plus a sense of air and somehow a lack of smoothness, I hesitate to use the term
"Blanket over my speakers" or "Veiling of the instruments" as it really is not that either
but a lack of detail and focus with somehow still being edgy and possibly irritative also.
I find the 5751 (IN MOST CASES) to be smoother then it's 12ax7 counterpart with better
detail and focus that generally does not get hard or edgy, I tend to like many other tubes
better but when the piece has to use a 12ax7 without being modded the 5751's an upgrade. IMHO
---------------------------------------------------
From a technical standpoint I don't build or rebuild something with the intent on using the
12ax7 or the 5751's for that matter as I find the gain not needed and feedback being used
to bring the gains back down most of the time anyway. Also there is a somewhat unwritten
rule to where a suggested plate load on a tube is in the neighborhood 5x the plate resistance
with the 12ax7's, 5751's having a pretty darn high plate resistance so at 5x for the load will
mean a power supply needed with some pretty large voltages to get some voltage to go past
that load to make it to the tube where there are plenty of good quality lowish plate resistance
tubes you can use a lower plate load on hence a lower voltage on your power supply. Most of
these lower plate resistance tubes don't have the demand of say the 12ax7 either so the cost
of such tubes is much lower which gives you choices of some of the premium grade ones while
not having to pay the premium grade price.
--------------------------------------------------------
Now all this is my personal findings with testing and research, by no means do I think this is
set in stone or my way is definitely the right way, but when asked my philosophy this is it.
--------------------------------------------------------
Also I do not spend the premium dollar on tubes, when there is a tube I'm after that I don't have
what I do is throw a bunch of cheap bids on tubes from ebay or whatnot and see what I land. I
have used this strategy to get some mighty fine tubes for some very exceptional prices. YMMV
----------------
In case anyone may have thought I took exception to anything said here I did not, just explaining
my way of doing/thinking what I have done and or do in my pursuit of good quality audio playback. |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2752
Registered: Dec-03
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| Posted on Monday, December 18, 2006 - 02:18 am: |
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On a somewhat related note I feel very close to the same way about the 12au7's.
And if the piece of equipment can handle a little more heater current I use 12bh7's. |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2753
Registered: Dec-03
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| Posted on Monday, December 18, 2006 - 02:34 am: |
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Nuck I believe the 5670 is a drop in replacement for the 6N3, plug and play. (not 100% sure though)
The data on that tube has 2 that come up, one says it's diode (but doesn't make sense)
and the other says a dual trode with specs of the 5670 with some sighting improvement.
The EL84 really has no substitute and as Rick has mentioned a mighty fine tube with
quite a loyal following, I would suggest after you get settled with the unit to search
out some mullard or sylvania EL84's (whatever you find the best price on) and try them. |
Gold Member Username: Nuck
Post Number: 4930
Registered: Dec-04
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| Posted on Monday, December 18, 2006 - 10:05 am: |
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Another aside, how do we count run-in hours?
Simply powered up, or under load? |
Gold Member Username: Nuck
Post Number: 4931
Registered: Dec-04
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| Posted on Monday, December 18, 2006 - 10:07 am: |
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The dealer is looking for syl or Phillips EL84's.
He is also looking for 5670's, no rush for either.
Thanks, folks.
Merry Christmas! |
Gold Member Username: Nuck
Post Number: 4935
Registered: Dec-04
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| Posted on Monday, December 18, 2006 - 09:41 pm: |
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Also, I tried turning the amp up this morning, for the first time.
I have 0ver 100 hrs 'on' time on it now, so I cranked the knob to 80% and let it go with 'Hotel California" on file(EQ'd),and large.
Jan asked me in an e-mail'why do you want a small tube amp'? I got this for shites and giggles, but this little amp has balls.
The Ling singles are too close to the rear wall at 8", and are on spikes into small sheets of pine(hand chosen solid)which are tacked onto a very heavy pine work surface, 10'long and a 4' return.
This little kit(I always come back to little), is a smasher! |
Gold Member Username: Nuck
Post Number: 4936
Registered: Dec-04
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| Posted on Monday, December 18, 2006 - 09:46 pm: |
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I wanna try some great all-round higher sensitivity speakers now.
Same size as the Ling.
Tim, are you there? |
Gold Member Username: Timn8ter
Seattle,
WA
USA
Post Number: 1148
Registered: Dec-03
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| Posted on Monday, December 18, 2006 - 10:58 pm: |
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Same size as in diameter or same (or close) cabinet size?
The similar sized full range drivers are not all that sensitive. In the "affordable and attainable" category would be Fostex. The FE126E is rated 93 db/w/m but should be horn loaded. The FE127E can be put into a small BR and is rated at 91 db/w/m.
The FE167E can be put into a small BR and is rated 94 db/w/m.
None of these drivers in a small BR is going to deliver the same bass response as Ling. The compromise made for higher efficiency is a lighter cone, lower strength motor and much less excursion. This means they require a larger cabinet such as a back loaded horn to deliver adequate bass response without sacrificing sensitivity.
Check out:
http://www.fostexinternational.com/docs/speaker_comp/rec_enc_1.shtml
Dave (Planet 10) and I have collaborated on some freely offered designs that you can read about here if you have a lot of time.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=46934 |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2754
Registered: Dec-03
|
| Posted on Tuesday, December 19, 2006 - 12:14 am: |
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A nice alternitave to horn loading with a smaller cab is the passive radiator, I'm using
8inch utah full range whizzer cone drivers in what is essentially a large 3 way 12" cab
but not using the tweeter and using a 12" passive instead of a woofer with extremely
satisfying results. I get exceptional bass response, nice clean clear mids with decent
top end, may add a super tweeter later but at this point on a SET 300B amplifier don't
find I'm "yearning" for more top end but I'm sure it wouldn't hurt either.
While these cabs are still not small by no means they are still much smaller then most
horn loaded designs will be and to me it's easier to get the cab and passive to workout
satsifactorly then designing a horn. Nothing against horns nor do I think there a tough
design but the passive has been so simple in what I've experimented with.
Cheers! |
Gold Member Username: Timn8ter
Seattle,
WA
USA
Post Number: 1150
Registered: Dec-03
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| Posted on Tuesday, December 19, 2006 - 12:27 pm: |
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Sorry, "attainable" should read "obtainable" or at least "readily available".
There are exceptions out there in indivdual's collections and some made of "Unobtainium". |
Gold Member Username: Nuck
Post Number: 4951
Registered: Dec-04
|
| Posted on Wednesday, December 20, 2006 - 10:58 am: |
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The footprint, Tim.
Maybe I will link a pic and show you, even! |
Gold Member Username: Timn8ter
Seattle,
WA
USA
Post Number: 1158
Registered: Dec-03
|
| Posted on Wednesday, December 20, 2006 - 11:29 am: |
|
One possibility is the Fostex FE127E in the recommended double bass reflex enclosure although it is still only 90db/w/m at best.
Just for fun you may want to try the Fostex FE167E in a small bass reflex box. Very easy to build and I think you might be able to get the drivers from Dave at Planet10 Hi-Fi in Victoria, B.C.
http://www.planet10-hifi.com/
The cabinet tuning frequency is 51Hz but the F3 is 84Hz. This design is obviously intended to be used with a bass unit.
Really though, you already own the best full range single driver speaker in a small cabinet for the money, even if I do say so myself.
These are better;
http://www.diyaudio.com/forums/showthread/t-76241.html |
Gold Member Username: Nuck
Post Number: 4956
Registered: Dec-04
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| Posted on Wednesday, December 20, 2006 - 11:35 am: |
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Those make greal cans.
I really would not go to anyone else for the speakers, Tim.
And knowing if you knew of something else yo would say so, then thanks.
I will post or send a pic later.
They can produce interesting waves in a hard room, and placed 6"from a rear wall. |
Gold Member Username: Timn8ter
Seattle,
WA
USA
Post Number: 1159
Registered: Dec-03
|
| Posted on Wednesday, December 20, 2006 - 11:53 am: |
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Thanks Nuck. I think this is a good example of the compromises made when it comes to speaker design. Many tube amp owners want affordable, small, full range, single driver, high sensitivity speakers but they simply don't exist. Not yet, at least. This then can lead to a compromise in amplifier design. The holy grail may be the SET but a good integrated push-pull running 30 to 40 watts/ch can produce wonderful sound and drive a large selection of speakers that are relatively small, affordable and well designed. |
Gold Member Username: Nuck
Post Number: 4957
Registered: Dec-04
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| Posted on Wednesday, December 20, 2006 - 12:15 pm: |
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The amp is bit small, but very effective.
I had friends over and they marvelled at the speakers, well, and the tube amp. But they arent stereoheads. The waves could change with a small speaker move, and the dead spots are not in the Captains chair or Mrs. Nuck's spot, so who cares?
Oh, and I will have fries with the small package, full-range single with full bass and sparkling highs, at 93db, please.
And cheap.
In your spare time.
Put the Elve's to work.
Merry Christmas! |
Gold Member Username: Timn8ter
Seattle,
WA
USA
Post Number: 1160
Registered: Dec-03
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| Posted on Wednesday, December 20, 2006 - 12:59 pm: |
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Ho! Ho! Ho!
 |
Gold Member Username: Nuck
Post Number: 4959
Registered: Dec-04
|
| Posted on Wednesday, December 20, 2006 - 01:48 pm: |
|
hehehe |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1156
Registered: Mar-05
|
| Posted on Friday, December 22, 2006 - 03:03 pm: |
|
Kegger,
can you give me advice please. I was switching out tubes in the Jolida today and when I turned the amp back on it was staticy on one channel. After switcing the tubes around and out and back again I have come to the conclusion that it is a loose circuit inside the amp. Now I do know to wait a day before messing with the electronics inside. But I am pretty handy when it comes to soldering and the such and was wondering if because of heat or just age the connections , which may have been a poor solder in the first place, come loose. It seems to crackle when I tap the bias trim and also when i move the pre tube in it's socket. I think it's either the trim knob or some connection with the pre tube. What is the best way , other than soldering every joing in that area (that may be the best option, I don't know) , to find a loose solder joint. I do have a multimeter of course, but I do not have any other caps or replacement parts. I will not rebuild this thing but I have a feeling it's as simple as I described. Just needing some direction. Thanks, Joe. |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1157
Registered: Mar-05
|
| Posted on Friday, December 22, 2006 - 03:08 pm: |
|
Correction, there is a popping sound when I tap the main board which the trim pot for the bias is on. It must be a loose connection because it pops loud when tapped. I do not want to damage my speakers so I am going to find a cheapie speaker around the house to use with fixing it(if that's what I need to do) |
Gold Member Username: Nuck
Post Number: 4986
Registered: Dec-04
|
| Posted on Friday, December 22, 2006 - 05:20 pm: |
|
That sounds like a better sacrifice, JC. Keep tapping and keep a hot iron. And a broad wick. |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2755
Registered: Dec-03
|
| Posted on Friday, December 22, 2006 - 08:04 pm: |
|
If this only occurred after swapping out tubes and you can make the sound happen when
moving a tube in it's socket, sounds to me as a loose or dirty contact pins on the socket.
If this is the case then tapping other places can make the tube loose contact as well.
If you can find a small thin blade type device you can "squeeze"/tighten the pins on
the socket back up and that may just do it, or you'll need a contact cleaner like DEOXIT.
That's were I would start first as it sounds the most logical not to mention easier fix.
OF'course this means the unit unplugged and no voltage present! Also to apply a contact
type cleaner put it on the tube pins then move it in and out of the sockets you are cleaning.
You'd be surprised how this method will bring back the oldest equipment from death. |
Gold Member Username: Nuck
Post Number: 4999
Registered: Dec-04
|
| Posted on Friday, December 22, 2006 - 09:34 pm: |
|
Beauty, Kegger! |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1158
Registered: Mar-05
|
| Posted on Saturday, December 23, 2006 - 12:12 am: |
|
Resoldered all joints relating to front end, all back to normal. I think it had just become defused? is all
Thanks for moral and psychological help |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1159
Registered: Mar-05
|
| Posted on Saturday, December 23, 2006 - 12:13 am: |
|
Back in business , thanks guys |
Gold Member Username: Nuck
Post Number: 5006
Registered: Dec-04
|
| Posted on Saturday, December 23, 2006 - 06:27 am: |
|
Play us a song, JC! |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1161
Registered: Mar-05
|
| Posted on Saturday, December 23, 2006 - 11:21 am: |
|
Hilary Hahn playing "The Lark Ascending" right now.  |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2756
Registered: Dec-03
|
| Posted on Saturday, December 23, 2006 - 11:33 am: |
|
Tracy Chapman "Telling Stories" Playing right now, here. LOL! |
Gold Member Username: Nuck
Post Number: 5015
Registered: Dec-04
|
| Posted on Sunday, December 24, 2006 - 12:22 am: |
|
Cartoon Classics on the tubes here! |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1164
Registered: Mar-05
|
| Posted on Sunday, December 24, 2006 - 12:51 pm: |
|
Makes me wonder how much of a difference I could make replacing all point to point wire with better quality and using siler solder. I wish I knew how to look at caps and decifer what type it is. I would love to do the upgrades myself. |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1165
Registered: Mar-05
|
| Posted on Sunday, December 24, 2006 - 12:52 pm: |
|
silver* |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1192
Registered: Mar-05
|
| Posted on Sunday, December 31, 2006 - 11:51 am: |
|
Keg, you think these would be worth trying?
http://www.tubedepot.com/nos-5751jan.html |
Gold Member Username: Nuck
Post Number: 5096
Registered: Dec-04
|
| Posted on Sunday, December 31, 2006 - 12:06 pm: |
|
JC, if you can't read the caps, a resonably priced Fluke meter will run the caps for you, but the voltage ratings will differ.
Measure your plate voltage to see, the EL84's are rated 300 volts.
Why not redo the wiring DIY?
You are certainly competent, just replace one lead at a time. One of the advantages of silver solder is it's low melting point, enabling a smaller solder head.
I like the capillary action of silver as well, to be able to draw the heat away from sensitive parts, and draw a longer, smoother joint than a hasty glob of lead/tin. |
Silver Member Username: Arande2
400dB could probably d...,
4000 isnt ev...
100,000dB FU...
Post Number: 532
Registered: Dec-06
|
| Posted on Sunday, December 31, 2006 - 12:13 pm: |
|
My response to the very first post on this thread, even though a lot of people have heard of it, is that Wavac makes a pair of 150 watt RMS SET's for the budget price of $350,000 |
Gold Member Username: Nuck
Post Number: 5098
Registered: Dec-04
|
| Posted on Sunday, December 31, 2006 - 12:21 pm: |
|
Andre, shut up and stay with the tour.
If you want to learn, then do so.
Comment on the current topic or ask a question.
Your contributions are valued, but stay on topic, ok?
This thread is full of valuable info for tube enthusiasts, not the dreamers.
Please stay on topic.
Nuck. |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1193
Registered: Mar-05
|
| Posted on Sunday, December 31, 2006 - 01:29 pm: |
|
Good idea Nuck. Any thoughts on the solder available from Partsexpress or should I try to find something higher end?
As far as the wire? |
Gold Member Username: Nuck
Post Number: 5101
Registered: Dec-04
|
| Posted on Sunday, December 31, 2006 - 02:37 pm: |
|
Now the wire, I would email Keger for.
Well, heck, for the solder, too.
There may be a reason for not using 100% silver (other than cost, don't flick off the excess), dunno.
Kegger, where art thou?
I want to know more about internal amp wiring. |
Silver Member Username: Arande2
400dB could probably d...,
4000 isnt ev...
100,000dB FU...
Post Number: 533
Registered: Dec-06
|
| Posted on Sunday, December 31, 2006 - 11:24 pm: |
|
Well I guess I'm a constant dreamer because I can't afford anything for a while |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9559
Registered: May-04
|
| Posted on Monday, January 01, 2007 - 01:32 pm: |
|
.
If I might inject an opinion here; if you are going to get serious about modififying an audio component, it is time to get past the Parts Express catalog.
http://www.percyaudio.com/Catalog.pdf
Percy sells some of the best products available at concomitantly superior pricing. In other words, it ain't cheap but it's the best available at any one time.
If you look at the make up of silver solder, you'll see there is no 100% pure silver solder. The silver content is relatively low at around 4% with the rest being made up of tin and lead. Pure silver doesn't flow very well, takes along time to cool completely and won't make a very good solder joint, particularly when the work is done by hand. The Wonder brand solder has been an inductry standard for a few decades. As to your choice in hookup cabling, you can see there are several to choose from. I would stay with a Teflon coated wire if you're going to put this in a tube amplifier.
You can also put something on the order of "diy audio amplifier ... anything; modifications, parts, connectors, etc." and get more selections for sources. Percy is exceptionally reliable but not always the cheapest source for any one part. And high quality parts are not cheap no matter where you shop. You can also go back to my oft referenced World Tube Directory and cruise through the numerous links to find diy parts sources.
Finally, consider the job before you jump into an amplifier. In the case of point to point wiring inside an amplifier, it is not always the case where you get to disconnect one wire at a time. Often several pieces must be unsoldered at the same time to remove just one wire. Screw this up when you are putting it back together and suddenly you've put the spark plug wires on the wrong terminals of the distributor cap of the V12 and you don't have a reference for how to get them back correctly. This isn't hard to mess up and sudenly all the wires look the same. If you are changing out wiring, don't cheap out. Buy spools of differently colored wire, it will pay for itself in the end. And, if you don't have a schematic to follow, keep in mind that a tech might not have a schematic to follow either. I speak from experience and I am not just preaching to the unconverted. One misplaced wire could be the end of your amplifier if not the beginning of a long, painful and expensive headache.
. |
Silver Member Username: Arande2
400dB could probably d...,
4000 isnt ev...
100,000dB FU...
Post Number: 544
Registered: Dec-06
|
| Posted on Monday, January 01, 2007 - 01:40 pm: |
|
Well, maybe I should look at some of that. I first am going to need a tube amp, any recommendations or anything? |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9560
Registered: May-04
|
| Posted on Monday, January 01, 2007 - 01:49 pm: |
|
.
Before you heat up the soldering iron, go back and look at the wiring layout on this amplifier.
http://www.sixmoons.com/audioreviews/genesis3/i60.html
It is close to magnificent and exceptional by anyone's standards for a production piece of equipment. One piece at a time hand assembly is the only thing I've seen that beats this work. Pay attention to the numerous cable ties to maintain parallel runs and near 90° angles. When modifying an amplifier pay close attention to the original layout and try to repeat the same work as closely as possible when it comes to laying cables near one another or crossing each other. Often this was a bit of attention to detail a top notch manufacturer will have worked out to minimixe noise. If you alter the layout, you could end up with buzzes and hums that weren't in the original design. Keep your work as neat as possible, if for no other reason that pride of workmanship but certainly to assist in troubleshooting wwhen that time comes. Make the runs straight and the solder connections neat. If you think you've let a connection slip before the solder sets up, reheat the connection rather than moving on and having cold solder joints later. Use lots of heatsinks on your connections to minimize the deterioration of the cabling. And consider buying a soldering station rather than a $10 iron.
. |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1195
Registered: Mar-05
|
| Posted on Monday, January 01, 2007 - 08:38 pm: |
|
Great advice Jan, thanks.
That amp looks amazing! The Jolida has a couple of boards in the amp wich I wish were not there, but it's still a great amp for the mony. And for now I am going to hold off untill I can afford a decent solder station and all the upgrade parts at once.
Thanks again. |
Gold Member Username: Nuck
Post Number: 5129
Registered: Dec-04
|
| Posted on Monday, January 01, 2007 - 08:50 pm: |
|
JC, I havn't opened mine yet, do you have a pic? |
Gold Member Username: Nuck
Post Number: 5130
Registered: Dec-04
|
| Posted on Monday, January 01, 2007 - 08:51 pm: |
|
or 10? |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1199
Registered: Mar-05
|
| Posted on Monday, January 01, 2007 - 09:15 pm: |
|
Gimme a cpl of days Nuck, I am going to the GA aquarium tomorrow and then it's back to work after 11 days off ( I expect a tsunami's worth of catchup) and then I will open up to resolder the left channel front end points. Will take a cpl of pics. By the way it's a Jolida 502B. |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2757
Registered: Dec-03
|
| Posted on Monday, January 01, 2007 - 11:22 pm: |
|
To the question of those 5751 tubes, they look fine to me.
As for rewiring the inside of the amp, to me it's probably not worth it.
Not saying different wires are different sonicaly from others, but will you
guess correctly as to what works better for you? And how much of a difference
are you going to get with how short that those runs of wire are in the first place?
An amp or system for that matter is the sum of ALL it's parts, just rewiring one thing
wirh short runs of wire to start with is more then likely not really going to get u very far.
Upgrading the passive parts in the signal path like resistors and caps if there not really
that great in the first place could have a very noticable improvement in the amps sound.
But the unit could also be voiced with the parts chosen originaly, so unless your familar
with the parts chosen and the unit to start with you may not be improving it at all.
I'm not saying upgrading the parts in the amp or preamp or whatever would not make an
improvement, but not knowing what your replacing and what your improving is guess work
at best. When I'm doing this it's usually based on passed knowledge of the circuit and or
the parts used, both original and replacement, sometimes it's try and see.
Nethier myself nor anyone else who hasn't worked on this unit could guide you to the correct
upgrades or rebuilds that would be best for you, this piece and your system. These kinds of
things are trial and error for the most part until you've gotten use to a certain piece and parts.
There are certain caps and resistors I like but for certain needs and certain areas of a piece
that are really hard to try and determine ecspecially without a schematic of the unit.
As to solder, for me it's the average 2-4% silver thin stuff that melts quick, the solder should
not be heard as you are not using the solder to make the connection, you should have a solid
mechanical connection, and the solder is there basically as a glue to hold the pieces in place. |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2758
Registered: Dec-03
|
| Posted on Monday, January 01, 2007 - 11:31 pm: |
|
When I said,
"Not saying different wires are different sonicaly from others, but will you
guess correctly as to what works better for you?"
I meant to say,
"Not saying different wires are not different"
Also I'm not trying to discourage anyone from performing mods or upgrades to there
system but just stating it's not as cut and try as it may look or seem to be is all.
Happy new year all! |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1201
Registered: Mar-05
|
| Posted on Tuesday, January 02, 2007 - 09:53 am: |
|
Thanks Keg, and I am in agreeance (is that spelled right?) with you. I wouldn't try anything without either guidance and or a schematic to work with. I do think that resoldering the contacts will help however, they helped on the side that was defused. Think I will do that today since my Daughter is sick and we cannot go to the aquarium. Will post some pics Nuck. |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1202
Registered: Mar-05
|
| Posted on Tuesday, January 02, 2007 - 03:23 pm: |
|
Just got done with the resoldering. Here's the pics NUCK:
 |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1214
Registered: Mar-05
|
| Posted on Thursday, January 04, 2007 - 02:17 pm: |
|
Jan, this one seem good?
http://shop1.outpost.com/product/1942888 |
Gold Member Username: Nuck
Post Number: 5135
Registered: Dec-04
|
| Posted on Thursday, January 04, 2007 - 02:52 pm: |
|
I wouldn't want to copy the wiring.
Thanks JC |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9577
Registered: May-04
|
| Posted on Thursday, January 04, 2007 - 05:21 pm: |
|
.
That station should cover all your basic needs and that's a pretty good price. Order a few extra tips to cover items that require either a fine point or a wide, spade type of iron tip. |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1220
Registered: Mar-05
|
| Posted on Thursday, January 04, 2007 - 10:38 pm: |
|
5751's on the way!!
Probably gonna drop by Fry's tomorrow and see about that soldering station. |
Gold Member Username: Nuck
Post Number: 5137
Registered: Dec-04
|
| Posted on Friday, January 05, 2007 - 06:47 am: |
|
JC, I had one like that except with a vaccumn pump for desoldering, which worked well.
Maybe see about that one as well? |
Gold Member Username: Nuck
Post Number: 5162
Registered: Dec-04
|
| Posted on Saturday, January 06, 2007 - 11:45 am: |
|
Heres a Dynaco ST70 on Ebay that I saw. On the panel, it says Dynakit ST70.
Was this a kit or the real McCoy?
http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem%26item%3D300066096144&indexURL=0&ph otoDisplayType=2#ebayphotohosting |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9583
Registered: May-04
|
| Posted on Saturday, January 06, 2007 - 12:25 pm: |
|
.
It's real McCoy but was built from a Dyna kit. |
Gold Member Username: Nuck
Post Number: 5163
Registered: Dec-04
|
| Posted on Saturday, January 06, 2007 - 12:33 pm: |
|
So it potentially assembled by 88 thumbs Flintstone on the kitchen counter, beside the toaster, and popped something on the first trial?
That part was replaced, but left some other componants less than spec? |
Gold Member Username: My_rantz
Australia
Post Number: 1025
Registered: Nov-05
|
| Posted on Saturday, January 06, 2007 - 12:59 pm: |
|
Wasn't sure where to put this, but since they started with tubes . . .
To see how the Macs are built:
http://www.hometheaterhifi.com/volume_14_1/mcintosh-factory-tour-1-2007-part-1.h tml |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9587
Registered: May-04
|
| Posted on Saturday, January 06, 2007 - 01:21 pm: |
|
.
Nice tour, Rantz. You can also see the old Mac factories on, I think, Roger Russel's site.
When buying vintage audio, you can find several brands which were offered in kit form. (McIntosh even offered their 30 watt tube amp as a kit for a short time period.) It is wise to consider the value of a kit vs. a fatcory asembled unit when buying older equipment as the kits usually come in at a lower price due to potential problems in construction. Some kit builders were exceptionally talented in soldering and layout, while others were less so. Some kits were simple wire "B" into hole "2" affairs. Some weren't. The Dyna kits were fairly simple assembly of stuffing one or two boards and connecting a few wires. You can usually tell which kits to worry about by the unruly wiring and globs of cold solder joints evident in pictures inside a less talented assembler's unit. Well built kits most often look very much like factory units. Solder joints were the largest problem most assemblers had with Dyna kits but that problem did lead most service departments away from troubleshooting assembled kits that didn't work properly.
Of, course, if you are going to tear the unit down for modification, kits offer a less expensive way to buy the amp you want to work on. After all these years, it is certainly not uncommon to have a Dyna unit hum due to bad caps. Dyna kits have now days pretty much lost their negative value against factory units since most poorly assembled units would have shown problems after forty plus years. Factory stock units have gained in price since they are rare now days. The seller indicates there are no hum or noise problems with this unit, so, it is safe to assume the unit is wired properly.
Kegger might add more information since he owns (owned?) a pair of ST70's and two pre amps.
. |
Gold Member Username: Nuck
Post Number: 5165
Registered: Dec-04
|
| Posted on Saturday, January 06, 2007 - 01:30 pm: |
|
Thanks, Jan. I might mail back and look for a beter price to play with, but then again, just yesterday this deal went down.
Day late and a dollar short.
http://cgi.audiogon.com/cgi-bin/auc.pl?ampstube&1167884192&1&3&1& |
Gold Member Username: Nuck
Post Number: 5166
Registered: Dec-04
|
| Posted on Saturday, January 06, 2007 - 01:31 pm: |
|
No points for the toaster? |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9589
Registered: May-04
|
| Posted on Saturday, January 06, 2007 - 02:50 pm: |
|
.
No points for the toaster and no points for "clones". The best part of the Dyna products are the transformers and any tube amp lives and dies by its transformers. There are newer transformers that probably can compete with the OEM units but, if you want to hear what a ST70 sounds like, you begin with the original transformers, at least. NOS transformers are available for those amplifiers that have bad units (which is pretty rare) and there are new units which can possibly improve the quality of the amp. But the Dyna transformers were among the best of their day and are the reason the amps are still highly regarded. The transformers and the introduction of Ultralinear operation are the hallmarks of Dyna. Be careful of any units which have been modified since some valuable parts might have been swapped out and left behind. You are more likely to find a modded unit today and that's OK if you know what you're buying and know you can make the amp work in your system. Not all mods created for the ST70 have proven their value over the years. The VanAlstine and the Curcio are, to my knowledge, still among the best mods. Again Kegger might have more knowledge since he has probbaly investigated this more recently than I.
Stick "Dynaco modifications" into a search engine and spend the day reading.
http://www.angelfire.com/ma2/AdamVon/dynaresto.html
http://www.avahifi.com/root/audio_basics/ab_index_complete.htm
http://www.tubes4hifi.com/ST70mods.htm
http://hometheater.about.com/od/vacuumtubeaudio/Vacuum_Tube_Audio_Products_and_T echnology.htm
http://audiotools.com/valve.html
From: http://www.quadesl.com/refurb/refurb_dynaST70.html
"From my measurements and listening tests, I believe that the Dyna ST-70 output transformers are of very good quality (at least the ones on my ST-70).
There are many modifications available for this amp. There are two problems that most modifications fall into. First there are the total mods. Basically, everything in the amp is removed except the iron, and the amp is rebuilt. This is all well and good, but don't forget that this is a budget amp, and the chassis is not so great either. If you are going to dump that much money into a tube amp, why not start with a new chassis, and design it from the ground up instead of making compromises to fit the mod into this chassis. The second type of modification class is just to replace the input board which contains the hard to find 7199 tubes. This can be a good way to go, but if the topology is changed significantly, the stability of the amp can be compromised. And if the original design is changed in one way, it can show the compromises in another area. For example, if the bias current is reduced on the output tubes to lengthen their lives, the power supply modulates more with the musical signal, and the IMD goes through the roof.
Based on my listening experience with various ST-70 mods. The most satisfying mods change the amp the least."
. |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2759
Registered: Dec-03
|
| Posted on Saturday, January 06, 2007 - 06:57 pm: |
|
Everything Jan's said about these Dynacos is spot on.
Yes they were mostly kit's, so no worries about buying one that was a kit.
Also if you want to hear the ST-70 in all it's glory you do want an old one with
the cloth lead output transformer wires. The two places or 3 really considering
power supply where they SHOULD be upgraded is the original front end circuit (the vta one is decent)
and there power trannies (not there outputs) could stand to be replaced with one
that has a little more beef to it so it runs cooler and quieter, then rebuild/upgrade
the power supply it'self and you'll have one fine sounding amplifier that would be
tough to outdo without spending quite a bit more money. IMHO
Yes also as Jan say's I have 2 st-70's and one pas3 left, the pas3 is no big deal
and I wouldn't bother with one, but the st-70's can be very special amplifiers.
Both mine run the vta board, the original one I did was a stock vta build and it does
sound very nice, BUT it does run 3 12at7's which supply a lot of gain and still uses
the output trannie to provide loop feedback to the input stage. The second one I have
built I bought a blank vta board (as the circuit is pretty nice and upto date) and made
my own build with it using lower gain tubes, 12au7,12bh7,6829,5965 and made a mod
to use less feedback and around just single stages, no longer using the loop feedback
from the output transformer, I like the second version much better then I do the first and
will be rebuilding the first one with this new circuit design.
Long story short I believe the ST-70 is a decent amp in it's original design but can be the
building block for something very very nice if one chooses to do so. It won't necasarily be
a cheap road as the 70 can command some decent money these days, then the rebuild. |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9605
Registered: May-04
|
| Posted on Saturday, January 06, 2007 - 08:57 pm: |
|
.
If you're actually thinking about a ST70, the good thing is there isn't much to swap out. Modding an ST70 is a good way to find out what various components do when you change them from stock. Most importantly, I think, with the ST70 is the way you can gradually build up the amp. I believe you'll get more out of slowly taking the amplifier through the various levels of modification rather than just jammimg every mod you can find into the amp first time out. Change something and then listen. Change something else and then listen. Unless you are just determined to have the very best sounding ST70 around, it doesn't have to cost lots of cash. Once you change too much, you no longer have a ST70.
You can also look for Dyna Mk III's as an alternative to the ST70.
. |
Gold Member Username: Kegger
Warren,
MICHIGAN
Post Number: 2760
Registered: Dec-03
|
| Posted on Saturday, January 06, 2007 - 10:04 pm: |
|
No arguement here and certainly agree the 70 or the mark III's would/could/are great learning tools.
But for me living with an amp that has rolled off highs and flabby bass was not going to cut it as the
main music supplier in my system so the mods had to come along. It's a decent amp in stock form.
I'm not sure when or where an ST-70 no longer is an ST-70 with mods, but for me it really does not
matter and don't see why it would anyone else, if the amp has shortcomings and modding/changing
it will overcome those then to me there really is nothing to discuss. Mod it till your hearts content.
If someones happy with a 70 in stock form then that is great, I am not. The stupidist mod I've seen is
I believe the van alstine mod where they limit the frequency response of the amp in the top and bottom.
After having ones that play a beautiful full spectrum I see no backing for some saying the ouputs need
to be bandwidth limited and on the contrary had mine on the bench with some very nice passing grades.
Doing mods in steps is great advice and makes affording them much easier, that's what I did. But now
after going through all that, I've learned a few things and like to share what I've heard/seen with others.
Buying a used one then tearing it apart to do all the full blown mods is a toss up to just building a nice
amp in the first place, as far as price and performance goes. But if you get one and decide to do so you
just may end up with something you can keep forever. So I'm never sure how to advise someone on that.
I just provide the info and left the perspective amp chooser decide what is best for them. Cheers! |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9607
Registered: May-04
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| Posted on Saturday, January 06, 2007 - 10:40 pm: |
|
.
A ST70 is no longer an ST70 when you loose what is inviting about the amp. For me that's the midrange quality and the bounce in the music which is evident in the stock 70. There are a few mods which have managed to turn the Dyna into a solid state sound alike. That's not a ST70. The stock amp is almost always too forward and has too much classic tube sound for my taste but there are aspects of the stock sound that are very appealing. Yes, improve the response at the ends but leave the middle pretty much alone. If I hear a ST70 that doesn't make me want to tap toes, then that's no longer a ST70.
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Gold Member Username: Nuck
Post Number: 5176
Registered: Dec-04
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| Posted on Sunday, January 07, 2007 - 07:16 am: |
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If I am able to persue an ST70 it would be modded(or poor parts replaced) in small steps, yes, as a learning tool, but also to have an amp I like.
By nature, I would want extension at the ends, but not something that sounds ss.
I'll chase down one of these Dyna(co)(kit) amps when I can get a good price.
Unfortunately, the little Mengyue amp has developed a crackle in one channel now, so I get to solder(and wick) today.
As I said before, the solder may have been applied with a mop. D'oh! |
Gold Member Username: Nuck
Post Number: 5183
Registered: Dec-04
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| Posted on Sunday, January 07, 2007 - 08:34 am: |
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As well, excepting the price, are these Mullard tubes desireable?
http://cls.audiogon.com/cgi-bin/cls.pl?accstube&1171556582 |
Silver Member Username: Two_cents
Post Number: 792
Registered: Feb-04
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| Posted on Sunday, January 07, 2007 - 01:20 pm: |
|
Have any of you experimented with different footers for your tube amps? I recently put small wood blocks underneath my Primaluna PL2 which comes with rubber feet. It helped solidify the sound and deepen the bass. I'm wondering now if there's another material for the footers that will improve the sound even more. |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9609
Registered: May-04
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| Posted on Sunday, January 07, 2007 - 05:01 pm: |
|
.
Ther are many different naterials that will help the sound of your tube amplifiers. Tubes are always going to be microphonic to some extent and isolating the amp should be a major concern. On the other hand, you want to drain chassis resonances from the power transformer. Doing both functions at the same time is difficult.
I've used spikes on my amplifiers for decades. The amps sit on a free layer damping complex that involves three layers of 3/4" MDF alternately sandwiching cork; rubber of several sizes, shapes and thickness; marble slabs and pumice stones with coins on top under the spikes. I also have a few old VPI bricks which sit on top of the power transformers and five pound lead scuba weights sit atop the output transformers.
If your amp has a tube cage, you might also find an improvement by removing the cage while you lsten. As a general rule, ignore soft squishy feet for your tube power amp. A tube amp typically weighs too much for the soft feet and will compress the material to the point where its effectiveness is compromised.
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Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9610
Registered: May-04
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| Posted on Sunday, January 07, 2007 - 05:08 pm: |
|
.
For anyone opening the chassis of their amp, get some high temperature silicone adhesive and place a dab of this material on and around each large cap in your amp. This is a fairly minor tweak if you've improved the isolation of the amp, but it minimizes microphonics in the internal components. There is no need to cover the cap, just enough to damp the cap and still allow the silicone to be removed easily during service is sufficient. Just look over the internals of the amp and consider where vibration might creep in and what you can reasonably do to stop its migration.
And do your housekeeping, clean all contacts in your system.
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Gold Member Username: Nuck
Post Number: 5191
Registered: Dec-04
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| Posted on Sunday, January 07, 2007 - 07:46 pm: |
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Well the amp seems intact inside. I checked the terminations, they seem solid enough. Gave the pots a sweep. Spray contacts with cleaner.
Put it back together and got the same thing.
Swap the EL84's around and the noise moved to the right side! Bad tube!
Sent email to the guy in Hong Kong, but I think I am gonna have to get tubes myself. 30 days.
Rats! |
Gold Member Username: Rick_b
Orlando,
FL
Post Number: 1422
Registered: Dec-03
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| Posted on Sunday, January 07, 2007 - 09:07 pm: |
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2C
In answer to your question, brass. Try the brass isolation cones from Mapleshade. I swear by them. |
Silver Member Username: Two_cents
Post Number: 794
Registered: Feb-04
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| Posted on Sunday, January 07, 2007 - 10:54 pm: |
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Rick and Jan,
Thanks for the ideas. I'll look into the Mapleshade cones... and some lead or brass weights. |
Gold Member Username: Joe_c
Atlanta,
GA
USA
Post Number: 1232
Registered: Mar-05
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| Posted on Monday, January 08, 2007 - 11:37 am: |
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5751'S in and playing.....after a while my first impressions are (with Vaughan Williams - Fantasia on a theme by Thomas Tallis) is that there maybe more depth to the soundstage and imaging more defined. I will continue listening and report back. They obviously have less gain therefore in my mind the signal should be clearer before it hits the power stage?? |
Gold Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 9613
Registered: May-04
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| Posted on Monday, January 08, 2007 - 12:34 pm: |
|
.
JC - You know how I hate to disagree, but lower gain doesn't necessarily equate to a cleaner signal. Lower gain is, in most respects, the same as lowering your volume control. As long as a gain device is within its linear operating range, there should be no difference in its distortion product. Once you begin operating outside of the linear range, say by pushing the next stage harder to compensate for lower input voltage, then you will increase the distortion product of the next stage. But that's mostly a design choice and shouldn't be affecting the output stages of your amplifier.
If the lower gain from a preceding tube still provides sufficient voltage to keep the next stage within its linear range, there should be no difference in signal purity - only a level change. I assume that's what you mean by "the signal should be clearer".
One thing you might notice, and, then again might not, is the lower gain in the amplifier puts your volume control in a more linear operating range. That's a small benefit but still would be considered a good thing in most cases.
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