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Thread: Amplifier gain question |
    
Bronze Member Username: Drumjunky
Boulder,
Colorado
Post Number: 31
Registered: Nov-04
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| Posted on Thursday, January 06, 2005 - 04:43 am: |
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So I understand that the gain on your amplifier is used to match the voltage coming from your HU to the amplifier and that setting the gain too high will cause clipping...
My question is more about the amplifier-gain relationship, I guess. Lets say the HU pre-amp voltage is 4V and you have the amp gain set at 2.5V. I'm assuming this is setting the gain too low and the the sound from the speaker is less than its potential loundess. How does the amplifier handle this situation?
This question comes from when I was setting the gain on my own amplifier...it seemed that there was more distortion when the gain was set at a lower voltage than at what I thought was a higher voltage(I didn't turn the gain all the way up, so I didn't really test the full spectrum). The gain spectrum on my amp is from 0.2V-6.5V and I have it set a little more than half...the sound seemed best at this location with the consideration of clipping in mind.
Thanks for the enlightment |
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Silver Member Username: Oleg
Santa Monica,
CA
USA
Post Number: 333
Registered: Nov-04
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| Posted on Thursday, January 06, 2005 - 10:51 am: |
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The way this works is the lower you turn the gain on the amp (i.e.: toward the 0.2V direction), the more sensetive the amplifier needs to be. Thus it thinks it's getting a weak signal so it needs to amplify it even more, and that's when you get distortion. Halfway point is just fine for that head unit, it's set at about 3.8V. |
Silver Member Username: Carguy
Post Number: 997
Registered: Nov-04
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| Posted on Thursday, January 06, 2005 - 03:30 pm: |
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Don't operate the amp at 2.5v setting. It will blow your amp sooner or later. |
Bronze Member Username: Drumjunky
Boulder,
Colorado
Post Number: 32
Registered: Nov-04
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| Posted on Thursday, January 06, 2005 - 03:55 pm: |
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that makes sense. thanks for the info
I was using 2.5V as an example to understand why I was hearing the distortion, but it's good to know that this could potentially blow my amp.
Thanks guys! |
Silver Member Username: Iamduff_87
Michigan
America!
Post Number: 328
Registered: May-04
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| Posted on Thursday, January 06, 2005 - 07:12 pm: |
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setting it at 2.5v compared to a 4v HU as an example would cause clipping, which causes distortion. the amp is trying to put out max power when it recieves a full 2.5v. the HU can put out 4v which is higher. therefore the amp will be putting out max way before your HU is turned all of the way up. at least that is how i have come to understand this setup. |
Silver Member Username: Oleg
Santa Monica,
CA
USA
Post Number: 335
Registered: Nov-04
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| Posted on Thursday, January 06, 2005 - 09:06 pm: |
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that is actually not right. There's also distortion at low volume levels because a weaker signal is being amplified...thus u get crap |
Bronze Member Username: Drumjunky
Boulder,
Colorado
Post Number: 33
Registered: Nov-04
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| Posted on Friday, January 07, 2005 - 01:25 pm: |
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hey oleg, what's not right? only distortion at high volumes(after 2.5V in the example)? |
Gold Member Username: Glasswolf
NorthWest,
Michigan
USA
Post Number: 7218
Registered: Dec-03
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| Posted on Friday, January 07, 2005 - 01:34 pm: |
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using a 4V pre-out with the amplifier, if you set the gain to 2.5V, that tells teh amplifier your pre-out voltage is 2.5V, and thus your amplifier's input sensitivity will be increased, overdriving the amplifier input and causing distortion and clipping.
If you had a 2V pre-out and set the amp to 4V at the input sensitivity dial (gain) then you'd under-drive the amp input stage, and you'd be amplifying a very weak signal, which results in moer THD, and a worse signal to noise ratio. your noise floor will be higher, and you'll get less volume due to the fact you're using the same amount of amp power to boost an already weaker signal.. like amplifying a whisper instead of a normal conversation.
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Silver Member Username: Oleg
Santa Monica,
CA
USA
Post Number: 337
Registered: Nov-04
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| Posted on Friday, January 07, 2005 - 01:48 pm: |
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There ya go. |
Bronze Member Username: Drumjunky
Boulder,
Colorado
Post Number: 36
Registered: Nov-04
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| Posted on Friday, January 07, 2005 - 01:57 pm: |
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jimmie cliff's song "i can see clearly now" comes to mind right now.
setting the gain too high is saying setting the input voltage too low...I guess that kinda seems counter intuitive to me
thanks for help!...it makes much more sense now |
Gold Member Username: Glasswolf
NorthWest,
Michigan
USA
Post Number: 7229
Registered: Dec-03
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| Posted on Friday, January 07, 2005 - 07:03 pm: |
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think of it this way:
the markings on the amp's gain (say 500mV to 4V) are markings made to match the pre-out voltage.
that means since the voltages need to match, then a weak pre-out voltage would need the most "gain" from the input stage of teh amp to get a clean, balanced signal.
If the line pre-out voltage from the head unit is strong, such as a good 4V signal, then the amplifier doesn't have to boost the signal, or do anything at the input stage, so:
the 4V setting on the amp's gain is the "least sensitive" position. (the lowest strength gain or sensitivity.)
The 500mV setting is the most sensitive, or strongest position, requiring the most sensitivity to get a clean balanced signal from the pre-out for the amplifier to amplify.
does that make more sense?
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Bronze Member Username: Drumjunky
Boulder,
Colorado
Post Number: 42
Registered: Nov-04
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| Posted on Friday, January 07, 2005 - 08:06 pm: |
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that makes sense...thanks! |
