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Thread: Passive Pre Amps |
    
Bronze Member Username: Jim1961
Dublin,
Texas
USA
Post Number: 13
Registered: Aug-07
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| Posted on Monday, August 20, 2007 - 12:05 pm: |
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Ive owned a Adcom SLC 505 and a Reference Line Preeminence One previously. While I enjoyed the super transparency of these units, I also experienced a rolloff at the lowend. Using both warble tone generators and measuring output voltage, and using spl meters, I was able to confirm what my ears told me. The reference line unit was a bit less prone to this than the adcom, but still displayed the basic tendency. My question is: Is this the experience all users have with these units or was it just my set up? I was using a CAL Aria CD player, KCAG 1/2 meter interconnect, and a Krell KSA-200 power amp. Could it have been the Aria output stage didnt like seeing a variable resister? Will my Rega Apollo act differently? I did discover that when I put a active unit like a EQ after the Aria, but before the passive unit, the problem was minmized considerably, which supports my theory that maybe this was just a effect caused by the Aria output stage. Anyway, if you have thoughts on this or recommend any particular passive device, please share it. My system is completely a line stage system, so no accommodations are needed for a turntable. |
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Platinum Member Username: Jan_b_vigne
Dallas,
TX
Post Number: 11145
Registered: May-04
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| Posted on Monday, August 20, 2007 - 09:19 pm: |
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More than likely a low frequency roll off was caused by impedance mismatches between the player and the passive pre amp. Using a low impedance pot will cause problems in most cases. If the problem was variable with the position of the pot, then you have your answer. Switching to a higher impedance pot is typically the correct approach. Then you only have to worry about the pot driving your power amplifier. The alternative is to use an autoformer/transformer based passive unit.
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