2. amps-preamps
  3. 125173-4976

can you alter the gain of an amplifier?

I never use active preamps and prefer sources with built-in volume controls over passive preamps when possible.  I've had great success using cd players by Consonance, Theta, & OPPO directly in my amp(s) but find that sometimes, even with the volume full up, the sound level is just not loud enough.  With my big, solid state amps, I know I'm not out of power, just not enough gain (this was particularly problematic with an Aleph clone).  I was wondering if it's possible/feasible to alter the gain of an amp to achieve better results using a passive volume control or the on-board volume control in the source?  I won't be doing the work myself.  I just want to know if a decent repair/mod shop could make the alterations.  Thanks!
lcherepkai

Showing 2 responses by almarg

almarg's avatar
almarg
9,670 posts
 
Perhaps in some cases, but I wouldn’t recommend it without first giving the designer/manufacturer some idea of how much you want to increase the gain, and getting his or her blessing.

For example, if the solid state amp uses a considerable amount of feedback, it may be possible to increase the gain simply by changing a resistor in each channel. However, doing that would to some degree increase total harmonic distortion, lower damping factor, increase output impedance, and affect sonics for those and other reasons.

In extreme cases increasing the gain of an amp might also change it into an oscillator, possibly resulting in damage to it and/or the speakers.  The possibility of oscillations would depend in part on the impedance characteristics of the particular speakers that are being used, so the modified amp could conceivably work fine for the tech but blow up in your application.

Basically, increasing the gain amounts to incorporating a design change, which should not be done without complete information and full understanding of the specifics of the existing design.

Regards,
-- Al

almarg's avatar
almarg
9,670 posts
 
Interesting suggestion by Erik. A number of people have reported here and elsewhere that they have found Jensen transformers of various models to have essentially no sonic downside, while a few have reported a slight loss of transparency.

A minor correction, though: If the particular transformer doubles the signal voltage (which would be a 6 db increase in gain) it would result in the preamp seeing the amp's input impedance divided by four, not two.

Regards,
-- Al
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