2. amps-preamps
  3. 1038091302

How can an active preamp possibly help?

When I pipe the line level out from my CD player straight into my variable gain amp, I must turn down my amp from unity gain lest I blow out my ears. If this is the case, what value can an active preamp possibly be adding? The signal from the CD player is already "too loud" for the amp.

This leads me to question why an active preamp is needed at all. Switching and volume I understand, but can someone please explain how an active preamp amplifying the signal before it gets to the amp helps the finished product sound better (especially in light of my it's-already-too-loud example).

Thanks!
matt8268

Showing 2 responses by sean

sean
6,231 posts
 
Some digital sources do not output enough signal to drive various amps to full power. As such, one can run into a lack of dynamics. Adding another gain stage takes care of that problem. Sean
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sean
6,231 posts
 
If the output of a CD player ( or any other line level device ) can EASILY drive an amp to clipping and beyond with normal signal levels, it should be fine to use in "direct drive" mode. As Twl points out though, you may have to pay attention to line lengths and impedances to obtain optimum results.

Other than that, some analogue outputs on CD players, etc... with built in potentiometers are of low quality. Obviously, if you spend the money on a more expensive unit, "chances are" that they will have used ( hopefully ) good quality components.

Just keep in mind that some CD players do NOT output as much voltage as they are rated for. On the same hand, some power amps require more voltage to attain full power than other amps. Mating a "weak" CD player with an insensitive power amp will typically result in the loss of dynamics / flat sound that many here have commented on. One can somewhat "make" this type of situation occur due to impedance mismatches between the CD output and amplifier input. In order to get around this, a CD player or DAC should be able to deliver at least 3 - 4 volts of output without putting up a fuss. If you can do this, you should have plenty of gain to compensate for even those "quietly recorded" CD's and slight impedance mismatches. In such a situation, you will still probably even be able to overcome major impedance mismatches but sonics ( tonal balance and transient response ) may suffer. Sean
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