2. amps-preamps
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Gain matching of power amps

How important is it to have amps of same gain when using amps from different manufacturers in a horizontal biamp? Currently using Audiolab 8000P's(29db gain) in vertical biamp configuration, but need to tame metal tweeter top end. Looking at McCormack(40db gain), and Classe power amps(anyone know the gain of these) as a solution. Do you have recommendation for other power amps that have a warm presentation that might suit? Does it matter if amps have different power ratings? Audiolab's are 100W, would you recommend more, less or same power for tweeter?
miketw
sean
6,231 posts
 
I agree with Herman. Having worked with many multi-amp set-ups, you have to do the best that you can possibly do to gain match the amps. If you don't, you'll run into some very "strange" problems in tonal balance and dynamic range that could vary frequency range to frequency range. Sean
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herman
2,216 posts
 
I've said it before, that Sean seems like a very reasonable and wise person.
sean
6,231 posts
 
Herman, I bet your opinion of me is bolstered when i agree with you : ) I bet that there are a lot of others that wish i would shut up :(

Honestly though, it's good that you and a few others take the time to present "details" and "formulas". It gives many of the others a good idea of what it takes to make this stuff tick and how engineers do their work. As mentioned, it is science that has gotten us this far in audio reproduction and forgetting that might be a grave mistake. Sean
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edesilva
768 posts
 
Kudos to you guys, you answered a question that I had in a different post. But, let me see if I've got this right.

I've got a Casablanca preamp, which is basically a big Theta card cage that you can slap different D/A output cards in and configure each output the way you want. I think (I don't have my manual here) that you can pre-set a gain for each output, so output set A could be configured with, say, 3 dB of additional gain over output set B, at 0 dB gain. If I then had an amp X with a gain of 26 dB and an amp Y with a gain of 29 dB, would I then achieve a uniform gain of 29 dB by hooking amp Y to output B and amp X to output A?

The reason I ask is because I always assumed that there was some nonlinearity in the gain as you increased the input voltage. I.e., that the gain you find in the specs is some average and is not a constant over the range of input voltages. Is this a dumb question?
karls
332 posts
 
Gain is gain, it is constant no matter what the input voltage (until clipping, that is). So yes, in theory your hookup would work. The only caution has to do with tolerances, i.e., is the gain exactly 29.0 dB or is it actually 28.2 dB? Same goes for the other amp. You would need a high quality calibrated voltmeter to be certain.
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