VAC owners, sound off

Did you mention Audio Horizons in particular because
you think it will better suit my needs or because they are a company with a 30
day? (or both)
Tholt (Threads | Answers)

I mentioned the AH preamp because it has a low output impedance spec that
should match with your amp, and because it has a home trial period.

I am not making a judgment about how it may suit your needs. Too much
personal preference enters into that question.

The VAC has an even lower output impedence than the AH. One of the lower ones i've seen in fact @ 350. Based on that you'd think it would mate fine with my amp rated at 55k input.

Tholt, I agree. VAC may state an output impedance of 350, but it doesn't tell
the whole story because output impedance varies with frequency. Output
impedance may be significantly higher in the lower bass frequencies, which
would correspond with weak or rolled-off bass that you're hearing.

If you read the test measurements section of a couple of Stereophile reviews of
preamps (tube or solid state, but particularly tube), you'll see verification of
preamp output impedance changing with frequency. It's common, and it
explains why some tube preamps that have low output impedances published by
the manufacturers sometimes don't match well with solid state amps.

The bottom line is the VAC likely doesn't match your amp based on your
comments. The AH will cost you only shipping to test it in your system. Isn't that
worth the experiment?

My last ditch-resort (prob just confirming the unfortunate known) is to put in a call to Kevin Hayes and go over some specs. Plan on doing that today. If that goes as expected, I'll put this VAC up on the 'gon and use the $ to get something that hopefully synergizes better.