2. amps-preamps
  3. 163599-140647

Gain Matching - need advice

I recently added an Audio Research Ref 6 to my system (it was a dealer demo unit so price was right).  The preamp is paired with Pass Labs XA 60.8 amps (26db gain and 100K ohm input impedance) and Avantgarde speakers (sensitivity of 108 db at nominal 8 ohms).  The problem I am having, that I did not have with my previous Joule Electra LA150, is volume control.  The AR preamp has a 103 position volume control.  At position #7 the volume is almost ear splitting.  Sure I can turn it down but it’s very difficult to dial in a suitable volume.  I am inclined to blame it on the new AR preamp (output impedance of 600 ohms and 12db of gain).  I am stuck into using balanced interconnects which I won’t go into.  My first conclusion was that I have a gain matching problem since the old preamp did not behave this way.  Looking at the difference between the output impedance of the preamp and input impedance of the preamp ... why would there be a gain matching problem (at least as I understand the subject ... which I may not.  Anything that can be done about this, or a new preamp the only solution?
chilli42

Showing 1 response by clearthinker

clearthinker's avatar
clearthinker
1,582 posts
 
Don't see Miller replying to this one:
'Dimwit, your speakers are way too sensitive, concentrate on getting speakers with less than 87dB efficiency'. :-))

Crazy to ask AR to modify the piece.  They would need to work out what to do and charge you $000s.  And the amp would be unresellable after.

In any case, the big matching problem is not with the Ref 6.
You need to change the power amp or the speakers.
Changing the Ref 6 for a pre-amp that's flat with no gain will only partially solve the problem.  Losing 12dB of gain will mean your volume tops out at position #(7 + 12/0.3), as each step is about 0.3db.  That's #47 which is still less than halfway up to #103.

Having said that, I run a Ref 6 too.  With Krell Reference 200s upgraded to 400w per side and Martin Logan CLX Anniversary specced at 90dB sensitivity but probably a bit less, the volume is certainly very full on at around #40-45 and I get enough differentiation from those 40 steps.

It wasn't so long ago when I upgraded to Ref 6 and vdH The Grail SB.
I calculated the system gain very carefully before diving in.  I recommend others do the same.
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