Replacing 6922 Preamp Tube in ARC LS7
Finally bought my first tube based audio equipment, an Audio Research LS7 Preamp. Being a newbie and dunno much about tube, I would like to ask for opinion on option in replacing the stock 4 x 6922 tube so that it sound more warm, mellow, and layback, am I asking too much? :D
Thank you so much.
I suggest tone controls instead.
A good friend of mine has an AR LS7 preamp in his system. Some time ago we spend several hours rolling tubes. Of all the ones we tried, which all were new old stock RCA, GE, Sylvania (JAN) and others, we liked Mullards and Amperex Bugle Boys the best.
But this, in no way, should suggest that these are right for you. Changing tubes makes only a subtle difference, unless one is defective. The sound that you hear from your system is dependant on all the componets of your system working together. Changing speakers makes much more of a difference then swapping tubes or interconnects. So replacing Chinese or Russian tubes with Mullards or Amperex may not get you where you want to be, but they can't hurt anything. Except maybe your wallet.
I'm not sure which brand ARC used in the LS7.
I worked for Sunfire when we ran out of our original buy of Sovtek 6922s for the Classic Tube Preamp. We tried the current production Sovteks and they were quite noisy. The old tubes had the black coating on the plates and the new tubes were shiny silver. Apparently the quality control at the original factory went to hell after the Soviet Union collapsed.
We tried NOS JAN Phillips tubes, which sucked, along with several other brands.
We finally went back to the beginning- the tubes which Sovtek rebrands as 6922s are actually Reflector 6H23 or 6N23 depending on how the cyrillic letter is translated. We were able to buy old Soviet era tubes in quantity from eastern European sources.
I believe you can still get these from Triode Electronics or Upscale Audio.
The Sunfire preamp was very demanding on its tubes due to its classic anode-follower design. The tone section was extremely demanding on the tubes used. The tone section would make some Phillips tubes oscillate.
I know some ARC hybrid preamps just use the tube as a cathode follower. This is far less demanding on the tube. You may be able to use Mullards or Amperex tubes without any problems. If you get microphonics (something true Western 6922s are prone to), and the ARC lacks them, then get some tube dampers on Ebay.
Audio Research units are designed to sound lean and neutral; you may prefer the sound of an older Conrad-Johnson.
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