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In Reply to: RE: Help choosing a quad of 6SN7 tubes posted by scruffy_ on January 11, 2017 at 14:44:12
Whan an amp or preamp doesn't sound right, the first thing I do is measure frequency response and distortion. It's a shot in the dark changing anything until that's done, and measurements are a lot cheaper than a quad of NOS 6SN7s.
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Buy Chinese. Bury freedom.
Follow Ups:
There was a midrange glare, but only on a few CDs that did not create any problem when I had my passive preamp installed, and I mistakenly called it "brightness" which people attribute to higher frequencies. It only occurred on a few female vocals and some piano. I now attribute this glare to poor recordings, but I'm still a little mystified why these CDs did not seem to have any glare with my passive preamp. I did order some used RCA 6SN7GTB getter tubes, but I'm now kicking myself because I now believe that they will probably restrict the extended frequencies and color the midrange.
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"Humility is the true mark of genius. Just get used to it."
-Anonymous
Hi,
I think those RCA's would actually sound better IMO. I haven't heard newer Russian SN7's, but the older Sovteks had that sound you described in the mids.. It's usually the operating points that shifts how it sounds too. In fact, it plays a bigger part as well as the overall circuit design. So cheer up, your new RCAs would most probably be still be an upgrade.
I also noticed that Schiit uses Wima MKP caps for coupling in their other tube preamp. I surmise they use the same on your preamp. I find Wima MKPs a bit dry and grainy in the upper mids. The only Wimas I liked are the smaller lower voltage FKP's in digital circuits and some solid state riaa analog eq filters. The (non-boutique) radial caps I liked better are the blue ones made by Epcos and Evox-Rifa. But since Schiit chose Wima, your best recourse is to try better tubes.
Well with a change in high frequencies per original post order Sylvania 6SN7GTA, The 'GTA' guarantees 1950-1953 era tubes. These tubes are ultra clear sounding unlike a lot of other 6SN7s and has nice clean treble.
I have read several times that the tubes can be mixed for better sound. I tried to coax Schiit into revealing the make of the stock tubes but they would not say!
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"Humility is the true mark of genius. Just get used to it."
-Anonymous
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