gofar99 Messages: 1950 Registered: May 2010 Location: Southern Arizona
Illuminati (5th Degree)
Hi everyone, an update. I built a second version and am listening to it as I type. About 99% the same, but with Auricap XO coupling caps and a revised grounding system. All the specs are the same except that both variants are now about 6 db quieter. They were just fine before. Now the 6AS7 version is at -94db wide band with a single peak at 60HZ of -82. That is IMO really quiet. There is no hum or noise. I redid the response curves. Still -0.7db at 20HZ, but the amps are flat to 100K HZ. The deviations are within the limits of the measuring set up (about 0.05db). The Bode plot is like a ruler straight line. The sound is really nice. I'll post the updated schematic and some photos when I get a chance. This is IMO the cleanest headphone amp I have ever heard. I don't usually like them as they seem to lack the sound qualities I like. This one is different.
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