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In Reply to: RE: Best 7199 Substitution posted by Bubbasweet on July 03, 2011 at 17:01:59
I don't want to pour cold water on this but they're all terrible. I recently did comparison of st-70 driver stages mostly looking a THD+N, IMD, noise and linearity over the output voltage range. By a wide margin the 7199 and the 6AN8 were superior to 6GH8 and 6U8 when used in the stock st-70 driver circuit. The 6GH8 samples I tried (5 samples) all showed very high THD+N and IMD (by a factor of 4 to 10 times worse) compared to the 7199's or 6AN8's.
Listening tests also confirmed the poor measured test scores with muted mids and rough (un-musical) high frequencies. Bass was pretty much the same.
When I get some time I will publish the test results.
Bottom line - opt for 7199's or use an all triode replacement module (which measures best BTW).
Follow Ups:
Did you ever publish the test results of your comparison of the 7199 to the 6GH8 when used in the stock Dynaco st-70 driver circuit? I am particularly interested in the IMD.
The 6AN8 (and 6AN8A) are common, too; and cheap. Use them in the Stereo 70 with the circuit values in the Mark II (I don't even know if they are different) and you'll be fine. Repinning required, but it is for the 6GH8 also.
GP49
I really hate it when people with measurements disagree with me. Blah!
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