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01A question
01A question
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Old 13th December 2017, 06:31 AM   #291
mogliaa is offline mogliaa  United Kingdom
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01A question
Hi Douglas
I tried using a 12V cell to bias top device. It improves the frequency response but not noticeable to sound. In fact using an IXTP08N100D as top device provides the best combination to maximise VDS of lower device. This way it performs really well and sounds better. I have also build a CCS version with mu-follower output as well and tried it. I preferred the gyrator one. Taking the output from the anode increased the distortion as the triode is loaded with the output load as well and not isolated with the bootstrapped mu resistor. With higher distortion, the sound is warmer but less transparent to my ears. Itís a matter of taste. If you want more H2, there you go.
"A mistake is always forgivable, rarely excusable and always unacceptable. " (Robert Fripp)
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Old 13th December 2017, 11:34 AM   #292
andyjevans is offline andyjevans  United Kingdom
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Originally Posted by Bandersnatch View Post
Andy, have you tried the mu-follower CCS load not operating as a gyrator? as in missing all that voltage setting stuff. It just seems to me that improving the CCS with some battery bias( say with a DN3545N3 on the bottom ), would work quite well...
I think Ale has answered you pretty well here. I'm on a plate choke expedition right now. I've been putting 2 of the Hammond 126C interstages in series and getting much better sound than a single one. Works nicely with the 10Y, and I really must try it with the 01A. I may also invest in an amorphous plate choke at some point. Will report the results if and when.
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Old 15th December 2017, 02:45 PM   #293
andyjevans is offline andyjevans  United Kingdom
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My plate choke quest has taken me back to an old friend from 8 years ago - two Hammond 156C in series. These are fastened bottom-to-bottom and connected out of phase. I was originally using these with the 26 which is another option, but this time I used 01As. I think I gave up on this before because I was getting hum. This time - miraculously - no hum at all.

This is good news for me, for a start, because I have several of them. And also because they sound really good. We have 300H here, so no shortage of Henries for the 01A. Sound is very clear and detailed. I've been using 2 x 126C in series with the 10Y, and I'll also try that with the 2P29L. They're good too and they can take 15mA instead of the 8mA for the 156C. Not much to choose between these options in terms of sound - both very good. I've just got this up and running so extended listening will tell me more, but I'm pleased with this. These chokes are also really, really cheap to buy. Nice result!
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