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In Reply to: RE: Another vote for the 12bh7 used as cathode follower ... posted by BCR on March 10, 2014 at 09:44:20
Hello and thanks for the interesting information.
I am not an expert but i have a humble and old preamp from Croft Audio where the line stage is just one tube connected as cathode follower, half tube for each channel.
The phono stage is two ecc83.
I took out the two ecc83 and put one 12bh7 in place of the existing 12au7.
I know that maybe it is not optimized for the 12bh7 but the resulting sound is so more powerful and crystal clear that there is no discussion.
I guess that a 12bh7 correctly used could be a spectacular line stage.
If i were able i would build a line stage on the principles illustrated here ...http://www.altavistaaudio.com/SA-1000.html#lsp
"... shunt more current through the line stage tube, lowering its output impedance so it can directly drive your power amplifier without that transistor sound.... Upgrading the resistors and capacitors in the line stage gives the tube the kind of support circuitry it needs to speak with exceptional clarity and purity; bypassing the output buffer eliminates solid-state colorations and lets you hear the tube.
The whole effect is a richer, livelier, more detailed sound with more precise focus and timbral accuracy... "so apart a high output impedance there are no drawbacks.
And i guess the resulting sound would be exceptional ...
But i do not have the skills required to design this stage ...
Just one 12bh7 ... and a pot before it ..
Thanks again.
Kind regards,
bg
Edits: 03/11/14 03/11/14Follow Ups:
Hi, an ecc 83 is a 12ax7,an ecc 82 is a 12au7. The 12ax7 has lots more gain than a 12au7. As far as replacing a 12 type tube with a 6922 tube ,which is what you say you want to do, I think you would be wasting your your time and money. But that's up to you. Since you like the 12bh7 so much why don't you just stick with that?
I think i expressed myself badly.
I am waiting to receive a tube buffer for the dac and this has only one 6922 or equivalent.
The preamp instead is an old Croft Micro ...
This preamp has two 12ax7 for phono and just one 12au7 as line stage (a buffer).
I took out the two 12ax7 and replaced the 12au7 with a 12bh7.
I liked the sound of the line stage section with the 12bh7 in place so much better.
More powerful, crystal clear ... very very good even if i guess the circuit is designed for a 12au7 of course.
And still the sound was much better to me.
So they are two different cases.
Kind regards,
bg
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