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In Reply to: RE: Because it sounds better :^) posted by Paul Joppa on July 11, 2016 at 12:36:39
Paul, which types were you using that produced improved sonics? Were they VR tubes or something else? I have only a little experience with regulation of tube preamps.
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Buy Chinese. Bury freedom.
Follow Ups:
We (Bottlehead) mostly use hybrid regulators, with a triode cascoded to a 431-type regulator chip; sometimes we've used gas regulators which are cheaper, and we have Zeners in one current product.Long ago we built a test bed with five or six different regulators including Zeners and gas regulators, plus three or four hybrid arrangements. The audio circuit was a single triode cathode follower, which is the most sensitive to power supply noise and linearity. The differences were small but there were two that tied for first place - we went for the simpler and less expensive one.
The other winning circuit was one developed by John Tucker; there are probably still some of his products around that use it.
Tre', the stock Foreplay II (it's no longer in production) used a gas reg, but the upgraded version replaced it with the hybrid shunt using a 12AU7.
Edits: 07/12/16
Hadn't thought about smaller tubes like the 'AU7. They're entirely adequate though for low current applications like preamps. Thanks for mentioning that, it might set me off in a different direction for some of the designs I'm contemplating.
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Buy Chinese. Bury freedom.
To all:
There are plenty of listening reports on the net regarding "regulator sound".
But I would really like to see a calibrated measurement on an AP box or equivalent of some audio distortion caused by this regulator over that one. Like the infamous LM7815/7915 versus the LM317/377.
To be clear I don't need proof that regulator impedance changes with load frequency. We know that happens. I want to see how it affects the audio band. And again, I want to see calibrated scales. Not some audio magazine where they show a waveform discrepancy but fail to tell you it's 0.01db in magnitude.
"I would really like to see a calibrated measurement on an AP box or equivalent of some audio distortion caused by this regulator over that one."
That's fairly easy to accomplish, but common measurement techniques don't tell the whole story. We all know that two amps with vanishingly low distortion, ruler flat response, similar damping factors, etc. can sound remarkably different. That's not to say specifications are unimportant. They do tell us about amplifier performance in critical areas, and I consider basic measurements to be a necessary step in the process of optimizing an amplifier. But something else is also in the mix, something we're not measuring. So, while I agree that the measurable effects of regulation are important, scientifically controlled listening tests must always be the final arbiter.
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Buy Chinese. Bury freedom.
TK, I know first hand that the Bottlehead Foreplay line stage is VR tube shunt regulated.
I assembled one for a friend.
I think both the one with plate resistors and the upgrade (with CCS plate loads) both used the VR tube shunt regulated B+ supply.
I use VR tube shunt regulation in both my phone pre and my driver stages. (no line stage, I use a AVC)
In both instances the VR tube (stacks) are CCS feed.
Tre'
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