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[DT-HWT] electrostatic headphone tube Amplifier/Preamplifier


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9 hours ago, johnwmclean said:

I do however spot one of my Carbons.

That looks just like mine, except it prolly don't got a normal bias socket.......:P

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  • 5 months later...
On 23 Jul 2017 at 8:16 AM, pham said:

just got benchmarked against a few other little cute friends coming from all around the world...

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Dude, whatever you think you are doing on here, or trying to do on here, forget it. It is a band of brothers morons who will slag off anything you have to say, even if it may be interesting, new or correct. And you won't gain any sales or any kind of acceptance here either. So suck up to Birgir or leave.

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So interesting is a substitute for good performance now?  No matter how bad the engineering is, just slap some transformers on there or a DHT and it is interesting aka great?  Fucking pathetic... 

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Actually, the schematic is in the first post in this thread, and is a copy of the classic Mullard 510 amp circuit from 1954, except with the feedback taken before the transformer instead of after, and the transformer being driven off the  cathode of the triode-connected output tubes rather than the plate, so your head isn't sitting between several hundred volts.  Nothing wrong with it, but nothing to be in awe of, either.

Mullard 510.jpg

Edited by JimL
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Now, the power supply, on the other hand, is "interesting." It appears to be a shunt regulated supply using the LM317 as a constant current source, and the TL431 shunt regulator IC. Both are protected from high voltage by tubes, the LM317 by a 5998, and the TL431 by the KT66. However, would expect the sonic impact of the regulator to be dominated by the TL431, which is the active shunt element, as the KT66 doesn't have any active role in the regulation. Nor does the 5998 play an active role in the constant current source, which is basically done by the LM317. Both are simply high voltage "umbrellas" to protect the solid state devices that are the active elements. So the tubes look nice but add the complication of filament supplies without (probably) contributing much if anything to the sound.

Edited by JimL
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That's indeed the issue, it's mediocre to a fault but fucktards like astroglide look at it and think it is the second coming.  Tubes...a wooden chassis!!???!!!???  Sign me up!!  Reminds me of the Demograph crap from Russia, exotic tubes, massive silver foil caps, ancient circuits but here is the kicker...things have progressed quite a bit since the 40's and we can design out all the expensive components needed for what ever reason you want. 

Let's take the above circuit and do some changes.  Get rid of the pentode and and put a LTP there or something so it is fully balanced.  Might even cross couple like the SRX and drive it all with CCS.  Even better, swap out the front end for a fet driving some bipolar stages and does anybody really think the original circuit is better than either of those? 

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So, here's the thing. A post on HF suggests that what they want is to have one amp for both electrostatic and dynamic/planar headphones. Also, it appears that they want single-ended in. This circuit does all of that, but of course it's a compromise. It's not going to be as good as a dedicated stat amp, and it's not going to be as good as a dedicated dynamic/planar amp. I would add that I agree that a triode LTP in place of the pentode would work equally well as an input for single-ended, and also allow for balanced inputs, so you don't lose anything there.

 

 I suppose if you wanted to do tubes and all headphones, you could take the SRX Plus and stick a transformer on the end of it for dynamic/planars. That would give all differential, all balanced, and work for everything - assuming you are willing to accept transformer outputs for dynamic/planar headphones.

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