4P1L as First gain stage or in Pre-Amp..? - diyAudio
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Old 6th July 2011, 06:46 PM   #1
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Default 4P1L as First gain stage or in Pre-Amp..?

Just thinking out loud....

Ive seen good stuff written about this little Russian D.H. Tube wired as triode...

I'm wondering how it would be to use as a gain-stage rather than driver/O/P stage, maybe with MOSFET on top....

Any thoughts....?
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Old 6th July 2011, 08:57 PM   #2
tomchr is offline tomchr  United States
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I'm thinking along the same lines. A grounded cathode stage has pretty high output impedance, though. One might have to add a cathode follower or similar to be able to drive interconnect cables.

~Tom
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Old 6th July 2011, 09:42 PM   #3
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I've never used this tube but I can supply a quote from someone who has regarding microphonics:

"Mark's tube dampening (solder coil+silicon) - first reports - I tried this technique - somewhat different. Instead of silicon (fear of corrosion) I used liquid urethane spray (for PCB masking). It claims to resist hot solder, and is definitely neutral (good for protecting polished copper). First applied a solder coil, then 3-4 coats of urethane. The tubes were soviet 4P1L DH pentodes driving my 6B4G PP amp. They have a long, 1-1.5 microphonic resonance, sometimes very audible on piano passages. Tubes run very hot (as hot as a typical EL84). So far no problems with urethane layer or the tube itself. With the coil, the sonic signature changed. The 1kHz ringing is very well muffled down. But there's ANOTHER resonance, somewhere in 200-300Hz area. Not the original bug shifted downwards - this is something completely new, although nowhere as loud, and decays quickly. It's not a problem with piano, - sometimes it interferes with male vocals. But still - definitely worth trying. With the 2-tube driver, I found the less fatuguing option to have 1 stage dampened, second untreated, - just marginally better than both stages dampened. BTW, the coil need not be too big - in my case, covering 1/3 of available glass (one layer) was as effective as covering the whole length"
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Old 6th July 2011, 10:43 PM   #4
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I had an experience with 4P1L tubes. They are very nice tubes for drivers and output stages when triode connected, better than 2A3. They are easy to parallel for more power. About 1.5K output resistance and great linearity without any feedback. But for an input stage I would use some smaller tube, like 6J4P, 6J5P, 6J9P in triode mode.
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Old 7th July 2011, 12:56 PM   #5
AJT is offline AJT  Philippines
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anyone for 3Q5GT's?
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Old 7th July 2011, 02:09 PM   #6
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What would you like to do with it ? Line stage ?

I have some experience as PP-UL output stage. I just built a 15 W amplifier with two 4P1L and Hammond 1608 (no the best OPT, I know).
It performed very well.
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Old 7th July 2011, 06:26 PM   #7
tomchr is offline tomchr  United States
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Quote:
Originally Posted by Wavebourn View Post
But for an input stage I would use some smaller tube, like 6J4P, 6J5P, 6J9P in triode mode.
Are you aware of a Russian DHT tube that's more suitable for an input stage?

~Tom
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Old 7th July 2011, 06:34 PM   #8
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Quote:
Originally Posted by tomchr View Post
Are you aware of a Russian DHT tube that's more suitable for an input stage?
This one fits better than 4P1L:

Click the image to open in full size.
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Old 7th July 2011, 09:27 PM   #9
tomchr is offline tomchr  United States
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Eh.... I think something went wrong with the link. Would you repost?

~Tom
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Old 7th July 2011, 09:55 PM   #10
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Quote:
Originally Posted by tomchr View Post
Eh.... I think something went wrong with the link. Would you repost?
It works:


227, 229, 41, 41, 101, 103, 121, 123, 1217 Hi-Fi
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