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Old 21st April 2010, 01:00 PM  
SY is offline SY  United States
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Location: Chicagoland
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Default His Master's Noise: A Thoroughly Modern Tube Phono Preamp

After more than 25 years of faithful service, it seemed that it might be time to redo my phono system. After all, I like to think that I've picked up a few tricks in the intervening years... The old system consisted of a VPI HW17-II, a Linn Ittok LVII tonearm, and a Troika cartridge. The Troika was...

Last edited by Variac; 2nd April 2011 at 01:17 AM.
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27th April 2010
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BudP
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Good God Stuart.... even I, with my utter lack of objective thought process can make sense of this.

Bud
"You and I and every other thing are a dependent arising, empty of any inherent reality" Tsong Ko Pa
27th April 2010
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SY
diyAudio Moderator
Uh-oh, I'd better reconsider...

Thanks, Bud.
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
20th May 2010
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grufti
diyAudio Member
".... a common-mode choke will make things even better, but I just didn't have one. If you do, feel free to use it."

I stumbled across this sentence and I'm wondering whether you mean:
"... use the common-mode choke instead of the dual regulator heater supply" or else: "... use the common-mode choke with the dual regulator supply, and if so where in your heater power supply?"

Well thought out indeed!
20th May 2010
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SY
diyAudio Moderator
"With," not "instead of." I'd put it between the raw supply and the regs.
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
22nd May 2010
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Irakli
diyAudio Member
Very nice article, thank you.

Just a quick question: is there a sub-miniature analog of D3a/7721 you know of? I searched and could not find any. It wuold be nice to build your amp with pencil sub-mini tubes.
22nd May 2010
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SY
diyAudio Moderator
I'm not aware of any. Subminis do look cool.
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
5th June 2010
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danielwritesbac
diyAudio Member
Wow!

Although I'm not familiar with tubes, its easy to spot that the high fidelity approach isn't tacked on but rather the high fidelity approach is integral to the design itself. That's just so graceful.
19th June 2010
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Globulator
diyAudio Member
Would a pentode like a 6j51p/EF184 be a reasonable sub. for the D3a?
19th June 2010
SY's Avatar
SY
diyAudio Moderator
The spec sheets I have don't give much info about triode operation. It does look like the gain is lower, as is the transconductance. Since the source impedance of the first stage is critical to getting the RIAA right, you'd want to measure the plate resistance and adjust the 20k build-out resistor accordingly. For an operating point, I'd probably start with 10mA and 1.2V on the cathode.
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
21st June 2010
Globulator's Avatar
Globulator
diyAudio Member
Thanks SY, sounds like it may be worth trying then. Some triode data is here:

Tube Tester Files - 6J51P



I'm still collecting the bits - I'll post back later when I've got a bit nearer!

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