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phono stage's [message #31476] Thu, 24 November 2005 16:12 Go to next message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
How cheaply could one build a tube phono stage?

I have seen the ET Seduction, and those guys are the King's of Thin. Different tubes? 2x 8532's? Little bit more gain is always good...:-) The 6DJ8 is quite attractive, but really good ones are 'spensive.

I can see plenty of ways to complicate it! L-C filaments, Tube rectified, L-C for B+. Shunt regs...Yamamoto sockets. Super 'spensive RCA jacks. Not quite sure one should abandon the L-C filters.
cheers,
Douglas

Re: phono stage's [message #31477 is a reply to message #31476] Fri, 25 November 2005 06:52 Go to previous messageGo to next message
Damir is currently offline  Damir
Messages: 1005
Registered: May 2009
Illuminati (2nd Degree)
Huh, almost a year ago I tinkered about this idea, simple RIAA stage, like "add-on" to "Guinevere". Two stages, direct coupling, two R and two C in between (low driving input impedance in network, and high impedance after it - necessary with this pasive arrangement). Perfect to "drive" 100k pot input of "Guinevere".
But, I never actually soldered it together, mostly because I don`t have a good enough instruments to check RIAA accuracy...


Re: phono stage's [message #31478 is a reply to message #31477] Fri, 25 November 2005 07:30 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
and of course, while getting away from cheapest, there are a few neat tricks. One to reduce the output Z of the first stage while simultaneously reducing noise: parallel sections of a twin triode.

This offers a few neat opportunities to pull from developed circuits, and make further improvements.

and I am already getting away from a 'Cheapest sol'n', heh-heh-heh...

Long skinny chassis, PS at one end, and amplifier at the other. Guinevere style plate loads on the final stage so it can drive a reasonable load.

Parts are sure cheaper than for a big, high power amp, yes?
cheers,
Douglas


Re: phono stage's [message #31479 is a reply to message #31478] Fri, 25 November 2005 11:25 Go to previous messageGo to next message
Damir is currently offline  Damir
Messages: 1005
Registered: May 2009
Illuminati (2nd Degree)
If I could - probably LCLC, then left ch LCLC and right ch LCLC, total 6 chokes and 6 caps - for "stand alone" unit. But, if we want to put it in the "Guinevere" chasis, probably some more modest solution is in order. For the heaters, Schottky bridge + IC regulator would do, IMO.
But, yes - how "simple" or "not expensive" can it be without too much compromise? I mean - building RIAA with cheap parts (Cs & Rs) and with "average, but cheap" tubes doesn`t have too much sense?!
I don`t have a ready PS for the moment (fire problems:-)), any chance that you can try this circuit, or similar?

Re: phono stage's [message #31480 is a reply to message #31479] Fri, 25 November 2005 11:41 Go to previous message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
Hey-Hey!!!,
For simplest RIAA, the pasive between the two triodes is quite appealing. I have a few that can be adjusted for almost *ANY* pair of triodes. It ought to be fairly easy to implement. I don't think I am going to go with mono supplies. The loads ought to give me a lot of PS isolation.

I have a pair of 9-pin sockets, salvaged from Tektronix diff amp plug-in's. The socket is suspended on Be-Cu springs. One of a kind( well..two of a kind ). Been saving them just for a phono pre.

now....which two triodes?

I'll fit this in between the construction of the 4E27 and 813 amps. The 813 really has me going. 80W from a pair, in Class A.
cheers,
Douglas

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