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-   -   tube preamp RIAA (http://www.diyaudio.com/forums/tubes-valves/129119-tube-preamp-riaa.html)

radiodieg 2nd September 2008 11:39 AM

tube preamp RIAA
 
I'am looking after tube preamp RIAA with ECC83 or 6SN7.
Can you help me to find schematic

Thank you.

azazello 2nd September 2008 03:20 PM

http://www.qrz.ru/schemes/contribute/audio/vinil.shtml
/From Russian site/
ECC83. This is my RIAA - ECC83-Telefunken !!
The sound is better than RIAA-Luxman !

kmaier 2nd September 2008 04:41 PM

And the classic RCA passive design that it was based on:

http://www.webace.com.au/~electron/tubes/PA/RCARIAA.jpg

I would add a cathode follower for a low-impedance output.

Regards, KM

Eli Duttman 2nd September 2008 11:56 PM

The "classic" RCA circuit suffers from 2 weaknesses: mediocre bass extension and wretched drive capability. Look here for a variation that deals with those issues.

JimL over at AA was kind enough to indicate that the 470 KOhm resistor should become as close to 255 KOhms as possible, without getting lower. Making that change maximizes conformance with the RIAA curve.

While the 6Н2П-ЕВ (6n2p-ev) shown pins out like a 6922, the triodes inside are the "same" as those in the 12AX7/ECC83. The tube I recommend is the Sovtek 12AX7LPS, which is clean, quiet, and affordable. That diagram was made from 1 of my narratives by Erick Bates, AKA Buzz. Buzz has a distinct predeliction for "boutique" parts. The 20 MOhm grid leak resistor is the only part that really should be "exotic". I suggest a Caddock there, for low noise. Vishay/Dale RN65 metal film resistors are FINE. A Soviet surplus PIO cap. in the 100 nF. coupling position would be nice.

BTW, the total capacitance at the O/P is too small, when working into the FUGLY 10 KOhm IHF "standard". At least 3.3 μF. are needed. A 5 μF. GE 40L3501 MPP part bypassed by a 470 nF. 716P orange drop does the job very well at little cost.

jeffdavison 3rd September 2008 05:15 AM

I highly recommend the "PhonoDude"

Doesn't use the ecc83 or 6sn7 however.

It uses a 420a/ 5755 and a 5751. Both are close enough to 6SL7 or 12AX7.

I've built the hardwired version. EXCELLENT phono pre.

Uses a passive RIAA between an input Mu stage and an output Mu stage.

Plenty of gain, dead quiet, fantastic sonics... tho I did use an octal ecc35 for the output instead of the 5751.

I actually like the sound better than my John Curl Vendetta SCP-2B phono stage.

Here's links to both the PCB and hardwaired version.
I believe he still has boards if you want.



http://www.dddac.de/tp06.htm
http://www.dddac.de/tp07.htm

JD

mashaffer 3rd September 2008 01:36 PM

That 6N23P looks like kind of a nice tube though.


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