DIY Balanced Valve Phono Preamp

[Mr Kipling]

Anyone seen a circuit for a high quality design?

[lurcher]

Maybe this

http://www.vacuumstate.com/images_upload/gross/rtp5_rev_1_s.gif

[hal55]

Vacuum State!!!!!!!!!!!!!

Now there is a name you rarely see, and sadly Allen Wright died some years back. I did have one of their early 90s FVP preamps, which Joe Rassmussen tweaked with an improved phono stage, and very lovely it was. Any idea where the circuit comes from, ie from an FVP or similar or the Jlit (just listen to it) design?

Hal55

[lurcher]

RTP5

Yep, Allen was/is greatly missed.

[Mr Kipling]

Thanks for posting the circuit Nick.

I'm looking to build my first and last valve preamp and I've got it into my head (rightly or wrongly) that a balanced design using octals might be - 'where it's at'!

[sjs]

I seem to recall the JC Morrison Siren Song has a differential input which could be used as a balanced input, and uses octal or loctal tubes. Dont have it to hand, so could be wrong :what:
Best of luck

[Mr Kipling]

I seem to recall the JC Morrison Siren Song has a differential input which could be used as a balanced input, and uses octal or loctal tubes. Dont have it to hand, so could be wrong :what:
Best of luck

Thanks Simon.

[6L6]

Yes, the Siren Song is balanced input. Not exactly sure where you will get a truly balanced phono cartridge (I.E., center-tapped) but you can still fake it with some creative wiring. :)

The Siren Song is a neat circuit. It needs a couple of power supplies, a long- out of production current-source diode (Although not impossible to get), and has no linestage. Still, I think it would be a road worth traveling. If you did it right, I'm sure it would compete with anything out there - - remember that the 6SL7 and 6SN7 were some of the last tubes designed specifically for audio.

10872

And by 'doing it right' I mean proper supply filtering, proper grounding, proper layout, etc... not £9 resistors and £40 capacitors. ;)

On the other hand, everything I have read from people who have built a RTP, in any version, have been completely, totally, and utterly happy with it. If I didn't have so many other projects right now I would build one. And you can get kit parts from VacuumState. Handy, as it makes the SirenSong look simple...

http://vacuumstate.com/index.dna?rubrik=8&lang=2&a=%2516%25B9%25925%25C9%25EFWU&b=735540.1295154144

[Mr Kipling]

Thanks for the information Jim.

[lurcher]

Yes, the Siren Song is balanced input. Not exactly sure where you will get a truly balanced phono cartridge (I.E., center-tapped) but you can still fake it with some creative wiring.

A centre tap is not required for balanced. A floating (not referenced to earth) output works just fine as a balanced output, so once you remove the link to ground from one pin of the cartridge then its a perfectly good balanced input.

[Mr Kipling]

Thanks Nick. I was hoping that would be the case.

[lurcher]

Oh, and


remember that the 6SL7 and 6SN7 were some of the last tubes designed specifically for audio

From the 1961 Maxda spec sheet for EF86

"Low Noise A.F. Pentode"

December 1969:

EL84: A.F. Output Pentode

6SN7: http://www.mif.pg.gda.pl/homepages/frank/sheets/137/6/6SN7GTA.pdf

All sorts of uses. Mainly in a TV deflection amp. Not saying its not a great audio valve.