Calling all Phono Preamp gurus, I'm looking for some plans - diyAudio
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Old 6th March 2007, 12:58 AM   #1
jduffy is offline jduffy  United States
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Default Calling all Phono Preamp gurus, I'm looking for some plans

I'm currently putting together my Preamp and while waiting for some parts to arrive I thought it would be a good time to get some info on a Phono Preamp as I'll be building that next. Any thoughts as to what I should be looking for? Plans or schematics that I can check out?

I like the inexpensive builds so if you have any suggestions or links that I should be looking at, I'd be really grateful. Really enjoy following up on all your leads. I learn a lot that way from this forum.

Thanks.
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Old 6th March 2007, 01:14 AM   #2
phn is offline phn  Sweden
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I would say a simple ECC88/6DJ8 phono stage offers the best bang for the buck.

http://www.geocities.com/rjm003.geo/.../diy_pho3.html

http://www.ptsoundlab.com/tubes/prea...ignecedric.htm

I guess a three-stage split RIAA 6SN7 will do the same for for the octal fans.

Edit: I'm no guru.
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Old 6th March 2007, 01:59 AM   #3
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I guess a three-stage split RIAA 6SN7 will do the same for for the octal fans.
No sir! That will be NOISY. If you want to do an Octal phono stage use 6SL7s in the "classic" RCA circuit.
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Old 6th March 2007, 02:18 AM   #4
phn is offline phn  Sweden
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Agreed. But I don't really see octals as ideal here.

This is for the gurus.

Being that the WE417A/5842 is quite expensive, how about the 6S45P and 5687? I assume matching will be a problem with the 6S45P, though.
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Old 6th March 2007, 05:37 PM   #5
jduffy is offline jduffy  United States
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Interesting! I've been reading old posts and such here and other places about building a phono preamp or amp or linestage and a lot of them say, "Turn back!"

Some people seem to like the Bottlehead Seduction and the Hagtech Cornet2 for quality and terms of cost.

Still interested in hearing people's opinions. Thanks.
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Old 7th March 2007, 01:04 AM   #6
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I built this one and I've been very happy. There's extensive discussion in that thread and even more, particularly about grounding, in this thread.

I think this is a great phono stage and, following Thorsten's grounding scheme, it's dead quiet.

Hope this helps.

Kofi
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Old 7th March 2007, 02:56 AM   #7
jduffy is offline jduffy  United States
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Thank you Mr. Annan for the links to the threads. It's great fun going through them and seeing the many twists and turns they take. A bit like reading the Norse Sagas!

If I can figure it all out maybe that will be my best bet for a build.
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Old 7th March 2007, 06:12 PM   #8
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The octals can be microphonic. You need to take care to mount sockets off chassis if possible.

If you don't want to go full P2P wiring, then try something like this:

My Cornet2 Tube Phono Preamp

jh
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Old 7th March 2007, 08:58 PM   #9
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Default Steve Bench 12ay7-7308 cascode

The RIAA curve is a considerable feat to equalize. You need a preamp with herculean overload margins and headroom. A cascode fits the bill best IMHO with passive EQ between stages. The 12ay7-6072a tube was designed for low noise in mind and very well balanced from side to side. The FAA used this tube as the first gain stage in Radar sets. And it was used very successfully in many high grade condenser mics that recorded much of the music of the 50s and 60s. AKG C12 used it, Telefunken/ELAM used it. Western Electric used it in mo pic sound mic preamps.
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Old 7th March 2007, 09:02 PM   #10
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I agree, the 6072 is a fabulous tube for the first stage in phono. It's what I'm using in my next design. Suprised there aren't more machines out there using it.

jh
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