Phonograph preamp DIY - schematic suggestions?

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bipedal
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Phonograph preamp DIY - schematic suggestions?

Post by bipedal » Mon Dec 03, 2007 10:30 am

Slightly off topic since not directly recording-related, but I'll throw it out there. Any suggested resources or tips are appreciated.

I recently acquired a mid-'80s phonograph. Works/sounds fine, but it's calling out for a simple preamp to boost the level going into the rest of my sound system.

Seems like a basic phono preamp ought to be rather easily to build, but I haven't found any schematics online...

- Jay

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A-Barr
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Post by A-Barr » Mon Dec 03, 2007 10:35 am

Here's the standard RCA version

http://www.tube-amp.de/6SL7-riaa/rca-manual.gif

Calls for a 7025 but I read somewhere that it specs out slightly better with 6SL7's. Worked great for me.

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Post by The Scum » Mon Dec 03, 2007 12:32 pm

Try searching for "RIAA preamp schematic" and you'll turn things up.

Here are a few from sources that are pretty reliable:

http://sound.westhost.com/project06.htm
http://www.paia.com/riaa.asp
http://www.borbelyaudio.com/eb199320.asp
http://www.passdiy.com/preamps.htm

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thesimulacre
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Post by thesimulacre » Tue Dec 04, 2007 7:43 pm

If you wanna get fancy with it I can break open my X-LPS and snap a hi-rez photo of the top & bottom for ya. You could do your own cheapo version and label it "The Behr-record Player Pre."

Make sure whatever design you choose has enough headroom to handle an-overly loud vinyl (eg won't clip it's own output).

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Re: Phonograph preamp DIY - schematic suggestions?

Post by Andy Peters » Thu Dec 06, 2007 11:31 pm

bipedal wrote:Slightly off topic since not directly recording-related, but I'll throw it out there. Any suggested resources or tips are appreciated.

I recently acquired a mid-'80s phonograph. Works/sounds fine, but it's calling out for a simple preamp to boost the level going into the rest of my sound system.

Seems like a basic phono preamp ought to be rather easily to build, but I haven't found any schematics online...

- Jay
National Semiconductor and Analog Devices should have examples of RIAA preamps in data sheets or app notes.

-a
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Post by gyraf » Mon Dec 10, 2007 12:30 am

yes. Look up the application notes on e.g. the NE5534 - usually has a simple high-grade RIAA described in detail..

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Post by crow » Mon Dec 10, 2007 8:25 am

A-Barr wrote:Here's the standard RCA version

http://www.tube-amp.de/6SL7-riaa/rca-manual.gif

Calls for a 7025 but I read somewhere that it specs out slightly better with 6SL7's. Worked great for me.
I just harvested a crapload of 6SN7's from an organ a friend of mine was throwing away. Would this be a good use for such a thing?

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Post by Jim Williams » Tue Dec 18, 2007 7:26 am

Look up the several examples of phono preamps on the National.com web site. Look to the apps on the LM4562 or the LME49740 quad opamp. They have passive/active EQ sections and precise RIAA curves and a unique psu filtration supply using these very low THD and noise opamps.
Jim Williams
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A-Barr
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Post by A-Barr » Tue Dec 18, 2007 8:52 am

crow wrote:
A-Barr wrote:Here's the standard RCA version

http://www.tube-amp.de/6SL7-riaa/rca-manual.gif

Calls for a 7025 but I read somewhere that it specs out slightly better with 6SL7's. Worked great for me.
I just harvested a crapload of 6SN7's from an organ a friend of mine was throwing away. Would this be a good use for such a thing?
Not so much. SN7's have lower gain, sort of like an octal 12AU7. They are good audio tubes though and worth keeping around.

...Another phono suggestion, if you want to get really fancy: http://www.johnhardyco.com/pdf/990-2007.pdf

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