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Old 11th October 2015, 10:28 AM   #1
DieterK is offline DieterK  Germany
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Default Balanced tube RIAA Preamplifier - Idea Search

Hello together,

I have the Idea to build a balanced RIAA Preamlifier. Passive Network with a mix of pentode and triode stages. Does anyone build some or has ideas for a project to build?

Best regards
Dieter
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Old 11th October 2015, 10:54 AM   #2
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RTP3 by the late Allen Wright, look for schematics on his website: Vacuum State - High End Hifi Equipment
If you're interested, you can still buy his "Tube Preamp Cookbook".
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Old 11th October 2015, 11:14 AM   #3
DieterK is offline DieterK  Germany
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Hello hidnplayr,

the schematic from the RTP3 is shown on the Homepage from VS. It has one thing that i dont want - Mos-Fets. My wish is an all and pure tube preamplifier.
But thank you for your comment.
Best regards
Dieter
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Old 11th October 2015, 11:33 AM   #4
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Hi,
to clarify, the RTP3C does not use mosfets, but it does use JFETS and/or Bipolar transistors for the input stage and current sinks.
These elements are key to the low noise design.

But hey, you are free to do what you want with your own creation
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Old 11th October 2015, 11:45 AM   #5
piano3 is offline piano3  United Kingdom
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Morgan Jones 3rd edition has a balanced valve RIAA described in detail; you can adjust the design to use whatever suitable valves you have available.
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Old 11th October 2015, 07:27 PM   #6
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Probably not your cup of tea - this K&K Audio design has a pair of MOSFET/tube cascodes configured as an LTP with MOSFET CCS plate loads and a BJT CCS "tail" for a VERY high output impedance "current source" input stage. This allows for the high resistance resistor in the HF roll-off portion of the RIAA filter to be shunt rather than series connected (this shunt connection also allows for CCSs to be used for both the cathode "tail" and plate loads). An ideal current source amp with a parallel resistance is equivalent to a voltage source amp with the same resistance in series.

There are also those nasty MOSFETs in the individual B+ CCS fed shunt regulators feeding each stage and all the other "tail" impedances. Trying to implement this design with all tubes would require a WAY bigger chassis. Believe me the quality of the "tail" current sources has a big effect on SQ. Ditto for the shunt reg. of the B+, despite the PSRR of an LTP.
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Old 11th October 2015, 07:33 PM   #7
Ketje is offline Ketje  Belgium
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How about this one
Mona
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Old 11th October 2015, 08:14 PM   #8
DieterK is offline DieterK  Germany
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Hello Mona,

Such a nice Design. I think this could be a good starting point....
Best regards
Dieter

Last edited by DieterK; 11th October 2015 at 08:17 PM.
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Old 11th October 2015, 08:17 PM   #9
DieterK is offline DieterK  Germany
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Hello john_tracy,

Sand in the Supply is no problem. I think that a ccs for feeding or for bias is a optimal solution.
BR
Dieter
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Old 12th October 2015, 12:59 AM   #10
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Have a look at "Siren Song, a phono preamplifier for hedonists" by J.C Morrison in SOUND PRACTICES Vol.1 #3 and Vol.1 #4 (update). Very nice preamp, it has a differential (balanced) input stage and passive RIAA which fits your criteria.
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