Accuphase's discrete jFET Input Operational Amplifier for Ultimate Sound Reproduction

tiefbassuebertr · 03:03 PM

Yesterday I have found Accuphase's discrete jFET Input Operational Amplifier for ultimate sound reproduction (see attachement).
An interesting feature are some parallel connected complementary LTP units behind the input j-FET's. Maybe also suited for I/U converter behind the DAC like PCM1704 or PCM1794

Are there any experience with this circuit topology?

To compare with the internal circuit topology from AD797 and OPA827 I have also add as PDF attachement

MRupp · 31st January 2010, 03:12 PM

This looks more like the MM input stage of their C-27 phono pre to me, there the input JFETs are just source followers to increase the impedance of the actual amplification stage.

Jan Dupont · 31st January 2010, 03:27 PM

Yes it sure looks like their MM stage

satoru · 2nd February 2010, 02:09 AM

A translation of the Japanese in the image:

"MM amplifier is required to achieve low noise while maintaining high input impedance. For this amplifier section, we chose low noise JFET as input device used as buffer (3 paralleled) followed by ultra-low noise Tr in differential push-pull configuration, 6 of them paralleled."

Sorry for my English,,,, sigh.

Satoru

31st January 2010, 03:12 PM	#2
MRupp diyAudio Member Join Date: Dec 2003 Location: Frankfurt area	This looks more like the MM input stage of their C-27 phono pre to me, there the input JFETs are just source followers to increase the impedance of the actual amplification stage. __________________ Martin Rupp

31st January 2010, 03:27 PM	#3
Jan Dupont diyAudio Member Join Date: Apr 2003 Location: Copenhagen, Denmark	Yes it sure looks like their MM stage __________________ Free Schematic and Service Manual downloads www.audio-circuit.dk, Company: www.dupont-audio.com, Joint venture: www.DupontMantra.com

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2nd February 2010, 02:09 AM	#4
satoru diyAudio Member Join Date: Jan 2007 Location: Berkeley, California	A translation of the Japanese in the image: "MM amplifier is required to achieve low noise while maintaining high input impedance. For this amplifier section, we chose low noise JFET as input device used as buffer (3 paralleled) followed by ultra-low noise Tr in differential push-pull configuration, 6 of them paralleled." Sorry for my English,,,, sigh. Satoru

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