Tetra Phono Preamp as a DAC analog stage

regal · 6th December 2009, 08:11 AM

My problem with tube DAC's is there is always a big compromise, either its just a cathode follower after an opamp or its a gain stage after a too large I/V resistor which causes non-linearities with the DAC chip.

Has anyone ever tried a phono preamp (minus the RIAA eq) as an analog stage for a current output DAC like the PCM1704? It has been shown elsewhere that the PCM1704 performs best with an I/V resistor smaller than 10ohms which requires a lot of gain. The first phonostage would basically be working like a step-up transformer in the old audionote patent. My concern is if the phono stage would be quiet enough to handle a mV p-p signal ?

Allen Wright · 6th December 2009, 08:48 AM

A MC phono stage has to handle sub millivolt signals, and a good one is down near the theoretical absolute as far as noise goes. No idea what a Tetra Phono pre is - but a good phono pre (without the RIAAS eq of course) is pretty much perfect for what you are suggesting.

Regards, Allen

Franz Gysi · 6th December 2009, 09:10 AM

Hi Allen

The Tetra Phono Pre is from John Broskie Tetra Phono All-in-One & Broskie Impedance Multiplier

Regards
Franz

Eli Duttman · 6th December 2009, 03:41 PM

The subject of current O/P DAC chips in a phono preamp like regime was discussed some time ago. Look here. AW may appreciate the mention of a 6922 cascode.

6th December 2009, 08:11 AM	#1
regal diyAudio Member Join Date: Jan 2004 Location: MD	Tetra Phono Preamp as a DAC analog stage My problem with tube DAC's is there is always a big compromise, either its just a cathode follower after an opamp or its a gain stage after a too large I/V resistor which causes non-linearities with the DAC chip. Has anyone ever tried a phono preamp (minus the RIAA eq) as an analog stage for a current output DAC like the PCM1704? It has been shown elsewhere that the PCM1704 performs best with an I/V resistor smaller than 10ohms which requires a lot of gain. The first phonostage would basically be working like a step-up transformer in the old audionote patent. My concern is if the phono stage would be quiet enough to handle a mV p-p signal ?

6th December 2009, 03:41 PM	#4
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	The subject of current O/P DAC chips in a phono preamp like regime was discussed some time ago. Look here. AW may appreciate the mention of a 6922 cascode. __________________ Eli D.

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6th December 2009, 08:48 AM	#2
Allen Wright R.I.P. Join Date: Dec 2001 Location: Schaffhausen Switzerland	A MC phono stage has to handle sub millivolt signals, and a good one is down near the theoretical absolute as far as noise goes. No idea what a Tetra Phono pre is - but a good phono pre (without the RIAAS eq of course) is pretty much perfect for what you are suggesting. Regards, Allen

6th December 2009, 09:10 AM	#3
Franz Gysi diyAudio Member Join Date: Oct 2007	Hi Allen The Tetra Phono Pre is from John Broskie Tetra Phono All-in-One & Broskie Impedance Multiplier Regards Franz