Opamp choice for filter in dac - diyAudio
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Old 10th August 2007, 09:38 PM   #1
ctong is offline ctong  United States
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Location: Clemson, South Carolina
Default Opamp choice for filter in dac

Some sacd players use one (Denon 2900 & 3910) or two (sony scd-1) stages of active filter immediately after the IV stage. In each filter two opamps form a closed loop as a shunt for high frequencies. The Denon players use BA15218F and the scd-1 uses LM6172. I do not know how critical the choice of the filter opamp is. Discussions usually focus on the IV and the output amp stages but I have not seen any suggestion regarding the filter opamps. Has anyone looked into this issue?
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Old 12th August 2007, 10:18 PM   #2
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I've been wondering about the same question after i started to review the 2900 circuitry trying to figure out how to upgrade it.
My current choice is 6172 for the filter/I/V and 4562 for the low-pass filters/buffers, all from National. (this is not based on experience, I am starting to build an external stage, based on the current one, to allow for testing of different opamps and to eventually have all six channels on the same topology)

I am not sure yet about best choice for I/V, but I understand that the I/V discussions happened on other threads.

Allan
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Old 16th August 2007, 12:31 PM   #3
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CT..for the IV stage a pair of OPA 627's(you'll need a brown dog adaptor) ...then for the buffer use a OPA2134.
I settled on this set-up in my OTARI DAT7 after experimenting with multiple configerations using 6172,8066,8620,826.
The 627 and 2134 sound marvellous together.beautifully balanced and focused with a deep and wide soundstage
This guy "Alex's Hardware" http://members.cox.net/alexhardware/opa.htm
also goes into quite a bit with the same results.

Good Luck
Dean
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Old 18th August 2007, 03:08 PM   #4
ctong is offline ctong  United States
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Quote:
Originally posted by dean1009
CT..for the IV stage a pair of OPA 627's(you'll need a brown dog adaptor) ...then for the buffer use a OPA2134.
I settled on this set-up in my OTARI DAT7 after experimenting with multiple configerations using 6172,8066,8620,826.
The 627 and 2134 sound marvellous together.beautifully balanced and focused with a deep and wide soundstage
This guy "Alex's Hardware" http://members.cox.net/alexhardware/opa.htm
also goes into quite a bit with the same results.

Good Luck
Dean

What I was referring to was the the loop filter (two opamps form a loop) between the IV and the buffer.

I have not tried 627 for IV. Have you compared it to 2132 (i.e., how much better)? I am using 2132 for both IV and buffer. It sounds much more transparent than 2134.
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