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#1 |
diyAudio Member
Join Date: Apr 2003
Location: .
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Hi,
I am quite sure this has been discussed before but I did not find it using the search function. I am going to bulid a DAC using CS8420, DF1704/06 and 2xPCM1704; followed by opamp for I/V conversion, passive HF filter and another opamp as output buffer. The output buffer will be Analog Devices AD8610, but I am not sure which one would be best for I/V conversion. Maybe AD8065? Any suggestions are welcome. Cheers Christian.
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former audiophile |
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#2 |
diyAudio Member
Join Date: Dec 2003
Location: Oslo, Norway
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If you got cash: OPA627.
I've implemented this setup a couple of times. Most of the times I use BB OPA2134. For my latest board I have also collected a pile of OPA2604, OPA2227, and 5534. But I must dissapoint you, I have not tested the sonic qualities of the different amps. Greetings, Børge |
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#3 |
diyAudio Member
Join Date: Oct 2003
Location: Gliwice
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The following ICs - OPA627&BUF634 were used in DIY DAC The First SE Mk2. The integrated buffer may be ommitted when a cable is not an output load.
Digital signal which comes from transport should be regenerated with fast TTL gates. What do you think about AD8610/AD8620? These amps have excellent capacitive load driving capability, much better than OPA627, whitout ringing. Supply voltage +/- 13 V but Peranders use 15 V whithout problems. |
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#5 | |
diyAudio Member
Join Date: May 2001
Location: London UK
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Quote:
I have the same experience as you. The 627 is inadequate and the 825 is better. Current load this to 3mA and the 825 sounds even better. |
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#6 |
R.I.P.
Join Date: May 2003
Location: Colorado
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The best op-amp for an I-V converter is no op-amp. As Barrie Gilbert (one of the top analog designers of all time) explains, an op-amp is in reality just an integrator. This causes all kinds of problems with input stage overload when presented with the step output of a DAC. Anything (transformer, resistor, discrete, etc.) will sound better than an op-amp for an I-V converter.
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#7 | |
diyAudio Member
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Quote:
Using a simple resistor, you would still be limited by the slew-rate of the transformer or buffer following it. However I would be interested in seeing measurements of simple resistor I/V with the PCM1704. Do you have a link? |
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#8 |
Banned
Join Date: Feb 2002
Location: As far from the NOSsers as possible
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Somehow, I suspect that if I had been the first to say it, it would have been dismissed as an extension of my contant ranting about that.
Back around.......'92 I think it was......Charlie sent me a copy of a magazine article titled "The current state of CD reproduction: who is doing it right?" Too bad that the name of the mag that it appeared in was not on the copy, and Charlie can't remember. They said........the best examples (in I/V stages) were from small American companies that were run by engineers, that used transimpedance amps, and not op-amps for that purpose. (For those who may be curious.........I was probably the first.....going back to '89.) Jocko |
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#9 |
Banned
Join Date: Apr 2002
Location: Germany, Clausthal
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what is a transimpedance amp?
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#10 | |
diyAudio Member
Join Date: Nov 2002
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Quote:
impedance is something that converts volts into amperes, so I assume that a transimpedance converts amperes into volts |
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Thread | Thread Starter | Forum | Replies | Last Post |
Single supply opamp - unequal rail voltage and opamp selection | Hans L | Parts | 8 | 19th February 2006 03:15 PM |
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Regulate the psu of a power opamp with a similar power opamp? | Franz G | Chip Amps | 34 | 19th October 2004 11:49 AM |
D1.I/V conversion | nar | Pass Labs | 2 | 20th April 2002 11:46 AM |
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