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What's the best dual I/V opamp these days???
What's the best dual I/V opamp these days???
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Old 7th April 2019, 04:24 AM   #1
georgehifi is offline georgehifi  Australia
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Default What's the best dual I/V opamp these days???

Hey guys had great success in the past using AD844 (with no nfb), just want simple this time, got a PCM1796 dac, looking for what's the best dual I/V opamp today. Even singles at a crunch, if I get a Brown Dog converter boards.


Just looked at the old AD812 seems to have some good specs for I/V duties.
What do you guys think
145mHZ
1600 V/us slew rate
50ns settling time
-90db distortion
can't find out if it's unity gain stable or not.

Cheers George
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Old 7th April 2019, 04:41 AM   #2
oohms is offline oohms  Australia
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You can try LM6172.. just make sure the board design is sensible
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Old 7th April 2019, 05:50 AM   #3
georgehifi is offline georgehifi  Australia
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Quote:
Originally Posted by oohms View Post
You can try LM6172.. just make sure the board design is sensible
This looks good, what about the distortion though, good enough???

Second Harmonic f = 10kHz −110 dB
Distortion(3) f = 5MHz −50 dB
Third Harmonic f = 10kHz −105 dB
Distortion(3) f = 5MHz −50 dB

Cheers George
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Last edited by georgehifi; 7th April 2019 at 05:53 AM.
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Old 7th April 2019, 05:59 AM   #4
abraxalito is online now abraxalito  United Kingdom
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Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
AD815 is rather good as I/V, not a standard opamp package though and its now on last-time buy. Plenty available on the secondary market and its pretty cheap there.
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Old 7th April 2019, 06:24 AM   #5
georgehifi is offline georgehifi  Australia
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Hi Abraxalito, yes it looks good also, but not easy just to play with.

I'm cradled in this dac and have tried many different ones, and so far the old OPA2132 has come up trumps, with clean sounding treble, great mid body, a nice strong bass if just a touch thick.

What do you think about the LM6172 for PCM1796? I've always valued your opinion, got some samples coming.

Cheres George
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Old 7th April 2019, 06:56 AM   #6
abraxalito is online now abraxalito  United Kingdom
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LM6172 has long been one of my recommendations for I/V ever since I tried it in an Asus soundcard many years ago. I think that card was using PCM1792 so probably its well suited to 1796 too.

I'm working on a DAC using AD815, first gen PCBs have some errors, hopefully after a re-spin I'll share gerbers.
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Old 7th April 2019, 07:12 AM   #7
chris719 is online now chris719  United States
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What's the best dual I/V opamp these days???
Quote:
Originally Posted by georgehifi View Post
Hey guys had great success in the past using AD844 (with no nfb), just want simple this time, got a PCM1796 dac, looking for what's the best dual I/V opamp today. Even singles at a crunch, if I get a Brown Dog converter boards.


Just looked at the old AD812 seems to have some good specs for I/V duties.
What do you guys think
145mHZ
1600 V/us slew rate
50ns settling time
-90db distortion
can't find out if it's unity gain stable or not.

Cheers George
Unpopular opinion-

If you are talking about measured performance in the audio band, it probably is OPA1612 or LME49720. Yes, I know everyone likes to think you need GHz op-amps for I/V.

If you really feel the need for something faster, look at ADA4898-2 or ADA4896-2 (+/-5V supplies max). Their distortion is not specified in the audio band.

OPA1656 is rather interesting for this, and if you like OPA2134 then you probably won't do any worse with OPA1642.


I would not use any fast op-amp with an adapter. I'd also want to verify anything faster than what the board was designed with is stable.

Last edited by chris719; 7th April 2019 at 07:24 AM.
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Old 7th April 2019, 08:35 AM   #8
dreamth is offline dreamth  Romania
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I tried ada4898-1 on a pcm1701 output(less than 1ma max iout) at +9v/-12v suply and in one minute was melting ...dead.
I tried lm6172 on tda1541 in Sony cdp-750(similar to nakamichi cdp 2e) who had only one ic for both channels so ut made a lot of sense using lm6172 and the rsult was magnificent.I had to admit that i fully appreciated a very old post made by abraxalito where he said that lm6172(at that time) was the best option.
Now i think that for a classical i/v based on virtual ground in closed loop op-amp we need to assess the noise of the circuit and its needed speed.
For modern dac's you don't need so much higher speed, opa1611 oe opa1612 is probably the best option, for old dac in NOS or even classic oversampling but still noisy output i have to agree that faster op-amps are better.Here's a catch though:
lm6172 works best on tda1541 because of its higher iout .
Some other old dacs of the past are much lower iout , 4 ...40 times lower iout than tda1541 and you need lower noise op-amps.I found THS4631(fet op-amp) better for its very low current noise while its voltage noise is only 2nv which is again better than many op-amps outhere.I didn't try it though...
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Old 7th April 2019, 08:42 AM   #9
chris719 is online now chris719  United States
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What's the best dual I/V opamp these days???
Quote:
Originally Posted by dreamth View Post
I tried ada4898-1 on a pcm1701 output(less than 1ma max iout) at +9v/-12v suply and in one minute was melting ...dead.
I've used ADA4898 before at unity gain and it didn't melt, so something was definitely wrong. The decoupling and layout have to be decent for high speed amplifiers.
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Old 7th April 2019, 09:10 AM   #10
BesPav is offline BesPav  Russian Federation
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Quote:
Originally Posted by georgehifi View Post
got a PCM1796 dac, looking for what's the best dual I/V opamp today.


Use LM6172, add BUF634 or any preferred buffer. It needs because 1796 output current are a bit on the high side and you better to decouple opamp crystal from relatively high I/V resistance.
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