ADA 4627 (ADA4627-1) outperform Burr Brown's OPA 627 (OPA627) - Page 2 - diyAudio
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Old 15th February 2011, 03:36 PM   #11
fjc is offline fjc  Taiwan
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Someone has to make a A/B test against the OPA627, and tell us the tonic flavor.
I am willingly to do the job also and express my thought sometimes soon. Have to obtain the OP and make DIP adoptors. By the way, there is also an ADA 4637-1, I wonder whether it is over-specification in the case of pre-amp. And, is it stable at low gain? similar as the case of OPA 37/ OPA637.
cheers,

fjc

Last edited by fjc; 15th February 2011 at 03:41 PM.
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Old 7th September 2011, 04:02 AM   #12
fjc is offline fjc  Taiwan
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Originally Posted by fjc View Post
Someone has to make a A/B test against the OPA627, and tell us the tonic flavor.
I am willingly to do the job also and express my thought sometimes soon. Have to obtain the OP and make DIP adoptors. By the way, there is also an ADA 4637-1, I wonder whether it is over-specification in the case of pre-amp. And, is it stable at low gain? similar as the case of OPA 37/ OPA637.
cheers,

fjc
Yes, strangely, it follows the BB rule, 4637 is not stable at gain<5.
I have tested the sonic effect of ADA4627-1, at gain of 10. It is good, sonic performance is beautiful(OPA637BP was replaced by ADA4627-1 ARZ).
I have trying to test the 4637-1 ARZ first, but fail, I think overheat soldening might be the reason. By improve my technology ( reduce heat time, use constant temperature ceramic heat soldering gun and use lower M.P lead solder), the make of soic 4627 is fine. I will try another pair of 4637, with already made of the heavy lost of very costlt pair of 4637. I will present my thought in the next mail.
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Old 10th September 2011, 04:42 PM   #13
fjc is offline fjc  Taiwan
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Default ADA4637-1

The problem may comes from soldering I guess. After a careful work, the new pair of ADA4637 performs well. Even the old pair becomes normal after a long run (self-healing?). It seems the a version of 4637 outperform even the more expensive B version of 4627. I am interesting to do a A/B sometimes now and try to be able to feel the difference.

Last edited by fjc; 10th September 2011 at 04:47 PM.
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Old 10th September 2011, 05:32 PM   #14
jcx is offline jcx  United States
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At the level of these op amps subtle circuit implementation details are likely more audible than the chips themselves

you might try "wringing out"/"blueprinting" the circuit's measurable performance before subjective comparison

high speed 'scope, function gen can help verify stability, matching bandwidth - spot gross noise/EMI which may differ between power supplies or setups

free sw like RMAA, AudioDiffMaker could help

if you can difference the outputs in a resistive summer amp you can look with good resolution with even a cheap soundcard - with ~40 dB notch from the difference the distortion performance requirement of the soundcard is much reduced in the comparison



I consider good subjective testing far too time consuming, difficult, error prone to not do everything possible with good measurements 1st

once everything matches within 0.1 dB, 1% between circuits in frequency response and your listening level is matched too, your switch box is proved transparent, blinding protocol doesn’t “leak” info… you will almost certainly need lots of trials, good statistical analysis to have a chance at picking out op amp differences starting with such good chips
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Old 11th September 2011, 08:12 PM   #15
fjc is offline fjc  Taiwan
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Default 4527 vs 4637

"I consider good subjective testing far too time consuming, difficult, error prone to not do everything possible with good measurements "

Now a pro is talking. So I will try to get the A/B sonic performance test result and keep it to myself, unless I can do a surgical analysis then to publish here. Yes, the test will be too subjective.
Thanks for the suggestion.
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Old 15th November 2011, 11:50 AM   #16
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thank you very much for reporting about the results.
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Old 16th November 2011, 12:47 AM   #17
fjc is offline fjc  Taiwan
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Default Subjective OP test.

Thanks for the encouragement.
I will try the A/B test in my system. It is not difficult to do. I will put 4627 in one channel, 4637 in a separated channel, use separated step ladder volume with 0.1% -0.5% and tested resistor for the volume match. Input by bi-wire phono jackets from a single channel CDP, test will be switched in 60 sec., also I will try to hear the direct sound; sit by in front of the speaker to avoid room effect, plus, switch position on right and left speaker.
Yes, the test still is subjective and might be misleading to different person, please keep this in mind.
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Old 16th November 2011, 02:32 PM   #18
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Thanks FJC
I would also be happy to read your observations.
I did put the 4627-1 B's in my digital recorder (after the D/A sections). And due to no offset, was able to remove the following blocking caps.
Sounds fantastic.
F5
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Old 16th November 2011, 09:33 PM   #19
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Originally Posted by jcx View Post
I consider good subjective testing far too time consuming, difficult, error prone to not do everything possible with good measurements 1st
Amen.

Subjective differences between opamps tend to miraculously vanish once they're being used sensibly. If the circuit designer has a fussy type oscillate, uses a TL072 for driving headphones or operates a noisy part at high gain, that's their fault, not the opamp's. A good part doesn't make a good circuit at all, but it can make a good one even better.

Sensible use involves knowing the parts' little ifs and buts. And a row of measurements (e.g. Samuel Groner style) sure tells a lot more about these than subjective evaluation in just one predefined circuit ever could.
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Old 30th January 2012, 07:10 AM   #20
fjc is offline fjc  Taiwan
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Test on sonic difference,
Anyway, I made listening test on ADA4627 Brz and 4637 Arz.
Sonically they are not much difference. Check the spec, 4627 has a 18 V/us slew rate, normally this should be enough for an audio purpose OP. 4637 has much faster slew of 100s. My feeling is the resolution of 4637 is slightly better,but the major difference is the sense of the instrument locations. It is more alive and sharper image for 4637. In other words, 4627 is more flat. I vote for the 4637, even it is a cheaper A version used.
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