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Subject: Re: replacing 5534 with ad797 or opa627 ?

Date: 07/27/01 at 1:36 PM
Posted by: Al
E-mail: Hools@surfree.com
Message Posted:

In Reply to: Re: replacing 5534 with ad797 or opa627 ? posted by Michel on 07/27/01 at 10:32 AM:

Michel,I'm a bit embarrassed to say that I have not actually auditioned the AD797, so forgive me for giving advice based on hypothetical intuition! However, I am thoroughly familiar with the OPA627, OP275, OP176, 5534, and 5532 as I have used them (and therefore auditioned all of them) extensively. All of my "A/B" listening tests are done "blind," where the A/B switch is toggled many times at random before the audition begins, so I am unaware which part is "A" and which is "B." This eliminates the "power of suggestion" psychological variable, which is frequently all too significant, particularly when there is not a large actual sonic difference between the two parts, or if there is a big specification, price, or marketing hype difference between the two. Levels are matched to within .1 dB to remove the subjective problem that "the louder one sounds better" even if it would not with matched levels. If the circuit allows, I will also replace as many part "A's" with part "B's" in order to exaggerate the sonic difference. Finally, I repeat the A/B test as many as 15 to 20 times, each time "voting" for "A" or "B," and only after each vote revealing to myself what I voted for.All that being said, my favorite sounding chips are the OPA627, and the OP275. This has proved consistently true in several different circuits. Despite the excellent specs of the 5532 I have never liked the sound of it, and upgrading to the OP275 produces stellar results. Oddly, the OP176 (a single op amp similar to the OP275) does not seem to sound quite as good as the OP275, although it sounds slightly better than the 5534. However, there is no question that the AD797 (a great chip) will sonically out-perform the 5534 and OP176 and would be an excellent upgrade (just check the specs to see if it has the output drive required in some 5534 circuits.) Maybe we do not all hear things the same way, but what I have learned over time is that as long as distortion and noise specs are reasonably low, the single largest factor affecting sonic quality is slew rate. If only Burr-Brown made a dual OPA627/37!Al

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