Pease "Troubleshpooting Analog Circuits" has a few pages on CMRR test circuit problems - actually measuring Av_ol is a big one
This makes-me remember of a story witch arrived to a friend of mine. I share-it with you because it is too much fun.
It was during a tour of 'Manu di Bango' in Africa, at the times where some famous exotic dictators where at the head of some countries, there.
They arrived at the Big official theater of the country, and began to set the PA with their mixing table. But the dictator himsel ordered them to use the theater's equipment. Despite all the induced problems, some offers are not good to be refused, they did so. When the show finished, the PA sound engenner began to reset this 'Shlumberger' mixing dest clean. He was just about to set the first fader to 0, that the local responsible of the theater's sound, in fact an ex Legionnaire', ordered, in a very threatening way, to let the desk as-it, 'Now that everything was tuned'.
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It is indeed the A-21. If your complaint has any effectiveness, see if you can get them to swap out the connectors on this amp and help me keep my job.
Maybe, but I though the discussion is about decent op amps, not 741's with .5V/uS.
How's a LM4562 (also 20V/uS), has the same "tight bass" than a 797?
How's a NE5532 (9V/us), has less "tight bass" than a 797?
I suppose an AD811 (2500V/us) has so much "tighter bass", it's out of any discussion.
Don't know (yet) for the 797 but i don't like NE55xxs for this reason: it is "hot" and "soft" oriented, and lacks a little both details and attack. Pure subjective and personal feeling.
Stretch a little the Locking pine, or threaten him of 'Sin bin' ?
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Never said anything like that. I always support the use of high quality parts if it brings benefits of better parameters or better subjective results. That means, I will vote for AD797 vs. LME49710/LM4562/NE5532. I will vote for gold plated Neutrik. I will vote for high quality shielded amplifier case and proper wiring. But I may disagree that the 7th is an evil of AD797 and may prove it as untrue.
I disagree.
While some of JC's stuff is probably OK (discounting notable fails like JC2 Mk1) and likely to be indistinguishable from properly implemented 4558 stuff, Blowtorch suffers from the faults that JC himself is at pains to remind us, ad nauseum, are important.
To whit, poor Hirata, Quan & evil 7th harmonic distortion.
Because of these faults and other reasons, I'm confident some true golden pinnae can distinguish it from an evil 4558 device. If the evil 4558 device is implemented properly, these true golden pinnae will prefer it to Blowtorch. Double Blind bla bla of course.
As you have probably gathered, I distinguish distortion/faults/evils into "detectable in Double Blind Listening Tests bla bla" and "not detectable bla bla". Blowtorch and JC2 Mk1 fall into the first category.
In design, I tend to concentrate on the first category.
IMHO, the details I (& Scott, Brad, Pavel & others) highlight are more important than the "only use stuff hand carved from solid Unobtainium by virgins" philosophy espoused by JC et al. That's cos they address the first category.
I have absolutely NO PROBLEM with "hand carved ..." stuff in product that can stand the cost, PROVIDED THEY DON'T AFFECT THE IMPORTANT DETAILS AND RESULT IN POORER SOUND.
So do I, but I'm not at all convinced that those tests you cite (and for which you have no data) have much, if any, audible consequence unless the results are grossly poor. Just because someone says, "Hirata Test!" doesn't mean they can correlate it with controlled listening results.
Dr. (professor) Hirata did his own listening tests 30 years ago.
Sorry SY, my boss tells me that your boss should not have purchased the A21, if he doesn't want or like the input connectors. Besides, he tells me that the Neutrik connectors that we use would not necessarily fit in the A21 chassis.
IF your boss bought the unit new, then it should be under warranty. He should be able to get it fixed that way.
Sorry SY, my boss tells me that your boss should not have purchased the A21, if he doesn't want or like the input connectors. Besides, he tells me that the Neutrik connectors that we use would not necessarily fit in the A21 chassis.
IF your boss bought the unit new, then it should be under warranty. He should be able to get it fixed that way.
Everyone, let me again remind you of the Hirata Test, that was put forth more than 30 years ago, by a Dr. Hirata. It is not an easy test to do or to make the test box to do it, but it measures SOMETHING that eludes typical sine wave testing, either single or multiple.
This is because it adds DYNAMIC ASYMMETRY to the test signal, and it tests for that, and that alone. What happens when a REAL audio signal is put through a gain stage? MOST gain stages will do OK with this test, but even I once error'd by trying to add an AC BALANCE CONTROL to a specific discrete gain stage. The Hirata box found the problem, and I removed it from consideration in future. That is PROGRESS!
This is because it adds DYNAMIC ASYMMETRY to the test signal, and it tests for that, and that alone. What happens when a REAL audio signal is put through a gain stage? MOST gain stages will do OK with this test, but even I once error'd by trying to add an AC BALANCE CONTROL to a specific discrete gain stage. The Hirata box found the problem, and I removed it from consideration in future. That is PROGRESS!
Really? Others would put their ears on the line for the 5532 bass:
http://www.diyaudio.com/forums/solid-state/209004-new-doug-self-pre-amp-design-40.html#post3074823
http://www.diyaudio.com/forums/digital-source/23944-one-more-tda1541a-dac-3.html#post717420
I am confused, who should I believe?
He did buy it new. It's not broken, this is a basic design flaw that ought to be corrected. A $100 Behringer has locking XLRs- at the money level of the 21, shouldn't the basic connectors be of an acceptable quality level?
I'm starting to regret my enthusiastic recommendation.
Sy,
Strike one for customer service on that preamp for your boss! Basically take it or leave it seems to be the answer. But at the same time I don't see how an XLR connector with a locking tab would let the connection disconnect from the male plug? You sure that it isn't the connector on the cable end that isn't causing the trouble? Perhaps you will have to help out your boss by changing the connectors yourself, that may be the easiest and fastest fix for such a simple problem? I guess you won't be recommending any Parasound products in the future. John I can see how a simple problem such as this can ruin your reputation even if you are not the cause of the problem. By association you are marked as a co-conspirator in something such as this. For the price that Parasound charges they should make sure that the few customers that they have are at least happy customers in such a fickle market. It doesn't seem to take much to ruin a companies stock in this industry with such simple correctable errors.
Strike one for customer service on that preamp for your boss! Basically take it or leave it seems to be the answer. But at the same time I don't see how an XLR connector with a locking tab would let the connection disconnect from the male plug? You sure that it isn't the connector on the cable end that isn't causing the trouble? Perhaps you will have to help out your boss by changing the connectors yourself, that may be the easiest and fastest fix for such a simple problem? I guess you won't be recommending any Parasound products in the future. John I can see how a simple problem such as this can ruin your reputation even if you are not the cause of the problem. By association you are marked as a co-conspirator in something such as this. For the price that Parasound charges they should make sure that the few customers that they have are at least happy customers in such a fickle market. It doesn't seem to take much to ruin a companies stock in this industry with such simple correctable errors.
Halo A21 is a power amplifier and really has the cheapest non-latching XLR connectors:
http://www.parasound.com/img/halo/a21_rear_big.jpg
http://www.parasound.com/img/halo/a21_rear_big.jpg
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