John Curl's Blowtorch preamplifier part II - Page 3357 - diyAudio
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Old 25th January 2013, 06:13 PM   #33561
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I just received a response from Parasound. That picture is from 2003, and after the first 50 sets of the JC-1, they did what we had instructed. Caused quite a stir at the time.
I don't make the JC series and try to get away with cheap connectors, but the builders will TRY!
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Old 25th January 2013, 06:14 PM   #33562
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To test a connector, USE A MAGNET!
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Old 25th January 2013, 06:15 PM   #33563
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Pease "Troubleshpooting Analog Circuits" has a few pages on CMRR test circuit problems - actually measuring Av_ol is a big one
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Old 25th January 2013, 06:20 PM   #33564
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PMA, you can't have it both ways. You tend to agree with those who think that expensive parts are a waste of money, and then you try to pin me with using cheap parts on purpose. Please, I want to be on your side, professionally.

Last edited by john curl; 25th January 2013 at 06:26 PM.
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Old 25th January 2013, 06:36 PM   #33565
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Quote:
Originally Posted by gpapag View Post
She ended with one mike and asked me to mark the final settings on the console.
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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Last edited by Esperado; 25th January 2013 at 06:41 PM.
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Old 25th January 2013, 06:36 PM   #33566
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Originally Posted by john curl View Post
If it is the HCA-21, I will contact Parasound and complain.
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.
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Old 25th January 2013, 06:43 PM   #33567
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Originally Posted by Esperado View Post
Limited slew-rate, witch gives the basses attacks to sound 'soft'. A kick drum can have a very fast attack edge, at high level, and we perceive-it as 'bass'.
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.
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Old 25th January 2013, 07:00 PM   #33568
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How's a NE5532 (9V/us), has less "tight bass" than a 797?
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.
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help me keep my job.
Stretch a little the Locking pine, or threaten him of 'Sin bin' ?
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Last edited by Esperado; 25th January 2013 at 07:04 PM.
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Old 25th January 2013, 07:19 PM   #33569
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Originally Posted by john curl View Post
You tend to agree with those who think that expensive parts are a waste of money,
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.
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Old 25th January 2013, 07:20 PM   #33570
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The BT is most likely just as audibly transparent as any other good preamp despite the voodoo atmosphere that John likes to create around it.
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.
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