hello... anybody home?

Relax in southern comfort on the east bank of the Mississippi. You're just around the corner from Beale Street and Sun Records. Watch the ducks, throw back a few and tell us what's on your mind.
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JR.
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hello... anybody home?

Post by JR. »

Anybody want to talk bad about tother people...?

JR
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mediatechnology
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Re: hello... anybody home?

Post by mediatechnology »

Hey John thanks for joining us.
Anybody want to talk bad about tother people...?
No, not really. Is this a trick question?
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JR.
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Re: hello... anybody home?

Post by JR. »

I am disappointed that you bailed on Prodigy.. You were one of the few guys who were smart enough to realize when I was right about something technical.

I never got to see the answer to my Rupert 5534 pull down/up question, the thread just disappeared. Do you know why?

It seems if it was known to the designers it could easily be noted in spec sheets. i don't recall ever seeing anything.

Oh well..

JR
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mediatechnology
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Re: hello... anybody home?

Post by mediatechnology »

Yes we're home.

John - I say this jokingly but sometimes (a few) I think you may have been "wrong," and known you were wrong, to see if I could defend a technical position in one of my posts. Maybe I've misread that when it happened but it was healthy and made me really think and prove to myself "am I right?" Sometimes I was full of it, other times we all learned something. You're very clever.

In my new gig I have a lot to learn from you about product cost structure.

To answer your question about the Class-A pulldown WRT Neve and the 5534:

One of the things I'm learning is that IC designers are keenly aware of supply current and budget the design to that parameter as well as others. From memory, the 5534 is typically 4mA at room temp. If a pulldown to Vee of 3K3 is used (a common value if I recall) and it was internal to a 5534, that would more than double Icc putting it over 10 mA at the datasheet max of -22V.

That, and the added internal dissipation, is my best guess. Maybe I should just phone Wimberly, Texas and ask Mr. Neve.

EDIT: Oh, one of the other things in my P-P post was that I recently had a chance to try the MC33178 LP version of the MC33078. It's a nice little dual with 1.5 mA/pkg. I was using it in a LP rail splitter so I really didn't get a chance to check AC performance (not as good as the MC33078 as you would expect) but I did look at output impedance vs. frequency. In that application it was as almost as good as a 5534. I think I had the thing sinking 25 mA p-p at 20 KHz with an output impedance of 100 milliohms.
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JR.
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Re: hello... anybody home?

Post by JR. »

I can guess some of the calculus surrounding IC design, especially for wider GP use. When putting a few hundred inside a console, current and heat matters. When most opamps in the middle ware are driving 10k-20k it doesn't need to deal with heavy lifting. That brings me full circle to one of my earlier comments where opamps are used selectively based on the demands of that particular circuit block. I used to design consoles with TL072 in some sockets and 5532 in other sockets for the lower output Z of the 5532 vs 072.

I looked at low current opamps when designing my battery powered tuner... they super low current opamps just acted squirrely on the bench so I defaulted to a known entity, the old TL064 series. Not uber low current but pretty well behaved. For my next generation design I'll probably just go discrete. For my DSP platform I'm interfacing a cheap mic directly with only a pull up resistor. If I drop the processor- A/D rail down to 3.3V the puny swing of the bare mic will be adequate as is.
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My suspicion the whole discussion about biasing opamp output stages into class A is overestimating the benefit for most applications, and just poor design otherwise. If the opamp needs a stronger driver, give it one. With an added driver there is merit to biasing the internal opamp stage class A to make it a little faster and this often occurs automatically with asymmetrical biasing of buffer stages. Reducing crossover lag in output stage improves performance as you close the feedback loop around the whole shebang.

People are in love with the thesis they can outsmart the system by hanging a few resistors off of common opamps. The whole audio industry is full of such magical thinking.

Of course I could just be wrong......... 8-)

I try not to intentionally post erroneous information, but I am human, and sometimes answer without digesting the question well, or go off into my own tangent.

JR
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mediatechnology
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Re: hello... anybody home?

Post by mediatechnology »

It would be interesting to measure a 5534 and see what improvement occurs if any.

I remember reading a review recently about the Neve Portico stuff using pulldowns with 5534s. Although the reviewer may have it wrong (it was a recent PAR IIRC) it would be a good question for Mr. Neve.

I probably wouldn't have responded to that post 'cause I'm not real passionate about "forced class A" but I was curious to see if the original poster had even gotten his question answered. It was a pretty "ripe" thread anyway but I don't think I want to "go there" here.
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JR.
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Re: hello... anybody home?

Post by JR. »

yo
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lofi
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Re: hello... anybody home?

Post by lofi »

hello :oops:
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mediatechnology
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Re: hello... anybody home?

Post by mediatechnology »

lofi!

Thanks for joining us man! Cool!

BTW we probably don't want to discuss the other place but I wanted to thank you for your support.

It really means a lot.

Wayne
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Re: hello... anybody home?

Post by lofi »

im here for a good time!!! thanks for making me welcome and please let me apologise in advance for the myriad of stupid questions i will throw at you guys!!!

still trying to get my head around all this stuff, or rather the point that you stop questioning and start accepting, after all i don't ring up Issac Newtons relatives to get the low down on gravity, i just accept its real :D

off to trawl around and she what gems you have hidden here

Iain
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