Dual OpAmp in input of amp?


2004-11-02 7:00 am
What is the catch here? Why not single opamp?


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My bad, i should look at a datasheet instead of talking from the less dense part of my head.
The (zener) diodes are Panasonic made, aka MAtsushita as in MA29/MA4082, Technics = Matsushita .

The SU-V85 is a specimen of the late 80s/early 90s AA series, cost around $500, the TH502 thermistor in the schematic is likely the Class AA thingy.
The opamp however is Mitsubishi manufacture, which is amusing because Matsuhita corp. and Mitsubishi corp. are competitors.
So the choice for that opamp was cost related, must have been the most affordable option, the main motive for the high volume market.


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Oops, forgot the opamp exchange part.

The Mitsu 5219P is operated with rails at +/- 7.5 Volt, which means it is able to handle the full 50mA output current it is capable of. (at a reasonable temperature, 375mW matches the 75C limit of the thermal rating graph in the datasheet)

An NE5532/4 is not a terrific replacement i think, if only because it is not intended to put out more than 10mA, i have no idea why someone would pick an LM1458.
I'd say you'd have a better chance with a TL071, but to match the 10 times lower distortion number of the Mitsubishi you'd have to pick something more contemporary like an OPA134.
I'd buy an original, a dip8 M5219 is around $2/each.

(as only 1 of the channels is used, a SIP8 L-version would probably fit too, and the M5219L is cheaper than the dip8 version)
In some cases the dual version is internally compensated while the single is not. Using the dual may save a penny or two bu reducing the parts cost plus one less component to stock and place.

Maybe they have another product that needs the dual and using it on both products increases the buy quantity enough to get the next volume break.

Maybe some other reason. Who knows?
If anyone has a schematic for the SU-V85a, would they mind posting it or e-mailing it to me? I am trying to fix one of these amplifiers, which appears to have developed a fault when it was new. It was sent to a repair center, but I am not confident that the people working on it had a schematic or have replaced parts correctly. It is still inoperative. This work was supposedly done under warranty many years ago. --Regards, HK