Quad 405 upgrade choice : LME49710 vs OPA604

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07-Oct-2018 12:00 PM

Ronan

Ronan

Posts: 8

Good day,

I am on the way to upgrade one or two 405-II. I have no reason to choice between the LME49710 and the OPA 604 version, could you give me some ?

Thank's for information.

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15-Oct-2018 05:00 AM

EJP

EJP

Posts: 1537

LME49710 is considerably better on all measures. See the datasheets.
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31-Oct-2018 05:09 AM

crite40

crite40

Posts: 1

Over the years I have worked on and built many Quad 405's. Made in my home town by members of my family.

I knew Peter Walker quite well back in the 1950's.

but just recently I have run into a sticky problem.

The output of the LM301 is shown as +1.7 volts, so there has to be an offset from somewhere, otherwise Tr1 will not conduct. I have gone over the circuit exhaustively, but for the life of me I cannot see how this is derived except

via the output level which is as it should be almost exactly 0 volts

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30-Nov-2018 09:47 AM

EJP

EJP

Posts: 1537

The offset is there to balance all the B/E voltages through Tr3-7, and results from DC servo action. Otherwise the output would be steady at -1.7V. See the Ludwig paper on the 405.
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