If you want to improve a 405 there are probably better ways about it than rolling the opamp. Check Keith Snook's pages on the subject.
~ QUAD 405 Amplifier Information and Modification ~
~ QUAD 405 Amplifier Information and Modification ~
From ADI that would be ADA4627-1 then.
https://www.analog.com/media/en/technical-documentation/data-sheets/ADA4627-1_4637-1.pdf
https://www.analog.com/media/en/technical-documentation/data-sheets/ADA4627-1_4637-1.pdf
These part numbers are available as samples from ADI for those qualified:
ADA4627-1ARZ (8 lead SOIC)
ADA4627-1ACPZ-R7 (8 lead LFCSP)
uA301ATC is a very old bipolar design, older than a jfet input TL071 as it is a few generations newer but still very old in the opamp world.
What is wrong with using a NE5534A?
BTW I do not know this Quad 405 design so I am speaking in general terms. It does depend on what the part is used for, if it is in the signal path.
I looked at the schematic they have on hifiengine, I think a NE5534 would be something to try. Or even the TL071 as they use in the other version. These are cheap parts to play with.
What is wrong with using a NE5534A?
BTW I do not know this Quad 405 design so I am speaking in general terms. It does depend on what the part is used for, if it is in the signal path.
I looked at the schematic they have on hifiengine, I think a NE5534 would be something to try. Or even the TL071 as they use in the other version. These are cheap parts to play with.
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The uA301 was used in the very first type of QUAD 405, so I guess you have an original QUAD 405 rather than a QUAD 405-2. The Acoustical Manufacturing Co. made many small improvements in the QUAD 405-2, the most important ones are halving the dead zone of the class-C stage and upgrading the op-amp from uA301 to TL071.
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Nothing, good idea, I should have mentioned it. Add 220uF across one of the Zeners to keep it operating at shutdown to avoid the dying scream.
Two things to be careful with:
-The op-amp is supplied from resistors and Zener diodes, so it should not draw too much current. (This rules out the TLE2071, because it draws excessive current while clipping to the negative rail.)
-Its input bias current should not be too high because of offset.
By the way, this thread might also be of interest:
Redesigning QUAD-405 DC bias loops
-The op-amp is supplied from resistors and Zener diodes, so it should not draw too much current. (This rules out the TLE2071, because it draws excessive current while clipping to the negative rail.)
-Its input bias current should not be too high because of offset.
By the way, this thread might also be of interest:
Redesigning QUAD-405 DC bias loops