I find myself confronted with a Quad 44 preamp. Unfortunately the owner was exposed to a similar unit which a now steadfastly retired friend had "done up" and customer wants the same "magic" worked on his unit. What he (Chris) did :
1: Replaced the TLO71 opamps with SSM2134 corksniffers These being low offset enabled him to rip out the coupling caps.. 2: Replaced the output opamps with AD845s to give a bit of drive capability 3: Replaced the CD4066 input switch matrix chips with little relays and driver transistors on homebrew daughterboards. 4066s are rather hideous distortion wise.
Chris DEFINITELY cannot be persuaded to do another one. The 2134s are obsolete and the 845s are hideously expensive. there is a corksniffer 4066 made by Maxim which may save me from CADing up some PCBs. Any suggestions for alternative currently available components before I run screaming from this job?.
1: Replaced the TLO71 opamps with SSM2134 corksniffers These being low offset enabled him to rip out the coupling caps.. 2: Replaced the output opamps with AD845s to give a bit of drive capability 3: Replaced the CD4066 input switch matrix chips with little relays and driver transistors on homebrew daughterboards. 4066s are rather hideous distortion wise.
Chris DEFINITELY cannot be persuaded to do another one. The 2134s are obsolete and the 845s are hideously expensive. there is a corksniffer 4066 made by Maxim which may save me from CADing up some PCBs. Any suggestions for alternative currently available components before I run screaming from this job?.
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Opamps: use OPA134, OPA604, etc, any of the usual suspects.
CD4066: definitely use MAX4066.
I don’t see any need for different output opamps unless you want to drive headphones.
leave the coupling caps around the volume and balance controls.
it is also possible to use NE5534 but there’s a trick to it ;-)
CD4066: definitely use MAX4066.
I don’t see any need for different output opamps unless you want to drive headphones.
leave the coupling caps around the volume and balance controls.
it is also possible to use NE5534 but there’s a trick to it ;-)