[sdiy] PCB op-amp layout - 2x2 or 1x4

[rsdio at audiobanshee.com]

Did your designer only switch from quad to dual or single op-amps? … or were other changes needed to reduce the crosstalk?

Brian

On Nov 8, 2015, at 2:34 PM, Quincas Moreira <quincas at gmail.com> wrote:
> Thanks David.  I noticed the crosstalk issue in a Module I was testing for production. Voltages in the buffer for the multiplexer was affecting the one for the CV input.  Our designer has since changed it to avoid the problem.
> 
> On Sat, Nov 7, 2015 at 11:46 PM, David G Dixon <dixon at mail.ubc.ca> wrote:
>> >> I don't get the issue with the power being on the "wrong side" as these
>> chips are symmetrical, one could just turn it around and have the power pins
>> facing the "right direction."  What I do worry about is interaction between
>> opamps in the same package.  Depending on what you're doing it may indeed be
>> better to use a few duals rather than quads.  In the real world, isolation
>> between Opamps in the same package can be less ideal than the specs say.
>> 
>> The quad power pin thing is an annoyance, but a bloody needless one.  Why
>> did they do it that way?  It just means all the quads need to be installed
>> upside-down.
>> 
>> The isolation thing is true.  "Crosstalk attenuation" for TL07X is rated at
>> 120dB.  It ain't!  At least not at 2000 Hz.  120dB should be dead silence.
>> However, high-pitched squeals will happily slip from one opamp to another in
>> a TL074.