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

[Quincas]

Good question, I'll ask him :)

Sent from my iPad

> On 08/11/2015, at 10:24 p.m., rsdio at audiobanshee.com wrote:
> 
> 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.
>