Lostgallifreyan writes:

I'm considering an op-amp for making a DC coupling adapter to a soundcard to
convert it to signal logging purposes while retaining its audio performance.
It uses a passive adder and a gain of 2 to add a bias voltage to the signal
before an ADC input.

The sound card is one with external analog circuitry in a rack unit, it has
20 bit signal conversion, so this op-amp will have to be good to maintain
that and the other specs this unit has.

Audio ADCs usually have bad DC specifications - why wouldn't they. You
may want to verify this before you try too hard to find the perfect
opamp.

[...]


--

John Devereux

John Devereux wrote in
:

Lostgallifreyan writes:

I'm considering an op-amp for making a DC coupling adapter to a
soundcard to convert it to signal logging purposes while retaining its
audio performance. It uses a passive adder and a gain of 2 to add a
bias voltage to the signal before an ADC input.

The sound card is one with external analog circuitry in a rack unit, it
has 20 bit signal conversion, so this op-amp will have to be good to
maintain that and the other specs this unit has.

Audio ADCs usually have bad DC specifications - why wouldn't they. You
may want to verify this before you try too hard to find the perfect
opamp.

[...]



Possibly so, but I have already done somethign similar with a DAC and found
it be be excellent at outputting any abitrary DC or slowly changing voltage
and holding it where it's meant to be, and the ADC's and DAC's in this
equipment were chosen from the same maker. I know I'm making an assumption
that it will work, but I do think it will. Besides, I have to make some
decent effort to get this op-amp decision right, partly to help me learn, and
not least, to make sure than when I do test that assumption, it isn't my
choice of ap-amp or adapter design method that is screwing it up.