I've also had some slight improvements by replacing TL06x with TL07x or OP475 in mixer modules and the HPF, but my old A-131s are the early version where the TL072 is just for CV input. Some of the improvement I'm hearing I'm sure is pure placebo, but that's fine with me.

What we need to bear in mind is that the TL062 is designed as a low power device and uses a mere 0.5 mA of supply, but the OP470 uses 11 mA. No problem if you've swapping one or two op-amps, but if you replace a whole load then whatever signal to noise improvements you might hear will be useless when your oscillators go all wobbly because your PSU isn't up to the job.

If you replace many TL06x or 7x opamps you will definitely need a bigger PSU and might need to consider where to dump the extra heat as well.

Sean

--- In Doepfer_a100@yahoogroups.com , Jim Credland <jim@...> wrote:
>
> I did the math in my head last night, but just repeated now on paper. Looks like you need to go low to high in 25us for a 20khz signal. You'd need close to a 1v per us slew. I think Check my working :)
>
> Sent from my fone
>
> On 4 Jul 2012, at 07:06, "therpocc" <dmitry.shtatnov@...> wrote:
>
> > Correct me if i wrong, but 0.4v/us is right how much wee need to process 10vpp ideal 20 kHz triangle waveform. One half-cycle is equal to 10v slew in 25us. Simple calculations give us exactly 0.4v/us to achieve this slew rate. Maybe this parameter is often overrated or requires some special conditions like +-18v power or some specific input impedance range
> >
> > btw, if slew rate is so important parameter, we can try to replace OA in an oscillator and possible increase frequency range. I'll try to mess up with it later.
> >
> > --- In Doepfer_a100@yahoogroups.com , Jim Credland <jim@> wrote:
> > >
> > >
> > >
> > > On 3 Jul 2012, at 21:11, Jim Credland <jim@> wrote:
> > >
> > > > I chucked the lm324s out of a previous design here, the dirty cheap and pin compatible tl084 sounds lots better. I think the slew rate was killing me. Alright for fast signals as long as the voltages were low, but with a 7v peak to peak signal it's gotta be rolling off at the top
> > > >
> > >
> > > Just to finish my own email. I think the 324 is about 0.5v/us, which if my mental math is right must mean it starts to do bad things at about 5khz. I didn't measure the noise - i imagine there are better chips than the 84 for that.
> > > J
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> >
> >
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> [Non-text portions of this message have been removed]
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