[sdiy] Speaking of OTAs....

[Happy Harry]

Hi Grant (et al)...
Inline:


>From: Grant Richter <grichter at asapnet.net>
>It seems to me the Lm13x00 chips tend to be very noisy and distort easily?
>Anyone else have problems with them, or fixes?

That's true. I don't know about VERY noisy, but they are noisy.
One trick I found is that the Iabc pin is very sensitive, and
can pick up EMI (RF?). I was getting (almost) radio reception, and
that made it very noisy. I added a small ferrite bead at the Iabc
pin and it helped quiet it A LOT !!!

>I have tried 100K/220 No Id and 100K/510 with 15K Id and could hardly tell 
>the difference.

I'd agree also. The diode will only help with linearity before clipping. It 
also lowers the input impedance. Try making those input
resistors a lot smaller... maybe 10K and 51 ohms if you can stand it.
That will help.

And DC offsets on the output buffers are all over the place.

I agree again: Trimpot for DC offset on the unused input is my
choice. Some folk use a pot across the inputs with the wiper to
ground... think National draws it that way.


>Just can't seem to get the hang of them.

Use Vactrols ???  ;^)

H^) harry

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