[sdiy] OT: TL07x Friend or Foe?

David G. Dixon dixon at interchange.ubc.ca
Thu Sep 30 08:43:24 CEST 2010

Wow, the list is very quiet lately.  Am I sensing a bit of "synthesizer
fatigue"?  I must confess, I'm feeling it a bit, but I have been extremely
busy at work and dealing with family issues, so that probably explains it.

> Of particular interest to me is the ability to compare results for the
> TL071 and TLE2072. It is clear to see the TLE2072 is quite well off
> compared to the older brother. Based on more ad-hoc testing with my
> JBL/Urei project, the depth of my wallet and these excellent
> measurement results from Mr. Groner it looks like the TLE2072 is the
> winner in my search for the ideal TL07x replacement.

I just got a pile of TL074s for about 16 cents per opamp.  The TLE207x
"Excelsior" version runs about 4 or 5 times more, but is still very
reasonable if one confines it to the audio path.  I looked into it for my
VCO because of the faster slew rate and lower offsets, but stayed with the
TL07x in the end.

> I also like that
> this device can run on 19 volt rails considering my compressor and
> some other equipment in my setup has 18V rails and the 07X devices
> tend to run pretty warm. Perhaps this has something to do with the
> poor performance of these devices in the 7110.

That's a good point.  I never stress the opamps in any design, but tend
instead to try to keep them well away from their current limits.  I never
notice opamps getting warm to the touch (unless I put them in backwards, of
course -- always an issue with those bloody quads, since the no good
so-and-so who laid them out oriented the power pins upsidedown).  However, I
did manage to heat up an OPA2132 when I replaced a TL072 with it one time.
It was acting as the servo current source and integrator in my 2164 Expo
VCO.  I never did figure out why, and the circuit works fine with the TL072,
which stays nice and cool.  In fact, that was the one time I actually tried
to replace a cheap opamp with a better one, and it was a total bust.

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