Splutter from the gutter...

[gez]

...or not as the case may be!

I needed to square up a guitar signal in the circuit I’m working on and used the following schematic



I didn’t have the op-amp I needed so I subbed in a TL072.  Pretty much what you’d expect from a comparator type fuzz, i.e. tons of sustain/compression and loads of splutter and blips as the note fades.  Out of curiosity I subbed in a few different op-amps and got a shock when I used the 7621 - it adds some dynamics!   The sustain is poorer and the fuzz fades out as the note tails off, plus the splutter is a LOT less!  I can only attribute this to the abysmal slew rate (.016V/us) and, perhaps, the natural compression of the CMOS output of the amp run without negative feedback?

It’s a little muffled compared with the TL072 so it could do with a high pass filter on the output, either that or a bright cap on the volume pot.  The intermodulation distortion is a little harsher too, but it does have some of that CMOS sound and feel to it.  

There’s not a HUGE dynamic range to be had from this circuit, but it does ‘feel’ and sound more natural  using this amp.  I should imagine that other CMOS amps with similar slew rates (and there are plenty of them!) would do the same.  It’s totally inappropriate for my needs, but thought I’d post it in case any were interested in a less spluttery comparator fuzz.