strange fuzz....

[casey]

how does this work?

[Jason Stout]

Datasheet here:

http://server-die.alc.upv.es/Electroweb/datasheet/analog/rc4136.pdf


:?: ?? :?:

[Jason Stout]

Bump

[gez]

At a guess I'd say it works like a comparator fuzz and the back to back diodes clip the square wave output to a useable level. The inputs are trannie so the first opamp must derive its input bias current from its output. Must bias up close to either V+ or 0V?? Slight signal on input flips output??

If someone could breadboard it and post voltages it would help.

Second amp has -ve terminal tied to V+ which is odd. Unless the output swing is rail-to-rail (and it isn't!) the output of the first amp can never trigger the second amp to go +ve...mystified...don't know...wanted to get ball rolling...need more brains...come on chaps!

[gez]

Er, are you sure this is drawn up correctly?  output cap taken from +ve rail?!

[niftydog]

I've got an RC4136N here, and if no one is on to it by monday, I'll breadboard it then and see what happens...

The ol' software simulation doesn't like whats connected to pin 11! Besides, don't have spice parameters for the 4136, so had to use 741s.... not quite the same methinks.

[casey]

it's definitely strange......i dont have a 4136.....but i would bet that
if it does work....it might sound pretty different.

[gez]

Casey, where did this schematic come from? (curious)

[casey]

if i remember right, i found it on a forein site....maybe russian?

i am sure that it was drawn up by someone who's been around
the forum, but im not for sure.....

i think either mark hammer or r.g. keen would probably
know who drew it or even how it works.....jack orman would
be a good one to ask as well.....this is assuming that the
circuit does work.

:roll:

[gez]

this is assuming that the circuit does work.

I'd be bloody amazed if it does!  Unless I'm missing something I think this has been drawn up incorrectly...

[casey]

according to the schem....that's why they call it "strange," is because
it shouldnt, but supposedly does.

i hope someone breadboards it so that we could know...

[Ge_Whiz]

Looking at it, the signal has a path through a capacitor, three resistors, a variable resistor shunted by two diodes, and another capacitor. Even if the rest of the circuit does nothing, this should produce some distortion.

[niftydog]

ok, here's my results.

I built it as shown and effectvely it did nothing. No change in output regardless of whether power was connected or not. All I got was the effect of the passive components, and the clipping of the diodes.

a large signal level loss, and top and tail clipping from the 1N4148s.

Obviously this is largely dependent on having the EXACT part. But it could also depend on the tolerance of the particular IC you use.

Basically, my diagnosis is that it technically a very poor design because of it's brittle nature. A good design works totally independent of the characteristics of it's components. This is obviously not the case here!

Having said that, it would be interesting to see it working "as intended" but I'm not about to go hunting for the exact part... it would only lead to dissapointment.

[casey]

ok, here's my results.

I built it as shown and effectvely it did nothing. No change in output regardless of whether power was connected or not. All I got was the effect of the passive components, and the clipping of the diodes.

a large signal level loss, and top and tail clipping from the 1N4148s.

Obviously this is largely dependent on having the EXACT part. But it could also depend on the tolerance of the particular IC you use.

Basically, my diagnosis is that it technically a very poor design because of it's brittle nature. A good design works totally independent of the characteristics of it's components. This is obviously not the case here!

Having said that, it would be interesting to see it working "as intended" but I'm not about to go hunting for the exact part... it would only lead to dissapointment.

yeah, supposedly only the exact part will work.....  i am glad somebody
built it.  i was very curious as to how it sounded if at all.

thanks for building it.  interesting indeed.  

[niftydog]

remove the IC from the picture, and you've got resistors in series, parallel diodes and a resistor...

That is how it sounds. Like two diodes in parallel and a whole lot of attenuation!

Still, curious to hear how it's intended to sound!