Crossover distortion

[WGTP]

http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html

The TMK has an interesting approach to varying crossover distortion.

I know this sounds silly, but the first time I inserted GE diodes in line with a distortion, I could have sworn I smelled that hot tube amp smell. 

The metal pedals usually insert the in-line diodes between a TS type op amp set up and the clipping diodes that go to ground.     

[frank_p]

and then some other (with sound):
cleany:
http://www.youtube.com/watch?v=z2fRXR-V_rw
gainier:
http://www.youtube.com/watch?v=Re2aKbVCeTc

A succession of images is worth a thousand succession of words.
Thanks again !

[Mark Hammer]

http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html

The TMK has an interesting approach to varying crossover distortion.

I know this sounds silly, but the first time I inserted GE diodes in line with a distortion, I could have sworn I smelled that hot tube amp smell.  (emphasis added)

When Class A/B is done right, you shouldn't smell that smell, but when it isn't I imagine you would.

[frank_p]

When Class A/B is done right, you shouldn't smell that smell, but when it isn't I imagine you would.

This phrase is very funny.  LOL

[R.G.]

Hmmm. Hadn't thought about it this before. Series diode pairs is the inverse of shunt diode pairs in the response to amplitude, too.

For signals less than the diode threshold, series pairs have zero output, shunt have full output. As you reach and go beyond threshold, the bigger the signal, the bigger the tonal effect of shunt diodes, but the smaller the effect of series pairs.

A bit of a synth module flitted across my mind. Something like a wavefolder, but separating signal out into voltage bands.

[frank_p]

(Amplitude)...but the smaller the effect of series pairs.

yes, that is what I saw on the oscilloscope Mr. K.
For a novice I was stupefied because it's quite simple.
But I was disapointed by the effect of changing the diode kinds (well on the oscilloscope).

[Joe Kramer]

In the same way that shunt diodes act as a crude compressor, series diodes act as a crude expander/gate.  I've even tried (without entire success) to exploit the crude noise-gate effect of series diodes on a noisy circuit.  A better designer/thinker than I may be able to perfect the idea as a cheap alternative to a gate.

[frank_p]

Just wanted to "thanks" to folks in this topic ...  It's fun to have a couples of days with simple comprension on some "electronic subjects". Even without makin a stompbox: you can have some "insights".  This is a basic thing but still...
Just with a breadboard and a scope you can uderstant somes things.

It is REALLY appreciated: as it gives more meat to carve in.

Plus with what P.T. has pointed out it gives material for more "basic reflexions".  I say basic because: I am still playing with basic electronics and that is what I can considerate.

Plus: M.H. and J.O. :  well what could be said ?

Puretube: why this was in the sidebar ?

http://www.youtube.com/watch?v=OAQ_c1C1JfQ&NR=1



   

   

[gez]

There are other ways...

And even more!

From reply 26 of this thread:

http://www.diystompboxes.com/smfforum/index.php?topic=69078.msg555306#msg555306

People are often lulled into a false sense of security by the 'virtual earth' effect seen at the input of an inverter biased like an inverting op-amp: input resistor and feedback resistor.  However, what people often overlook is that once an amplifier clips negative feedback is lost.  When this happens a voltage builds up on the input of the inverter.  Buffer the input with an op-amp follower and scope it and you'll see something akin to cross-over distortion: negative earth (no voltage change) for part of the cycle and, once the output clips, a build up of voltage at the input for the peaks only.

Turned out to be irrelevant info within that thread, but some useful info for this one?  The amount of crossover can be controlled by varying the ratio of the input resistor to the feedback resistor (no input resistor = no crossover).  Works best on final stage(s) as the the output is guaranteed to clip and the input signal is always strong enough to break over the threshold.

[puretube]

Anybody of those skilled in the art of oscilloscoping ever had a closer look at the "through-resistor-to-diodes-to-ground" clipperz?
(aka: diodes to ground, or iirc: "R*t" ?)

And if so: anybody looked at the difference between (dry) signalsource and the R/D-node?

Never mind the amplitude discrepancy, but since nowadays "gain doesn`t matter", who cares?

Have fun varying the amplificationfactor from 1-5 of the 1st channel, and ditto of the 2nd (inverted) channel,
in "added" mode... 

[frank_p]

I think you don't even need a scope.  I am not "too fast": but you're right P.T.

Everything disapears exept the nipple that is brought back against the navel...

[amz-fx]

The DOD FX56 American Metal has a pair of 1N34 diodes in series with the signal as part of its rather unique clipping stage. Possibly for the noise gate effect and/or crossover distortion. I think there is a Boss or Ibanez pedal with a similar arrangement but I can't remember the model off the top of my head.

regards, Jack