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 Forum index » DIY Hardware and Software
Any schematics for soft or hard clipping modules?
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mikeb



Joined: Nov 20, 2006
Posts: 57
Location: The Automotive Capital of Canada

PostPosted: Wed Aug 21, 2019 2:56 pm    Post subject: Any schematics for soft or hard clipping modules?
Subject description: Looking to nicely clip signals above 10VPP
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Hey guys,
I'm trying to find a schematic for something that can do some nice sounding clipping of a synth level audio signal. So the waveform stays untouched if below 10Vpp and starts to get clipped as it rises above 10Vpp.

I've looked into a few schematics, but they're all for guitar effects.. and they all seem to attenuate the signal very low so it can use diodes to clip at like .7V and then amplify back up. I'd really like to avoid having to attenuate and then re-amplify to avoid adding excess noise into the circuit. I'd just like something that leaves the signal untouched up until 10Vpp and then starts chopping the tops off of the waveforms as it gets higher than that. Thoughts?

Thanks!
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AlanP



Joined: Mar 11, 2014
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PostPosted: Wed Aug 21, 2019 3:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Phobos' WaveWiper module does that, if you only use one input.

http://stickneysynthyards.000space.com/wavewiper/
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mikeb



Joined: Nov 20, 2006
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Location: The Automotive Capital of Canada

PostPosted: Wed Aug 21, 2019 5:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

AlanP wrote:
Phobos' WaveWiper module does that, if you only use one input.

http://stickneysynthyards.000space.com/wavewiper/


Hi Alan, reading the operation instructions for that page I don't see that it does any clipping. I see that it does rectifying and splitting the signal out to separate outputs for the positive and negative swing of the input.
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AlanP



Joined: Mar 11, 2014
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PostPosted: Wed Aug 21, 2019 5:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

The RYO OptoDist also has clippers. Four LEDs in series, for maybe 6 or 7V ceiling?
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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Wed Aug 21, 2019 6:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

heh, I hadn't considered the WaveWiper, but I guess it does some extreme clipping.
But yes, some LEDs in series should do it.

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ixtern



Joined: Jun 25, 2018
Posts: 124
Location: Poland

PostPosted: Thu Aug 22, 2019 1:38 am    Post subject: Reply with quote  Mark this post and the followings unread

"How does the WaveWiper work ?
...
The opamps also invert and
attenuate (gain = 0,5x) the signals. The attenuation is added to prevent clipping."

http://stickneysynthyards.000space.com/wavewiper/?i=1
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PHOBoS



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PostPosted: Thu Aug 22, 2019 4:33 am    Post subject: Reply with quote  Mark this post and the followings unread

ixtern wrote:
The opamps also invert and
attenuate (gain = 0,5x) the signals. The attenuation is added to prevent clipping."

That would be clipping if the signals are higher than what the opamps can handle because it gets too close to the supply voltage.
But the WaveWiper does work by 'clipping off' the top/bottom of the signals (and stitching them together). Of course that's not
how a fuzz/distortion/overdrive usually works,. hence why I called it extreme cliiping.

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ixtern



Joined: Jun 25, 2018
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Location: Poland

PostPosted: Thu Aug 22, 2019 5:06 am    Post subject: Reply with quote  Mark this post and the followings unread

PHOBoS wrote:
ixtern wrote:
The opamps also invert and
attenuate (gain = 0,5x) the signals. The attenuation is added to prevent clipping."

That would be clipping if the signals are higher than what the opamps can handle because it gets too close to the supply voltage.
But the WaveWiper does work by 'clipping off' the top/bottom of the signals (and stitching them together). Of course that's not
how a fuzz/distortion/overdrive usually works,. hence why I called it extreme cliiping.

Right, but I am not sure if it was original idea of this design.
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electrotech



Joined: Apr 24, 2013
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PostPosted: Fri Aug 23, 2019 3:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,
A simpler method could just use a couple of Zener diodes and resistors like I've shown below - no op-amps required !
This is from a circuit simulator and I haven't tried it, so not sure how it will sound.
For a sharper clipping effect, lower the value of the 150R resistor or for a more rounded effect, increase it.
The 1k resistor is for current limiting and may need to be increased in value but that will depend on the drive capabilities of the source.
BZX55C 4.7V (500mW) zener's will be fine.
(I used BZV85's in the simulation as it's an old program with limited models)


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PHOBoS



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PostPosted: Fri Aug 23, 2019 4:57 am    Post subject: Reply with quote  Mark this post and the followings unread

ah of course zenerdiodes DO work. It was the first thing that came to mind but I had forgotten you have to put them in series Embarassed
If you place them in parallel it doesn't work of course. It's actually a method I have used myself a couple of times to limit a voltage
so I feel quite stupid now.

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Last edited by PHOBoS on Fri Aug 23, 2019 10:11 am; edited 1 time in total
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gabbagabi



Joined: Nov 29, 2008
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PostPosted: Fri Aug 23, 2019 7:42 am    Post subject: Reply with quote  Mark this post and the followings unread

if you first multiply the 10Vpp signal just before the clipping points of an opamp, and then divide it back by the same factor -> gives you an unclipped output
(@15V that is roughly factor 3)

if you then raise the input over the 10Vpp you get some clipping

inverting and noninverting example attached


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mikeb



Joined: Nov 20, 2006
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PostPosted: Fri Aug 23, 2019 11:33 am    Post subject: Reply with quote  Mark this post and the followings unread

gabbagabi wrote:
if you first multiply the 10Vpp signal just before the clipping points of an opamp, and then divide it back by the same factor -> gives you an unclipped output
(@15V that is roughly factor 3)

if you then raise the input over the 10Vpp you get some clipping

inverting and noninverting example attached


Thanks gabbagabi.. but I don't want to slam an opamp past the rails to get my clipping. I'm not sure why not though, that just seems "dirty" and not best practice. Will try to breadboard that zener example above though..
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gabbagabi



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PostPosted: Fri Aug 23, 2019 2:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

past the rails ?
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AlanP



Joined: Mar 11, 2014
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PostPosted: Fri Aug 23, 2019 2:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

Heh, here's a project -- redesign a Big Muff to work with 10V synth signals natively, not 50mV guitar signals.
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mikeb



Joined: Nov 20, 2006
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PostPosted: Fri Aug 23, 2019 5:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

gabbagabi wrote:
past the rails ?


Sorry, "into" the rails Smile

That being said, I looked at the schematic for the OCD distortion and noticed that the amplification stage slams the signal into the rails for some distortion before it hits the Diode clipper stage.. so maybe I shouldn't be afraid to hit the rails of the op-amp too..
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gabbagabi



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PostPosted: Sat Aug 24, 2019 1:54 am    Post subject: Reply with quote  Mark this post and the followings unread

well,
indeed "we" are using the into-the-rails (itr) effect for producing square waves more or less often - so dont be afraid my friend this way is save to go alien clown smurf batman Shocked

Very Happy
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Ayab



Joined: Oct 27, 2015
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PostPosted: Sat Aug 24, 2019 4:01 am    Post subject: Reply with quote  Mark this post and the followings unread

This is transistor pre-amp then 3 different clipping circuits (and a bypass) - it is for 9V but uses only resistors and capacitors.

I wonder if part of it could be easily converted to 12V? Maybe without the transistor.

I am not sure how the clipping would be trimmed to only be above 10v either. There must be a better way than "trial and error" that I could suggest Embarassed Very Happy


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Electric Druid



Joined: Mar 13, 2012
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PostPosted: Thu Oct 10, 2019 5:00 am    Post subject: Reply with quote  Mark this post and the followings unread

AlanP wrote:
Heh, here's a project -- redesign a Big Muff to work with 10V synth signals natively, not 50mV guitar signals.


Like most good ideas, this has already been done!

http://www.frequencycentral.co.uk/?page_id=1489

(Full Disclosure - I helped Rick a little bit with adding CV control to the tone control circuit, and designed the PCB).

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