Problems with an Analog Bitcrusher

[Oz32]

Hi everybody, I need your help
I've recently built an analog bitcrusher following this project (https://tagboardeffects.blogspot.com/2012/10/analog-bit-crusher.html).
Once I finished and plugged it into my synth I only get clean signal and the pot doesn't affect the sound at all. As suggested in the comments of the project I tried to swap different OPamps (Ne5532, TL072, LM386...) in different positions but I don't sense any big difference. I also tried to swap the JFET with a J201 but again, nothing changed. I checked the board twice and everything is properly connected, so I don't know what I did wrong.
Do you have any tips?

Thanks a lot,

Oz

[PRR]

The original article:
https://www.freestompboxes.org/viewtopic.php?t=15709

[Mark Hammer]

Verify that all the pins on the FET are precisely the pins you think they are.

It never ceases to amaze me how something with only 3 pins can have so many damn variations, depending on who produced it.

[bluebunny]

Best to show us what you've done, Oz, and to take voltages at your active devices (aka. the "Debugging" sticky).

[ElectricDruid]

It tweaks my OCD when people call this type of effect a "bitcrusher". It's not, it's a sample-rate reducer.

The difference is one changes the *vertical* resolution of the signal (bitcrusher) and the other changes the *horizontal* resolution (sample rate reduction).

They actually sound pretty different. Bitcrushing creates harmonic distortion of the waveform, adding crunchy overtones. Sample-rate reduction introduces aliasing, which is generally enharmonic (unless you get *really* lucky and happen to play a note which is related to the sample rate!) and much weirder and less obviously musical.
<moan over>

Oh, and I'm going to guess that the clock isn't running, but like Bunny said, we need to see what you've done and have some voltages to know for sure. Mark's theory is good too, but he's already bagged that one.

[diffeq]

It tweaks my OCD when people call this type of effect a "bitcrusher". It's not, it's a sample-rate reducer.

you're not wrong, it's very confusing.

truth be told, bitcrusher should be called amplitude quantizer, and this effect should be variable rate Sample and Hold

[ElectricDruid]

this effect should be variable rate Sample and Hold

Yes, that's more accurate still.

[Mark Hammer]

There are many effects that don't technically do what they may be called or described as, but produce sounds kinda sorta resembling sounds kinda like other FX.  For instance, frequency shifters are NOT the same as ring modulators, but they sure sound like it.  Modulation effects (tremolo, chorus, phaser, flanger, vibrato) are obviously not ring modulators but if you crank the modulation rate up into the audio range, they sure sound like it.

It's a bit like facial recognition by humans (not machines).  We look at someone, and there is this or that feature - maybe eyes, or nose, or eyebrows - that makes us think of someone else, even though neither would be easily mistaken for the other.

Of course, the "sin" is not in how we might use such FX, but how we might label or describe them.  If someone wants to use a rapidly undersampled sound, OR a ring modulator, OR a phaser with a sped-up LFO, OR a frequency shifter, OR a vocoder. to create a kind of "disembodied" sound, more power to them, regardless of how they get there or label the strategy. That said, in the interests of NOT fostering technical misunderstandings, it IS best to refer to the technology accurately and precisely.

[SprinkleSpraycan]

It's spicy in this thread. What schematic, layouts etc could I look at that would be true bit crushers and not Variable Rate Sample Holders.

[FiveseveN]

Well it would involve an ADC and DAC and the means to control them (a uC). Or just a uC that integrates the former as peripherals. Is that what you're looking for?

[SprinkleSpraycan]

So the answer is no, not in an analog setting. Got it.

[Eb7+9]

truth be told, bitcrusher should be called amplitude quantizer, and this effect should be variable rate Sample and Hold

I appreciate your effort diffeq, for what it's worth ...


When I published the schematic to my first Aliaser (2005) I called it an Audio Rate Sampler

later on, people started referring to this sort of circuit as an analog bit crusher
and it seems to have stuck ...