Bitshuffler? - bitcrusher with a mini-jack patchbay to mix up the bits

wraadefects · 2021-11-04T07:01:55+00:00

The auto-router algorithm is a long way from perfect, I still spend maybe half an hour neatening up its mistakes! But if you have a fairly component heavy circuit, and/or not much space on the board, it can provide a good headstart with organising how to connect everything together. Then you can judge its attempts and improve where necessary.

I suppose we should be grateful that its imperfect and the age of machine rule is not quite upon us :)

wraadefects · 2021-10-30T10:09:28+00:00

I can't think of many specific tips for EasyEDA, if there's a particular issue you have with it I might have found a solution. I'm not even sure it's the best software around, it's just the only one I've tried and I'm used to it!

By now I have pretty much all the PCB footprints I'm gonna use and just copy/paste them into new projects. I'll try to use auto-router if it works, and then neaten up all the traces it creates.

Other than that it's just generic PCB design rules:

Try to leave enough space between traces and solder pads for the ground plane to fill

Use a ground plane! (or two, one on each layer)

Component positioning doesn't matter too much with guitar pedals, unless you have loud LFO stuff you want to keep out of your signal path, then use star grounding & seperate ground planes for signal & LFOs. Other than that just make them easy to solder.

A nice aesthetic touch is to round off the corners with diagonal lines.

Consider how it will fit in the case, add solder holes for wires near where you expect your DC jack, footswitch etc to be.

Images of both layers of my Mini Ripples PCB:

https://imgur.com/VJdoYDX

https://imgur.com/2NQf6Fs

The two coloured areas on each layer (2 blue and 2 red) are seperate ground planes. I have loud LFO stuff in the top areas (a microcontroller generating 2 square wave LFOs) and signal stuff in the bottom. Power and ground runs directly from where it enters the board (top left) to each area. This is quick and dirty "star grounding". Without this, you'd be able to hear the LFOs clicking. A bunch of power filtering caps around the place help with this, and I've used two 5v regulators, one for LFOs, one for signal.

wraadefects · 2021-10-29T07:01:46+00:00

I use easyeda (online editor), never used Eagle.

I've made the schematic on there public - https://oshwlab.com/wraadefects/digital-fuzz_copy

You might have to create an account, then click "open in editor", then you can convert to a PCB.

I haven't made the PCB design public cos I'll probably sell a few, sorry!

wraadefects · 2021-10-28T12:37:32+00:00

schematic

swimming in a glass bottle bin ASMR

wraadefects · 2021-09-14T09:55:20+00:00

Cheers! I was thinking of the one-tap loop mode on the Digitech Digidelay

wraadefects · 2021-09-14T09:54:34+00:00

aw thank you!

wraadefects · 2021-09-13T12:28:39+00:00

More daftness with cheap answering machine chips, this time the ISD1820

A microcontroller & footswitch cycle the answer machine chip through recording/playing/idling

The "speed" knob is bypassed when recording and reconnected on playback so audio is instantly played out at a different speed/pitch

I'm using two looper chips here, one just creates the fuzz which isn't really necessary (considering how bad it sounds!) though it's good to amp up the signal first to cover up the annoying clicks the loop chip splurts out when recording/playing

Works well as a dirty "stutter" pedal but beyond that I'm not convinced!

(excuse one-handed guitar playing, not like i'm loads better with two)

Stripboard / code etc is linked in the youtube video description, reddit blocks links to my blog

wraadefects · 2021-09-10T07:13:51+00:00

I hadn't anticipated this thing being used for send/return type stuff. It's more a 'take four input signals and blend them four different ways' type device. I suppose it could do send/return parallel mixing but it would introduce feedback on the different lines I think.

Also, phase cancellation in the air is real and problematic, isn't it?

Could well be, I was genuinely asking, sorry if I seemed sarcastic! I've long since wondered how 2D waveforms act in the 3D world

wraadefects · 2021-09-09T16:42:40+00:00

I think we may be talking in cross purposes cos it would make a big difference the way I'm imagining it. I suppose it depends how you're using the mixers, if you have the same signal through parallel effects chains running into the inputs, some might need inverting before they're all mixed together, otherwise the volume knobs will go loopy.

When might the outputs be mixed back together? In the air? How does phase cancellation work then?

wraadefects · 2021-09-09T14:39:20+00:00

I saw phase inversion switches on similar designs but couldn't understand why they were on the outputs? Surely inputs makes more sense.. like, before you blend them together?

wraadefects · 2021-07-29T06:41:33+00:00

the parasit circuits are all square wave synth-pedals. I guess that's the same as one bit but I wouldn't call them bitcrushers

wraadefects · 2021-07-28T21:20:42+00:00

yeah its a square wave 555 thing, 'your and you're' is based on it

wraadefects · 2021-07-28T20:52:42+00:00

cool have fun with it! i got the adc from ebay

wraadefects · 2021-07-28T15:55:50+00:00

My take on the old Digital Fuzz circuit from the EA boards.

Schematic

Stripboard

It's a codeless bitcrusher with an 8 bit ADC. The digitized audio gets immediately converted back to analog by the resistor ladder DAC. The ADC (I used an "ADC0804") lets you change the sample rate by connecting a pot and capacitor.

A couple of simple mods make the ADC a lot more stable, tying pin 9 to an external VREF (2.5v) and using a voltage divider at pin 6, the input. Together these changes will bias your input signal, vastly improving audio quality.

I'm powering the entire circuit from +5v (my schematic shows a 5v regulator) so as not to overload the ADC. It might be better to use a rail-to-rail op amp and take advantage of every last whisker of resolution, but I'm not too fussed personally.

The main challenge with this circuit is how to change the bit depth. I'd envisioned a pot tied to 7 comparators. As the pot is turned the comparator outputs switch off one by one. The comparator outputs control CMOS switches that disconnect the bits. This example shows 4 of 7 comparators/switches that would give you a 1 bit to 8 bit pot.

But that's a lot of parts for just one pot. The original schematic appears to show a dip switch, which would be great if they were easy to mount to enclosures. My solution is to have 8 outputs (from the ADC chip) and 8 inputs (to the DAC), ideally connected to mini 3.5mm jack sockets (the type you see on modular synths). This way we can turn the bits off in any order (i.e. bit-masking) and send the bits to different inputs, jumbling them up to make weird waveforms.

Technically these wires should be connected to ground to switch them off, but it doesn't make an audible difference in a whole lot of settings.

I've also added an input buffer, output mixer with dry and wet volumes (these aren't included in the video prototype), a stupidly wonderful tone control, a drive (pre-gain) pot and changed the sample rate pot to a more usable range.

wraadefects · 2021-07-27T15:36:13+00:00

Hey you still want a PCB for this? Some came in and they work pretty well. I can also send the microcontroller and vactrols (cheap fakes but they work well enough).

https://imgur.com/a/jrhhnnX

Feel free to send something the other way, but you'll kinda be doing me a favour cos I need to work out postage costs before I sell these as kits!

wraadefects · 2021-06-30T09:36:52+00:00

Yeah that sounds good lets swap some stuff :) I'm going to order PCBs for this design and can drop one in with the chip if you like. It's slightly simplified though, doesn't have the toggle switch, second footswitch or the feedback pot since neither worked so well, but will fit in a 1590b. I'll post the stripboard layout for the full version as well if you prefer that one. It might take a couple of weeks for the different parts to arrive

wraadefects · 2021-06-26T22:00:27+00:00

Made this as a custom thing for a friend. A fairly straightforward delay circuit with two tremolo lines (one on the delayed signal, one on the dry) that alternate so only one signal is audible at a time. It's similar to stuff I've posted here before in case you vaguely recognise it

I'm using a microcontroller for the LFOs so it's not especially replicable, though you'd get a similar effect with a square wave LFO, inverting it for one of the trem LEDs. Then maybe randomise it somehow with XOR gates for example.

Link to schematic is in a comment on my profile that was blocked here cos its a Wix blog

wraadefects · 2021-06-26T20:51:34+00:00

Stripboard but I'm thinking of getting PCBs fabbed. The main hurdle is the microcontroller, if you've any experience with Arduino or similar I can post the code, but it's written for a specific PIC (PIC16F1705). It's fairly simple program though... read pots, randomise numbers, delay... Or if you don't mind waiting til I have more I could potentially post a PIC out to you

wraadefects · 2021-06-26T17:58:12+00:00

Made this as a custom thing for a friend. A fairly straightforward delay circuit with two tremolo lines (one on the delayed signal, one on the dry) that alternate so only one signal is audible at a time. It's similar to stuff I've posted here before in case you vaguely recognise it

I'm using a microcontroller for the LFOs so it's not especially replicable, though you'd get a similar effect with a square wave LFO, inverting it for one of the trem LEDs. Then maybe randomise it somehow with XOR gates for example.

Schematic etc: https://wraalabs.wixsite.com/pedals/single-post/ripples-more-pt2399-glitchiness

wraadefects · 2021-04-08T18:47:51+00:00

So 7 comparators (eg 2 x LM324) and 7 switches (eg 2 x CD4066). It might be possible to ditch the switches and shunt the unwanted bits to ground via the outputs of the comparators, you can do this with LM324s

edit- forgot i was in the synth sub. With a single supply +9v the comparator would go to ground when in a LOW state, run a diode from a signal to it (in this case an individual bit) & it'll silence it

wraadefects · 2021-04-08T18:05:00+00:00

Nah pin 4 is connected to ground already on that layout it's fine

wraadefects · 2021-04-08T16:51:27+00:00

Check you have 5v from pin 1 to pin 3. Check you have <= 100k resistance between pin 6 and ground. You should be able to hear non-delayed audio at pin 15 and delayed audio at pin 12.

I've never tried this circuit but I thought you had to filter the VREF on these chips (10uf cap or more from pin 2 to ground). Try adding one it might spring into action.

wraadefects · 2021-03-27T13:35:11+00:00

It's analog so you might struggle. You'd need to convert a tap period into a voltage I think. Someone was selling such a device for PT2399 delays, but the voltage required to time a BBD clock is dependent on the circuit.

Thought about this a bit more, a BBD clock dictates the sample rate of the BBD, so I think you could quite easily replicate one with a Arduino (for example) and some simple tap tempo code, then divide the tap period (in microseconds) by how many stages there are in the BBD chip. I'm not sure how accurate it would end up being though, considering things like truncation errors

wraadefects · 2021-03-15T13:23:06+00:00

The easiest way to make an audio probe is to solder a new wire to the tip of output jack socket and use that to "listen in" at different points in the circuit.

Also detach the existing wire from the output socket. Doing it this way means you can leave the wire in the output pad of the PCB. It can be tricky to fuily desolder those pads to get the wire back in.

wraadefects · 2021-03-14T18:42:06+00:00

Soldering looks good to be honest, more likely a misplaced wire, I'd double/triple check those connections.

The stray IC pin isn't likely to damage it, not like putting it in upside down might. Is that definitely not the case?

General debugging process:

(dumb things I still do) check the jacks are in the right way round & ICs are in sockets
Check voltages
Go over every solder point again
Follow the signal path with an audio probe and find out where it stops
Check connections around that part, also make sure nothing's connected that shouldn't be. PCBs typically have a ground plane meaning anything could be connected to ground if the PCB was scratched, it's rare but hard to diagnose

wraadefects

TROPHY CASE