Who likes lo-fi?

Hi all,

I’ve made good progress with the digital filter board. Well, at least now I don’t want to throw it away and bite my fingers for having ordered 25 PCBs of it. I’ve tried very hard to make the DSP code sound as good as I can, but I have discovered that there’s not much you can get out of an AVR with 2k of RAM, 8-bit sampling with slow ADCs and 400 instructions per sample. So there’s no secret that this thing is as lo-fi as lo-fi can be.

Final, definitive, feature list:

  • 18dB/octave digital filter with resonance. Filter can be configured as high-pass, low-pass, or disabled.
  • 16 FX programs. FX can be applied before or after the filter (hence you can filter a distorted sound or distort a filtered sound).
  • Each FX program has two settings, which are controlled on a dedicated page or through CV1/CV2 in the modulation matrix.
  • Exhaustive list of FX programs:
    • Distortion with fold / fuzz.
    • Bitcrusher with sample reduction / bit depth reduction.
    • Positive and negative feedback comb filter with cutoff frequency / feedback.
    • Ringmodulator (pitch / amount).
    • Delay, 30% feedback and 80% feedback delays (time / amount).
    • 30% feedback and 80% feedback crunchy delays without anti-aliasing (time / amount).
    • Delay synchronized to tempo at 1/16, 1/12, 1/8 and 3/16 - doesn’t work with external MIDI clock though (feedback / amount).
    • Microlooper (loop time + pitch / trigger).
    • Pitch shifter.

Huge caveat: It doesn’t use the VCA, Cutoff, Q, CV1, CV2 inputs. instead the values of all those parameters are gently sent digitally by firmware 0.93. This way, the ADC can be dedicated to only one thing: capture the audio signal! So this filter board will be next to useless without a Shruthi digital board.

Overall demo
Tap delays
Another overall demo
High-pass filter > delay

I’ll try recording a sample of the board processing some fine Mr Scruff signals.

Anybody interested? I’ll probably do this as a board + flashed ATMega + 4921 DAC ; and as a bare board.

HERE! Including ATMega and 4921…

I LOOOOOVE the Sound and i’ve got enough HIFI Synths . . .

I like it too! and I’m addicted! i would like to have one

i’m in too, obviously!
complete with ATMega and DAC please

btw will you provide the 274 or 2474 too or should i get in touch with Farnell, as they stock both in EU?

I was thinking about this - the version with chips will include 2474s.


Here’s the Scruff sample

This makes me realize that all the multi-effects I have used so far lacked one thing: a modulation matrix :slight_smile:

This is the hifi of the LoFi…

So its MidFi?

edit: F**K. Hearing the new Scruff samples i need 2 for stereo!

edit edit: Drop theese Oscidingens and market its as a creative MultiFX :wink:

8 bits is Low-Fi, 16 bits is Hi-Fi, 24 bits is TooHi-Fi. 12-bits is MidFi, yeah.

The filter and the mixing is 12 bits, the delay lines are 8 bits.

very nice Olivier! really cool what you do
my first (DIY) synths and I love them the building gives me a lot of fun!

absolutely bad ass! sounds great. you’ve created a wtp-shruthi! all you need now is an sd card control board ;).

love the nasty samples.

good grief. Should I just send you all my money now or wait for the next board? Can I maybe just get like a monthly subscription or something?

Damn Olivier, you sure don’t waste much time with this stuff Good work :slight_smile:
It’s encroaching on Biscuit territory too… (No bad thing!)

@Luap: Yeah, I’ve figured out it would be quite easy to do a Biscuit-like device (some bits from this digital board + the SVF from the dual SVF board), but I’m not much interested in doing it. The Biscuit man is a nice guy, and the build/assembly quality of his stuff is top notch!

So this board is the closest I’ll be to the Biscuit territory :slight_smile:

And now it pitch-shifts!

Mission accomplished!

I thought that the pitch-shifter would be useful only on external signal, but I was wrong. Set to 1 quarter-tone and applied before the filter, it can thicken the oscillator signals a lot. Also, you can route a LFO to the shifting amount and get a chorus effect. I have no idea how this will sound on external audio but I suspect it’ll be quite similar to early Jungle/Akai time-stretchy effects.

Yes Plz, but I only want 2 or 3 of them.

; )

The Biscuit man is a nice guy, and the build/assembly quality of his stuff is top notch

Agreed, and agreed! I bought one… Not cheap, but you can certainly see where the money goes…