Barton 4046 Wave Shaper

Anyone ever build one? I just finished a stripboard layout. Built it and it seems to be working, though I seem to be getting a bit of modulation somewhere? Is this normal?
Pretty cool sounding module.

No Sequence


With Sequence. Modulation not as noticeable.
4 Likes

Link:
http://www.bartonmusicalcircuits.com/4046/

Looks interesting, your version has four frequencies? (Original has 7.) It’d be interesting to have outputs for each frequency separately, then feed them into a VCA mixer to mix them under voltage control.

Edit to add: I just realized since this thing generates square waves, could you use an analog switch as a VCA? Maybe not a MAX313 but maybe a DG412? Actually two. That’d give the same functionality but with voltage control, or at least I’m guessing it’d work. Others would know better.

4 Likes

Aw this thing looks awesome!

2 Likes

Sweeping this in some geometric way could be really cool

2 Likes

I just added 4 for testing. It will have all 7 divisions… There’s a few ideas for mods I have rolling around. If anyone is interested in the stripboard layout, I’ll post it once I can verify it is all working correctly.

4 Likes

Could the “modulation” you refer to be caused by occasional double triggering in the square wave converter? I’m looking at the schematic and I see this comparator:
image
This is not dissimilar to the input stage on Barton’s drum modules, with a threshold of ~0.12V. If I try to trigger my drum modules directly from my KeyStep it triggers on both gate on and gate off; I don’t have a good enough scope to try to diagnose that, but my guess is there’s some ringing on gate off that causes it to retrigger. What waveform are you putting in? I know for instance the 3340 pulse wave has seen some ringing problems.

That threshold seems kind of low for the drum modules’ gate to trigger conversion to me. For square wave conversion things are different, you probably don’t want too high an input. Still, maybe increasing that 1k resistor is an experiment worth doing to see if it affects your “modulation”. I dunno, just a guess and maybe not all that likely.

3 Likes

That kinda makes sense! I may give it a whirl to see if it makes a difference. Thanks!

1 Like

I’m wondering if it’d make sense to use the input stage of Carmello Azzarello’s sub oscillator instead. Supposedly he did work hard on making it work well with a variety of input waveforms.

(Not that I’ve used it myself.)

2 Likes

I made his Sub oscillator. It works well! I haven’t noticed the modulation on other demo videos, that’s why I’m guessing maybe I botched something? I’ve been sending various triangle,saw, and square waves at it. Seems to be the same with all.
Quite noticeable here.

4 Likes

Are there any filters on this thing that could be introducing that modulation frequency? One thing to notice is the rate of the modulation is consistent even with the changes of the divisions.

2 Likes

It sounds like interference, or something in the power. If it’s static as you say that’s where I’d start. Try a temporary shield/cage (aka tin) or with battery power.

2 Likes

Here’s my Stripboard layout. I was a bit confused by the power supply schematic. Maybe I did something silly?


2 Likes

You don’t need C10 and C12 near the power header. You do appear to have bypass capacitors near all your ICs on the power pins, and that’s good. Bypass capacitors are shown in the schematic close to the power header but on the board that’s not where they go.

Barton always specifies 10nF for bypass capacitors but almost everyone else uses and recommends 100nF.

Other than that I don’t see any power issues. But what are you using for a supply and how does it get to the board?

2 Likes

Barton’s PCB has 10 nF capacitors both near the ICs and near the power header (also on the unused −12 V rail). no it doesn’t, see below.

1 Like

Really? In the schematic there are only four bypass capacitors, all in the power section on the lower left: one for the 4046N, one for the 4040N, and two for the dual op amp (which does use -12V).

1 Like

No, you’re right – I thought it was a single supply opamp, but the supply lines for that one are nicely hidden among the caps.

2 Likes

Cool. I’l take em out. I’m using a standard eurorack cable from a Tip Top power supply. Case power is good for sure!

*took caps out. No change”

2 Likes

Here it is complete except gotta figure out the strange issue. Issue or not, it’s still very neat sounding.

7 Likes

I talked with Michael Barton. He seems to think it’s interference from another module in my case. I’ve been using it a lot, and to be honest, doesn’t bother me a bit. I’ll post my layout in the Verified Stripboard Layout thread if anyone wants to give it a go.

5 Likes

I want to experiment with making a voltage controlled version. Should be easy impossible interesting.

3 Likes