Mini Synth demo (that one on 'GGG' originally from Funway Into Electronics 3)

[TFJames]

Hello all,

I hope this is the right place to post this.

When I first started this project I could never find a demo, and I saw a number of people mentioning it here and asking about samples/demos.
Well I built it (on faith / blind hope) and it works! I kind of love it, for all it's cheesy, retro, glitchy, glory. And here's a demo!



I didn't say it was a great demo did I?!

Anyway, the 'mini synth' was a project (#10) in Funway Into Electronics 3 published by Dick Smith in 1983, four years before I was born! It was intended to be used with a microphone, but it works surprisingly well with an electric guitar!

I've just discovered that http://www.funwayelectronics.com​ is now the public face of Funway Into Electronics. The site looks like it's been abandoned since 2016 unfortunately. However they do mention 'the intent of bringing the material back into the public domain', which would suggest the various book scans floating around the net possibly can be downloaded legally. Maybe?

There are scans of all three Funway books on the Internet Archive:
https://archive.org/details/funway_into_electronics/funway_into_electronics_vol_3_17th_printing/page/n81/mode/2up

Or just the mini synth project on General Guitar Gadgets, which is probably how most people here will have come across it. I actually think the above archive version/s might be clearer, but anyway, this is the GGG scan:
http://www.generalguitargadgets.com/how-to-build-it/technical-help/articles/mini-synth/.

Originally you were able to get a printed/etched circuit board, but since these appear to be no longer in production I made it on 'perfboard', wiring each individual connection!
I'm amazed it worked to be honest! So many opportunities for mistakes!

In the book it's described as follows:
"This musical-based circuit is the most complex in the book, but it's a load of fun. By using a microphone sound detecting input, a whistle, hum or voice can be the note generator. In this way, you can be your own oneman-band (sorry, girls: one-personband) without being able to read a musical note! Based on a Phaselocked-loop (PLl.) design, the circuit 'reads' the incoming  note frequency and I holds' it until the next input signal. This note is available at the output of two channels determined by an adjustable decay circuit Tremolo can be added as a further extension of the basic note which, incidentally, can also be halved or doubled in frequency to give a multitude of different sounds."

[duck_arse]

stylophone! gets my vote. I like the octave hopping. welcome to the forum.

all the kids will be wanting to see the/your perf layout, and gut shots. Dick has gone, now, closed all his shops a while back.

[iainpunk]

welcome to the forum,

despite the hiss, that's a nice demo.
i don't believe the PLL can go out of tune, considering that it has feedback to match the output frequency with the input freq.
i like the broken, glitchy nature of the pedal, and if i were to build something similar, i'd add deliberate glitches and problems in the feedback loop to degrade the tracking.

cheers

[deadastronaut]

hi and welcome...very cool.


is it more stable with a compressor in front?.

[ElectricDruid]

Welcome!

That is pretty bonkers. Like it.

It *really* makes me want to add an envelope-follower and filter to it, for extra synthiness. And then maybe stick a StompLFO in it too, and..and..and!!

But a filter would be an excellent addition. With those buzzy waveforms, you'd be in guitar-playable monosynth territory in a big way.

[Mark Hammer]

Looking at the schematic, there are a number of possibilities immediately evident.  First, the two "channels" deserve  a simple mixer so that they can be blended into a single voice.  The schematic shows that the LFO (IC1D) feeds them individually, such that one channel can be modulated while the other remains "pitch-stable".  Having individual decay controls for each voice, when they are blended, is also a nice feature.  Presumably, the pitch of one of the voices could be changed to a 5th above or below, but would require changing to a different CMOS divider chip other than the 4013 flip-flop.  That is certainly feasible, but I think many would prefer what can be done with as little changes to the original layout as possible.  However, if one perfs it, as you did, then I gather a 4017 or 4024 would be called for.

I gather C11 can be increased to slow down the modulation rate below its stock range.  And if the pitch of the 4046 VCO is being modulated, then taming that modulation amount might be a good thing.

Did you change anything to use it with a guitar, or was the Mic Input Level control sufficient for tracking purposes?

[TFJames]

stylophone! gets my vote. I like the octave hopping. welcome to the forum.

all the kids will be wanting to see the/your perf layout, and gut shots. Dick has gone, now, closed all his shops a while back.

Haha I suppose it does sound a little like those! Thank you!

As far as the perf layout goes, I just printed out two copies of the original layout (flipping it for the underside) and lined them up with the holes as best I could. Then I wired following where the traces would have been! It maybe wasn't the best way of doing it, I don't know, but it gave me a clear guide for each connection and helped me keep track of what I'd done as I slowly worked on it. I've cut some areas away, but you get the idea.




Yes, sadly I believe you're right about the physical stores, although there does seem to be an online store still.

Thanks again!

[TFJames]

welcome to the forum,

despite the hiss, that's a nice demo.
i don't believe the PLL can go out of tune, considering that it has feedback to match the output frequency with the input freq.
i like the broken, glitchy nature of the pedal, and if i were to build something similar, i'd add deliberate glitches and problems in the feedback loop to degrade the tracking.

cheers

Thank you!

Ssorry about the hiss, I couldn't get my video editor to eliminate that, and didn't have time (and I was lazy!) to extract the audio and fix it properly. Anyway thanks!

Yeah, I think it's more that it isn't matching the output frequency correctly, so everything is shifted slightly. Maybe?!

Haha each very much to their own, but I'm glad you like it! Maybe you could have a switch, or even a knobe that would dial up the clitchyness.

Thanks again!

[TFJames]

hi and welcome...very cool.


is it more stable with a compressor in front?.

Thank you, thank you!

Oh I'm not sure, I'll have to try at some point! I think it would need more some kind of filter or tone control to minimize sub-harmonics, but still worth a try.

Thanks again!

[TFJames]

Welcome!

That is pretty bonkers. Like it.

It *really* makes me want to add an envelope-follower and filter to it, for extra synthiness. And then maybe stick a StompLFO in it too, and..and..and!!

But a filter would be an excellent addition. With those buzzy waveforms, you'd be in guitar-playable monosynth territory in a big way.

Thanks!

Yeah, it is! Thank you, I'm glad you do!

Haha so many possibilities! I've been thinking about making a filter pedal/box actually, and you're right that would probably go really well with this.

Thanks again!

[TFJames]

Looking at the schematic, there are a number of possibilities immediately evident.  First, the two "channels" deserve  a simple mixer so that they can be blended into a single voice.  The schematic shows that the LFO (IC1D) feeds them individually, such that one channel can be modulated while the other remains "pitch-stable".  Having individual decay controls for each voice, when they are blended, is also a nice feature.  Presumably, the pitch of one of the voices could be changed to a 5th above or below, but would require changing to a different CMOS divider chip other than the 4013 flip-flop.  That is certainly feasible, but I think many would prefer what can be done with as little changes to the original layout as possible.  However, if one perfs it, as you did, then I gather a 4017 or 4024 would be called for.

I gather C11 can be increased to slow down the modulation rate below its stock range.  And if the pitch of the 4046 VCO is being modulated, then taming that modulation amount might be a good thing.

Did you change anything to use it with a guitar, or was the Mic Input Level control sufficient for tracking purposes?

Yes, I would have liked to have done some kind of blend option for a single output. However having them separate does allow for a cool stereo effect!
And I'm sure you're right about the '5th above or below' change, which would be a really cool feature to see someone do (someone with more understanding than me!)

Oh yes, I'd forgotten about the C11! I think I intended to socket it, to allow some experimentation, but completely forgot when I was putting it together. I guess you could have a switch to allow changing between different ranges which would be quite cool. Or maybe you'd just change the pot to suit the new range?

No I didn't change anything. I was expecting I might have to do some troubleshooting, but it just worked!

Thanks again!

[Mark Hammer]

I have been spending the "better" part of the day digitally editing the parts layout diagram in the Funway book to remove all the parts numbers and other stuff, in order to leave the basic PCB pattern.  I hope to have it finished and posted here tomorrow.

PLEASE tell me such a PCB pattern, suitable for toner transfer does not currently exist out there.

[TFJames]

I have been spending the "better" part of the day digitally editing the parts layout diagram in the Funway book to remove all the parts numbers and other stuff, in order to leave the basic PCB pattern.  I hope to have it finished and posted here tomorrow.

PLEASE tell me such a PCB pattern, suitable for toner transfer does not currently exist out there.

Oh wow, that's quite the job to take on! Originally I wondered if one of PCB layout programs might let you 'draw' over an image using it as a guide, to get a really nice clean vector pattern for toner transfer, or even cnc, but didn't end up bothering since I ruled out making my own board.

No, I couldn't find any such PCB pattern, so pretty sure your efforts are definitely not wasted!

[Mark Hammer]

Good.  My efforts will not be wasted.  I can sleep soundly tonight.

[11-90-an]

Cool... 

Welcome to the forum too..   

[anotherjim]

Using the 4046 phase pulse detector at pin1 to make the envelope for the VCA is cool. Not seen that before.

[Marcos - Munky]

Originally I wondered if one of PCB layout programs might let you 'draw' over an image using it as a guide

I know there's one that do this, but didn't bothered too much to learn how to use it. But anyway, people who are used to work with some image editing software (corel, photoshop) may prefer to just use the one they already know how to work with.

Very nice demo, it shows lots of possibilities this one can do. I really liked how it sounds, and may be building one in the future. Thanks for the demo.

Just out of curiosity, have you tried it with a mic? It may be fun.

[ElectricDruid]

Using the 4046 phase pulse detector at pin1 to make the envelope for the VCA is cool. Not seen that before.

Yeah, I liked that too. It's kind-of a variation on the Roland "swing type" VCA, where you use a pulse waveform to switch a voltage on and off, rather than changing the actual volume of the pulses with a proper VCA. The CV feedthrough is bad because the resulting waveform is unipolar, but it's cheap and simple.

[rutabaga bob]

Not to go off on a tangent, but doesn’t Illustrator allow you to import an image, and then add a ‘layer’ over it where you can do the tracing, without messing up the original?

[ElectricDruid]

Not to go off on a tangent, but doesn’t Illustrator allow you to import an image, and then add a ‘layer’ over it where you can do the tracing, without messing up the original?

Pretty much any graphics package beyond MS Paint allows you to do that, so yes.