Dub stuff

[Kipper4]

or should I go with a discrete design like so?


https://synthnerd.files.wordpress.com/2016/06/discrete-ar.jpg

running on 9v though.

[ElectricDruid]

For envelopes, most of the synths ones probably need a bipolar supply, so that second one looks more like it to me. You could try doing a search for "Lunetta CMOS synth" - that'll turn up a lot of stuff you can use, all 4000-series based and unipolar supplies, works great at 9V.
(Stanley Lunetta was the guy who made these things famous)

https://docs.google.com/document/d/1V9qerry_PsXTZqt_UDx7C-wcuMe_6_gyy6M_MyAgQoA/edit

No-one has mentioned the 4047 astable chip, so I'll do that. It makes a nice square wave oscillator and has an 'Osc' output and two (Q and ~Q) outputs an octave below that, which can be mixed in. And that raises another point - feeding these square waves into a flip-flop (4013) or counter chip (4516) will give you octaves below the output frequency - more bass for your dub! You can also do *really* weird stuff feeding the sounds through logic gates. AND will switch a sound on and off (pulsed), but XOR will do a basic square-wave Ring Mod effect - very clangorous.

Finally, I'd like to put a word in for Tom Duncan, whose book "Adventures with micro-electronics" covers a lot of this sort of stuff and got me interested in synths and electronics for music in the first place.

HTH,
Tom

[anotherjim]

If you want easy volume/envelope control and your signal is square/pulse, the I'd go for a "swing" type VCA. 1 BJT does it simple.

It really is just a common emitter amp. The envelope is the collector load resistor supply voltage. As the envelope voltage falls, the signal is clipped to the lower voltage until it is zero. Causes distortion of course, but you can clip square/pulse all you want.

[Kipper4]

Hows my values here? Jim.



Thanks Tom I'll look into that and btw I've ordered the book.

Cheers guys

Edited

[anotherjim]

Those values look about right for 9v Rich. Those output filter caps to ground may not be necessary. Boss/Roland originals have them as the source is the sine output of a Bridged T type drum oscillator and the caps smooth off some of the clipping distortion the VCA causes.

[ElectricDruid]

Those output filter caps to ground may not be necessary.

+1 agree. They weren't when I tried it:

http://electricdruid.net/adding-vintage-hiss-crackle-and-pop/

I did ok with just the two resistors, the diode, and the BJT.

T.

[Kipper4]

Brilliant when I clear enough space on the breadboard I'll try that.

Curiously hungry now Tom.


Thanks guys.

[ElectricDruid]

Enjoy the book, btw! I hope it's not a disappointment. It's pretty basic, but it covers the stuff you're dealing with and like I said, it was what got me interested in the first place - discovering how to generate sounds from circuits. That was a Wow! moment for me, aged maybe 11 or 12. After that, I tried listening to all of the signals in the circuits in the book, and started to learn how to use the other non-audio stuff in the book to make more noises. This experimentation gave me a fascination with audio electronics and analog synthesisers - strange devices for creating sounds no-one has heard before (ok, maybe now they have...but it seemed like that at the time). I have a lot to thank Tom Duncan and that slim yellow volume for!

T.

[Kipper4]

I'm a few years behind you Tom in the synth stakes. Still hoping for that wow moment.

Thanks for the continued support guys.

I have tried this mod with good results today.
Critique welcome.
I do wonder if it needs a buffer on the output.
The 1uf I'm using to Gnd is Non Polar.



My chip supplier for the 555's has let me down with a postage failure. So they're on back order. also some cd4046s hopefully on the way. Cant wait to hear the 4046 vco. Oh and some CD4093/CD4093be.

Even when I've exhausted these chips capabilitys in my humble hands. I intend to induge some other avenues/chips.
VCF?
Who knows maybe one day a transformer. The skys the limits....

[diffeq]

According to the schematic of a PICsynth:
http://picsynth.000space.com/schematic.html
the decay diode should be backward and there is indeed a buffer afterwards. In your case it might be redundant since it will connect to pin5 of a that 555.
Anyway, cool project - sirens are fun to mess with. I think there were a plenty of simple 3 transistor sirens circuits published during 70s. Might worth a look.

[Kipper4]

Good spot. Thanks.

D44 is back to front in the above.

I need to update and go through my drawings.

No Buffer needed.

Thanks for the link.

[anotherjim]

I use 4093's lots. Make dead simple oscillators with a gate control.

Trick to play with...
The Schmitt trigger osc frequency is very sensitive to supply volts. Chip supply should be regulated if you want a stable fixed freq. However, if the chip supply it treated as a control voltage, you can get a usefully wide sweep of frequency. Chip can run down to a little under 3v supply. Amplitude reduces too (which is good for space drums), but as it's a square wave, you can amplify after (simple BJT CE amp) intoto clipping, so amplitude remains constant.
4 sirens at different freq spacing. #fun.

[Kipper4]

Here I am living the dream.
I spent a few more days tweeking. I hope I've drawn it all ok.....
Anybody see anything wrong. Please chime in.
I'm worried about grounding the IC2_B output. Should I be, Is it a bad plan?
It took me a while to find the wailing siren 555 circuit.....to increase the rise and fall time make the 47uf (C8) larger. eg.100uf
Not shown Is a rise and fall LED indicator for the wail. +9v>10k>LED(a), LED(k)>Q3 emitter
Credit to Stephen for the Q1 shunt mute. It works a treat under breadboard conditions.

[ElectricDruid]

Why *are* you tying the output of IC2 to ground, anyway? If you want to "turn it off", you'd be better off tying the op-amps *input* to ground instead, and then letting the op-amp deal with its output itself. I don't like the idea of tying it to ground with some input trying to force it somewhere else. Even if the op-amp can cope with it (aka doesn't die immediately), it doesn't seem like a great idea.

Aside from that, I like it, I think.

HTH,
Tom

[duck_arse]

that's a well named switch there kipper [ask nice and I'll tell you what it means downunder], but you've connected the emitter to ground, shorting the emitter resistors. nice work, can anotherjim hear it?

[anotherjim]

Some drawing "typos" I think.
LFOmanual switch is probably backwards.
Q1 output should probably be from collector....
... or else, yes, mute control is moot indeed.

....DuckA, I canna 'ear nuttin mon.

[Kipper4]

Thanks fellas.
I've had another lookie see at what's on the breadboard.
I should have known better.

Doing a redraw.
Expect more pics, much the same different chip.
I need to verify the pot pins and the moot is different now, not so much a mute as a pass signal. Fiya.
I'd welcome some improvements on the Fiya. If you think it could be done better please say.

[Kipper4]

[Kipper4]

I'll just leave this here.


https://www.hobbielektronika.hu/forum/getfile.php?id=215


@Tom.
The grounding of the lfo output was a response to a different lfo being used on my other breadboard. P90 style single op amp. It was wrenching the power supply more than the current one. So it's moot.

[Kipper4]

Question.
Can I get more mileage (pitch variation) by restricting the +supply voltage to the 556 timer chip?
Say +5~7v.