Atari Punk Console with CV and Gate (APC)

Hello,
I want to share project I found based on APC:

https://www.matthewedmondson.com/atari-punk-console

I build it, but I do not have any sound on the output. Do I need to add any signal to the CV in or GATE in or it should make any sound itself and be possible to control it using knobs?

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His schematics doesn’t match the stripboard layout, so not sure what his gate and CV does (*) (too lazy to decipher it right now). Also, the 100k pots look pretty low – most designs have 500k or even 1M there – but it’s pretty hard not to get any sound out of an APC if everything is wired up correctly and you mess with the knobs a bit. Probably some trivial build glitch. Check everyone one more time.

*) APC CV is usually connected to the 555’s control input, which messes with the internal voltage thresholds in slightly odd ways – “neutral” CV is 2/3 of the supply language, and you can dial the frequency up and down from there. Not sure what his gate does.

EDIT: Looks like GATE goes to the RESET pin, which is left floating if nothing’s plugged in. That may interfere with the function; the datasheet recommends pulling it high if not used (which is also how it’s done in the schematics), even if I don’t think it’ll completely block oscillation. You may want to add a pullup resistor between pin 4 and the supply rail on the upper 555 (the lower has a wire from 9V to pin 4 already).

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Schematic is straight from Wikipedia, without adding CV and Gate. If you have any ideas how they should be proper connected I am open for suggestions : )

See my edit (no time to fully debug the layout, but the gate connection is wonky, since it leave the reset pin floating if nothing’s plugged in).

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Thanks, will try tomorrow. Adding same value resistor should help to get sound without input any signal into CV? If not, still some issues with my build or/and this layout?

I may be misunderstanding, but isn’t the point of a gate exactly that no sound should come out unless it’s triggered?

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Maybe, but some defined behaviour other than “dunno, maybe” if nothing’s plugged in cannot hurt. If not else it helps with testing :slight_smile:

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@ChristianBloch are right, i 've checked the schem and without Gate signal it is normal that it does not work, because in the diagram without Gate In of an APC pin 4 of the 555 from the top should go to +.
so it is the gate signal that sends current and operates the beast.
if you add a switch you could have both possibilities.

and for the CVin, for me it should go to pin 7 of the 555 of the top

EDIT :

CV pin 7 like this schem with baby 8:

or here

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Not sure that’s correct – the gate is connected to the 555’s reset pin, which is a PNP transistor that turns on when the pin is low, and resets the flip flop that drives the output. If the pin is high, or not connected at all (like when no gate signal is present), the transistor is off and the flip flop flips and flops as usual.

(the datasheet recommends against leaving the input floating to avoid glitches, which is why I suggested adding a pullup. a few k to +9V should be ok I think).

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I found some more documentation, I ope that will help you smarter guys find out what exactly changes layout from first post needs.

https://www.instructables.com/id/Voltage-Controlled-Atari-Punk-Console-mini-PCB/- 2x CV, does it make any sense in practical way?
http://getlofi.com/control-voltage-output-from-555-timer-circuit/
https://youtu.be/ZwjSA13xRhY

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I read your comments again, so for the summary:

  • Add ON/ON switch for the Gate Signal/Top 555 5th pin/+ power. 5 pin is also pot, should go like that?
  • Connect CV to the top 555 7th pin instead of the bottom 555 5th pin

Anything for the resistor you wrote? Any additional capacitors for synchronize chips? I read back about adding 0.01uf between 1 and 8 pin of each 555.

About pots - I can solder 1M, will it give me more control, but leave some dead-zones?

EDIT: I use it with 12V+ power, should I solder some stability/filtrating circuit using 100uF and 0.1uF capacitors between + and -, near the power socket?

EDIT2 - Is it possible to use 3 pin that is out of the jack socket to make circuit use GATE only when any jack is plugged in? Or you recommend from you experience to use switch instead of that?

if you have a breadboard, I would advise you already to try to realize the basic circuit (without CV, Gate)
also normally the APC diagrams that we find are made for a 9V , like in your links :wink:

original schem of Forrest Mims

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The only thing I’ve suggested is a pull-up resistor for pin 4, to make sure the RESET input isn’t floating if gate is left unplugged (another option would be to use a switched jack and feed in a voltage that way).

No idea about the other mods; at least the first schematic Dud links to uses the CV to charge the timing capacitor, which makes a certain sense, but that also means connecting it to DISCHARGE (pin 7) which is shorted directly to ground in the discharge part of each oscillator cycle (not entirely sure what the other schematic does). Your original stripboard layout feeds CV to CONTROL VOLTAGE (pin 5) instead, which besides making a certain sense based on naming :slight_smile: tweaks the internal thresholds instead, modifying the behaviour rather than driving it. Quoth the datasheet:

I’d assume charging from CV gives you a wider and more linear CV range (Hz/V), unlike the other approach that just modulates the APC’s base frequency given by the frequency pot, but connecting arbitrary external CV directly to ground through an internal transistor seems a bit risky. I’d at least add something in series there, to limit the current. And it obviously no longer works without the CV, with this approach.

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Thanks, will try. I soldered this project because I though that will be simple and entry level and finally give me some sound signal to check another modules I did before - divider and VCF as I remember. However I am still on the basics of reading of schematics, meaning I can connect components in the way they are drawn, having no deeper idea about the logic is going on there. When 2 chips are triggering each other - this maybe seems basic, but is hard for me : )

You and Fredrik made research here and for sure did good job helping someone more advanced than me, but please, for the beginning may we simplify, just the conclusions for the drawing from the first post:

  • Add 1k resistor between top 555 4th pin and ground?

  • Add ON/ON switch for the Gate Signal/Top 555 5th pin/+ power. 5 pin is also pot, should go like that?

  • Connect CV to the top 555 7th pin instead of the bottom 555 5th pin

  • I can solder 1M pots, will it give me more control, but leave some dead-zones?

  • I use it with 12V+ power, should I solder some stability/filtrating circuit using 100uF and 0.1uF capacitors between + and -, near the power socket?

  • Is it possible to use 3 pin that is out of the jack socket to make circuit use GATE only when any jack is plugged in? Or you recommend from you experience to use switch instead of that?

Before you do anything else, make sure you can get your current stripboard APC to oscillate, without anything plugged into CV or GATE. If you’ve checked everything twice, you could try:

  • Add 1k resistor between top 555 4th pin and +12 V (the RESET input is active low, so needs a pull-up, not a pull-down).

but I don’t think that’s very likely to change anything, just make things a bit more robust.

The supply voltage doesn’t matter much, since the 555 bases its behaviour on internally calculated thresholds at 1/3 and 2/3 of the supply voltage. The higher voltage will affect the output level, though.

Once you have it working, you can consider further improvements. If you’re not happy with the pot ranges, try 500k or 1M pots (*). If it’s too loud, add an output attenuator or just a fixed voltage divider. If you have stability issues, consider adding some supply rail capacitors. Moving the CV in will completely change how things work; it’s no longer an APC, and won’t do anything unless you feed in a CV. But maybe that’s fine, just make sure you know what to expect when you’re changing things.

*) Mims’ original design uses 500k, some other layouts use 1M (470k isn’t really a thing these days so not sure why people keep using that in their schematics).

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Thanks.
I added 1k for 4 leg of top 555 to +12V. No luck yet. I am tired today, maybe someone will spot obvious mistake. LED is always OFF. Sound sample - https://vocaroo.com/h2yO9EE4IHr Pots seems to have large dead-zone. I still use 100k here.

Pics:


Maybe it’s just the angle, but it looks like the power isn’t connected to anything?

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See link to the audio record - I get more than just noise : )
On the second picture, power goes from bottom-right pin into left from it. Double checked before connecting, no problem here I guess.

I soldered 500k pots, same result.

I don’t know if the problem is just that, but in my opinion there are some bad welds

have you make a continuity test with multimeter to see if there are no welds that are in contact (and that should not be)

why don’t you use a stripboard rather than a plate with only studs ? it would simplify your life for your soldering.

without really wanting to be unpleasant, you would have to take care of your welds, look here at the result with beautiful welds on the same type of plate

good welds are very important and your problem may come from poor contact between components

(I hope you understand that this review is friendly)

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I don’t get to build as often as I’d like and very quickly fall out of good habits when working with proto or strip board. Often I forget to clean the board, mark it up or take my time. In my rush I end up making more work. That said I am a continuity and reflow master now with a bin full of scorched stripboard! Slow down, use flux, work from and make notes on the schematic as you go. I know we all watch Sam dab his way through a grove of resister legs like demon but I find if I take my time and care with each component the overall build time to a working circuit is not that much longer.
Sorry @Dud this was a reply to @Piecho or to all really.
We are all artists of sound. Take care!

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