Swell machine

[Kipper4]

It's the same in the original Sam
Heres the link Mark posted earlier

https://www.paia.com/talk/viewtopic.php?f=6&t=204

I'm not terribly sure how it works to be honest. Theres an explanation in the PAIA pdf. I'm not sure I get it.

It would be really good if I could sort it out though because a lot of people report being unhappy with the slow gear and this is a viable low parts alternative with more perameters. I just need to figure it out.

edit
if found this too in he search function

http://www.diystompboxes.com/smfforum/index.php?topic=105105.0

[samhay]

I see - http://www.diystompboxes.com/smfforum/index.php?topic=105105.msg945956#msg945956
Thanks PRR

The Iabc pin sits about 2 diode drops above V- in the LM13700 vs 1 diode drop in the 3080. I guess this may translate to slightly different behaviour in this design. Doesn't explain why it doesn't work with your 3080s, unless these are fakes (lots of fake CA3080s in the wild).

Fig 2 (http://www.ti.com/lit/ds/symlink/lm13700.pdf)
vs
pp2 (http://www.ti.com/lit/ds/snosbq5a/snosbq5a.pdf)

[Kipper4]

Not fake mate. I'll mess with the breadboard again tonight and see if I have more luck
Maybe I need to use the diode bias pin on lm13700?

[anotherjim]

Me forgot how OTA's work. The output feeding the opamp via 10k is fine.
I'd try working the OTA manually. Set up a temporary pot across the power supply (10k at least) and feed the wiper via a 33k to the OTA control pin (disconnect the existing feed). If you have audio as far as the OTA, then you should be able to volume control it out of the following opamp  using the pot.
You nearly always see a resistor in series with OTA control - at least in synth circuits. Don't know why there isn't here, but obviously there are working examples out there.

[Kipper4]

I found a mistake on the breadboard a big one ooops. still trying.

[lars-musik]

Keep on keeping on!

[Kipper4]

Will do Lars