4U / LW Digisound 3340 VCO

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dksynth
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4U / LW Digisound 3340 VCO

Post by dksynth » Sat Oct 06, 2018 12:20 pm

Something else I've had kicking around for a bit, an adaption of the digisound 3340 VCO. Trying to get it redrawn for LW/4U format

Image

SMT single board module like the other things I've been working on.

One question it would be nice to answer before I order the first boards:

Who would rather more sync jacks rather than dual v/oct? The way it is right now you can choose between Hard+ Hard- and soft sync... just wire the one you want to the single sync jack.

Changes from original:
All inputs/outputs will have opamp buffers and there are attenuverting inputs for FM, both linear and exponential.
Last edited by dksynth on Sat Oct 06, 2018 1:52 pm, edited 1 time in total.

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oldenjon
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Re: 4U / LW Digisound 3340 VCO

Post by oldenjon » Sat Oct 06, 2018 12:53 pm

Looks good. IMO, it makes more sense to have a switch for hard/soft sync than a 2nd 1v/oct input.
"We all dance by ourselves, that's why we only play electronic music"

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Post by unrecordings » Sat Oct 06, 2018 12:54 pm

I built a pair of Digisound clones, and I think the sync facilities make this a superb VCO over many of the other classic designs

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Post by dksynth » Sat Oct 06, 2018 1:07 pm

sounds like we're in favor of having more sync options broken out .... I'll swap the second V/OCT out to add a soft sync jack and add a mini toggle switch to swap between +/- hard sync

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Post by dksynth » Thu Nov 01, 2018 12:31 am

This is what I ended up with.

Image

I've verified it in an SMD version, but it sounds like people are after a THT version of a CEM3340 for 4U so here we go.

It didn't end up entirely like the digisound implementation. Sine shaper different, PW cv voltage mixer different. CEM3340 powered by +12v and -5v. Using REF02 for nice steady +/-5V to the frequency pots. There is a soft sync input and you can chose to wire either - or + hard sync to the hard sync input.

All outputs except the Pulse go through inverting buffers to make it easier to scale and offset the outputs. I've set values for SAW and PULSE to be 0-5v signals with TRI and SINE being +/-2.5v. If you want different output amplitudes or offsets you'll have to do some math.

Most fun part, it implements Rob Hordijk's tuning set up from this paper: http://www.alfarzpp.lv/eng/sc/Tuning%20the%20AS3340.pdf . So tuning on my first one was a snap, but I need to check with other makes of 3340.

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Post by Jarno » Thu Nov 01, 2018 3:49 am

Nice work!
Like yourself, I would go for SMT, but there you go.
What are the PCB dimensions?

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dksynth
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Post by dksynth » Thu Nov 01, 2018 7:26 am

Jarno wrote:What are the PCB dimensions?
6x1.8 inches or 46x152mm

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Post by ashleym » Thu Nov 01, 2018 8:28 am

Great work. Digisound was my first unfinished build back in the day.

As you’ve asked. 3 way switch for all the sync options. Through hole. Lastly in a very non-Serge philosophical way........octave switch........I find it so much more useful but it’s not my project !!

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Post by CLee » Thu Nov 01, 2018 10:41 am

Interested

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dksynth
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Post by dksynth » Thu Nov 01, 2018 4:59 pm

ashleym wrote: As you’ve asked. 3 way switch for all the sync options. Through hole. Lastly in a very non-Serge philosophical way........octave switch........I find it so much more useful!!
I'd love to have the sync switch especially, and octave switches are always a bonus. But I don't want to make it more than 2 spaces and something had to give :homer:

I put corner mounting holes so if anyone wants to use it as the "core" of something more extensive, it should be pretty easy. (But booo on panel wiring.)

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Post by ashleym » Thu Nov 01, 2018 6:34 pm

dksynth wrote:
I'd love to have the sync switch especially, and octave switches are always a bonus. But I don't want to make it more than 2 spaces and something had to give :homer:

I put corner mounting holes so if anyone wants to use it as the "core" of something more extensive, it should be pretty easy. (But booo on panel wiring.)
Thanks for replying.

My thoughts, theoretical of course, would be a toggle switch in place of one v/octave bananas for sync options. Plus an octave rotary switch in place of the coarse tuning pot. The fine control can cover most of the gaps between octaves. Ergonomically an octave on the fine control works for me, as opposed to the engineering solution of less with the gap covered by the octave switch with the extra bonus of finer tuning.

I’m sure if you ran out of room for a rotary switch (I’m sure CK will do a cute small one) another 3 way toggle could work with 2 octaves on the (not so) fine.

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Post by dksynth » Mon Nov 12, 2018 11:20 pm

thruhole version is confirmed working ... waiting to get some of the other brands of 3340 chips in to double check if any values need to be tweaked for different manufacturers.

Image

Image

[/img]

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Post by CLee » Tue Nov 13, 2018 12:50 am

Nice!

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Post by ashleym » Tue Nov 13, 2018 1:57 pm

Simple sync solution. Good work. Exciting to see it finished.

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Post by anto32 » Tue Jan 08, 2019 3:47 am

Bravo! Where can I order, please

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Post by hallospceboy » Tue Jun 11, 2019 11:53 pm

I’m about to finish up an order with Charlie, this is in my panel but I want to know if you’ve tried the 3340 rev G? About to place an order with Thonk and would personally like to get this over the coolaudio.
Current rig: Modulargrid!

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