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[ORDER] OCTOGINTA-II Digisound 80-2 eurorack version
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2, 3  Next [all]
Author [ORDER] OCTOGINTA-II Digisound 80-2 eurorack version
whoop_john
I have been working on a compact version of the Digisound 80-2 VCO module. As I am sure everyone is now aware, the infamous CEM3340 VCO chip has now been remanufactured by no less than three different sources and this project takes advantage of the rock solid tuning on these VCO chips.

The module is in a compact 10HP width, ie 2". We envision that a complete DIY VCO build should be possible for under GBP £50, including the VCO chip, PCBs and front panel. This may depend on where you source the VCO chip from.

Particular care has been taken to provide an easy build for the DIY community - I have now built five with no difficulty. All components are through-hole in a straightforward layout. No inter-wiring of panel components is needed. The trimmers afford ease of access.

I would like to thank Julian for collaborating on the front panel design and David 'mrmrshoes' for his beta testing and modification suggestions for 12v use.







Julian will be able to ship both PCBs and panels together for a saving on shipping costs. The cost of the PCB set is GBP £9 and Julian's front panel will cost GBP £20. PCB shipping will be £1.50 in the UK and £3.50 elsewhere in the world.

Kits may be offered in future, or complete builds, if people would rather have one-stop shopping or a complete plug in and go module. Please message me if this is more attractive for people and I will work out costs.

The only issue arising has been that on a 12v supply rather than 15v the raw saw wave output has an amplitude of around 7.6 volts rather than 10v. The other waveforms have been buffered and adjusted to give nearer 10v to be more faithful to the original. It would be possible to adjust the other waveforms so they matched the 7.6v, but the team's view has been to keep things as they are as waveforms will usually be attenuated further down the signal chain anyway.

Documentation
The original ETI magazine article is here ETI article
The original Digisound article is here Digisound article
Pav
I'm interested in PCb+panel . I could not view the articles from my iPad for some reason. I see the links on BT cloud...but clicking on link fails. I'll try from PC later. Will these be the BOM to work from?
whoop_john
Pav wrote:
I'm interested in PCb+panel . I could not view the articles from my iPad for some reason. I see the links on BT cloud...but clicking on link fails. I'll try from PC later. Will these be the BOM to work from?


No, I will do a correct updated BOM for 12v in due course. Links to the documentation now changed and should work.
Sparkey
Hi John,
I'd be interested in getting the PCBs and panel. If a there was enough interest and kit happened before I was ready to purchase, I'd certainly look at that, but I'm not desperate to have everything handed to me.

Cheers,
Alyn
Ayab
Excellent features and very compact - Good work. I love it! Very neat panel too.

Did you use a cool audio 3340 (which Julian is proposing a group sale of on another thread on here)? Was it easy to tune?

I would like three pcb sets.
whoop_john
Ayab wrote:
Excellent features and very compact - Good work. I love it! Very neat panel too.

Did you use a cool audio 3340 (which Julian is proposing a group sale of on another thread on here)? Was it easy to tune?

I would like three pcb sets.


Yes I used the Cool Audio version of the 3340. Setting up the sine wave shape and zero point is easy and the tuning should pose no problem if the correct procedure is observed. Once the low frequency span has been set then the high frequency compensation can be adjusted.

It is suggested that the coarse knob is set to off and the fine tune knob be disconnected until tuning has been set up.
whoop_john
Thank you to all those who messaged me and have ordered PCBs. Your PCBs will be in the post to you tomorrow and your support and encouragement for the project is very much appreciated.

I have just a few PCBs left still if you wish to be an early adopter. I have more PCBs on order, coming in about 10 days, so don't worry if you didn't order one yet, I will have plenty and Julian will have stock for those that want to get a beautiful alumin(i)um engraved panel and PCB together, to save shipping.

A BOM will follow very shortly.
cretaceousear
Nice job - good to see Digisound designs gettting a new lease of life!

While getting mine back into action a few years ago I had a brief discussion here on MW about the zero based outputs:
https://www.muffwiggler.com/forum/viewtopic.php?t=110511

I concluded Mr Blakey should have made the four base outputs bipolar and then added 0-10 for the pulse.
No other designers seem to have followed this positive going output format - do you have an opinion or is it neither here nor there?
whoop_john
cretaceousear wrote:
Nice job - good to see Digisound designs gettting a new lease of life!

While getting mine back into action a few years ago I had a brief discussion here on MW about the zero based outputs:
https://www.muffwiggler.com/forum/viewtopic.php?t=110511

I concluded Mr Blakey should have made the four base outputs bipolar and then added 0-10 for the pulse.
No other designers seem to have followed this positive going output format - do you have an opinion or is it neither here nor there?


Food for though certainly. I was trying to be faithful to the original. Perhaps if I do a second iteration I will address this issue. What do the others think?
Synthsense
Interested in x2 PCB + Panel Sets please Guinness ftw!
whoop_john
A BOM and information on sourcing the components is now available. View or download the information in PDF form.
Modulart_JP
Have been offering a version of the module since last year:
http://www.pharmasonic.jp/vcolfo_e.htm
jaidee
Quote:
Have been offering a version of the module since last year:


... but not any DIY option as far as I can see.

If you are supplying DIY PCBs and panels, particularly for the VCDO (and the appropriate eprom) I'd be very interested - otherwise I'm not sure what this and your other post is doing in this DIY thread.
Modulart_JP
Well...
The Eagle files to make your own PCBs and the FPE file to make your own front panel are available to download.
If that's not DIY then what is it ?
flts
Easy links to board file and panel here: https://www.muffwiggler.com/forum/viewtopic.php?t=197467

Having trouble finding them on site as well!
Modulart_JP
flts wrote:
Easy links to board file and panel here: https://www.muffwiggler.com/forum/viewtopic.php?t=197467

Having trouble finding them on site as well!

OK, let's continue there then.
I just wanted to point out that there was another incarnation of the module in eurorack.
Didn't mean to troll.
Mine sticks to the original design and parts when whoop_john's one has been slightly adapted to "modern life".
It is good to have a couple of alternatives to this nice design.
julian
When you say that John's is an adaptation, can i ask you what you mean?

So far as im aware the only changes made were to allow the unit to run on 12v. I would assume that your unit required the same alterations?
unrecordings
I've got far too many unfinished projects, but...

John - It looks like the PCB is '15V Ready' with an MTA156 footprint - is that correct ?

Would you simply sell a circuit pcb without the panel pcb so that us 5U types can panel mount our pots etc ?
julian
edit - misread question
unrecordings
Thanks Julian
I might have misunderstood your answer though - I would only be looking for the one pcb, not the panel pcb and not the panel (I don't need the pcb for the panel mount components because I can simply wire everything from the long header on the main board)
julian
It was my fault - i read your question incorrectly.

I cant be sure, but i think John gets the pcbs made in sets that contain both boards as one (and then are broken along the score lines).

...but, at £9 for the pair, even junking the panel board, although wasteful of resources, is hardly a cost consideration?
julian
The foils for the original 80-2 modules are here -

http://www.digisound80.co.uk/digisound/modules/80-2_files/80-2&3_PCB.g if

Years ago, i used one to isolation mill a 1-off of the ring modulator -



ie from this file -

http://www.digisound80.co.uk/digisound/modules/80-11_files/80-11A_PCB. gif


I reckon though, unless youre proper keen on etching etc, it would be way more bother than just junking the panel board from John! : )
unrecordings
julian wrote:

...but, at £9 for the pair, even junking the panel board, although wasteful of resources, is hardly a cost consideration?


Yeah I know, It's just the whole waste thing. I'd rather pay the £9 and insist John keep the panel boards as spares though...

I don't need two more VCOs though (inner voice is naysaying), but I've run out of things to solder and it's been too cold to make panels...

John - are you going to move further into Digisound modules ?
whoop_john
unrecordings wrote:
I've got far too many unfinished projects, but...

John - It looks like the PCB is '15V Ready' with an MTA156 footprint - is that correct ?

Would you simply sell a circuit pcb without the panel pcb so that us 5U types can panel mount our pots etc ?


Yes I stuck an alternative MOTM style power socket there. I can sell a PCB without the panel PCB but the cost is still £9. After all, what am I going to do with the spare front panels and no main PCB? The PCB is 15v ready, it just needs the original component values installing.
whoop_john
Modulart_JP wrote:
Have been offering a version of the module since last year:
http://www.pharmasonic.jp/vcolfo_e.htm


I am all for diversity and choice. If HP is an issue then my version saves you 2HP. I am considering offering complete built modules, but the cost won't be anything like $240.
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