7Dials CV Express DIY Expression Pedal Interface

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woodster
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7Dials CV Express DIY Expression Pedal Interface

Post by woodster » Tue Sep 15, 2015 4:59 am

Hello everybody,

My good friend mcop and I have been surreptitiously developing a new range of Eurorack Modules and we are now happy to share the first fruits of our electronic creative labours.

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The 7 Dials CV Express module is a dual input device that primarily features an expression pedal input interface which produces a variety of control voltages for use in controlling other modules.
In addition to the expression pedal interface there is also a secondary CV input which can be used in conjunction with the expression pedal input to provide the user with multiple CV outputs, a Gate output and also a Trigger output.

Of the three dedicated expression pedal CV outputs, the first is a dual polarity variable output.
The polarity of this output is switchable (via the toggle switch) between both Rising (Heel to Toe), and Falling (Toe to Heel) polarities. This output can be modified further by the Vari Output Scale and Vari Output Offset potentiometers.
The next two CV outputs are for a dedicated Rising output, and also its Falling output counterpart, each with an associated front panel offset control.
The final aspect of the CV Express is a Comparator which generates Gate and Trigger outputs with control over the switching threshold.

The module can be used in a number of ways. The expression pedal or a CV input can be used independently or both can be used simultaneously. When using both at the same time, the two signals are mixed and the voltage range produced by the expression pedal is halved to ensure the output stays within a usable range of +/-5v to 0-10v.

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The module runs on either 12v or 15v and has a dual power header footprint on the pcb.

Full Kits are currently available from Thonk.
Loose Panels (Both Aluminium or Green PCB Material) and PCB's are soon to be listed on Thonk.

Synthcube are also soon to be stocking Full Kits as well as Aluminum Panels and PCB sets.

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Attachments
CV Express V1.41 Schematic.pdf
(137.69 KiB) Downloaded 87 times
7 Dials CV Express Build Guide.pdf
(1.14 MiB) Downloaded 61 times
7 Dials CV Express Bill of Materials.pdf
(84.91 KiB) Downloaded 72 times
CVExpress User Guide.pdf
(752.4 KiB) Downloaded 77 times
Last edited by woodster on Fri May 19, 2017 1:00 pm, edited 17 times in total.

sammy123
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Post by sammy123 » Tue Sep 15, 2015 6:44 am

Congratulations. This looks very cool and is dedinately something I'd like to build. :nana:

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regenbot
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Post by regenbot » Tue Sep 15, 2015 6:59 am

great idea! interested. How deep is it? my cases are quite shallow.

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woodster
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Post by woodster » Tue Sep 15, 2015 7:34 am

Many thanks sammy123,

Will be available soon at Thonk as kits, Ali Panels (silver and black print) and PCB's.
There is also the possibility that we'll have some of the PCB material Panels available, they will look like the one pictured above in a rather fetching green. :mrgreen:
Last edited by woodster on Thu Sep 17, 2015 3:13 pm, edited 2 times in total.

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woodster
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Post by woodster » Tue Sep 15, 2015 7:40 am

regenbot,

I think your in luck, as its a 2 PCB sandwich.
37mm depth from the back of the panel to the tallest component (trimmer or electrolytic caps)

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regenbot
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Post by regenbot » Tue Sep 15, 2015 8:56 am

perfect :party:

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Post by sammy123 » Tue Sep 15, 2015 12:13 pm

I'm into a pcb panel if that becomes available.

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gbiz
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Post by gbiz » Tue Sep 15, 2015 12:42 pm

Well done mcop & woodster :yay:

(I was going to say something about it only having 5 dials ... :hihi: )

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mcop
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Post by mcop » Tue Sep 15, 2015 12:52 pm

gbiz wrote:Well done mcop & woodster :yay:

(I was going to say something about it only having 5 dials ... :hihi: )
I though of calling it the minus 2 :hihi:

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Eloc
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Post by Eloc » Tue Sep 15, 2015 2:04 pm

mcop wrote:
gbiz wrote:Well done mcop & woodster :yay:

(I was going to say something about it only having 5 dials ... :hihi: )
I though of calling it the minus 2 :hihi:
Are you guys particularly fond of the Covent Garden Area?

I made myself a similar (if somewhat more basic and ad hoc) module like this for my system using an attenuverter chicklet normalled to 5V, I had to build a custom 100K expression pedal to use it however... this looks great though, and pretty unique in the Eurorack world. Speaking of expression pedal pot value, does this work with any expression pedal resistance?

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woodster
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Post by woodster » Tue Sep 15, 2015 2:44 pm

Eloc wrote:
Are you guys particularly fond of the Covent Garden Area?

I made myself a similar (if somewhat more basic and ad hoc) module like this for my system using an attenuverter chicklet normalled to 5V, I had to build a custom 100K expression pedal to use it however... this looks great though, and pretty unique in the Eurorack world. Speaking of expression pedal pot value, does this work with any expression pedal resistance?
Hey Eloc,
Many thanks.
Not the Covent Garden area, but Brighton !

With regards to the expression pedal pot values, as far as I'm aware the CV Express should work with any value.
There is a trimmer on the PCB which enables you to calibrate the unit (full details of calibration will be outlined in the manual/build guide).

We tested the unit with the following expression pedal models we had on hand -

Moog EP-2
Roland EV-5
Boss FV500L
M-Audio EX-P
Ernie Ball VP Jnr 25k (courtesy of regenbot)


I've got multiples of some of those pedals listed above and when we measured the pots in these pedals we pretty quickly found some drastic differences between them. I opened them up and they often had different pot values, not just the wide tolerances of pots in general.
I've also got some Ernie Ball Volume Pedals which work just fine, I think the vpJr has 100k pots inside.

On another point, the expression pedal input on the CV Express is not solely restricted to only using an expression pedal...

It expects a TRS jack into the expression pedal input, but the unit does feature some protection to prevent damage if you plug in (for example) a momentary footswitch with a TS cable.
Last edited by woodster on Mon Nov 23, 2015 3:42 pm, edited 2 times in total.

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mcop
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Post by mcop » Tue Sep 15, 2015 2:48 pm

We've tried it with a few and I can't see any reason it wouldn't. I've got a BOSS FV-500L and Woody has a Moog and M-Audio pedals if I recall. It works fine with all.
It will only work with TRS types that are wired the varying voltage on the Tip. The ring carries the reference voltage and the sleeve is 0v.

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Post by adam » Tue Sep 15, 2015 3:19 pm

i vaguely recollect there can be impedance issues with different pedals too - maybe it's a stompbox thing, i remember some expression pedals having an impedance matching circuit or something

http://www.muzique.com/lab/imp.htm

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woodster
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Post by woodster » Tue Sep 15, 2015 4:59 pm

No impedance issues with this I shouldn't think, seeing as the expression pedal just operates as a potential divider.

I've got a massive guitar pedalboard, and indeed impedance can be a pain to the unwary.
Some buffers in stompbox effect pedals are better than others, and then add into that mix the whole True Bypass thing which can also exacerbate impedance problems on larger pedalboards.
Volume pedals can be a bit finicky with guitar pick up loading, and can often result in major tone suck, especially if you also use the Tuner output on a Volume pedal like the vpjr.

Again though this is not a related problem with Expression pedals.

Of the 7 expression pedals I've got, all work as expected with the CV Express (they were either 10k, 22k or 100k pots inside).
I've swapped between using these different expression pedals on numerous occasions without calibrating or re-calibrating the CV Express.
All without problem.
Last edited by woodster on Thu Sep 17, 2015 3:19 pm, edited 1 time in total.

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Post by Thonk Support » Wed Sep 16, 2015 9:08 am

Looking forward to getting this one on sale :yay:

For everyone who doesn't know, 7 dials is like the roughest/toughest neighbourhood in the whole of the UK, a bit like 7 mile in Detroit.
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Reality Checkpoint
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Post by Reality Checkpoint » Thu Sep 17, 2015 5:42 am

Monobass wrote:For everyone who doesn't know, 7 dials is like the roughest/toughest neighbourhood in the whole of the UK, a bit like 7 mile in Detroit.
Dontcha know it. I live a 7 minute walk from there, and you do not want to go there during the day time, let alone at night.

P.S. I will order one!

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Post by mcop » Sat Sep 19, 2015 4:10 pm

I have a few sets of boards and panels available from the run I did to check the some revisions before ordering a full run. The only difference between these pcb's and the final boards is they are missing the text 'red stripe' next to the power connector.

If anyone is interestd in a set PM me.

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woodster
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Post by woodster » Fri Oct 09, 2015 2:29 pm

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Not long now.
We just had the final panel drill prototype delivered from the manufacturer, so should only now be a matter of weeks before we can start shipping out kits with Ali panels.

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Post by mcop » Sun Oct 11, 2015 7:58 am

PCB's have already arrived.

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meatbeatz
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Post by meatbeatz » Wed Oct 14, 2015 6:01 am

ah 7 dials! nice, I used to live around the corner :) roughest neighbourhood for sure. :hihi:

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woodster
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Post by woodster » Wed Oct 28, 2015 1:21 pm

Had a fun filled couple of hours playing with a little light sensitive resistor based gadget Matt's just cooked up.
It works really well with the CV Express and is lots of fun using your waving jazz hands or curtains, or even clouds passing in front of the sun to modulate stuff.
I want to try it with a strobe light and smoke machine now. :hihi:

I don't have access to the Koma unit, but I imagine this works along the same lines...

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Starspawn
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Post by Starspawn » Wed Oct 28, 2015 2:25 pm

Hmm, have you tried it with a ribbon?

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woodster
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Post by woodster » Wed Oct 28, 2015 2:31 pm

Starspawn wrote:Hmm, have you tried it with a ribbon?
Not yet, but it's on the list of things we'd like to try :tu:

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Post by Thonk Support » Wed Oct 28, 2015 4:42 pm

oooh! yeah I hadn't even considered using it with my Koma Kommander, you're welcome to borrow it for some demo vids woodster.
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woodster
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Post by woodster » Thu Oct 29, 2015 11:46 am

Yes Please Steve, I really do need to get some video content sorted out.

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