Doepfer A-151 Quad Sequ. Switch: Digital outputs on the back

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Plugler
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Doepfer A-151 Quad Sequ. Switch: Digital outputs on the back

Post by Plugler » Sun Jan 06, 2019 6:57 am

Hi,

does anybody know, what we can do with the digital outputs on the back? I can not find any documentation about this, nor any website mentioning details. Even not in the Yahoo group. :-(

Only one blog entry, but not with any clues, what is possible with this outputs:


I have a new version of the A-151 (PCB v3, sticker "Test 0918"), with better labeling on the PCB.

Directly nearby the DG409DJ:

DIGITAL OUTPUTS 5 4 3 2 6


Image
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yoho
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Post by yoho » Sun Jan 06, 2019 11:06 am

You can use those pins to have an extra sequencer like in the image attachedImage
The Gnd pin (6) is connected to all pots.

Or use it as a compliment gate section. But this topic you be in the Diy section.

If you have more questions please ask. I'm off to my own eurorack to see if I have the same version as you...
[/img]

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Navs
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Post by Navs » Sun Jan 06, 2019 11:12 am

Thanks for pointing this out, Plugler. My DIY curiosity was roused ...

The blogpost you link to has all the information. The chip used is an 8-channel or dual 4-channel multiplexer. The A-151 uses one half for switching and the other to light the LEDs.

So, I guess you have an on/off voltage at the digital outputs that you could use to trigger other modules. I don't know if you would need to buffer them, but at the least a resistor between the pin and your next module would be prudent. Best bet is to ask Dieter directly.

That said, I think all you will get is a four step sequential gate sequencer 'for free', if you do not already have one ... :hmm:

edit: Yoho has it :)

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MvK
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Post by MvK » Sun Jan 06, 2019 12:06 pm

I also wondered about that. "Digital" outputs of the a151 would make for some great logic possibilities. I believe it would also give you a flip-flop and its negation if length is set to 2. Very handy! I want to do this! But I dont have any DIY experience. But this seems to be a nice 1st project, given that I have all the tools needed in my house.

Sooo, the picture above shows clearly another application. We don't need knobs for the a151. Do I only have to connect the 4 digital outputs to the pins of 4 jacks and the ground to the ring of all of them?

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Post by Plugler » Sun Jan 06, 2019 2:27 pm

@Mods:
This is getting clearly into DIY. Can you please move this thread to the subforum?

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Post by Plugler » Sun Jan 06, 2019 2:31 pm

MvK wrote:I also wondered about that. "Digital" outputs of the a151 would make for some great logic possibilities. I believe it would also give you a flip-flop and its negation if length is set to 2. Very handy! I want to do this! But I dont have any DIY experience. But this seems to be a nice 1st project, given that I have all the tools needed in my house.

Sooo, the picture above shows clearly another application. We don't need knobs for the a151. Do I only have to connect the 4 digital outputs to the pins of 4 jacks and the ground to the ring of all of them?
Hmmm, I have to analyze the schematics and measure the voltages at these headers.

The picture above is from here (thanks google picture search :razz: ):
https://www.ginkosynthese.com/support/
It's for their Voltage Controlled Sequencer. But there are no more infos available.
Last edited by Plugler on Sun Jan 06, 2019 3:06 pm, edited 2 times in total.

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Post by Plugler » Sun Jan 06, 2019 3:05 pm

I measured the current at the outputs.

The outputs correspond to the four I/Os from up to down:

6 = GND
2 = I/O 1
3 = I/O 2
4 = I/O 3
5 = I/O 4

I measure at each output 11,84 V, only when the corresponding I/O LED is on. Otherwise they are on 0,0 V.
So it seems, as navs already supposed, these outputs can be used as trigger or gate.
Have to make a breakout module for this... :-)

What do you recommend as resistor at each output? 100 Ohm or 1K?


BTW: My +12 V bus power is exactly 12,0 V.

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Trebbers
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Post by Trebbers » Sun Jan 06, 2019 3:34 pm

Is there any reason that you wouldn't use/split the voltage from the digital outs to drive individual gates and a single CV out using pots as attenuators?

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Post by Plugler » Sun Jan 06, 2019 3:51 pm

Trebbers wrote:Is there any reason that you wouldn't use/split the voltage from the digital outs to drive individual gates and a single CV out using pots as attenuators?
Yes, that would be also possible. Like the solution yoho posted above, but not with one global "mixed" output, rather one output per channel.

I'm still thinking over a good solution for a breakout module...

Your solution would result in a simple 4 step sequencer.
Good idea!

EDIT 1:
Here is my 1st draft for a DIY A-151 BOM. What do you think?
This is 12 HP. Maybe I can shrink it to 10 HP. But 8 HP would be to small, the attenuators need space for my thick fingers. :mrgreen:


Image


EDIT 2:
2nd Draft - 8HP - that is enough size to handle 4 Outputs:

Image



BTW:
I've just discovered the "big brother" (or sister?) of the DG409:
DG408, a Single 8-Channel monolithic CMOS analog multiplexer.
With the DG408, it should be possible to create an simple 8 step sequencer... Combined with another one to a 16 step sequencer... But this would result in an other (much larger) DIY project... :nana:

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Post by Plugler » Sun Jan 06, 2019 6:34 pm

Here is my first draft of a schematic.

As attenuators: 50 K lin
Resistors for Gate Out: 1 K
R5 - R8 to limit CV Out to max. 10 V: 1 K 5%

What do you think? Will this work?

Image

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msboude
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Post by msboude » Mon Jan 07, 2019 2:46 pm

Off the top of my head, maybe throw a BC547 NPN transistor buffer in on each channel. Not sure if it will have enough current on it's own??


+12 on the collector

From each digital output -> use a 200k to 330k resistor to the base of each BC547.

From the emitter, use a 10k resistor to ground.

your outputs will come the junction of the emitter and the 10k resistor.

Make sense?

Image

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Post by msboude » Mon Jan 07, 2019 2:48 pm

you may need to up the value of the 10k resistor.. this is just off the top of my head.

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Post by Plugler » Tue Jan 08, 2019 12:15 pm

msboude wrote:Off the top of my head, maybe throw a BC547 NPN transistor buffer in on each channel. Not sure if it will have enough current on it's own??


+12 on the collector

From each digital output -> use a 200k to 330k resistor to the base of each BC547.

From the emitter, use a 10k resistor to ground.

your outputs will come the junction of the emitter and the 10k resistor.

Make sense?
I asked Mr. Doepfer, if my schematic will work and if a buffer is recommended. And if he plans a break out module for the A-151.

He answered (translated with Google Translate):

"Your thoughts are correct. At the undocumented "Digital Outputs" are the control signals (0 (+ 12V), with which the LEDs are also controlled.
Your circuit should work as it is. I do not think that buffering the CV outputs is necessary unless low-impedance loads are to be controlled. Normally, this does not happen within the module system and you probably set the voltages on the 50k potentiometers primarily by ear. Without buffering, the output voltage changes when the load changes (for example, if you pass the output voltage to a multiple and then patch a second load to it).

We do not plan a break-out module for the A-151."

So I will build the first version according to my schematic.
And for the first prototype, I use a 8HP blind panel and drill the holes myself.

At a later point (when everything works nice), I maybe will optimize the design of the frontplate and order one at schaeffer-ag.de.

But before, I will post pictures here. Maybe someone wants a frontpanel too. The more I order, the cheaper the single frontpanel becomes...

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Post by Navs » Tue Jan 08, 2019 3:39 pm

Well done and good luck :yay:

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Post by andybizarre » Sun Jan 20, 2019 1:01 pm

Plugler wrote: At a later point (when everything works nice), I maybe will optimize the design of the frontplate and order one at schaeffer-ag.de.

But before, I will post pictures here. Maybe someone wants a frontpanel too. The more I order, the cheaper the single frontpanel becomes...
Count me in, if you`re willing to sell me the complete build, I`ll have two!

Cheers & good luck

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Post by Plugler » Tue Feb 05, 2019 5:51 pm

andybizarre wrote:
Plugler wrote: At a later point (when everything works nice), I maybe will optimize the design of the frontplate and order one at schaeffer-ag.de.

But before, I will post pictures here. Maybe someone wants a frontpanel too. The more I order, the cheaper the single frontpanel becomes...
Count me in, if you`re willing to sell me the complete build, I`ll have two!

Cheers & good luck

Only a short update...

I plan to include a LED and a small on/of switch for the gate of every channel. The LED will show, if the channel is powered by the A-151. Not if gate is on/off.

After I got all parts (including original Doepfer Pots and knobs!) for my first version, today I've drilled my first prototype. But after inserting the first parts, I've immediatelly realized, that I have to position everything 2.25mm further up. Otherwise it will not fit between the rails. :doh:

In the next days, I will drill the optimized second one...
And use better drills. :confused:
As you can see, at one hole I had problems. Because the 7,0mm drill had some kind of unbalance. That was the first 7,0mm hole of 4 and at the other ones I've managed the handling better to compensate this.


Image


That is the layout of this version (v1.8):

Image


In the next version I will bring all the elements a little bit closer together...

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Post by electricanada » Tue Feb 05, 2019 7:57 pm

Great project! Please continue to keep us updated.
Eléctrica (electric) Nāda (the yoga of sound).

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artilect99
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Post by artilect99 » Mon Apr 29, 2019 10:22 pm

Just a thought -- you could use a 4-channel DC mixer, like the CGS one, to mix the CV outputs to one main out, then you would have a regular sequencer CV output for melody lines, etc.

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prephylve
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Re:

Post by prephylve » Mon Feb 22, 2021 6:32 pm

Any chance of an update on this? Really interested :) thanks for all of the hard work

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