[Build Thread] MFOS 12 Channel Vocoder

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Bodo1967
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[Build Thread] MFOS 12 Channel Vocoder

Post by Bodo1967 » Mon Mar 27, 2017 8:12 am

Hi,

I just started building the MFOS vocoder so I figured we might as well have some documentation, pics etc.

The pcb arrived last week, they are now black instead of green :):

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I just started the usual way - small parts first. It doesn't look like much yet, but there's already about 100 resistors on the pcb:

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I just went the "first use what you have at home anyway, then double check with the BOM and order what you need" route.

In the meantime (pics will follow), most of the resistors are on the pcb, except for 28 (or so) 10 kOhm, which are on their way, and a few of the less common values such as 160 kOhm or 1.2 MOhm, which I have to order since I don't have these values in stock.

I'm using 1 % metal film reistors throughout.

The diodes are all on the pcb as well - I used 1N4148 instead of 1N914 since I had them, and never encountered any problems in previous projects when using the 4148 instead of a 914.

And yesterday I soldered all but one (since I was short of one DIP 14 socket :hihi: :ripbanana: ) IC sockets.

That's it for now, more to come soon :D.
... why buy it for $100 when you can build it yourself for $150?

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Post by frankaponte » Mon Mar 27, 2017 8:54 pm

This one has been on my list for a while. Excited to see the process.
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Post by Bodo1967 » Sun Apr 02, 2017 3:21 pm

Some progress with the Vocoder.

Most resistors (what I had at home, there's only a few missing now), all diodes and all IC sockets are on the board:

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Then I did the 100 nF caps. 86 of them :).

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Some more caps, and 11 of the 17 transistors - as I said, what I had lying around.

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That's it for today :). I just ordered the remaining parts so hopefully I can continue soon.

I also hope to get my Jasper synth finished within the next few weeks, and I am building a self-designed keyboard for my TTSH, which will include outputs two LFOs, portamento/glide, and a pitch bend wheel (it's not the 3620). I tested the LFOs today, and they work great, just need a little calibration concerning the sine shape. I think I will present it (including build pics) when it's finished.
Last edited by Bodo1967 on Tue Nov 21, 2017 8:06 am, edited 1 time in total.
... why buy it for $100 when you can build it yourself for $150?

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Post by Bodo1967 » Fri Apr 07, 2017 3:48 pm

I received the rest of the parts today and found the time to solder them in...

All resistors and transistors are now on the board:

Image

Trimmer pots came next:

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Then the remaining caps - the green ones are the 5 % film caps:

Image

Image

Image

Image

The next things to do...

* design and build a case
* design and make a panel
* put the ICs into their sockets
* connect the panel mounted parts
* test and calibrate
... why buy it for $100 when you can build it yourself for $150?

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Post by frankaponte » Mon Apr 10, 2017 8:35 pm

Looking good, thanks for the update.

-Frank
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Post by Bodo1967 » Thu Apr 20, 2017 3:09 pm

Case building is mostly finished by now. It'll be a desktop unit, not a 19 inch rack device. I just so managed to cram the 10 pots, 3 jacks and 3 switches on the front panel. The layout print is still attached to it, but the aluminum panel is ready* and has all required holes drilled in it.

* I'll print the layout on transparent self-adhesive inkjet foil, cover it with varnish spray, and attach it to the sheet aluminum. This has proven to work out well (I made the front panel of the MFOS synth on my avatar pic in the same way).

Image

The cover plate and the 'frame' for the aluminum panel are also ready, the paint is drying just now. These will not be glued but mounted with a few screws for better access.
... why buy it for $100 when you can build it yourself for $150?

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Post by Bodo1967 » Mon May 01, 2017 7:56 am

The enclosure is now ready for the final assembly (the casing itself is glued, the cover and the font panel in its 'frame' will be mouted with some screws after the pcb & psu are installed inside.

Image

The next things to do (updated)...

[done] design and build a case
[done] design and make a panel
* put the ICs into their sockets
* connect the panel mounted parts
* test and calibrate
... why buy it for $100 when you can build it yourself for $150?

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Post by Bodo1967 » Thu May 11, 2017 1:57 am

I have now started wiring the front panel.

Preparing the shielded wire according to Ray's instructions on the MFOS site. The green wire will be connected to ground on the panel side.

Image

About half of it is done now, hope I can do the rest tomorrow or on the weekend.

Image

Image

The PSU is firmly mounted and tested to my satisfaction.
... why buy it for $100 when you can build it yourself for $150?

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Post by synthcube » Thu May 11, 2017 8:22 am

fantastic! thank you for posting!

for anyone interested in the mundane business of producing pcbs, the original stock of Ray's PCBs that we acquired are GREEN while new runs of the PCBs (when the legacy stock is sold out) are BLACK- like outer space, get it?

The Vocoder was one of the first designs to reequire a new run of PCBS, hence the black color.
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Post by Bodo1967 » Fri May 12, 2017 3:36 pm

Bodo1967 wrote:I have now started wiring the front panel. [...]

About half of it is done now, hope I can do the rest tomorrow or on the weekend.

Did the rest today. Wire bundle for the mic/line level switches located at the intrument and control inputs:

Image

And that's how it looks now:

Image

The next things to do (updated)...

[done] design and build a case
[done] design and make a panel
* put the ICs into their sockets
[done] connect the panel mounted parts/panel side
* connect the panel mounted parts/pcb side
* test and calibrate
... why buy it for $100 when you can build it yourself for $150?

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Post by Bodo1967 » Sun May 14, 2017 3:03 pm

S'more, I more or less finished the build - hopefully! - yesterday and today.

Connected the front panel wires to the pcb:

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An overview of the panel and the pcb, wiring finished:

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PSU connected, pcb mounted in the enclosure, and ICs placed in their sockets:

Image

Image

The next things to do (updated)...

[done] design and build a case
[done] design and make a panel
[done] put the ICs into their sockets
[done] connect the panel mounted parts/panel side
[done] connect the panel mounted parts/pcb side
* test and calibrate
* put knobs on the pots
* put cover on
... why buy it for $100 when you can build it yourself for $150?

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Post by Bodo1967 » Mon Jul 03, 2017 3:52 am

Well then...
Bodo1967 wrote:The next things to do (updated)...
* test and calibrate
* put knobs on the pots
* put cover on
I calibrated and tested the vocoder on Saturday - just had one minor issue (pulse width ofthe internal oscillator was about 15 % or so, and changed only very little when turning the knob. Desoldered the pot, made sure I had the correct value installed (which was the case), soldered it back in... dan then it worked :D. Probably some bad solder point, whatever :despair: .

Anyway, it's now in my music room where it belongs :D.

This is how it looks with the knobs (the cover is of course now on top, while the vocoder is still open on this pic):

Image
... why buy it for $100 when you can build it yourself for $150?

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Post by synthcube » Mon Jul 03, 2017 11:47 am

lovely!
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Post by Eric the Red » Thu May 24, 2018 8:10 am

Damn!! That looks awesome!
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MFOS Vocoder bild

Post by Moogmad » Sun Jun 23, 2019 6:04 am

Here's my take on the MFOS Vocoder.

I've added the 12 band level pots and an additional board to give a LED level indication for all 12 bands plus the audio and control signals.

This is based on the YuSynth mixer level indicator circuit (x14). Gives a nice visual representation of what's going on inside the box.

As you can see the wiring is bit of a nightmare so I used thin audio coax for all of the connections to the front panel.

Image


Image

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Post by synthcube » Sun Jun 23, 2019 9:21 am

that is beautiful. Your wiring is magnificent!
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Post by Moogmad » Sun Jun 23, 2019 9:39 am

Thanks for he compliment. I'm pleased with the result. It works pretty good too.

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Post by Kevin Mitchell » Fri Jul 12, 2019 3:41 pm

Very impressive, Moogmad! I've been considering building one of these myself. Your mod with the mixer circuit is brilliant and a must have!

You've certainly aced this one :party:

-KM

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Post by The_hitcher » Mon Aug 26, 2019 8:50 am

Having just completed some tiny little boards for my first couple projects. This looks insane. How many hours are we talking here? I guess the bigger boards might be easier to work with rather than the tiny little projects I was putting together?

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Post by Bodo1967 » Wed Aug 28, 2019 5:03 am

The_hitcher wrote:Having just completed some tiny little boards for my first couple projects. This looks insane. How many hours are we talking here?
I don't know precisely how long I took (I don't keep a log of my soldering time :hihi: ) but I think the PCB itself can be populated within maybe 3 - 5 hours or so. The build itself is pretty straightforward. The wiring, however, needs some attention due to using shielded wire (which is, of course, a little less convenient to handle than the "thin" stranded wire).

There is one issue though which I couldn't resolve - the VCA always stays open a little if the control/voice input is set to "mic" (in other words, there's some carrier bleedthrough). It's not a big deal to me since I use a microphone preamp anyway and set the input to "line", which makes it disappear.
This issue has also been addressed in the Electro-Music forums.
The_hitcher wrote:I guess the bigger boards might be easier to work with rather than the tiny little projects I was putting together?
The parts are all THT, so there's no fiddling with ever-so-tiny SMD parts whatsoever :D.
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Post by The_hitcher » Thu Aug 29, 2019 9:50 am

Electro-Music, eh? Great bunch of guys. I went to their festival a few times. Off-topic I guess. Anyway build looks great. Someday I'll get to that level.

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