Another modified Ambika SMR-4 voice card

@Bjarne How do you like your modified SMR4 so far? I enjoyed the sound samples.

@matrix12x Thanks, I like my modified SMR4x cards quite a lot so far. Admittedly, I haven’t actually been playing that much with them, and I only have three of them ready. The 4LP with boosted resonance is much preferable for resonant bass duty. For shiny pads, the attenuated low-end of the original 4LP is nice, so it’s a good thing that option is still available. The 2LP is nice, but maybe a bit too polished for my taste, so I might modify the resonance compensation on that one.


I know it’s been a while but, I just ordered some of the modified PCB’s. Finally going to get around to the build. I’ll let you know how it goes (hopefully in less than a couple of years this time).

Nice, I find DIY should be enjoyed, not rushed :slight_smile:

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Where did you order your boards from?

Packaged and submitted the Gerber files from Eagle.

Ok thank you.

Boards showed up today :slight_smile:


It looks great, I am struggling to convert the .brd file to gerbers, i seem to lose the silkscreens, could you share your gerber zip?

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Here’s the gerbers I made (I downloaded them from my PCBway account to be sure).

If I remember correctly the silk screen was on an odd layer. (213.2 KB)

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Many thanks, I’ll get them ordered this evening.

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I’m ordering some parts to populate these boards.
Since the Pharmasonic GitHub is gone (I never saw it) I just examined your schematic to check out the new parts you added.

From what I can see in the schematic, new parts in excluding the original parts are as follows:

2 x 2N7000
1 x 220n (0.22uF) Radial Capacitor
2 x 33k 1/4w resistors
1 x 4052N
1 x 50k potentiometer
2 x 100nF bypass radial capacitors

Anything I’m missing?

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That seems about right

Edit: actually you need an 1k resistor for the modified board with working resonance boost



Awesome! I have some spare 1k resistors laying around.

BOM x6 ordered :smiley:

Any special firmware changes I need to be aware of for for the YAM firmware to use this modded PCB?

Finally almost done with my Mutable Instruments Bjarnebika!

Ha ha,

That’s great. You won’t need any special firmware to support the hardware changes, but I’d of course recommend the latest YAM :slight_smile:

And remember to cut the traces on the pcb’s before you start soldering the IC’s if you want the proper resonance boost modification as described a couple of posts up in this thread.


Well it wouldn’t be a Bjarnebika without YAM :slight_smile:

Thanks for the PCB cut reminder, YAM, and the SMR-4X!

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What happens when you have PCB’s lying around waiting for parts to arrive?


Parts showed up. I was able to squeeze in some soldering between things today.

This is all I was able to get done today.

Ordered the wrong 4052’s :confused:

Now I have to wait until Monday for the correct ones.
Somehow I ordered CD74HC4052E’s
Instead of CD4052BE’s :man_facepalming:
Whoops :grimacing:

I literally did the same thing. I ordered 74HC4052’s on accident this week for a SMR-4 board I was building. it got super hot when I plugged it in. I could swear I ordered CD4052’s though.

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New 4052’s arrived!
All I have left to do is tune the V/OCT, Filter Cutoff, and put the lid on it :slight_smile: