Northern Light Modular - Dual CV Polymorpher Model 2OC

Discussing some incredible modules that don't quite fit into the other forum categories.

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Reese P. Dubin
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Post by Reese P. Dubin » Sat Apr 14, 2018 9:30 am

Synesthesia wrote:
Reese P. Dubin wrote:I found that this module does not fit exactly into SAModular boats. Anyone else experience this?
So, I haven't experienced this personally( even though I have a Samodular boat), but i know some people had to sand their tinnerman nuts.

no issue on Buchla or Samodular bot without tinnemans.
I will pull the tinnermans on that slot when my pal decides on a 'final' layout.

Hoping to be building all the other Northern Lights panels as they become DIYable.

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ArguZ
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Post by ArguZ » Sat Apr 14, 2018 4:02 pm

Yes, i can confirm that there are def. three versions of tinnermans...or more
Basically they all suck :P
he idea of using wood screws in a 20k $ rack does not fly with me.
I prefer boats with proper threaded nuts like Buchla USA is using and Steffen is also offering afaik.
The module fits perfectly fine into the boat, if you got a set of tins that add 1-2mm to the boats edge you might want to switch em.
I tried sanding them down and it is a hell of a work.
Boops sold boats with tinnermans that where level with the edge.

This is one of the reasons we pulled the modules and there will be no more kits of this exact model.
We designed the modules to work with original Buchla systems, but it seems the DIY crowd has some special needs that we could not anticipate.
Same thing with the +5V yes/no topic.
it is quite hard to foresee situations in a not very much regulated environment.

monokinetic
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Post by monokinetic » Mon May 14, 2018 4:01 am

Hi guys,
after a reasonable amount of testing of my DIY 20C from the kit I'm pretty sure the module is putting a bunch of digital noise on to my PSU lines. It seems to be related to the OLEDs. I've tested OLEDs from 2 sources now, always the same problem. I run a clone Buchla PSU, with CINCON DC/DC converters, but without separated analogue / digital grounds. That seems a moot point given that the 20C doesn't separate those.

Anyway, I noticed some discussion about this, and also that the card o_c schematic has 10uH filters / 470uF capacitors on the power going to the OLED. My plan is to retro fit something similar to my OLEDs. Do you think that's worth it? And if so, would you recommend some part numbers for those parts please?

Thanks

David

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ArguZ
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Post by ArguZ » Mon May 14, 2018 5:03 am

Yeah, the caps totally help.
When we built them we added one 470uF cap to the 3,3v power and ground pin between Teensy and OLED.
The inductor was another attempt, the main problem is that the OLED is actually getting power through the data lines as well and nothing really cures it 100%.
On top of that some newer Easel PSUs simply reject booting the Teensy when the cap is installed, but in a big rack there is enough power.
What i found out that helped most is to move the 2OC to the central power board and the mixer far away from it.
The 291e and the iProgram card have similar issues, and also there the position seemed to solve most of the noise.

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Post by monokinetic » Tue May 15, 2018 12:06 pm

Hey Arguz,
thanks for the (continuing) support!

Shame that this is problematic. It makes me wonder a few things:

would a software update that enables us to turn off the screen, rather than have the screen savers running, reduce the noise? i.e. is it related to constantly drawing to the OLED?

have you tested on a PSU with a noisy separated ground? I'm considering jury rigging something on my PSU based on rf's publicly released design (big uH filter between basically) and connecting the ground from the 20C to a noisy ground. Just wondering if you think that would be of any use before I solder that up :)

Cheers

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ArguZ
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Post by ArguZ » Wed May 16, 2018 3:22 am

I have even built one unit with the OLED being driven by its own PSU
Actually with a battery at first.
Then one with the OLED ground isolated to NGND , no change.
Its the nature of the OLEd in general that it leads noise to this kind of system.
Almost like ever module builds up a ground loop and the more you have the worse it gets.

Basically i tried all the fixed discussed here:
https://forum.mutable-instruments.net/t ... se/3458/47
Did you try moving it to the central board yet ?
That was the best thing i could do to it after all sorts of experiences.
And the filter cap mod of course.

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cygmu
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Post by cygmu » Wed May 16, 2018 6:09 am

Sascha, it sounds like you have tried a lot of things to quieten this down. Did you happen to try a filter made of a ferrite bead and capacitor, rather than inductor / capacitor? I don't have a good reason to believe that this would work other than that it is what is commonly done to suppress high frequency noise, so it could be a waste of time but I wondered if you'd tried.

Mutable designs (e.g. Peaks) have an arrangement like that to separate the 3V3 which powers the STM from the "analog" 3V3 reference. Olivier specifies a bead with 2200Ohm impedance at 100MHz which I think lets him get away with a smaller capacitor, which might give the power supplies an easier time and avoid the boot issues you mentioned -- 470uF is quite a bit of capacitance to add.

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ArguZ
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Post by ArguZ » Wed May 16, 2018 7:00 am

Yes, and we also tried a resistor instead of the inductor...
Same or no effect.
Like i said, the problem is that the OLEd is getting power also through the data lines.
Try it, cut ground or power , it will still work...
The 3,3V is actually being generated by the Teensy, it does not sit on the 3,3A.

I incorporated most of the enhancements in the 2TT design, and also a possible re-launch of the 2OC
Right now the best is to add two 470uF caps and move the module closer to the power board.

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cygmu
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Post by cygmu » Wed May 16, 2018 7:56 am

Argh, how annoying.

Have people had issues along these lines with the Euro O&C? I've searched a bit but not found any. I did find plenty of stuff about using OLEDs on a Shruthi being problematic, and the best fix was exactly as you suggest, fairly large caps.

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pickleinn
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Post by pickleinn » Wed May 16, 2018 10:53 pm

cygmu wrote:Argh, how annoying.

Have people had issues along these lines with the Euro O&C? I've searched a bit but not found any. I did find plenty of stuff about using OLEDs on a Shruthi being problematic, and the best fix was exactly as you suggest, fairly large caps.
I have a 2oc I built in my center row and don't notice any noise. What should I listen for to see if I just got lucky or didn't notice.

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ArguZ
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Post by ArguZ » Thu May 17, 2018 2:25 am

Tja, exactly...
The problem is not the OLED itself.
It is the Mixer...or better the last piece in the audio chain .
I had a 207r in mine, had the 2OC up top, no noise.
I had a bit of back and forth with other e users about the phenomenon and one had the noise only in one system.
We tested all sorts of things, changing the ground of the rack etc.
Then i swapped my 207 out for a 206e and the trouble started.
I actually have the same kind of switching noise with my brand new 291e, and the iProgram card if driven on the same rail inside the rack.
So it is defacto not so trivial just adding a coil or cap.
Especially when hunting ghosts ;)

monokinetic
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Post by monokinetic » Fri May 18, 2018 8:08 am

Thanks for the insights. FWIW the signal chain I noticed the noise in the most was a simple
patch going 20C quantizer output to 258j 1/v oct input. Then 258j variable waveform out 292r, and that out to 207r.

Anyway I moved the 20C to the central boat with the Cincons actually on the PSU PCB. It improved things noticeably. So no need to unsolder to 20C to fit caps, phew :)

Cheers guys!

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ArguZ
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Post by ArguZ » Fri May 18, 2018 8:58 am

Oh, there is no unsoldering needed actually.
We retrofit them just on the backside in between the Teensies .
Let me find a picture , its a 5 min operation.

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beautyofdecay_
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Post by beautyofdecay_ » Sun Jun 10, 2018 4:07 pm

So the 470u capacitor should go in parallel to C24 and C39 (470n)? Like shown in orange in the schematic below?

Image

That is between pin 1 and 2 of the OLED header. Looking from the component side of the PCB these are the 2 rightmost pins.

Image

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ArguZ
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Post by ArguZ » Mon Jun 11, 2018 3:10 am

That is correct.

here is a picture

Image


The big caps prevent most of the OLEDs noise, but they will also but stress on the PSU.
This mod for example does not work well in a BEMI Easel case with the 500mAH PSU.
It will simple not start and stay black until the cap is charged enough.

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beautyofdecay_
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Post by beautyofdecay_ » Mon Jun 11, 2018 5:34 am

Thanks!

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d.simon
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Post by d.simon » Mon Jun 18, 2018 2:01 am

I probably don't understand something, but what about optoisolator on data lines?

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pathein
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Post by pathein » Sun Jul 15, 2018 12:44 am

i have just fnished with a diy build of the 2OC and wondering if the ground wire on the pcb should be connected to noisy or quiet ground pin on the power connector?

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ArguZ
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Post by ArguZ » Fri May 17, 2019 4:24 am

Totally the NGND.
But that requires that your bus power has a strong NGND line.
In older boards that line seems to be underwhelming, leaving people with leaking 292s, mixers and bleeding Oscis.

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