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General Serge power supply/distribution
MUFF WIGGLER Forum Index -> Buchla, EMS & Serge  
Author General Serge power supply/distribution
flx
After the great feedback from my previous "Interested in Serge" thread and doing some more research I bought a reasonably priced, used Best of CGS panel set (BOG, SWAMP, MARSH + power) to get the full 4U Banana Serge experience applause

The first thing I noticed was severe VCO instability on the BOG. I was told that LFO bleed usually is the culprit (it is, but not alone in my situation). Then I noticed that I get severe bleed from the SWAMP's Digital Noise into the BOG as well. And then I finally realized that the power supply is defective. So I'll have that fixed or replaced.

In the meantime I connected a Eurorack power supply to power just the BOG. The VCOs are more stable now, but the LFOs still do bleed into them enough to make tuning impossible. When I connect the SWAMP too, the Digital Noise also bleeds again and everything just warbles around.

Possible solutions I was presented with were:
- Don't connect the VCOs to distribution boards but feed them directly from the PSU (I will try that)
- Use shielded wiring (that would be a lot of work now, as nothing uses shielded wires inside the BOG)
- Don't braid wires (all the power wires in the BOG are braided and others are ziptied together, it's all looking very nice and tidy cry)

Coming from Eurorack and a little 5U, this seems really crazy. I know that those systems can have issues with bleed as well, but with the many different PSUs and distribution systems I've used so far, I've never had any issues.

Do I just have a subpar Serge build or is this normal and nobody really talks too much about it?


Sorry for the ranting ... I thought that getting into Serge would be easier, with my extensive Eurorack knowledge and some DIY experience. It's very hard to find any information, probably because everybody just builds their own thing and it's such a tiny market?



EDIT:
From further down the thread

flx wrote:
Thanks a lot for the replies, everyone! we're not worthy

I rewired my Eurorack PSU (making sure to connect ground to 0V this time), rewired the distribution board, untangled the power cables inside the BOG, cut some zip ties and rearranged the power distribution in there as well. Lo and behold: it's working now!!!
SlayerBadger! screaming goo yo w00t applause


Got solid pitch on the VCOs, DUSGs and LFOs, very little bleed (that I can totally live with) and no interference from the SWAMP's random module any more either. I can't believe it!



flx wrote:
Just an FYI, because I haven't found a good answer on Google regarding how much mA the Serge panels consume. I measured mine with a multimeter and came to the following results, which I rounded up to the next 10mA.

CGS BOG Panel:
+12V 230mA
-12V 190mA

CGS MARSH Panel:
+12V 200mA
-12V 160mA

CGS SWAMP Panel: (with almost all LEDs lit)
+12V 250mA
-12V 40mA

Total power consumption of all three Best of CGS Serge boats:
+12V 680 mA
-12V 390 mA

Of course, those values depend on how the panels are actually built and are not universally applicable to others.

For me this means that the big and heavy power supply which I bought with the panels (and which I will have repaired soon hopefully), is really not necessary and I might just get another one of those Meanwell RT-65B PSUs for less than 30€ which I'm currently using. I haven't had any issues with this one and it provides +12V 2.8A and -12V 0.5A.
BugBrand
My quick guess would be a combination:
- poor PSU - what design is it?
- poor power distribution & solid 0V
- lack of v-refs in the VCO design
drip.feed
The BOG is known for this fault. The CGS LFO design injects current fluctuations into the power lines.

(1) Some builders live with it.
(2) Others use two power inlets to 'solve' the problem (the VCOs get their power from one inlet, everything else gets powered from the other inlet).

I 'solved' the problem by taking the 2nd approach, but using a single power inlet and splitting the power lines inside the boat. The VCOs are powered from one line, everything else is powered from the other line. I used thick cables for power (probably 16 gauge, maybe thicker). The bleed is almost unnoticeable.

EDIT: if you decide to go with dedicated VCO power, and your BOG uses those long, thin CGS power rail PCBs, then you will need to physically cut the 3 power rail tracks on the PCB to ensure that the VCOs are definitely isolated from the other modules.

And yes, don't zip-tie wires together - leave them loose and live with the mess. As someone else said hereabouts, loose wiring is quiet wiring. Braided power wires are okay.
revtor
Definitely not a “Serge” thing. My 3 STS panels have no bleed or instability issues.
drip.feed
revtor wrote:
Definitely not a “Serge” thing. My 3 STS panels have no bleed or instability issues.

Not, it's not a Serge thing. It is down to the design of some CGS modules and the abilities of each builder to eradicate problems as they show up. Ken Stone is very good at offering help but, in fairness, his CGS module build notes assume a goodly level of synth DIY experience.
GenusModu
The bleed is from the long wires in the power distribution and less than optimal VCO design. As drip.feed said, route separate power wires from VCOs to the power source. It is the IR (current-resistance) drop across the shared power lines causing the issue. Braiding or bundling power wire will cause very little bleed.

I have a video on this issue on youtube, oriented towards eurorack systems but applicable for any modular power set up.

https://www.youtube.com/watch?v=v1n94KSwZPY
flx
Thanks a lot for the replies, everyone! we're not worthy

I rewired my Eurorack PSU (making sure to connect ground to 0V this time), rewired the distribution board, untangled the power cables inside the BOG, cut some zip ties and rearranged the power distribution in there as well. Lo and behold: it's working now!!!
SlayerBadger! screaming goo yo w00t applause


Got solid pitch on the VCOs, DUSGs and LFOs, very little bleed (that I can totally live with) and no interference from the SWAMP's random module any more either. I can't believe it!


Here's my first Serge Modular Synth music ever:

https://www.youtube.com/watch?v=qZRdJBC5KRg
drip.feed
Rockin' Banana!
Graham Hinton
Serge power distribution leaves a lot to be desired, but it is not hard to improve. Shorten the long wires and remove pcb distribution, then fit a central busbar distribution and ground the 0V busbar. If used with other systems connect the 0Vs with Dinse connectors, the use of a banana jack on a PSU for this purpose should be deprecated.

revtor
Nice patch!! Glad to hear you got it straightened out!
cygmu
What a thread! It started out seeming like a slightly sad story of a poorly built BOG/SWAMP that was going to be trouble and finished up with everything working, that great video from Felix, and Graham's amazing picture of probably the best specified Serge power supply and distribution that has ever been constructed.
drip.feed
Pics of Graham’s power solutions will improve any thread.
the bad producer
Video made me think of this It's peanut butter jelly time!

flx
Graham Hinton wrote:
Serge power distribution leaves a lot to be desired, but it is not hard to improve. Shorten the long wires and remove pcb distribution, then fit a central busbar distribution and ground the 0V busbar. If used with other systems connect the 0Vs with Dinse connectors, the use of a banana jack on a PSU for this purpose should be deprecated.

Thank you, Graham. I read a lot of your previous posts in the past couple of days (a suggestion by the bad producer) and it has been really enlightening we're not worthy That power distribution looks amazing!
Graham Hinton
flx wrote:

I read a lot of your previous posts in the past couple of days (a suggestion by the bad producer) and it has been really enlightening we're not worthy That power distribution looks amazing!


Well you seem to have worked out most of it on your own, well done! Most modular systems have been plagued by power distribution problems since the first Moog modular.

You mentioned some LFO bleedthrough. Check that the LFO is not sharing a power cable with another module, if it is try to separate them.

If you can hear any crosstalk at all it needs to be reduced by about 20dB and that means identifying the wiring where it occurs and decreasing its resistance by a factor of ten. You can't get enough copper on pcbs to achieve that which is why you see the large busbars. This is quite a simple solution, it just doesn't lend itself to being sold in cardboard boxes by retailers.

The Serge system in the picture belongs in Darkest Avalon studio where it has Buchla, Wiard, Euro and Emu systems for company. All are connected together with a ZeroVolt busbar which provides a common reference so that they may all be freely crosspatched. Before that went in nothing could be crosspatched without ac hum modulation and half the Serge system was powered from a Power One that you could hear buzzing the other side of the room.
flx
Just an FYI, because I haven't found a good answer on Google regarding how much mA the Serge panels consume. I measured mine with a multimeter and came to the following results, which I rounded up to the next 10mA.

CGS BOG Panel:
+12V 230mA
-12V 190mA

CGS MARSH Panel:
+12V 200mA
-12V 160mA

CGS SWAMP Panel: (with almost all LEDs lit)
+12V 250mA
-12V 40mA

Total power consumption of all three Best of CGS Serge boats:
+12V 680 mA
-12V 390 mA

Of course, those values depend on how the panels are actually built and are not universally applicable to others.

For me this means that the big and heavy power supply which I bought with the panels (and which I will have repaired soon hopefully), is really not necessary and I might just get another one of those Meanwell RT-65B PSUs for less than 30€ which I'm currently using. I haven't had any issues with this one and it provides +12V 2.8A and -12V 0.5A.


EDIT:
And another Serge Jam:

https://www.youtube.com/watch?v=dzPd4YCII4E&list=PLa9Em_H8Xs_YW5V2tt41 55Zpe84SHDshG&index=3
flx
Another update, for anyone who's interested wink

I built myself some 19" rack ears from a 5€ aluminum L profile today. Not my best DIY job, but it works for now. I also installed a Meanwell RT-65B PSU which I mentioned above and which still does its job without issues.

Here are some pictures Mr. Green

Sawing metal:


Testing if the drilled holes fit the 19" rails:


Power supply and bus board:


All done:



Here's a link to my thread about my IKEA PAX synth wardrobe by the way:
https://www.muffwiggler.com/forum/viewtopic.php?t=183139&highlight=
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