strophlex

I feed 12V DC into my MB6582 where it's supposed to have 9V AC. The voltage goes through the rectifying bridge (loose some voltage) smoothing caps (no change) and finally through regulator (regulated down to 9V). It works fine and doesn't seem to generate much neat (actually I think it generates less heat than the standard 9V AC way). One thing I am thinking about though is if the dc cable is more prone to pick up noise than an ac ditto. Edit: Changed a misplaced DC to AC.

Yes, 2A for 7,5V but just 0,625A for the 12V rails. The same transformer is used for both + and - 12V. @technobreath: I didn't write the wiki entry, just used the design. I added some diodes to the output part to protect against reverse voltages. @m00dawg: I will provide some pictures. THe base board is not fitted in the box. The synth is in a P-10 enclosure. The 1U box contains PSU and expansion stuff. It is very crowded...

I made this one: http://www.midibox.org/dokuwiki/doku.php?id=bipolar_12v_psu&s[]=psu and then a separate 5V psu. Used these transformers: https://www.elfa.se/elfa3~eu_en/elfa/init.do?item=56-200-67&toc=0 https://www.elfa.se/elfa3~eu_en/elfa/init.do?item=56-200-26&toc=0 They are very small and neat. I fit the PSU, 4xAOUT_NG, 4xSSM2044 and 2xSSM2164 in a 1U rack unit. It is not 100% finnished yet though, but I have verified the PSU.

:thumbsup:

These look nice, hope they will be cheap...

I would say you would be safe with 2A on the 5V and 0.5A on the 9V/12V. I am building a PSU now and I use a 15VA 7.5V transformer (2A) for the 5V and a 15VA +12V/-12V center tap transformer (0.625A) for the 9V and it works. Right now I have some noise in the audio, but I don't think it is because the transformers are too small.

I guess I might have ground loops. And I think they might come from the connections between my MB6582 and the filter box. The filter box contains PSU, AOUT_NG modules, SSM2044 modules and SSM2164 modules. Connections between the box and the MB6582 are: PSU - (+12V, +5V and GND) Expansion port - (link to AOUT_NG, 3 wires (GND and +5V omitted to avoid loops) and one digital out for bypass relay. Audio - Audio jacks out from MB6582 connected to audio jacks in to the box (L, R, GND) So there is a separate ground for each audio channel in addition to the PSU GND. Should I just cut the GND for the audio connection? The same question arrises for the CV connections. GND is connected once more for each CV in addition to the power supply GND.

Really nice! Is this without any analog filters connected?

What are the best ways to avoid that hum and other noises get into the audio signal path? I am building a box with filters (SSM2044) in it and I have realized both the cables connecting input and the cables connecting output pick up noise. I am using standard hook up whire with left signal, right signal and gnd twisted. Would it be better to use a shielded cable and send gnd through the shield? Any other tips?

Thanks for the update.

How is it going? :whistle:

I adjusted P3 to get 1.43 k ohm between pin 3 of LM13700 and gnd. I adjusted P4 to get 1.43 k ohm between pin 14 of LM13700 and gnd. Then I adjuseted P1 to get 26.8 k ohm between pin 1 and pin 11 of LM13700. That meant turning it all the way counterclockwise. Then I adjuseted P2 to get 26.8 k ohm between pin 16 and pin 11 of LM13700. That meant turning it all the way counterclockwise. I adusted P3 and P4 a bit more to get a bit more resonace, ended up at 1.46 k ohm I think. Now my relays start to die off... EDIT: It seems like it is my crimpings that die off. Hope the relays are OK.

Yes! I got some oscillation!!! I didn't expect the callibration to be that tricky, guess I was impatient. Thanks for all your help Imp! :flowers:

The highest voltage I manage to get out of my aout_ng or rather into my ssm2044 is 11.12 V. This gives pin 2 of the SSM2044 a voltage of 0.84V. The lowest voltage is of course 0 V and that gives a -5.18 on the SSM2044. It seems I don't get enough amplification... The power supply should be close enough to 12 V (-12.15 / +11.85). Now that I look at the numbers from my previous post it looks like I made things worse, but I didn't check them carefully before, so I guess they are about the same...

Thanks Imp! Since I know your setup works, now I have something to go on. I think the jumpy voltages might have to do with linear expnential convertion of some cv... Anyway it seems strange to me with all the negative voltages, but it your work, then I guess it is right... I will try with some more juce from the aout...

I want two of those too!

I had a look at the schematic and the SMM2044 datasheet. The datasheet says: "The sense of the Q control is from GND up with minimum resonance at GND." Now, when I measure the voltage at pin 2 of my SMM2044s I get a reading of about -7 to 1 V or -5 to .5 V depending on trimmer setting max / min. It doesn't look right to me. The control voltage into the board is from 0 to 10.6 V which should be right for Q. I don't understand how the LM13700 cirquit works but I guess there is something wrong in there somewhere... Also I have tried another board. Behaves the same.

I am using exactly the same caps as seppoman so I doubt that is the reason, at least not for me...

Did you get this sorted? I have the same problem...

Finally built and tested this with a 7.5V trafo. 15VA. It works nicely, but the regulator gets pretty hot. I use a big heat sink from an ATX PSU.

:flowers:

I could do the mouser / digikey stuff but swedish taxes would make them more expensive than necessary...

Sounds awesome! I am so very in! My 9090 really wants to get out of its recycled VCR case with masonite panel. I saw TwinX offered to run a PCB bulk order. Maybe he is still in.

Nice to hear Sasha! I am definitely interested in a set of the pcbs if there will be a bulk order. Anyone more than me that would be in for panel and case for 9090 with this sequencer?