Jump to content

midibox SID rack 1U project [completed]


Recommended Posts


As i said in an other message, my original plan was simply to put my old SID V1 back to life.
I wanted to put it in a RACK 1U because i have too many little boxes everywhere around here.
Very quickly i decided to upgrade the PIC and add a second SID to have a stereo V2.

Then the project has grown. Here is the current status...

The rack front panel (screenshot from front panel designer) :


The knobs will be pots. I played a little with one pot on my mockup and it's very fun to control parameters with them.


The 2 surface control PCBs : 
(They include the 74hc595 and 165 so they can directly be plugged on J8/J9 on core)




And the most ambitious one :



This is a Core + 2 SID on 10x10cm PCB + CAN (diode & resistor) + 4 mem chips.
(With one jumper and 2 wires it's possible to use the 4 other 24LC512 of another PCB in adition to the main local 4.)
One of the goal is to easily link up to 4 PCBs like this as SID v2 allows.

I'll double check the PCBs and will order them.
So there will be some time before the next update.

I'll make all the files of this project available when it's finished. PCB are made with Kicad.

Thanks Thorsten for documenting so well everthing,



Edited by Ixox
Link to comment
Share on other sites

Cool boards! For the Core+SID, maybe check a few clearances:

  • bottom left mounting hole + J5 header (header may be more convenient as a 2*5, or even 2* 2*5 as is done in the Core8. But I see there's not much space)
  • LCD and CAN headers
  • trimmer pot on the left might be too close to the board edge, normally they don't like holes/plating near to the the milling cutter. (Shouldn't there be two pots, one for brightness and one for contrast?)

I would put the voltage regulators at the edge of the board, this way they're easier to heatsink if needed and they radiate heat away from the SIDs/capacitors etc. 

Is there a reason for two bridge rectifiers?

Have you thought about the grounding scheme around the SIDs? I know the MB-6582 board has a gap in the ground plane, presumably to keep the digital noise off the audio circuits. 

You can check the sammichSID layout for inspiration, although it's a little bigger than your 10*10cm.


  • Like 1
Link to comment
Share on other sites

Hey, thanks a lot for the feedback.

. Good idea to modify J5, specially to ground the useless analog entry. I'll do that.
. LCD and CAN  : I use simple female to female wire so there's no need to much space around the connector. Should work like this.
. Trimmer pot too close to the board edge ? Yes right :)
. I removed the brightness pot. Too many components, in adition the original one does not work on the LCD i have. On this PCB : simple GND/VCC + resistor for the LCD LED.
. voltage regulators would be better elsewhere. Yes. Not sure i'll modify that, too time consuming ;)
. Two bridge rectifiers because the idea is to feed it with 2 transformers:  one 6V and one 9V. There's a jumper though to short both power input after the bridge rectifier for eventually feed the 7805 and 7809 with a unique 9V only source.
. It would be great to have a ground zone around the SIDs. Does it include all SID GND pins ? Do you have any detail about that ? (EDITED : just realized there is only one GND pin on the SID !)

10x10 cm was a major constraint to get cheap PCBs from elecrow.com ;)

Thanks again :)


Edited by Ixox
Link to comment
Share on other sites

I would consider moving the group of traces on the right hand side away from the edge of the board. Also the trace width seems kind of small? 6mil? I would go with 10mil minimum, but use 16mil if possible. Power traces even thicker.

You can save a few header pins (and slightly move apart) the Banksticks by "preconfiguring" them with address pins connected to ground or +5V.

Link to comment
Share on other sites

OK will be easy to move the right group of track to the left. There's space. thanks :)

Trace widths is 8mil. It's Kicad default.
That's what i used for the preenfm2 PCB it works well.
I may make them wider for the analog part though.

Power trace width are 16.

Yes the four banksticks can be 1234 or 5678 depending of mem_sel switch in the top left which sets 24LC512 A2 pin to GND or 5V.
They are not by default connected to pic. Need 2 jumpers P4=>P3. Top left.

Master PCB/PIC : P4=>P3 shorted. Bankstick set to 1234. And the 2 left pins of P3 connected to the first salve PCB P3.
Slave PCB/PIC #1 : P4=>P3 free. Bankstick set to 5678. And P3 connected to the master P3. Banksticks on this PCB are so seen by the master PIC only.

Like this the Master PIC see 8 banksticks.



Edited by Ixox
Link to comment
Share on other sites

I've ordered the PCBs with this aditional one :



This will mix all SID's voices to the main right and left jacks.
Pluging individual SID2, 3 or 4 jack will remove them from the mix.
Copied from Ambika mixer :innocent:
This one requires a dedicated -9/+9 DC but it can be done with a very small transformer.




Link to comment
Share on other sites

  • 2 weeks later...

PCBs arrived... :happy:


I soldered the Mainboard and it works fine (sound, midi, mem, display, DIN). But i found a few mistakes, i'll fix them in SIDMB v0.4.

If you have small PCBs (<10cmx10cm) to make, look at elecrow.com, prices are amazing and service is great.

I just ordered the front and rear panel. 
Next step, solder the other PCBs and put everything in the rack.


Edited by Ixox
Link to comment
Share on other sites

  • 5 weeks later...

Work in progress.

The background noise is terrible with the current solution when i power more than 1 voice card. I assume it's because of the multiple ground reference.
I'm waiting for a RT-65b power supply and hope it will fix the problem.



Edited by Ixox
  • Like 1
Link to comment
Share on other sites

Great job!
Regarding the background noise - which kind of power supply are you currently using? If you are using a low-quality switcher, then it could be upgraded... but, if you are already using a linear voltage regulator, than that should be always more noise free than any switcher. On the other hand, modern switchers have a very high switching frequency, so that they are inaudible in the audio domain, and the latest consensus is, that they are just as good as linear voltage regulators...
I therefore also suspect it is either chip noise (if you are using 6581s, these are quite noisy) or indeed a ground loop inducing hum (as you suspected)... A good idea is to star-wire and avoid multiple ground "backflows" to the power supply. Other sources of noise in other MIDIboxes include cooling fans, but I have not seen any in your build. You'll fix the noise problem, the unit is looking great!

Many greets and have a nice weekend!


Link to comment
Share on other sites

Thanks :)

I use SID 8580 only.
With only 1 board, the ratio signal/noise is very good.

I have 2 transformers 6Vac and 9Vac, that goes to the boards in parallel.
Each board has 2 diode bridges, one 7805 and one 7809.
The result is a high background noise as soon as i plug a second board. 

The meanwell rt-65b is a switching power supply which has a very good reputation among eurorack users.
It provides a triple output : 5v, 12v and -12v and one ground. I need the -12v for my mixing PCB. 
And it's 38mm high which is perfect for the 1U racks.

I should have it early next week.



Edited by Ixox
Link to comment
Share on other sites

That looks lovely! I was trying to combine a sammichSID and FM into a 1U a while back. Never did get around to it :/ Can I ask where you purchased the 1U rackmount enclosure? That has always been the big headache for me with rackmount-anything.

Link to comment
Share on other sites

Everything is now powered with the meanwell  rt-65b power supply and the signal/noise ratio is very good.
All 4 boards are in place, though i only have 3 pairs of  8580.

I still have a few things to check/fix/finish then i'll post all my files in case someone is interested.








Edited by Ixox
  • Like 1
Link to comment
Share on other sites

  • 2 weeks later...

Everything is working fine, so here are my files.

I didn't have time to play a lot with this great machine, but i'm very very happy with the result :

  • Looks great :innocent:
  • Sounds fantastic 
  • The 3 analogs Knobs are very usefull (awesome on Filter Freq and Detune)
  • The oled screen is readable under any angle
  • Powered through a single power cable (Transformer is in the rack).
  • Active mixer (-12/+12 v) for all 4 full volume voices mixed together... or independant output when plugged.
  • 1U rack allow it to be always usable ever if my desk is a big mess !

Thanks a lot Thorsten for all you work that allowed me to spend a great time building this :grin:


Edited by Ixox
  • Like 1
Link to comment
Share on other sites

  • 3 weeks later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...