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powering digital and analog modules
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author powering digital and analog modules
Granny
noob question here:
i bought some digital and analog modules, can i just connect them to the same multi power cable without problems?
Parnelli
Depends; some digital modules require a 5V supply, others do not, and not all power supplies have a 5V output along with their +12V and -12V supplies. You have to check each module for it's power requirements along with what your power supply delivers.

Not knowing what you have my guess is probably, the only problem I could see arise would be that they need 5V and your power supply doesn't have it, but it shouldn't harm anything.

Because no mention of format was given, I answered for Euro...
sduck
Sure. If you want to elaborate on which modules you have, perhaps we could provide some deeper insight.
Granny
no 5V modules

Parnelli
Shouldn't be any problems then! thumbs up

Although I see the PS has 5V output should you need it in the future.
Granny
ok, thanks for the feedback grin
Parnelli
You bet! thumbs up
ersatzplanet
Also check the modules themselves for optional +5V operation. Some modules have internal jumper to allow using +5V instead of the +12V and Modulargrid sometime only shows the +12V ratings. If possible, it is better to run digital modules off the +5V supply separate from the analog modules that use the +12v. Be aware that some supplies that offer +5V do so at VERY low levels of current.
Keltie
ersatzplanet wrote:
Also check the modules themselves for optional +5V operation. Some modules have internal jumper to allow using +5V instead of the +12V and Modulargrid sometime only shows the +12V ratings. If possible, it is better to run digital modules off the +5V supply separate from the analog modules that use the +12v. Be aware that some supplies that offer +5V do so at VERY low levels of current.


I’ve wondered about the pros/cons of running modules with that option off 12v or 5v. Are you able to elaborate the benefits of going off 5v where possible? Noise, heat or ???

Cheers
Yes Powder
Keltie wrote:
I’ve wondered about the pros/cons of running modules with that option off 12v or 5v. Are you able to elaborate the benefits of going off 5v where possible? Noise, heat or ???
Cheers

The most commonly stated reason would be to keep your analog and digital modules separate. Digital modules can sometimes have clock noise that can interfere with other modules on the same rail. Whether or not this actually makes a difference will depend on the modules in question, and a bunch of other factors.
That being said, one of my cases with a PSU3 uses the 5-volt rail to power the tube heaters on my Metasonix R55 and Bard Vacuform. Those two modules using +5v instead of +/-12v for filament heating is the reason I can actually run seven tube modules off a single PSU3.
ersatzplanet
Keltie wrote:
ersatzplanet wrote:
Also check the modules themselves for optional +5V operation. Some modules have internal jumper to allow using +5V instead of the +12V and Modulargrid sometime only shows the +12V ratings. If possible, it is better to run digital modules off the +5V supply separate from the analog modules that use the +12v. Be aware that some supplies that offer +5V do so at VERY low levels of current.


I’ve wondered about the pros/cons of running modules with that option off 12v or 5v. Are you able to elaborate the benefits of going off 5v where possible? Noise, heat or ???

Cheers


Yes Powder has it right. Basically it is to give some isolation between modules but whether is will help or is needed all depends on how the modules are made. As with all things Eurorack, the modules may be well designed or not. If the digital side of things on the module is noisy, this little bit of isolation may help. If the design is poor enough, it may not do much. If you have a true +5V supply, one that is generated separately from the +12V and is not created via an adaptor or such, it will lessen the current dra on the +12V supply which can help with a larger system.
Keltie
Thanks ersatzplanet and Yes Powder, that’s very helpful.

I have PSU3s as well Yes Powder, do you happen to know if the 5v is separately generated as ersatzplanet describes?
Graham Hinton
Keltie wrote:
I have PSU3s as well Yes Powder, do you happen to know if the 5v is separately generated as ersatzplanet describes?


The PSU3 has three AC-DC converters on a comon pcb so they are not truly separate. The bigger problem is that there is only one common 0V so the digital return currents are mixing with the analogue 0V reference in the PSU cables. To be truly separate a 5V supply needs separate +ve and -ve outputs that joins the 0V at the distribution as well as a separate input.

If you regulate 12V down to 5V either internally to the module or externally you get common impedance coupling in the path from the PSU +12V to the regulator and this couples the 5V usage to everything else using that +12V.

Whether you do that or have a separate PSU the digital currents still go in to the 0V and everything sees that as a reference. That means that the 0V has to be very low resistance to minimise the voltage drops and that means very careful attention has to be paid to the whole power distribution architecture.
Keltie
Graham Hinton wrote:
Keltie wrote:
I have PSU3s as well Yes Powder, do you happen to know if the 5v is separately generated as ersatzplanet describes?


The PSU3 has three AC-DC converters on a comon pcb so they are not truly separate. The bigger problem is that there is only one common 0V so the digital return currents are mixing with the analogue 0V reference in the PSU cables. To be truly separate a 5V supply needs separate +ve and -ve outputs that joins the 0V at the distribution as well as a separate input.

If you regulate 12V down to 5V either internally to the module or externally you get common impedance coupling in the path from the PSU +12V to the regulator and this couples the 5V usage to everything else using that +12V.

Whether you do that or have a separate PSU the digital currents still go in to the 0V and everything sees that as a reference. That means that the 0V has to be very low resistance to minimise the voltage drops and that means very careful attention has to be paid to the whole power distribution architecture.


Thanks Graham.
ersatzplanet
Graham Hinton wrote:

The PSU3 has three AC-DC converters on a comon pcb so they are not truly separate.


The 12V converters are followed by linear regulators, does that help any with the digital switcher noise, or does the shared 0V negate any benefits that may be gained from using them?
cornutt
Graham Hinton wrote:


The PSU3 has three AC-DC converters on a comon pcb so they are not truly separate. The bigger problem is that there is only one common 0V so the digital return currents are mixing with the analogue 0V reference in the PSU cables.


The little-used MOTM 6-pin power standard had separate pins for the analog and digital returns. That's the only setup I've seen that does that, and there were only a couple of MOTM modules (notably, the MOTM-650 MIDI interface) that used it.
Graham Hinton
cornutt wrote:
The little-used MOTM 6-pin power standard had separate pins for the analog and digital returns.


I meant more the PSU end because those cables are carrying the current for the whole system. If you have 2A or more of digital you really don't want the voltage drops that causes in the main analogue 0V.

However there are digital modules now with lots of blinky displays and they can take as much as 250mA more on the +ve than the -ve supply, meaning that difference is in the 0V wiring and dynamically changing, so you need something with lower resistance than pcbs and ribbon cable.

There have been misconceived attempted to separate digital and analogue 0Vs, like the Buchla Quiet and Noisy Grounds (calling them that doesn't make them that), but that doen't work in a modular system with multiple joins.
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