do all cv inputs/ouputs need to be grounded?

[caress]

my subject says it all...

i'm wondering if i can use ungrounded banana jacks for cv inputs/outputs....?  difficult to find this info

[Mark Hammer]

CVs don't have to be shielded, since they normally do not carry audio signal.  The consequence of that is that one will often see large modular synths with banana or pin jacks in the modules, or in patch matrices.

Make no mistake, though, that the CVs have to be DC voltages with reference to a ground, but the ground does not have to physically accompany the "hot" on the same connecting patch cable. The ground could be shared by every module faceplate screwed into the same rack unit, and all that gets moved around by patching is the (unshielded) "hot" lead carrying the CV.

I fully understand why you are puzzled by this, since there is no apparent standard for patch-over connectors.  Some use unshielded banana and pin plugs/jacks, others use 1/4" or 1/8" shielded phone plugs/jacks.  Small wonder there is confusion.

If you have one of those Boss pedals that can use an external expression pedal, you will see that the expression pedal does plug into a "normal" phone jack, complete with ground connection.

[caress]

this makes sense, but leads me to a further question...

specifically, i am asking about the cv input on jc maillets nyquist aliaser (revised schem by moosapotamus).  it shows a mono jack with the sleeve grounded.  i wanted to use an ungrounded banana jack to interface with a cv box with dedicated lfos, s/h, noise, etc...  if i understand you correctly, though, i need to share grounds between the cv box and the aliaser...in which case i would need to use a grounded jack.  yes?

[Mark Hammer]

Yup.

[caress]

damn   

[caress]

good so far...one more teeny tiny little question, though.   

The ground could be shared by every module faceplate screwed into the same rack unit

can i share grounds between devices of differing voltages?  in my case, there are two cv circuits which use +/- (9-15v) and one that is a standard stompbox (9v- ground).  the two are going to be in seperate cases, but i need to ground the cv input on the stompbox with the cv outs from the control box.  pleeeeeease don't say that i can't share ground  or else i need to make another aliaser...
i mean, say no if i really can't, though.  haha

[Paul Perry (Frostwave)]

can i share grounds between devices of differing voltages?  in my case, there are two cv circuits which use +/- (9-15v) and one that is a standard stompbox (9v- ground).  the two are going to be in seperate cases, but i need to ground the cv input on the stompbox with the cv outs from the control box.  pleeeeeease don't say that i can't share ground  or else i need to make another aliaser...
i mean, say no if i really can't, though.  haha

You probably can't. But maybe you can. Obviously you can't connect together a + ground unit & a - ground unit. But you can connect together a +- bipolar supply unit with a +-15
unit, because they bot have grounds at zero (the control voltages going from one to another might be over different ranges, though.)
I'd have to see the circuits to be sure.

Incidentally a great source of confusion, are the 'expression' and so-called 'CV' footrocker pedals that plug into various commercial FX (including some Moog gear) and don't actually generate a CV themselves (at least, not in the way a modular synth understands it). These pedals usually have a pot inside & a tip/ring/sleeve [plug so that the unit being controlled, supplys a steady voltage to the pot (eg via the ring) and then the pot picks off a voltage & sends it back via the tip. There is no standardisation whatever in this area - different pots, different connections, different circuitry. With a lead coming from an analog synth, the voltage is right there on the end of the plug.

[caress]

well i guess i should disclose my project...

i'm using jc maillet's nyquist aliaser with the cv input idea from moosapotamus.

i'm building a control box to be used with the aliaser, some other pedals and some traditional modular synth blocks.  so far i've perfed a musicfromouterspace Multi Noise and Random Gate/Trigger Generator, Single Chip Simple Sample and Hold and i'm working on a VCLFO, a stairstep LFO, another dual LFO, ADSR, a DC mixer, maybe one or two more sources...(logic, etc.) 

in the past, i've grounded together in one box a +/-9v circuit with a neg ground 9v circuit...but this would be interfacing neg ground 9v circuits with +/-12 or 15v circuits...i just don't want to destroy anything after i've perfed up 10 or 12 modules.

[caress]

ok i just had another idea....what about using ungrounded banana jacks on the control box since all the ins/outs will be sharing a common ground, then porting that through a ungrounded banana connection to a grounded 1/4" jack to send to my pedals?  this way i can still use cheaper (and stackable!) banana jacks for the control sources...

like this:  (0 = ungrounded banana, O = grounded 1/4")

       (cv input)          (cv out)
              0 -------------- O --------> (to ground)
                 (connection)

possible?!  it would make life soooo much easier...

[Paul Perry (Frostwave)]

Sure, nothing wrong with using unsheilded banana jacks, and cables with a banana plug one end & a phono on the other end.
You can get away with unshielded banana patch leads when a signal is coming from a low impedance source (eg an op amp output).
Or you can use sheilded cable & just have the shield at teh 1/4 jack end.

Whether the various bits of circuitry like having a ground in common, depends on their power supplies.