AOUT wiring questions

[creatorlars]

Few quick Q's...

1) For the 8 gate outputs on the core board, where do I connect ground of the jacks? (my SEQ is using 1/4 inch jacks)  It's not shown in the SEQ AOUT wiring PDF.

2) What's the difference between the 2 gate outs on the AOUT board and the 8 on the core board?  Any advantage to using the ones on the AOUT board?  I was just going to leave them unconnected and use the 8 outs on the core board instead.

3) What's the difference between the 8 gate outs on the core, and the 48 drum pulse outputs?  Will I still be able to trigger analog drum modules from the 8 gate outs?

[creatorlars]

One more question...

Do the AOUT/Gate output jacks need to be isolated from the chassis?

...I hope not. :)

[seppoman]

1) For the 8 gate outputs on the core board, where do I connect ground of the jacks? (my SEQ is using 1/4 inch jacks)  It's not shown in the SEQ AOUT wiring PDF.

ground is the same everywhere - actually, with an AOUT you make a logical difference between digital and analog ground, mostly to have things a bit separated. you don't want digital artefacts in your analog signal. If you use the gate outs from the core, use some ground from the core. If you use the AOUT gates, then take the ground from the AOUT module (the AOUT doesn't really have separate analog or digital ground, but at least your reference is from the same area of the box).

2) What's the difference between the 2 gate outs on the AOUT board and the 8 on the core board?  Any advantage to using the ones on the AOUT board?  I was just going to leave them unconnected and use the 8 outs on the core board instead.

I'd say the main advantage in using the ones from the AOUT is that you've got J5 free for other uses. There's no such thing as the "quality" of a gate signal (on or off ;)). so it mostly depends on how many you need. if two are enough, use the ones on the AOUT. if you need more, then use the ones on the Core.

3) What's the difference between the 8 gate outs on the core, and the 48 drum pulse outputs?  Will I still be able to trigger analog drum modules from the 8 gate outs?

no idea, sorry.

Do the AOUT/Gate output jacks need to be isolated from the chassis?

That depends on your jacks. if the sleeve of the jack is made from plastic, no problem. If it is made from metal and somehow connected to ground, this is a great way of building dozens of ground loops (which you want to avoid at all costs). I once had a problem with a DC plug connecting ground to the case, plus the output jacks of the SID doing the same. made a loud hum. I used a rubber ring to isolate the DC plug from the case and everything was silent.

S

[creatorlars]

If it is made from metal and somehow connected to ground, this is a great way of building dozens of ground loops (which you want to avoid at all costs)

Damn!  Yeah, they're metal jacks.  And they're already mounted and wired (and not easily, in this case.)  I wonder, though -- since these are CV instead of audio outs, how would this affect what I'm using it for?  Would a little ground hum inhibit the accuracy of the control voltage?

Thanks very much for your help, very useful info. :)

[wicked1]

for my modular, all the CV inputs/outputs are grounded on the panel.  I don't run a separate ground wire to each jack.  If you have no other ground connections on your panel, you'll have to ground one of the jacks, and all the others should be taken care of as well.  This seems to be the common way to do things in the modular synth community.

[seppoman]

hi guys,

even while CV is not audio, you really don't want any ground hum on it - you won't directly hear the hum, but it will modulate what you're controlling with the CV. A ground hum of 100 mV going to a VCO would modulate the osc frequency by two semitones and a mod freq of 50/60 hz! You won't like that.

But the "panel as common ground" concept sounds very good to me. It's not forbidden to have ground on the  panel and this saves some wires :) You just need to take care that it's really only one SINGLE ground -> panel connection.

S

[creatorlars]

Okay, that makes sense.  Thank you all for your help, much appreciated.  Glad I got that tip before wiring up my first 5 drum modules.  :)

I guess as long as _one_ thing on the panel is grounded, i should be able to just snip the leads between the ground pins I soldered between the jacks, and it should eliminate any hum I may experience?

MBHP Burner built & 18F4620 + four 16F88's burned with firmware successfully last night... 90% of the frontpanel wiring/mounting is done... I think tonight might be the night!

Thanks!

Lars