flyweight

D-Sub 25 output question

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Hi All,

I have a question regarding the Dsub 25 output connector that I would like to use without the transmitter PCB, but with a Aout-ng and D-out.
Do I need to use a seperate ground for every output or can these be shared in some case?
I mean is the max 12 outputs total; using 24 wires or can i get more my sharing the ground?

Thanks,

 

Cheers

Tim

 

 

 

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Hello Tim

It depend what is at the other side of the connector...

I guess you better separate analogue and digital reference, at least.

Best

Zam

Edited by Zam
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MBHP makes no distinction betwen 0V for analogue and digital; the AOUT_NG boards are routed with separate planes that join at one place.

The input impedance for analogue is typically 100k or so, thus very little return current. I've had an 8 channel AOUT/DOUT system on a DB-25 cable for several years now with all spare wires and the cable screen tied to 0V, +/-12V power coming in through the same cable.

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Thanks a lot, I think what I will have todo.  Great idea to also put the +/-12V connections there. Probably I will juts make a eurorack panel with all 32 Dout, 8 cv outs and the +/-12V going to the MidiBox.

Cheers,

Tim

 

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6 hours ago, latigid on said:

MBHP makes no distinction betwen 0V for analogue and digital; the AOUT_NG boards are routed with separate planes that join at one place.

Hello

Having two separate planes mean distinction !

If you see it this way no system at all have distinctive 0V ref... as all finally end to the same safety earth point :rolleyes:

Connecting only one 0v will make ether digital or analogue return path through the other circuit, may not be trouble as you experienced, but it's easy to avoid this and make it fine at start, it's just one more wire...

So I still recommand to hook TWO 0V wire, one hooked do DOUT pcb for D signal and one connected to AOUT (analogue side) PCB for CV signal.

Best

Zam

Edited by Zam

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I think with two separate wires it won't hurt, but it won't make a difference either. It's just the nature of how the MIDIbox boards are set up. They share a power rail (+5V) without any filters (excluding a few capacitors on the DAC, but no RF choke etc.) so they already share common-mode noise. Thankfully we're not switching huge amounts of current...

Use the thickest gauge wire possible. On a DB-25 connector this means putting many of the thin wires together in parallel for 0V.

 

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