Using Acopian supplies--no audio ground

kakumei47 · Post by **kakumei47** » Tue Jun 21, 2011 12:36 am

I'm finally getting around to setting up Acopian supplies for my MCI 528c. The one issue I have is the lack of an audio ground/common connection. Each has +/-whatever volts, sense for each, then the two AC connections and a ground, which I assume is for the third ground leg on the IEC cable.

So should I chain my ground up to that ground or what?

Nate Dort · Post by **Nate Dort** » Tue Jun 21, 2011 6:37 am

If each supply has an isolated (not connected to the chassis) + and - connection, you'll need to create a virtual ground between them to get the +/- 36V (or whatever it is) that the board needs. Sort of like a center-tap on an audio transformer. I recently had to do this with some Power One linear supplies for a JH-416B console.

kakumei47 · Post by **kakumei47** » Tue Jun 21, 2011 9:43 pm

Ok I think I get it but don't really know how to implement it. So the virtual ground would be tying the + and - legs together, with a resistor on each end? Is that right? How would I find the value of that resistor?

The Scum · Post by **The Scum** » Tue Jun 21, 2011 10:51 pm

A little more information would be helpful. Every MCI desk seems to me a little different than it's brethren.

What Acopian supplies are you using, specifically?

And how many of them are there?

And which of those dozen MCI rails are you putting them on?

Rail splitting with resistors like you're describing is a messy technique, usually used in stuff like guitar pedals where you need a reference voltage between 0 and 9V. It can't sink or source much current without shifting away from the midpoint. TI make some rail-splitter ICs to do the job better, but they still crap out at small currents...nothing that's going to get Jeep's toaster oven running for you.

kakumei47 · Post by **kakumei47** » Wed Jun 22, 2011 7:32 am

Ok. Yeah I've never dealt with this issue. I've built several kit supplies but they always have the 0v reference.

I need to use it on audio power
That's +/- 32v and +/-15v. I have acopian a range gold box supplies. 9a for 32 and 6a for 15.

I'd like to use them also for the logic and lights, which need +24 and +5. On my mci supply 24v is ok, but 5v is really putting out like 1.6v so I have to sort that out. There is a bad 3watt resistor there but I haven't looked it over

The Scum · Post by **The Scum** » Wed Jun 22, 2011 7:53 am

I have acopian a range gold box supplies. 9a for 32 and 6a for 15.

Assuming that you have a pair of each of those:

Take one, call it the + rail, and strap it's - output to ground, and use the + output. Then take the other, call it the - rail, and strap it's + output to ground, and use the - output.

Then repeat for the other pair.

The ground nexus should also be tied to ground from the AC inputs. Use the heaviest wire you can manage.

kakumei47 · Post by **kakumei47** » Wed Jun 22, 2011 8:17 am

Yeah, I just got off the phone with acopian and the tech suggested strapping the + of one to the - of the other for each voltage and using that as the common.

If I used the strapping it to ground method you mentioned on each box, then the two grounds get tied together and I use that?

Also, is it a problem to use two supplies with different amp ratings or not? I messed up and didn't realize I needed two supplies to do this since each had a + and -. But I do have an extra 15v, but it's like 10a or something while my other one is 6

kakumei47 · Post by **kakumei47** » Wed Jun 22, 2011 10:19 am

And one more thing:
For the single + supplies for the logic and lights(+24 and +5), i can get the common ground then by tying the - terminal to the ground terminal, right? So for those I'm assuming I just need one supply for each voltage

Dominick Costanzo · Post by **Dominick Costanzo** » Thu Jun 23, 2011 9:10 am

re 2 supplies with different output ampere ratings
As long as the console draws less than 6A of that voltage you're OK using the 2 supplies you have.

re single rail supplies (+24v & +5v)
Yes, tie the - output of these supplies to ground.

Message Board

Using Acopian supplies--no audio ground

Using Acopian supplies--no audio ground

Who is online