Combining Power Supplies

[critterkllr]

I have a power supply project for a Tac Scorpion II console that I've been collecting parts for. The console will take +/-17V at around 6 amps. I have 4 EZ1290 preamps and am planning on making 4 API style preamps shortly. In the future, my plan is to have 16 preamps total (haven't decided the other 8). I've been considering a way to include all of my future external power needs into one rack unit.

So far, I have 2 Condor/SL linear power supplies. They are +/- 15Vs at 5 amps each. I also have a +48V .5 amp supply for phantom power. There is space inside the enclosure to fit one more large sized psu. The +/-15V PSU will be set as close to +/-17 as I can get it for the Tac Scorpion. I will need to lower the voltage from the +/-17v to +/16V for the api/500 series hardware. These are the Condor power supplies I have:

http://www.mouser.com/Search/ProductDetail.aspx?R=HDD15-5-A%2bGvirtualkey67500000virtualkey675-HDD15-5A-G
http://www.mouser.com/Search/ProductDetail.aspx?R=HB48-0.5-A%2bGvirtualkey67500000virtualkey675-HB48-0.5A-G



I am not very experienced in PSU design, so I am being as cautious as I can be. Since I'm dealing with deadly voltages, I will not move forward with anything unless I am comfortable. I want to know if this is a safe and economical route to take:

I will purchase one last power supply to go in the rack. A +24V 4.8 amp for the Neve gear.
All PSU output will connect to terminals near the rear.
The terminals will give me the option to connect to multiple connectors at whatever voltage/pin I specify.
I will need to lower the +/-17v to +/-16v for 500 series gear. Since I have approx 4 amps left from the psu's, I'm thinking this will be okay?
The terminals will be +17v, -17v, +16v, -16v, +24v, Audio Ground (100 ohms between ground and chassis), Ground (connected to chassis and outlet ground)
They will all connect to 4 pin XLR connectors that will be used to run the power

The PSU chassis is a 3U Hammond that is much more heavy duty than any other rack I've worked with. It is supporting the 3 psus I currently have without an issue.

 

[abbey road d enfer]

So far, I have 2 Condor/SL linear power supplies. They are +/- 15Vs at 5 amps each. I also have a +48V .5 amp supply for phantom power. There is space inside the enclosure to fit one more large sized psu. The +/-15V PSU will be set as close to +/-17 as I can get it for the Tac Scorpion.

If I understand well, you intend to connect these PSU's in parallels. I would not recommend to do that, unless they have been designed specifically for that, which I doubt (I bet it would be mentioned in the datasheet). You run the risk of incorrect current share with associated overheating and premature wear.

I will need to lower the voltage from the +/-17v to +/16V for the api/500 series hardware.

You don't need to lower the rails for the 500 modules, they can easily run on +/- 17.

The terminals will be +17v, -17v, +16v, -16v, +24v, Audio Ground (100 ohms between ground and chassis), Ground (connected to chassis and outlet ground)
They will all connect to 4 pin XLR connectors that will be used to run the power

  How can you run 5 rails + gnd on a 4-pin XLR? BTW I see no provision for a +48V rail...

 

[critterkllr]

If I understand well, you intend to connect these PSU's in parallels. I would not recommend to do that, unless they have been designed specifically for that, which I doubt (I bet it would be mentioned in the datasheet). You run the risk of incorrect current share with associated overheating and premature wear.

That was my plan. I was told this was told by an engineer I trust that this is what I should do. I was also under the impression that this is what GRS does for this power supplies.

You don't need to lower the rails for the 500 modules, they can easily run on +/- 17.

Good news!

How can you run 5 rails + gnd on a 4-pin XLR? BTW I see no provision for a +48V rail...

I guess I was being ambiguous in my previous wording. I'm planning to have a terminal strip where I can connect whatever combination I'd like for the XLRs. So, one XLR for Neves, one for 500 series, one for the console, etc. Since all of them would use +48V, all XLRs would have a pin that went to the +48V Rail on the terminal strip.

 

[abbey road d enfer]

If I understand well, you intend to connect these PSU's in parallels. I would not recommend to do that, unless they have been designed specifically for that, which I doubt (I bet it would be mentioned in the datasheet). You run the risk of incorrect current share with associated overheating and premature wear.

That was my plan. I was told this was told by an engineer I trust that this is what I should do.

Advice is cheap... did that engineer tell you how to balance currents?

I was also under the impression that this is what GRS does for this power supplies.

Who's GRS?

How can you run 5 rails + gnd on a 4-pin XLR? BTW I see no provision for a +48V rail...

I guess I was being ambiguous in my previous wording. I'm planning to have a terminal strip where I can connect whatever combination I'd like for the XLRs. So, one XLR for Neves, one for 500 series, one for the console, etc. Since all of them would use +48V, all XLRs would have a pin that went to the +48V Rail on the terminal strip.

I would be a little nervous having identical connectors carrying varying voltages. You know you have a choice of 4, 5, 6 & 7 pin XLR's?