Studer 963 DC/DC-stuff

[chriss]

Hello there,

for their Talkback-Box Studer went the way creating the +/-15V out of a -6V-Line via DC/DC-Conversion. Since these Boxes are unaffordable if available anyway I think of building one on my own. Only difficult thing is this convertor. The schematics for that part of the circuit:

I guess the part between the -6V-Rail and the Transformer is a generator generating sine- or pulse-wave to feed the Transformer and behind the transformer rectifiing and so on. Now I wonder: Is there any idea out there what Transformer could fit in here and do the job? The parts-list only says "converter trafo"...

On the LED-Meters of the desk they do a similar strange thing converting the +3V for the LED's out of +/-15V via DC/DC-Conversion. But in this case it is at least stated the transformer is 3:1.

Ah and a German or European source for the 72µH Inductor would also be welcome!

Why this conversion-stuff anyway?

Thanks in advance

Chris

 

[PRR]

> I think of building one on my own.

Why not use a conventional readily-available +/-15V supply?

 

[gyraf]

The 72uH inductor is a minor problem (wind one yourself) - the T104 transformer is much harder to re-create

Jakob E.

 

[joaquins]

something like this maybe?
http://dx.com/p/lm2587-high-power-dc-dc-3-5-30v-boost-converter-module-green-155170

JS

 

[chriss]

Why not use a conventional readily-available +/-15V supply?

The Studer-Idea was one single cable from Mixer to this Box. This cable has the audio, the -6V and some lines for signalling. Would be nice not to need a further cable for PSU. But I really wonder why they didn't send +/-15V to the Box - would be ready available from the Mixer's PSU. Maybe for long cables this way it's smarter?! Oh, and the -6V is also used directly for the singalling-Lamps.
The Box might sit on the producer's lap or been given around in the control-room or whatever, so a PSU-cable is a No-Go.

The 72uH inductor is a minor problem (wind one yourself) - the T104 transformer is much harder to re-create

Jakob E.

Yes, you are right Jakob. I also found them at RS Components. I really hope I will not need to recreate this transformer - I don't think this would be realistic. There must be something compatible out there - It's not rocket-science, is it?

something like this maybe?
http://dx.com/p/lm2587-high-power-dc-dc-3-5-30v-boost-converter-module-green-155170

JS

Yeah, that looks like a possible solution Joaquin! I only wonder if the transformer's isolation was an important part of the original DC/DC. But I think I should give this route a chance!

Thank you already for the answers - more are welcome!

Chris

 

[PRR]

> The Studer-Idea was one single cable from Mixer to this Box

OK, that makes a lot of sense.

Need to know the output current/power.

2-Watt (66mA at +/-15V, which will power a lot of chips) are pretty stock items.

TI DCP020515D Miniature, 2W Isolated Unregulated DC/DC Converters
http://www.ti.com/product/dcp020515d

The "5V" model will stand 7V max input, so should be OK on a clean 6V supply.

$9 at Newark, but stock is in the UK?? So there's a stupid shipping surcharge to the US. DigiKey is showing $12.

muRata has made such stuff since Neve was a puppy.
http://www.murata-ps.com/data/power/ncl/kdc_nma.pdf

The "5V" model is rated 5.5V max. I doubt it will blow-up before 7V, but you could stick a diode in series to get 6.0V down to 5.4V. Note that this part suggests 10uFd maximum output capacitance, where your Studer shows 100uFd.

 

[joaquins]

something like this maybe?
http://dx.com/p/lm2587-high-power-dc-dc-3-5-30v-boost-converter-module-green-155170

JS

Yeah, that looks like a possible solution Joaquin! I only wonder if the transformer's isolation was an important part of the original DC/DC. But I think I should give this route a chance!

Thank you already for the answers - more are welcome!

Chris

It is, you need ±15V and with this you could get up to 30V with the same 0V reference, then use +15V and an inverter, or maybe smarter is to use +30, generate a 15V reference and use as new 0V and work AC coupled from the desk... like any single supply design, there are a couple more of this stuff in there, see which goes better for your app, may not work from 6V to 30V, but you may send 15V from your desk instead of 6V, just change the connection.

JS

PD: if you can change the supply voltage in the connection to 15V you may prefer use an inverter instead of a booster...

 

[chriss]

Wow, that's a lot of input - thanks!

First I think it makes more sense to bring up the whole schematics for the box:
963-tbb.jpg

[quote author=joaquins]
It is, you need ±15V and with this you could get up to 30V with the same 0V reference, then use +15V and an inverter, or maybe smarter is to use +30, generate a 15V reference and use as new 0V and work AC coupled from the desk... like any single supply design, there are a couple more of this stuff in there, see which goes better for your app, may not work from 6V to 30V, but you may send 15V from your desk instead of 6V, just change the connection.

JS

PD: if you can change the supply voltage in the connection to 15V you may prefer use an inverter instead of a booster...
[/quote]
Yes but the datasheet of the LM2587 shows ideas how to step up to +/-12V anyway without splitting it and this also has an transformer-decoupling with it. The schematics demanding the sym. PSU is a stupid Power Amplifier and I guess it wouldn't matter too much if it gets +/-12V instead of +/-15V?
And if you look at the whole schematics you'll see that the -6V can't be replaced since it is also needed. This box is a kind of copy of the Talkback-Section of the desk's Master-Module so the producer doesn't have to share this with the Engineer. For this reason it also has some switching and lighting-stuff in it.
Anyway the LM2587 IS an interesting item for this circuit, even though I couldn't find any of the transformers from the datasheet yet.

[quote author=PRR]
Need to know the output current/power.

2-Watt (66mA at +/-15V, which will power a lot of chips) are pretty stock items.
[/quote]
Well, I don't know how much current this might draw. Maybe the schematics can be of help. Little Power Amplifier for small Talk-Back-Speaker or Headphones? The DCP020515DP would be an easy solution if the 0,066A were enough. If not more of them might be connected in parallel as the datasheet suggests.

Does one of you have an idea how much current there could be involved?!...

It's always difficult to have choices...

Thanks

Chris