dingo as dual output -10dbV/+4dbu converter.is it possible?

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pietro_moog
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Joined: Fri Mar 06, 2009 2:16 am

dingo as dual output -10dbV/+4dbu converter.is it possible?

Post by pietro_moog »

hi guys, hi Joe !

i was wondering: can the Dingo with 5532s be used as a -10dbv to + 4dbu converter for 2 outputs, instead of 1 In and 1 out ?
and, at best, can be powered with a JLM 48v power supply?
a thing like this would be awesome for all Apogee Duet owners who want to use Duet with a buss compressor.

thanks for your patience guys

chrisp
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Joined: Sun Mar 04, 2007 11:46 am
Location: Sydney, Australia

Re: dingo as dual output -10dbV/+4dbu converter.is it possible?

Post by chrisp »

Hi Pietro

In short, no. There is a difference between converting balanced to unbalanced from vice-versa, such that you cannot just run the signal path in reverse to get 2 channels from the one dingo. 2 dingos would of course do it, but that's a real sledgehammer to crack a walnut.

Also, the DINGO as you note has a bipolar (+/- volts) power design, rather than a single-sided +48V design. Not impossible to mod, but messy. The 5532 has a maximum supply range of +/-22V, so you're also faced with dropping the supply from 48V anyway or you'll fry the IC (an OPA chip would be better in this regard) or at least heat it beyond its specified operating range. And perhaps more importantly, what you want to do is not that difficult to do, so much so that there are many "off the shelf" versions available to buy (a quick net search of "balanced unbalanced converter" will give you the idea). At the risk of promoting a site with which I have no affiliation, see Rob Squire's balancing interfaces at http://www.proharmonic.com/products.htm as one example.

If fact, do you need to do anything at all? Try wiring the + of the unbalanced out to pin 2 of an XLR, and the - of the unbalanced to pin 3. The signal will still be about 12db down compared to a "pro" level, but you can turn up the Duet's outputs a little to compensate, and your compressor will have a makeup gain stage (in fact, you won't be needing to squish the signal as much to begin, and thats a good thing, right?) For short cable runs and EMF friendly environments (no fluorescent lights), this shouldn't be a problem.

However, if you WANT to build your own, it would be easier to start with a simple bipolar power (say +/- 15V) supply. For each channel you need a simple non-inverting opamp stage to deliver around 12db of gain as well as buffer the signal, and then usually a couple of other opamps to drive each side of the balanced output. You can get the idea from the DINGO schematic, or there are plenty of web resources that show the circuit. Alternatively, you could perhaps make up a nice design using a single dual opamp and a pair of 1:1 or 1:2 output transformers - but that's getting expensive again.

I'd try the simple wiring solution above first and see if that does what you need.
Chris P
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I do lots of things. I believe eclectic skills are best.

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Joe Malone
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Re: dingo as dual output -10dbV/+4dbu converter.is it possible?

Post by Joe Malone »

pietro_moog wrote:hi guys, hi Joe !

i was wondering: can the Dingo with 5532s be used as a -10dbv to + 4dbu converter for 2 outputs, instead of 1 In and 1 out ?
and, at best, can be powered with a JLM 48v power supply?
a thing like this would be awesome for all Apogee Duet owners who want to use Duet with a buss compressor.

thanks for your patience guys
Would be much easier to do this with 2 BA PCBs with OPA2604AP opamp and no input transformers. Use a cap on input instead to remove the DC. And run it on our 48v SMPS.

I do have a a heap of old tiny PCB called the microDi which mounts direct to a male XLR and runs on +12v to 36v which is made to exactly what you want as it was used to convert RCA outputs on non pro gear to balance +4dBu balanced out. PCB is about 20mm x 45mm

Otherwise if you are only driving modern 10k balanced input loads and the duet can drive 600ohm loads you can use 2 x JLM14 transformers to passive convert the signal up.
Joe :-)
JLM Audio
Capturing Audio without Injury

pietro_moog
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Joined: Fri Mar 06, 2009 2:16 am

Re: dingo as dual output -10dbV/+4dbu converter.is it possible?

Post by pietro_moog »

thanks guys.
i don't care about bal/unbal, i just need gain.
i was looking at the dingo because it could have been a low cost solution, and can fit in a pedal box.

so, i imagine that plug the signal in a BA mic pre or in the FEt DI connected won't be the same..

joe, the MIcroDI idea seems cool! and it's small!
is it just a balancing board or can it provide 12db of gain?

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Joe Malone
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Re: dingo as dual output -10dbV/+4dbu converter.is it possible?

Post by Joe Malone »

pietro_moog wrote:thanks guys.
i don't care about bal/unbal, i just need gain.

i was looking at the dingo because it could have been a low cost solution, and can fit in a pedal box.

so, i imagine that plug the signal in a BA mic pre or in the FEt DI connected won't be the same...
Umm not sure what you mean by the last line but two BA PCB (or one BAD PCB) used without input transformers is the same circuit as the dingo output amp but setup to run on one 48v rail. No DI kit is needed. You can do this on one dINgO PCB but you will need to reset a heap of values and really know what you are doing.
joe, the MIcroDI idea seems cool! and it's small!
is it just a balancing board or can it provide 12db of gain?
Balancing with 12dB gain
Joe :-)
JLM Audio
Capturing Audio without Injury

chrisp
Posts: 184
Joined: Sun Mar 04, 2007 11:46 am
Location: Sydney, Australia

Re: dingo as dual output -10dbV/+4dbu converter.is it possible?

Post by chrisp »

FWIW I use Joe's transformer trick in a couple of applications, including a DI box, and this would certainly fit in a pedal box.

The wiring is pretty straightforward. You need 2 transformers (one per channel) and wire each channel as follows

Transformer Wire Goes To
Red RCA Hot
Green RCA Shield
Yellow XLR Pin 2
Blue XLR Pin 3
Black Not Connected (Trim and tape off)

This gives the big three: gain, balancing and impedance, assuming as Joe says that the Duet output can drive a 600K load.

That said, what is at the other end of the chain, after the compressor? Are you going through an amp to your speakers, or are the speakers self-powered?
Chris P
---------------------------------------------------------
I do lots of things. I believe eclectic skills are best.

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