Suitable audio transformer for balanced to unbalanced

[UHF]

Hello, I'm making a pair of small, powered desktop speakers to take the main balanced output from a PreSonus Studio 1810c audio interface. The single speaker will be an 8 ohm full range driver, driven by a "TPA3110 PBTL Mono Digital Power Amplifier Board" from Aliexpress, with 12V power from outside. I want to take the balanced output from the PreSonus and then send it through an audio transformer (passive) - balanced to unbalanced and then feed this into the TPA3110 PCB, again an Aliexpress transformer for cost reasons. The PreSonus main outs produce up to 2Vpp from GND to "hot". The idea is to just use 12V to power each speaker and set the volume from the PreSonus unit.

Is this acceptable? What value transformer should I use, 10K:10K? I feel the output impedance from the PreSonus is high, but I've no idea what a typical value might be. Many thanks.

[langwadt]

why do you want a transformer?

[UHF]

Can I just connect GND and 'hot' to the amp input and forget about converting balanced -> unbalanced?

[Phil1977]

Direct connection may work but with lots of noise and it´s definitely not the way it should be.

I´d take an opamp: https://community.element14.com/technologies/test-and-measurement/b/blog/posts/opamp-basics-balanced-to-unbalanced-signal-with-difference-amplifier-699051511

[langwadt]

Direct connection may work but with lots of noise and it´s definitely not the way it should be.

I´d take an opamp: https://community.element14.com/technologies/test-and-measurement/b/blog/posts/opamp-basics-balanced-to-unbalanced-signal-with-difference-amplifier-699051511

lots of noise from where? it a line level signal, presumably a short distance

[Phil1977]

Noise e.g. from common mode currents that originate from the power supplies?

Most devices with symmetrical outputs easily provide unsymmetrical signals if you connect GND and + from the symmetrical output to GND and signal of the unsymmetrical input. But why not make use of the the symmetrical transmission if it only costs one opamp and protects you from a lot of ground loop issues?

For sure it´s worth a try to connect it directly. I just say I think it´s better to use an opamp instead of a transformer.



PS: Sorry, I didn't see the OP has also directly asked about that. Yes, it´s possible to directly connect. But it´s more sensible to noise.

[themadhippy]

cheap skate method thats been used for years were isolation aint required is to tie the - (pin 3 on an xlr) to the ground(pin 1)

[UHF]

The cable from audio interface to speaker won't be more than a metre, but I'd like to do it properly. I'd prefer to stick to having 12V from a power adapter rather than an internal PSU in the speakers. Using an op-amp or line receiver to convert from balanced would require a bipolar supply I think.

What transformer would be appropriate? Theres's a range on Aliexpress for audio/DI boxes with 600:600, 600:10K, 10K:10K etc.

[ftg]

I have used 600:600 for some radio audio interfaces.
But that is for just 300 - 3000 Hz or so.

[TimFox]

For full-audio range, at higher price, I have had good results with these small transformers from Lehle:
https://www.tubesandmore.com/products/transformers_chokes?filters=2341a3027
"HZ" goes from low impedance to high impedance
"LZ" is 1:1 in impedance
Click on the individual listing to get full specs.

[edavid]

Can I just connect GND and 'hot' to the amp input and forget about converting balanced -> unbalanced?

Yes!  This is definitely the first thing to try.  Don't worry about anything fancier if you don't have to.

[abeyer]

What transformer would be appropriate? Theres's a range on Aliexpress for audio/DI boxes with 600:600, 600:10K, 10K:10K etc.

Would just using or scavenging parts from a DI make sense vs trying to source from cheap aliex options yourself? Dunno where you are, but at least around me, I see nice pro grade DI boxes on the secondhand market for cheap all the time. I picked up a pretty nice two channel one for ~5 USD a few months ago.

[wasedadoc]

Using an op-amp or line receiver to convert from balanced would require a bipolar supply I think.

I disagree.

[floobydust]

TPA3110 does have differential inputs, but not brought out on those boards. You'd have to solder a wire to that cap. Or just be lazy and run it it single-ended.
The amplifier is Class D and I would expect it to make so much EMI and only a top quality audio transformer is going to do something for that - which is none of the ones on Aliexpress. Those will just add colouration and distortion and no proper CM rejection. They haven't learned how to wind them properly, and commonly use power ferrites.