Would you be able to turn two SE dacs into balanced by running them in mono and inverting the phase on one of the outputs.

[kazuviking]

Got this showerthought a few days ago and its bugging me since.

What i was thinking of is in EQ APO sending the L channel to DAC 1 and R to DAC 2. The audio channels would be duplicated so it runs in mono but the left channel output on both dacs would be inverted in phase. The R output would be the positive phase and the L output would be the inverter phase.

In my head it should work but not so sure about the real world.

 

[Multicore]

I enjoy the question. Assuming a 2-channel SE DAC that

1. has a common ground for its L and R outputs, which is often the case,
2. the time alignment of the inversion is precise in the data sent to the DAC, which is up to you,
3. the DAC maintains time alignment of the input digital signals through to the analog outputs, which one would in any case hope,
4. each channel of the DAC works correctly (linear, same FS output voltage, etc.), which we may as well assume,

then I'd say yes, why not?

I'm not sure this is a good idea in practice but somewhat educational idea to think through.

 

[NTK]

Sure. It is one of the suggested method to generate one differential signal from two single-ended channels for function/arbitrary waveform generators (FAWG). Of course the 2 channels must be well synchronized.

https://www.newark.com/pdfs/techarticles/agilent/5990-5897EN.pdf

 

[LTig]

It won't work in sync via USB since almost all DACs use their own clock. If you feed them via SPDIF it should work if the DACs are identical (same internal data processing).

 

[Multicore]

It won't work in sync via USB since almost all DACs use their own clock. If you feed them via SPDIF it should work if the DACs are identical (same internal data processing).

Let's say you just wanted to produce a balanced mono analog signal using one 2-channel DAC, i.e. the mono version of OP. Then?

 

[kemmler3D]

I'm not an expert, I think it can work but per @LTig 's comment, two DACs do not necessarily stay in sync as well as you'd expect.

That said, for USB I think we are talking a few ms of drift between left and right that varies over time. This will certainly cause problems, even audible ones, but not super overtly. Depending on the use case I think it can work.

 

[gvl]

In my head it should work but not so sure about the real world.

AFAIK in the real world you buy a DAC with balanced outputs.

 

[DVDdoug]

Let's say you just wanted to produce a balanced mono analog signal using one 2-channel DAC, i.e. the mono version of OP. Then?

That should work fine. Otherwise it doesn't seem practical. And you'd have to modify your files to make them dual-mono with the polarity flipped on one channel.

Or you could use a multi-channel DAC but you'd have to edit all of your stereo files to make them 4-channel.



...If you wanted to learn a little electronics an inverting buffer is one of the easiest things you can make with an op-amp. (That's not exactly a complete schematic. Op-amps usually need plus & minus power supplies with bypass capacitors on both voltages. And you MIGHT want to add DC-blocking capacitors on the inputs & outputs.)

 

[solderdude]

Got this showerthought a few days ago and its bugging me since.

What i was thinking of is in EQ APO sending the L channel to DAC 1 and R to DAC 2. The audio channels would be duplicated so it runs in mono but the left channel output on both dacs would be inverted in phase. The R output would be the positive phase and the L output would be the inverter phase.

In my head it should work but not so sure about the real world.

Won't work well in practice.
There are many solutions for this both passive and active, DIY or built devices.

 

[unpluggged]

sending the L channel to DAC 1 and R to DAC 2. The audio channels would be duplicated so it runs in mono but the left channel output on both dacs would be inverted in phase. The R output would be the positive phase and the L output would be the inverter phase.

In my head it should work but not so sure about the real world.

That's basically how balanced mode is implemented for headphone outputs of the RME ADI-2 Pro (also can be used as two balanced mono line outs):

Won't work well in practice.

And it works very well in practice

 

[solderdude]

You would need to do signal processing + drive 2 (identical) DACs at the same time (I2s or SPDIF).
Not a very practical solution but fun if you want to experiment with DSP and 2 DACs (or a DAC that has 4 or more channels).

 

[unpluggged]

You would need to do signal processing + drive 2 (identical) DACs at the same time (I2s or SPDIF).
Not a very practical solution but fun if you want to experiment with DSP and 2 DACs (or a DAC that has 4 or more channels).

Well, this is what the OP has in mind, if I get it right. Provided the EqAPO has the needed signal inversion and routing features, it's otherwise not a bigger problem with synchronization than with sending any other multichannel audio signal to a USB audio device, IMO.

 

[Multicore]

I'm not an expert, I think it can work but per @LTig 's comment, two DACs do not necessarily stay in sync as well as you'd expect.

That said, for USB I think we are talking a few ms of drift between left and right that varies over time. This will certainly cause problems, even audible ones, but not super overtly. Depending on the use case I think it can work.

Isn't that essentially the same kind of concern when trying to build a quadraphonic system using two separate 2-ch DACs?

 

[RayDunzl]

An easy test that I would try for the result of sending two DAC outputs to create a differential source:

Don't invert one channel.

Play something.

You should (I'd think) hear nothing.

Let it run for a while, to test the DACs remaining in sync.

You should still hear nothing.

 

[kemmler3D]

Isn't that essentially the same kind of concern when trying to build a quadraphonic system using two separate 2-ch DACs?

Yes, I think so.

 

[Multicore]

Yes, I think so.

Right. OP combines two questions. 1) using a 2-ch SE DAC to make a 1-ch balanced output. 2) using two DACs to double the number of channels.