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TOPIC: Balanced application of DAC8 and/or miniSharc

Balanced application of DAC8 and/or miniSharc 7 months 3 weeks ago #35727

  • cutedaddy
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Hi,

With respect to the U DAC8 i was wondering if it could be used in a balanced config, using the 8 analog out channels as 4 pairs, each pair carrying one signal and one inverted signal, fed to the DAC8 by for instance the 8-channel out miniSharc board, or the 2x8 nanoDigi. Haven't tested those boards, but they do 8 channels of DSP, correct? So that would make inverting 4 of those 8 a possibility?

How the grounding of the eventually three conductors for each of the four channels would be routed is a separate matter, but i'm just curious if the DAC8 could be made to serve in a balanced config.

My use would be four-way active loudspeakers, with a balanced poweramp for each driver, so i would need two 2x8 DSP boards and two 4x2 (4 inverted/4 non-inverted) DAC8 boards for the stereo pair.

Am i completely deluded? I would suppose if this is possible, someone would have mentioned it already, but can't find any relevant posts. Slightly frightened i'm gonna be the laughing stock out here, but still, curiosity won the battle, so here goes..
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Balanced application of DAC8 and/or miniSharc 7 months 2 weeks ago #35801

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Hi

Interesting idea, but just to confirm the UDAC8 is USB to 8ch DAC. It has "no" DSP processing inside whatsoever..
Please check out the user manual for more details. Bottom line, you'd need to do that inversion of polarity somewhere in your PC. Not as trivial but I guess with some sort of PC processing software doing DSP it could be possible.. Wondering if it's worth it to be honest, as much as we'd love having you as a customer, maybe another balanced DAC studio unit would be easiest I'd say..

DevTeam
MiniDSP, building a DIY DSP community one board at a time.
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Balanced application of DAC8 and/or miniSharc 7 months 2 weeks ago #35819

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Hi, tx for your reply.

As you are pointing out i should, i actually did check manuals and datasheets before posting. It appears you may have misread my question, since your reply doesn't actually provide any answer (although i appreciate your effort).

My question was regarding use of the UDAC8 at the output of (two different 8-channel-capable) DSP units from your own product range.
The miniSharc for instance, features I2S IN/OUT, while the UDAC8 features I2S IN. The miniDSP website itself promotes using these two together, which makes perfect sense of course.

So my question really remains:

Could it be that using miniSharc as an 8x I2S OUT (in a 4x INVERTED OUT / 4x NON-INVERTED OUT configuration) would enable application of the (1x miniSharc + 1x UDAC8) combo to achieve 4x balanced analog OUT, to feed (a set of 4x) balanced-IN amplifiers?

Don't want to be a pest, but a few of us are still really curious for the answer to this question, judging by some forum posts...

Tx in advance for any intel!
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Balanced application of DAC8 and/or miniSharc 7 months 2 weeks ago #35821

  • john.reekie
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It's come up before e.g. www.minidsp.com/forum/software-support/1...t-from-2x4-and-2x4hd

However just adding an unbalanced->balanced buffer (or transformer) seems like a better and simpler solution.
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
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Balanced application of DAC8 and/or miniSharc 7 months 2 weeks ago #35823

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O wow, THE John Reekie honoured me w/an answer. Sir, your name comes up when surfing on topics tending to objective-minded audio. I really appreciate your effort to reply!

If you allow me one follow up question:
Does the transformer based solution not void one of the main advantages of balanced audio (doubling of SNR) because one signal is split into two in the analogue domain, where the noise is also split into two? Or am i mistaken?

Thanks again for your generosity!
Yuri Halberstadt, Amsterdam.
Last Edit: 7 months 2 weeks ago by cutedaddy. Reason: typo
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Balanced application of DAC8 and/or miniSharc 7 months 2 weeks ago #35824

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Investigating design of stereo open baffle floorstanders, a 1xminiSharc+1xUDAC8 per speaker seems quite attractive and straightforward to me (for fully active, wireless, full range, 4-way, quad-amped speakers, XO approx. 80/300/3000).
Last Edit: 7 months 2 weeks ago by cutedaddy.
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Balanced application of DAC8 and/or miniSharc 7 months 2 weeks ago #35850

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Hi Yuri, no worries :) I don't understand your question about the transformer, a transformer doesn't introduce noise or for that matter split the signal into two (unless it has a centre tap and you ground it). It will have higher distortion than a solid state stage, or be very expensive. Just mentioned it as an option :)
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Balanced application of DAC8 and/or miniSharc 7 months 2 weeks ago #35863

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Eehhrm.. oops, sir, i seem to have introduced a misunderstanding.

Trying to learn, and trying to word my line of thinking such that my mistakes and assumptions become obvious, so others may also learn from them...

My initial question concerned using a certain miniDSP-combo (i.e. 1x miniSharc / 1x UDAC8) to treat four already balanced channels, in order to feed four balanced amplifiers that will drive four speaker drivers in a (left or right) 4-way active speaker.
Judging from the devteam answer in the other topic ("they never tried it, but think it should work") i should give it a shot. I'll be needing two separate combos to drive the stereo pair.
Which is fine, since i'll need DSP for active XO anyway, and it already was gonna be a separate combo per speaker, since each speaker is to be an independent wireless quad-amplified unit.

Your suggestion of a SE>BAL buffer seemingly refers to creating 4xBAL signal from an originally 4xSE signal, inside the miniSharc DSP. This is also very interesting, and if it works, treating the aforementioned signal --already on 8 conductors-- should certainly work.

But when we're using a single analogue voltage referenced to ground, to create an extra inverted version of itself, to end up with two opposite (balanced) polarities of the original, we're doubling the amplitude (e.g. a single ended +6V sine referenced to ground has an amplitude of 6V, whereas a balanced +6V sine referenced to -6V results in an amplitude of 12V)
In that example don't we also double the amplitude of the noise floor (as opposed to the situation where the balanced signal is provided by the digital source)?

If this becomes too elaborate for you, just ignore the whole thing. Hope it is of interest to some miniDSP-users.
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Balanced application of DAC8 and/or miniSharc 7 months 2 weeks ago #35864

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Or to put these (by now two) topics better:

1.
Can some of the basically SE miniDSP units be used in a completely BAL setup?
Meaning an 8-channel unit would be applied as a 4x positive + 4x negative conductor, for a total of 1/2/3/4x BAL IN > 4x BAL OUT?

2.
Can some of the basically SE miniDSP units be used to create BAL OUT's from initially SE IN's?
Meaning inside the DSP of the (for instance) MiniSharc or MiniDigi 2x8, we would create up to 4x BAL OUT from 1x (or 2x) SE IN?
And then use 8 channels of DAC (1x UDAC8 or 4x Curryman) to convert those 4 signals, travelling on 8 conductors?

Hope this clarifies my original topic a bit.
Last Edit: 7 months 2 weeks ago by cutedaddy. Reason: mistake
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Balanced application of DAC8 and/or miniSharc 7 months 2 weeks ago #35882

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I've been meaning to buy some Curryman DACs for a project and just looked, seems they are no longer available :(

I think the method of using two single ended outputs, and inverting one to obtain a signal you can send down a balanced line, will work fine. However, for any change in output channel processing, both channels must be updated. You could link two channels to make this easier but you can't then link left and right.

It's not like it can't be done, it's just whether you really want to do it.
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"You must ask the right questions." - Dr. Alfred Lanning's hologram.
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Balanced application of DAC8 and/or miniSharc 7 months 2 weeks ago #35883

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Also, you may find this article from Rane helpful;
www.rane.com/note110.html
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
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-> Have you posted your config file?
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Balanced application of DAC8 and/or miniSharc 7 months 2 weeks ago #35890

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Ah yes, the indispensable Rane notes. Have read most of 'em and just re-read 110.

For the wireless project, grounding may add yet another variety, with the signal entering this part of it's path wirelessly (but in digital form, 5,4GHz).
So neither RF nor hum are an issue, up to the Rx/liaison unit feeding the MiniSharc. But the speaker itself and all PCB's incorporated in its setup are plugged into AC wall outlet, and although interconnected XLR style may present some issues.

Will share when done (may be a while though).

Tx for your patient feedback, John, you rock.
Last Edit: 7 months 2 weeks ago by cutedaddy. Reason: typo
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Balanced application of DAC8 and/or miniSharc 7 months 2 weeks ago #35891

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To anyone stumbling on this topic after the fact: i just noticed that i'm inadvertently sometimes referring to the UDAC8. In fact, in my mind it always was about the miniDAC8 (combined with an 8-channel all digital DSP board, like nanoDigi or miniSharc). Sorry about that.
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Balanced application of DAC8 and/or miniSharc 7 months 1 week ago #35922

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Overhere thay advertise Curryman boards in stock.

www.audiophonics.fr/en/diy-dac/minidsp-c...o-analog-p-8450.html

Pricey, but i bet you can get the tax free price for shipping overseas. When marked "computer circuit samples, no commercial value", in my country i ususally don't have import tax issues. There's more and possibly cheaper internet retailers carrying miniDSP boards..
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Balanced application of DAC8 and/or miniSharc 7 months 1 week ago #35923

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