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Unbalance to balance converter?

dasdoing

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As much as I admire Neutrik, that particular adapter I think is rather poor. It only handles a level of -3dBu at 50Hz and with 1% distortion, so at sub-woofer levels, down to 20Hz, the distortion will be a lot higher and/or the maximum level a lot lower.

-3dBu is only just over 500mV so unless the subwoofer is unusually sensitive, the maximum output is insufficient.

That Neutrik device I think is far more useful for stage use where its solidity will be appreciated and the LF limitations possibly less problematic.

S.

line level is -10dBV
balanced is +4 dBu


I don't realy understand this voltage stuff, but a balanced signal is dubbled at the target since the cable runs normal and an inverted signal which will be reinverted and summed (that's how the noise cancels out)
 
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solderdude

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-10 dBV = 0.32 Vrms
+4 dBu = 1.2 Vrms
most line-level DACs however are 2Vrms (+8.2 dBu / +6dBV) and for balanced 4Vrms (+14.2 dBu / +12dBV)
Phones etc. often are closer to 1Vrms (+2.2 dBu / 0dBV)
 

sergeauckland

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-10 dBV = 0.32 Vrms
+4 dBu = 1.2 Vrms
most line-level DACs however are 2Vrms (+8.2 dBu / +6dBV) and for balanced 4Vrms (+14.2 dBu / +12dBV)
Phones etc. often are closer to 1Vrms (+2.2 dBu / 0dBV)
Although Pro DACs can be +18dBu at 0dBFS if they're set to EBU standards, +20dBu, +22dBu or +24dBu if they're more VU orientated than PPM.

Aren't standards great? That's why we have so many.

S.
 

sergeauckland

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line level is -10dBV
balanced is +4 dBu


I don't realy understand this voltage stuff, but a balanced signal is dubbled at the target since the cable runs normal and an inverted signal which will be summed (that's how the noise cancels out)
That's a myth that still seems to be prevalent. There is no doubling on a balanced signal, a balanced, or a better term is 'differential' signal just has two legs that have voltages of opposite polarity with respect to each other. Whether that's double a single-ended voltage is only apparent when trying to unbalance a balanced and differential line. If it's centre-tapped, i.e. earth referenced, then it can be simply unbalanced by going between either leg and ground, ignoring the other leg. That will result in an unbalanced signal half the size. However, if it's a fully-floating balanced differential line, whether transformer or electronically balanced, then either leg can be grounded and the signal taken from the other leg, in which case there is no halving of signal.

It's necessary to know what sort of balanced differential output one has to know the best way of getting a single-ended output as earthing one side of a centre-tapped (earth referenced) output will short out one side, which at best will most likely increase distortion and at worse damage the output driver.

I won't even go to impedance balanced single ended outputs!

Going the other way, from a single-ended source to a balanced differential input is very easy, just go between XLR pins 2 for signal and 1-3 strapped together for ground. If there's a hum loop created, try removing the link between pins 1 and 3, leaving pin 1 floating.

S.
 

dasdoing

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a balanced signal, a balanced, or a better term is 'differential' signal just has two legs that have voltages of opposite polarity

but at the reciever the inverted signal will be inverted once again and added to the other afaiui.

cable: signal+ noise+ | signal- noise+

then you reinvert: signal+ noise+ | signal+ noise-

now they are added so you have: signal*2 noise(canceld)
 

sergeauckland

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but at the reciever the inverted signal will be inverted once again and added to the other afaiui.

cable: signal+ noise+ | signal- noise+

then you reinvert: signal+ noise+ | signal+ noise-

now they are added so you have: signal*2 noise(canceld)
With a balanced receiver, any noise induced into both the signal wires will cancel to the extent of the common-mode rejection of the receiver.
With an unbalanced receiver, any noise induced into both wires will not cancel, as there's no differential action in the unbalanced receiver.

There's no 2x signal in a balanced differential receiver, it only looks at the difference between the two legs. That's why you can have impedance balanced outputs working into a balanced differential receiver where there's signal on only one of the two legs. Any noise still cancels as the receiver only looks at the difference between the leg with signal and the other leg which has nothing on it, any noise that's common to both legs will be ignored.

S.
 

DonH56

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Single-ended vs. differential: https://www.audiosciencereview.com/...d-balanced-unbalanced-and-all-that-jazz.1352/

The signal is the same at the transmitter and receiver, less typically infinitesimal loss through the cable. The two "sides" are opposite in polarity so signal(+) - signal(-) = 2 x signal. Uncorrelated (random) noise is not canceled, but because it is uncorrelated, the noise sums in root-sum-square (RSS) fashion (instead of linearly adding) since noise is random in phase for each path. The net result is that signal increases 6 dB and noise 3dB for a net 3 dB increase (improvement) in SNR going from single-ended to differential signals of the same amplitude.

Truly differential circuits ideally cancel common-mode noise (noise that is the same in both sides; not all noise is!) and even-order harmonic distortion.
 
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Atanasi

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Veri

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Why are products based on DRV134 not sold by local retailers? DRV134 implementations are mostly sold as DIY projects.
I... don't really know :p

If anyone in EU is looking for one I have a 220V version of the DRV134 box WolfX reviewed that I can part with. Not using it atm.
 

Atanasi

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If anyone in EU is looking for one I have a 220V version of the DRV134 box WolfX reviewed that I can part with. Not using it atm.
I considered it but I think I end up with Radial Stagebug SB-6.
 

pma

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This is one of the best ways, with a huge advantage - the output is floating and yields output CMRR. Effective to suppress hum on output ground loops. Verified, measured, working for years.

balpre_schema.png
 

datrumole

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You can build your own conversion box with these two items in a project box of your choice

Can do SE to BAL with the 1646, there is a 1206 to do BAL to SE

1603226007089.png
 

BigE

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If you wish to DIY, there is this neurochrome buffer. I am using one to go Balanced to SE. As far as I can tell, it is totally transparent. I am using it to feed a DCB1 buffer, with an Allo volume control. It uses the 10V power from the DCB1 to power the convertor.

The Allo ladder network volume control and following buffer stage have more colouration than the neurochrome buffer. I'm not affiliated with them. I am just a customer. I may convert the other side of the DCB1, as I am that impressed.

https://neurochrome.com/collections/buffers-preamps/products/universal-buffer
 

phoenixsong

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Just came across a tonne of these in a local online store but didn't know how they worked so came here searching in the forums haha! Thought they could have been a gimmick after many experiences with snake oil audiophile products, but it doesn't seem like the case from the tone here?

 

AnalogSteph

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Just came across a tonne of these in a local online store but didn't know how they worked so came here searching in the forums haha! Thought they could have been a gimmick after many experiences with snake oil audiophile products, but it doesn't seem like the case from the tone here?
Nope. Line isolators (as most but not all of them are) work well within their limits. I would advise keeping cable length after them moderate (like 1.5 m or so), as even the 600 ohm jobs are eventually going to display ultrasonic peaking. I've been using a HD400 myself for several years now, it's fine. CMRR is decent, if you want better you'd have to go to higher-impedance transformers which may make permissible cable length shrink to near zero or even below.

The CleanBox Pro is one of the few outliers, sporting active electronics with no galvanic isolation. If memory serves, parts quality is supposedly a bit meh.
 
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