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Balanced vs Single Ended

jcbrum said:
If you have a massive reduction in noise and hum, simply by inserting a 1 metre XLR cable, that would suggest to me that you have a still un-resolved defect, or fault, on your system,
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I'd agree, surely a basic feature of any system should be an inaudible noise floor at full gain?
Something has to be wrong, do we still suspect earthing first?

Having said that even when our kitchen taps gave a decent 12 / 15V there was no hum from my old NADs.
 
jcbrum said:
If you have a massive reduction in noise and hum, simply by inserting a 1 metre XLR cable, that would suggest to me that you have a still un-resolved defect, or fault, on your system, which is now merely disguised.

JC

p.s. unless of course it was the previous RCA cable which was defective, in which case replacing it with any type of good one would have been effective.
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Indeed, it is hardly likely that you would have had a huge amount of pickup on a 1 metre cable, more likely an earthing problem or PSU problem within the DAC.
 
Possibly. It doesn't hum like a bastard, but you can hear it, sitting 3m from the speakers, input gain set to max. With the XLR leads the problem goes away.

They're very old red and white RCA leads I was using, so that won't help.

My feeling is that the bundled wall wart that comes with the DM+ is adequate rather than good.
 
I run balanced from my Weiss to my power amp. Does it sound any different to the single ended inputs? Nope it sounds exactly the same once you trim the level 3db.

I would be interested in a genuinely balanced phonostage though, Carts are inherently floating so perfect for use with a balanced phono amplification stage.
 
sq225917 said:
I run balanced from my Weiss to my power amp. Does it sound any different to the single ended inputs? Nope it sounds exactly the same once you trim the level 3db.

I would be interested in a genuinely balanced phonostage though, Carts are inherently floating so perfect for use with a balanced phono amplification stage.
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This is something I may well look into in the future... As it happens, some of the ideas I have used in the mods to the 640P are eminently suitable for a balanced phono stage ;)

Universal compatibility can be an issue though... as i mentioned earlier in the thread, there are a few arms that are not suitable unless re-wired.
 
A major problem with balanced circuits is the signal has to travel through double the number of components (both passive and active) than it would need to on a single ended circuit. The power supply is more complicated too because you have to have a positive supply rail and a negative supply rail. Also you find lots of feedback is normally applied to keep the crossover distortion low.

For a phono stage it makes no sense to run balanced unless you have a fully balanced system. Very few preamps are fully balanced all the way through anyway as the cost of fitting a four gang volume control is very expensive. Often balanced circuits are converted to singled ended to go through the volume control and then it is then inverted again to carry on "balanced" in the pre output stage. What you now have is a larger number of components, plus at least one active device (maybe more) in the signal "-" (negative) than in the signal "+" (positive) part of the wave form. As has been said earlier not all cartridges and tonearms were designed to be used with balanced phono stages due to they way the manufacturer designs and wires them.

IMO there are many more negatives aspects to balanced circuits than the main reason balance operation is chosen i.e. reduction of noise. If a single-ended phono stage is correctly designed then there should be no noise anyway.
 
G T Audio said:
What you now have is a larger number of components, plus at least one active device (maybe more) in the signal "-" (negative) than in the signal "+" (positive) part of the wave form.
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That's not really fair. So we might have two op-amps in parallel for each half of the signal (+ and - phases) and you could say that you get twice as much distortion, but you also get twice as much signal. So the result is no more distortion from additional parts. What is really interesting is that any distortions which are the same (common-mode) from each op-amp will cancel out! So you get a significant reduction in even order harmonics compared to using a single op-amp and a single-ended signal.
 
This may be apocryphal but I once read that the single ended electronics of the Studer B62 sounded better than the balanced electronics of the slightly earlier and more expensive A80 because of the great reduction in the number of components and that some A80s were fitted with B62 electronics for that reason.
 
G T Audio said:
A major problem with balanced circuits is the signal has to travel through double the number of components (both passive and active) than it would need to on a single ended circuit. The power supply is more complicated too because you have to have a positive supply rail and a negative supply rail. Also you find lots of feedback is normally applied to keep the crossover distortion low.

For a phono stage it makes no sense to run balanced unless you have a fully balanced system. Very few preamps are fully balanced all the way through anyway as the cost of fitting a four gang volume control is very expensive. Often balanced circuits are converted to singled ended to go through the volume control and then it is then inverted again to carry on "balanced" in the pre output stage. What you now have is a larger number of components, plus at least one active device (maybe more) in the signal "-" (negative) than in the signal "+" (positive) part of the wave form. As has been said earlier not all cartridges and tonearms were designed to be used with balanced phono stages due to they way the manufacturer designs and wires them.

IMO there are many more negatives aspects to balanced circuits than the main reason balance operation is chosen i.e. reduction of noise. If a single-ended phono stage is correctly designed then there should be no noise anyway.
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Technically incorrect on more different levels than farting in a lift!
 
Barrymagrec said:
This may be apocryphal but I once read that the single ended electronics of the Studer B62 sounded better than the balanced electronics of the slightly earlier and more expensive A80 because of the great reduction in the number of components and that some A80s were fitted with B62 electronics for that reason.
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I've got a B62! Nice machine but my PR99 MKIII beats it ;)
 
Tenson said:
What is really interesting is that any distortions which are the same (common-mode) from each op-amp will cancel out! So you get a significant reduction in even order harmonics compared to using a single op-amp and a single-ended signal.
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Try it, in practice it requires exquisite matching of not just every part involved (and the strays in the layout) but even the opamps OL gain too. Deep-ish (up to 60dB) nulls are only really possible at very low frequencies. If what you need is reliable common-mode rejection then a transformer is the way to go, though there are other tradeoffs already mentioned!

If Balanced circuitry is 'needed' at home there's probably something wrong somewhere else - like the CM noise being injected in the first place from some cheap and nasty SMPS wallwart (These things are beloved of many a box-shifter as being the cheapest route to regulatory compliances worldwide - 'hey, this ones UL listed, it'll do'...)
 
Hi Martin, yeah by significant reduction I meant about 6dB ;)

Still, those Analog Devices SSM ICs do a very good job of matching all parts I guess, they quote 70dB CMRR at 20KHz.
 
Pandapple said:
This will effectively turn your Behringer into a 10W amp (might be all you need though).
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hammeredklavier said:
It'll be more than 10W I would think, but after a bit of experimentation I discovered that taking 20 dB out of the signal still drives the power amp louder than I'd ever want to go.
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DacMagic Plus XLR output: 4.2V RMS = 12.5dBV
Behringer A500 voltage gain at max: 26dB
Speaker-level voltage with 20dB attenuation = 18.5dBV = 8.4 V
Power into a nominal 8-ohm resistive load = 8.8W

As you found out, all you personally need.
 
Pandapple said:
DacMagic Plus XLR output: 4.2V RMS = 12.5dBV
Behringer A500 voltage gain at max: 26dB
Speaker-level voltage with 20dB attenuation = 18.5dBV = 8.4 V
Power into a nominal 8-ohm resistive load = 8.8W

As you found out, all you personally need.
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Indeed. With a different front end, but the same speakers (89dB/WM) I measured 7.5W at the speaker terminals - at which they were uncomfortably loud in quite a large room!
 
When I measured the power consumption I think it was with a test tone - which I suppose is guaranteed to be unpleasant! I listen almost exclusively to classical. With the Cambridge/Behringer combo, most of the recordings I tried were as loud as I'd ever want them to be with 20 dB of attenuation. Not deafening, but certainly plenty loud enough.
 
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