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[ajcamlet]

im curious. power amps for monitors?

[ssltech]

Anything which couples ground to one leg... capacitively or otherwise.

I know I always say it, and I'm like a broken record, but I do NOT believe in balanced power as a 'fix'.

Keith

[ajcamlet]

examples Keith??

broadly of course....

Im asking because there is no information regarding this from either of the two major manufacturers (equi= & Furman). Equi=tech has more information, but they more of less say pretty much everything is ok...

[Andy Peters]

ajcamlet wrote on Fri, 24 August 2007 11:29

examples Keith?? broadly of course....

Keith said, "Anything which couples ground to one leg... capacitively or otherwise."

That would include most unmodified vintage guitar amps that have a "ground" switch.

-a

[J.J. Blair]

I don't have Keith's technical knowledge.  However, I must say that I have been running everything off balanced for power without issue for twelve years.

[dcollins]

Andy Peters wrote on Fri, 24 August 2007 17:09

ajcamlet wrote on Fri, 24 August 2007 11:29 examples Keith?? broadly of course.... Keith said, "Anything which couples ground to one leg... capacitively or otherwise." That would include most unmodified vintage guitar amps that have a "ground" switch. -a

What about things that capacitively couple both legs to ground?

DC  (a fan of balanced power for everything but the power amp)

[bruno putzeys]

The most obvious issue "balanced power" deals with is the mains voltage capacitively coupling into the audio ground across the mains transformer. The primary winding of a mains transformer consists of several layers of wire. Only the top layer will be capacitively coupled to the secondary. Presuming the secondary voltage to be much lower than the primary, we can reduce the whole thing to one capacitance tied between whichever mains wire is connected to the outermost layer of the primary on one end and the audio ground on the other end. Effectively the same situation arises with SMPS with a Y cap between the "primary circuit ground" (which is basically any one of the mains wires) and secondary ground.

It follows that the best situation is when the neutral conductor is connected to the outermost winding of the primary and the live conductor is connected to the innermost winding. The worst situation is the reverse. Balanced power cuts the middle between the two, but is by no means the best option.

It is very rare for any electronic device to have identical leakage capacitances from both mains wires. If the equipment you're using has not been designed to deal with the capacitive coupling problem, you're better off checking the optimum polarity on each one of them rather than going for balanced power as a blanket measure.

Checking the optimum polarity is done as follows:
0) Use normal power (i.e. with a definite neutral and live connection)
1) Disconnect all signal cables from the device. If you suspect a galvanic contact to the rack, unmount the device.
2) Connect it to mains using a cheater plug and power it up.
3) With an AC voltmeter measure between any pin 1 and mains ground.
4) If you measure less than half the mains voltage, polarity is optimal. If you measure more than half the mains voltage, reverse the mains plug. By now you understand you can expect up to the full mains voltage on the casework (albeit with a highish impedance). DON'T TOUCH ANY CONDUCTIVE PART ON THE DEVICE YOU'RE TESTING WITH YOUR BARE HANDS. Some switch-mode supplies have several nanofarads sticking between mains and secondary. The current won't kill you but it's quite unpleasant.

If your equipment responds to the difference between normal and balanced power, you'll find that doing this for all your gear will give a substantial improvement over balanced power.

From an equipment design perspective the only advice I can give is to mind the flow of this leakage current through the circuit ground. The surefire solution also happens to be the most expensive one: use two shields between primary and secondary, ground the innermost shield to mains earth and the outermost shield to audio ground. When you're designing per AES48 and the whole box is grounded anyway you can do with a single shield of course.

[ajcamlet]

great info here guys, thank you.

i just started mulling this question about in my head because ive had some irregularities in the control room. more on that later....
cuz if the balanced power is not an issue (and i dont think it is in my case, then i have to trouble shoot elsewhere....)

thanks again..
alan

[Larrchild]

Quote:

Anything that should not be run off balanced power?

Anything the LA Electrical Code Inspectors plug their testers into.
That's the rub.

[J.J. Blair]

Larry, I built my room with inspectors doing their job.  At least thirteen years ago, they didn't care!  Maybe they've changed their minds since?

But then again, I was the second room in LA to have balanced power, so they may not have been hip to it yet.

[Larrchild]

Quote:

With the inclusion of balanced power in the 1996 National Electrical Code (Art. 530 Part "G"), the technology is no longer a myth. The advantages of using balanced power are a proven fact.  When at one time a technician might have asked, "Do I dare use balanced AC to keep the system clean?  The question today is different.  The question today is, "Do I dare not use balanced AC?"

http://www.equitech.com/articles/origin.html

'96, they blessed it. (sorry about the misinfo) National Code did, anyway.

[Dan Mills]

Just for any UK contingent, do NOT go do this unless you know EXACTLY what you are doing and have thought thru all the implications, it is an electrical engineer problem, not something to talk to an electrician about...

For the US crowd, the reason not to do this in the UK are many, but basically come down to the assumption (standard in the EU) that the neutral is a grounded conductor and that because of this only the live needs fusing in the equipment (Come to think of it, do you not have this assumption as well?).

Furthermore, with our somewhat higher supply voltage a fault connecting neutral to exposed metalwork would put 120V on the case, not 60V as in the US, this obviously makes a potential failure mode considerably more dangerous.

Also, with only 120V behind it, making the disconnection time requirements of our wiring regs is far from certain if retrofitting an existing install.

Now, it can be done safely, but is seriously non trivial to do (RCD (GFI) on every outlet, with double pole breakers on each outlet sized for the connected load, everything is home runs (No multiway extensions), Think 240V delta as found on cruise ships, it is a nightmare).

For myself, I strongly suspect it is at best a bandaid for poor grounding, spurious extra connections between grounded and grounding conductors in sub distribution (I think those are the US terms?) and badly designed gear, in any of those cases, fixing the real problem is probably cheaper.

Regards Dan (Who does not really buy it, and thinks it is far too easy to do in a way that makes it dangerous).

[ssltech]

heh...

Dan, you're singin' my song!

The problem with 'balanced wiring evangelists' is that when they installed the transformer, they had to re-wire the distribution with VERY STRICT care requirements. Then they attribute all the improvements to the transformer!

In an installation several years ago, (which cured a general low-level hum) the transformer went bad. In a work-around, just to get the studio back up and running, I wired past the transformer and put them back on standard UNBALANCED power, just fed into the new, carefully-wired distribution.

Hey-presto!!! -Silence. absolutely NO improvement when the replacement transformer was installed.

Made a disbeliever out of me.

I'll get down off my soap box now!



Keith

[zmix]

Thank you Bruno for the clear description..!!

I have often noticed in A/B testing that the expectation of a change or an improvement will cause the listener to 'hear' one.   It is usually not possible to A/B an electrical wiring scheme, so any 'findings' are often anecdotal and any improvements undocumented.  As Keith pointed out, the attention to detail in the wiring may be of greater benefit than any other factor.

I'd like to add as an aside that in at least two studios in the US and A which commissioned SSL consoles we've run 240 to the machine room and set the console PSU for that voltage.  
By it's nature 240 (here in the US) -is- balanced.
 Both rooms were eerily quiet.

[bigaudioblowhard]

I recall doing a little something from a 1/2" tape recorded at JJ's FF5 studio shortly after he installed the balanced power. I also recall remarking how low the noise floor was.

Tell me that wasn't 12 years ago.

bab

[Dan Mills]

zmix wrote on Tue, 28 August 2007 16:00

I have often noticed in A/B testing that the expectation of a change or an improvement will cause the listener to 'hear' one.

Can any of us honestly say we have never tweaked an EQ that turned out 5 minutes later to have been in bypass the whole time?

Quote:

As Keith pointed out, the attention to detail in the wiring may be of greater benefit than any other factor.

I would be slightly surprised if it was any other way.

Quote:

I'd like to add as an aside that in at least two studios in the US and A which commissioned SSL consoles we've run 240 to the machine room and set the console PSU for that voltage.   By it's nature 240 (here in the US) -is- balanced.  Both rooms were eerily quiet.

I just hope you revised the fusing on those power supplies, they are almost certain to have shipped with fuses in only the nominal live leg on the reasonable assumption that neutral = grounded conductor.

Regards, Dan.

[zmix]

 

[maarvold]

J.J. Blair wrote on Sat, 25 August 2007 19:12

...But then again, I was the second room in LA to have balanced power...

J.J., in your recollection, how much quieter (or not) did balanced power make Stratocasters and other single coil pickup guitars through cranked-up Marshalls?  I'm assuming your in-wall wiring is balanced and the idea that radiated hum from the ac lines would largely null itself, to me, seemed like one of the potential main advantages of balanced power.  

[Dan Mills]

maarvold wrote on Sun, 23 September 2007 18:45

J.J., in your recollection, how much quieter (or not) did balanced power make Stratocasters and other single coil pickup guitars through cranked-up Marshalls?  I'm assuming your in-wall wiring is balanced and the idea that hum from the ac lines would largely null itself, to me, seemed like one of the potential main advantages of balanced power.

Something VERY wrong if it does!

The hum pickup with single coil guitars is (By and large) MAGNETIC, not electric in nature, balanced power will do nothing for this.

About the only way it might help is if the original wiring was wired with a large live/neutral loop area which shouldn't happen, but can if someone stuffs up. The old standby of a subpanel with the earth link fitted would potentially do this as the earth paths are not necessarily the same as the current carrying conductor paths, and it doesn't take a lot of current if the loop area is large.  

Regards, Dan.

[maarvold]

Dan Mills wrote on Sun, 23 September 2007 15:13

maarvold wrote on Sun, 23 September 2007 18:45 ...hum from the ac lines would largely null itself... ...The hum pickup with single coil guitars is (By and large) MAGNETIC,

Maybe I should have said: "...radiated hum from the ac lines seems like it would largely null itself..."

It has always been my understanding that, for example, when one touches the tip (but not the sleeve) of a guitar cord that is plugged into an amp the resulting loud hum is that person's body acting as an antenna for radiated ac fields which are amplified by the guitar amp.  If this is true (which doesn't seem unreasonable to me) then balanced power's equal, yet opposite, radiation fields seem like they ought to largely cancel each other out.  Add to this that I read an article close to 20 years ago about a studio in Los Angeles that installed balanced power and received exactly this benefit: the guy plugged in his Strat and thought his amp was broken because it was so quiet.  I had always wondered about this and that is why I asked the question of J.J.: "ask the man who owns one" as the saying goes.  

[Fibes]

maarvold wrote on Mon, 24 September 2007 02:34

Dan Mills wrote on Sun, 23 September 2007 15:13 maarvold wrote on Sun, 23 September 2007 18:45 ...hum from the ac lines would largely null itself... ...The hum pickup with single coil guitars is (By and large) MAGNETIC, Maybe I should have said: "...radiated hum from the ac lines seems like it would largely null itself..." It has always been my understanding that, for example, when one touches the tip (but not the sleeve) of a guitar cord that is plugged into an amp the resulting loud hum is that person's body acting as an antenna for radiated ac fields which are amplified by the guitar amp.  If this is true (which doesn't seem unreasonable to me) then balanced power's equal, yet opposite, radiation fields seem like they ought to largely cancel each other out.  Add to this that I read an article close to 20 years ago about a studio in Los Angeles that installed balanced power and received exactly this benefit: the guy plugged in his Strat and thought his amp was broken because it was so quiet.  I had always wondered about this and that is why I asked the question of J.J.: "ask the man who owns one" as the saying goes.

Funny.

Sometimes it helps other times it doesn't but the noise issue is usually an amp thing, not single coil related.

I'm no tech but everything was quieter when we went balanced.

[Andy Peters]

maarvold wrote on Sun, 23 September 2007 23:34

It has always been my understanding that, for example, when one touches the tip (but not the sleeve) of a guitar cord that is plugged into an amp the resulting loud hum is that person's body acting as an antenna for radiated ac fields which are amplified by the guitar amp.

More likely it's simply electrostatic discharge.

Quote:

If this is true (which doesn't seem unreasonable to me) then balanced power's equal, yet opposite, radiation fields seem like they ought to largely cancel each other out.

'cept it's the magnetic fields generated by the mains hot and neutral wires which cancel.  And that's true regardless of whether it's "balanced" power or standard mains power.  Why?  Because magnetic fields are caused by current flow, and the currents in the hot and neutral must be equal and opposite, and by code they are run together.

-a

[ssltech]

The 'electrostatic discharge' is the 'click' at the start of the hum when you touch the tip...

Easy demonstration: touch the tip. Listen to the hum/buzz.

Now, rub your right foot vigorously on the carpet. Not touch the tip again.

-You hear it? -Same buzz, but now with a loud-ish "Crack!" at the start.

Plus, one more clue: There's no such thing as AC charge... ask any capacitor! AC can indeed be electrocapacitively COUPLED, but that's it.

The simple truth is this: "balanced power" changes the ABSOLUTE potential of the lines from 120/0V to 60/60V. The CURRENT passing through the wires remains UNCHANGED.

MAGNETIC radiation does not care one tiny little bit about the potential: only the current. Demonstrate this any number of ways (example omitted to keep the post shorter)

ELECTOSTATIC interference may be reduced by balanced power, but this requires A CONDUCTION PATH (usually capacitive) to introduce itself into signal lines.

CONCLUSION: The aforegoing suggests that there is no POSSIBLE way that balanced power can improve magnetically radiated noise without repealing one or two laws of physics. Electostatic noise may be improved, but by careful (read: "Correct") work to ensure properly-installed gear in the first place, such noise can be eliminated WITHOUT balanced power.

Balanced power does not 'cure' the noise: it HIDES the noise.

Viewed that way... balanced power is the LESS desirable option...

But do it if you want... it's your money. -I suggest that a clever installation tech should be able to match ANY balanced power noise numbers WITHOUT spending all that money, and that the reuslt will arguably be better.

Keith

[maarvold]

ssltech wrote on Tue, 25 September 2007 06:08

...Easy demonstration: touch the tip. Listen to the hum/buzz... ...The simple truth is this: "balanced power" changes the ABSOLUTE potential of the lines from 120/0V to 60/60V. The CURRENT passing through the wires remains UNCHANGED. MAGNETIC radiation does not care one tiny little bit about the potential: only the current. Demonstrate this any number of ways (example omitted to keep the post shorter) ELECTOSTATIC interference may be reduced by balanced power, but this requires A CONDUCTION PATH (usually capacitive) to introduce itself into signal lines. CONCLUSION: The aforegoing suggests that there is no POSSIBLE way that balanced power can improve magnetically radiated noise without repealing one or two laws of physics...

Good points, Keith--just 'shows to go you' that when one reads something in a magazine, and it seems somewhat plausible, the temptation is to believe without further questioning (referencing my earlier post about balanced power and the Strat owner thinking his amp was broken).  

I'm curious though: how would you explain the loud (continuous) buzz when one touches the tip only of a guitar cable plugged into a powered up guitar amp?  Very high resistance ground loop?  Or is it because the connection requires some sort of termination to be 'happy'?  Clearly there is a big audible difference between just holding the unplugged cable by its insulated jacket and by touching the tip with your finger.  Just wondering...

[David Kulka]

ssltech wrote on Tue, 25 September 2007 06:08

...I suggest that a clever installation tech should be able to match ANY balanced power noise numbers WITHOUT spending all that money, and that the reuslt will arguably be better. Keith

Agree 100%.

[ssltech]

maarvold wrote on Tue, 25 September 2007 23:04

I'm curious though: how would you explain the loud (continuous) buzz when one touches the tip only of a guitar cable plugged into a powered up guitar amp?

Well, that's pickup of a combination of nasty things... For a partial answer, do that test while putting your OTHER hand (the one NOT touching the guitar jack) around the insulated power cable... then move your hand away...

Yes, your body is an inefficient antenna, but there's no ground "loop". If it were a ground effect (a signal induced on the ground wire) it WOULDN'T diminish when you touch another finger on the same hand to the ground "sleeve" contact...

Move your hand closer to the power cable (or for REAL 'gits & shiggles', try a CRT monitor!!!) and hear the changes that improved coupling makes.

Hey, I'm actually surprised at the degree of consensus in terms of balanced power not being 'magical'...

The trouble is that -since nobody (nobody that I've ever met, at least!) likes to spend money needlessly- when you INSTALL balanced power it's usually because people have a pervasive hum issue and they're ready to spend money to make it go away.

A combination of the subsequent re-thinking of the power distribution, and the ability of the balanced power to conceal some electrostatic issues (remember: it can do absolutely NOTHING for electromagnetic, inductively-sourced issues) leads to the noise (usually) being finally dealt with.

Result? a quiet studio and a balanced-power 'evangelist'.

For a real "apples-to-apples" demonstration/comparison however, remove the balancing transformer, and listen to it with the new wiring layout alone...

Keith

[Rader Ranch]

What about those who don't have the option to rewire the building they're in?

[ssltech]

Dass what I'm tryin'a 'splaina-you...

You shouldn't need to rewire the AC supply:

Dismantle your audio wiring. Disconnect EVERYTHING except the monitor loudspeakers and whatever feeds them. Swtich them on. Listen. -All nice and quiet? -Move on.

Connect a SINGLE piece of gear at a time. If you get an audible hummmmm, lift the audio shield at the gear end (my personal preference , but there are other approaches) and the hum should be gone.

STAR-GROUND at patchbays, lift at the far end.

in simplified terms this is how you do it. It may be largely simplifying, but the origin of inductively soupled noise is -at the root of it all- largely simple, so I beg no forgiveness...

Keith

[Rader Ranch]

Thanks....unfortunately, wiring for dummies is all some of us like me can handle. For some reason electronics are like philosophy for me. Just a little reading of it makes me angry. The terminology is confusing, non-intuitive...I just can't get it. Fortunately, I usually get music et.al. so I try not to sweat it. Which is little help when one has to be ones own tech on a regular basis.

[Martin Kantola]

Would like to chime in with a couple of points here, this has been discussed elsewhere too?

My studio is in the countryside, and I'm running all audio gear on a big 230V-to-230V transformer. For a few reasons:

- it seems to me that it works as a simple lowpass filter on the AC, filtering out sounds from machinery turning on and off, whining of electric drills etc, or whatever my neighbour is up to...

- it allows me to disconnect my ground from the one supplied by the electrical company. Again, that wire is a pretty dirty line once it reaches my house. Running massive electrical heating. Also, my UPS and computers are not sharing ground with the audio equipment.

- might offer a bit of protection against lightning, although any surges will go through if I'm powered up.

So, balanced or not, a transformer can still be useful. But as pointed out, can't do an A/B easily, just a happy user for a decade. On the other hand, if some assistant by mistake ties my audio power ground to a normal outlet, I can usually hear it in the system, it's normally very quiet.

Martin