Hi,

I bought a 2500 Watt Constant Voltage Transformer (CVT) from Advance Electronics (http://aelgroup.co.uk/htm/agt.htm). The CVT takes the incoming electricity and generates a new, perfect sine wave. It can deal with extreme spikes and surges, and I have seen it argued that the perfect sine wave can improve recording/listening quality. Personally, I can't hear this, so we'll ignore that aspect for now.

Unfortunately, my guitar (Peavey Blues Classic) and bass amplfiers (SWR 750x) both have an added buzz/hum when plugged into the CVT, rather than when they're plugged into a regular wall socket. My PMC TB2-A's sound the same when plugged into either. The technical director from Advance is away until Monday andt he is going to get back to me then. I have tried not connecting the Earth (temporarily!) of my Peavey to the CVT sockets to see if this made any difference but it didn't. In one of the configuration option for the CVT they suggest connecting the Earth to Neutral in the CVT (in order to create a 0-volt reference point rather than have a floating earth). I have tried this but it made no difference. I should note that they do recommend having a Residual Current Circuit Breaker fitted if you're feeding sockets. As I'm just testing I haven't done this at present.

I'm at a bit of a loss. The CVT was £700 and whilst it is nice to know that my electrical/computer equipment is protected from spikes/surges I would like to think my amps would be quieter when plugged into it rather than the mains I have isolated the CVT by turning off all the other outlets in my fusebox except the one the CVT is plugged into and I have I have conducted my guitar/bass amp tests with just them connected.

I've created some recordings which clearly illustrate the added hum/buzz from the CVT but I don't seem to be able to attach anything on the SOS forum. Maybe if anyone's interested I could e-mail them?

Any advice/comments are appreciated. When I orginally looked into sorting the power for my set-up it seemed that most 'conditioners' are nothing more than glorified splitters with 'surge protectors'. The CVT seemed to address a real need and yet it has actually had a negative impact on my amps.

Thanks,

Alex

Have you tried moving your equipment around? I'm just wondering whether your CVT is generating the same kind of interference that some wall warts / carpet carbuncles do. Their location in relation to each other can make interference problems better or worse.
Do your amps buzz with nothing plugged in to them, or is it your guitars themselves that are picking up the hum?

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There's nothing we can't face... Except for bunnies

If you read the CVT docs, one thing they tend to generate is a large fringing field. If the CVT close to your audio gear, (and especially if you are using single coil pickups) then induced hum can be a problem. The fix is to put the CVT further away (A good idea anyway as they can be a bit loud under load).

You definitely want that link between the output side neutral and earth or the circuit protection may not work correctly, and an RCD following this is a very good plan.

CVTs are an excellent cure for some problems, but if the power was not acting up before, they will not magically remove a problem that you did not have, and they will not magically fix poor grounding practice.

Regards, Dan.

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Audiophiles use phono leads because they are unbalanced people!

Edited by dmills (15/02/07 04:16 PM)

Thanks Dan. My sentiments entirely. I'd expect the hum to be radiated from the power conditioner. Distance and possible angles will improve it.

Hugh

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Technical Editor, Sound On Sound

Quote Alex A:

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Unfortunately, my guitar (Peavey Blues Classic) and bass amplfiers (SWR 750x) both have an added buzz/hum when plugged into the CVT, rather than when they're plugged into a regular wall socket.

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So keep them plugged into a regular wall socket then.

I'd have to say that I'm not clear why you would need a CVT on a normal mains supply in the UK anyway. Are you in a remote location that suffers from voltage sags or thunderstorms?

Cheers

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

Hi. Thanks for all the responses. The CVT is more for peace of mind than anyhthing else. The flat I've moved into has initially had problems with everything and as my gear is getting of a higher and higher value I simply want to protect it in the best possible way. For example, you can hear the lights 'surging' on and off as the dimmers seem to be picked up by the phone and amplifiers. Sometimes when the lights are on long enough in various parts of the house I get surges building up into buzzes that remain on the phone and in the power supply. I've learned which lights to keep off (the bathroom and hallway underneath my studio area) to keep the interference away but initially I was freaked out there was the potential to damage my studio equipment. There were enough other things wrong to mean I'm nervous about the power.

As it turns out, the lights are being picked up electromagnetically, anyway, and moving the amps around and away from where they are sited underneath does change the level to which they are picked up. As it's caused by the distance from the various lights below the floor (and on the ceiling of the room below), the CVT hasn't fixed this problem.

I accept I may have made the wrong choice. When I started looking into this problem I was thinking of just getting Furman power condtioners and the like but I saw a lot of opinion that they were nothing more than glorified power splitters and for a true solution you need online UPS's, power 're-generators' or balanced power (and after reading the SOS article I saw a lot of potential problems with this in the UK from comments here and elsewhere).

The question is, now I have the device, surely it's better to run my stuff through it than not? Take a look a the before and after pictures of the scope waveforms and the job it does putting out a perfect sine wave, even from a square wave:

http://aelgroup.co.uk/hb/hb002.htm

I would have thought this would cause less noise not more! I've read quite a lot of opinions by people that this kind of regenerating can even cause a lot of improvement in the sound of audio equipment. Advance even have a product that has been prepared for that purpose (http://aelgroup.co.uk/htm/asr.htm). It's essentially the same as the CVT but specially cased so that it can't be heard operating. It was the product I originally looked at but it only gives off 200 watts which is why I moved up to a larger unit.

The noise isn't an issue because my CVT is actually kept behind a wall in my 'studio' and extensions are ran from it through the wall. My computer and hard drives are also in there, and I keep them about 3/4m from the CVT to avoid any possibility of electromagnetic interference. I've always seen 2 choices with gear and audio - get silent gear or put it somewhere so you don't care if it's noisy! I find the latter (once the hard work of holes or the like is done) is easier and simpler.

The amplifiers are a good 25 to 35 feet away from the CVT. Surely this is enough distance? As for moving the amps around, this makes no difference.

Obviously, I guess I now have a choice for gear between the two, but it seems strange to be using the normal sockets for 'cleaner' sounding power than the 'cleaned' power. Especially after looking at the before and after CVT waveforms! More than that, though, is the fact that I calculated the power consumptions of all my equipment and then left room to spare when buying the CVT. The amps are some of the devices that consume quite a lot of watts by comparison to other devices. If I'm not plugging those in then I really don't need a 2500-watt CVT (which by itself consumes about 200 watts or so of power). After "An Inconvenient Truth" to consume an additional 200-watts to power only say 400 watts or so seems like an almost sickening waste.

Sometimes I think I over-think these things!

Cheers for all the advice/comments. At Advance they have a large range of other more regular power 'protectors' and UPS devices so if anyone thinks it's worth it I'm glad to listen to any recommendations on what to change the CVT for!

What do you all do?

Alex

Quote Alex A:

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For example, you can hear the lights 'surging' on and off as the dimmers seem to be picked up by the phone and amplifiers.

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Don't even think about power conditioning if you have dimmers in the house - getting rid of the dimmers will do wonders for the quality of your electricity supply. With these problems you really mustn't look for the miracle quick fix. If you pay attention to sensible wiring you'll usually find that you can clean up your mains supply for very little expense.

You should also ignore any advice intended for people in the US. Their power wiring is different and often more susceptible to interference than ours.

You really need to spend some time getting the basics right first before even thinking about power conditioners. By the time you've got the basics right you should find that you don't need any sort of power conditioning.

Cheers

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

The cure for dimmer-switch induced noise: £1.09 and 2 minutes work - http://www.tlc-direct.co.uk/Products/MKK4870.html

Don't forget to turn the power off....

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Dynamite with a laser beam...

Quote Steve Hill:

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The cure for dimmer-switch induced noise: £1.09 and 2 minutes work - http://www.tlc-direct.co.uk/Products/MKK4870.html

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How am I supposed to give my girlfriend nice romantic dinners if my lights aren't dimmable?

So you all honestly just plug all of your expensive equipment straight into the wall sockets? No worries about any types of surges? If you do, you just rely on £20 surge protectors that'll just catch the big one's (if you're lucky). I have seen a good few posts by people who've had most of their studio equipment damaged by surges.

Alex

Quote Alex A:

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How am I supposed to give my girlfriend nice romantic dinners if my lights aren't dimmable?

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Here you go... even more romantic than dimmers, and they won't interfere with your gear... don't know about the ones you stick in your ears though!

http://www.somethingforthewickend.co.uk/

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Battle flags are flown at the feet of a garden gnome.

You can give her the nice romantic dimmers instead.

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"Ignorance more frequently begets confidence than does knowledge" Charles Darwin.

Quote:

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How am I supposed to give my girlfriend nice romantic dinners if my lights aren't dimmable?

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I simply have multiple small lights. If I want dim, I turn only some on. If I want bright, I turn all on. No evil dimmers needed!

Quote Alex A:

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So you all honestly just plug all of your expensive equipment straight into the wall sockets? No worries about any types of surges? If you do, you just rely on £20 surge protectors that'll just catch the big one's (if you're lucky). I have seen a good few posts by people who've had most of their studio equipment damaged by surges.
Alex

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For most of the UK population this is just not a problem if the gear is halfway competent. In the cities in the UK power distribution is typically underground and thus largely immune to lightning produced surges. Personally I would pull the MOVs from those 'surge protected' 4 ways (at least as far as anything to ground is concerned) as they offer little protection and just contaminate the ground system.

Now connections to external overhead lines are a good candidate for some protection (Phone lines connected to computers for example, BTDT), but this really needs to be done right at the line entrance and taken directly to earth via a low Z copper strap.

Now if I was in a village on the far end of miles of dodgy overhead cable, then the CVT becomes an excellent investment (As does the generator, UPS and AMF panel).

Of course in a PME setup (most city based UK people will have this), there are all kinds of fun issues around interconnecting grounds for system that extend outside the equipotential zone (Like say that telecoms isolation barrier), so thats a whole can of worms and here be dragons.

I have a couple of small AEL CVTs in use on critical services (One on the input of the 'phone switch at one site for example), and another in the lab for some data acquisition gear, but by and large most things just get stuck straight into the wall. In the event of a lost neutral I am in a world of pain, but that is what the insurance company is for, and in any case under these conditions repairing the studio kit is MINOR compared to the other problems.

Regards, Dan.

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Audiophiles use phono leads because they are unbalanced people!

The only time we've ever had a mains surge that I can remember was when someone drove a pneumatic drill through the supply cable in the road and managed to send us a few extra volts for a few seconds. A couple of fuses blew and one of the tape machines seemed a little less reliable in the weeks after the incident but otherwise everything was fine. I don't think a surge suppressor would have helped in this situation as the voltage difference would have been too small for most suppressors.

Audio gear is really far more resilient than you think.

Cheers

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

Hey guys. The thing is, if I'm stuck with the CVT surely it's worth using, right? Or should I consider it a really heavy paper weight (it ways more than 70kg - more than me!).

My mains fusebox has all the different things from the house going through it, the lights, the air conditioning units, etc. Won't the operation of these high-energy drawing devices cause interference and surges/spikes for the other equipment connected to my mains?

Also, has no one ever come across the supposed benefits of powering your audio equipment from a perfect sine wave?

Alex

Quote Alex A:

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Also, has no one ever come across the supposed benefits of powering your audio equipment from a perfect sine wave?

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Not wanting to be too jingoistic, UK mains is the best in the world. Really. No-one else has e.g. shuttered mains plugs (acoustically irrelevant, I concede), overwhelmingly earthed systems, the whole ring mains idea (pretty well unique).

I genuinely don't think you need this thing. Is it too late to get a refund?

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Dynamite with a laser beam...

Amen, they are a cure for some situations, but if you are in one of those, you tend to KNOW IT.

If you are running a server that really needs less then 15 minutes per year downtime, they are good on the input side of the UPSs (Before the generator auto changeover, they are frequency sensitive), or if you hack around with particle physics then they help to keep the really nasty hash from multi megawatt pulse discharges out of things like He3 neutron detectors (And believe me, you appreciate all the help you can get), but in both those situations you tend to know that you need the gear.

It will not harm anything, and may help if it all goes pearshaped, but somewhat surprisingly, mains powered gear is normally designed to cope with the sorts of things you find on the mains!

As I say, if everything else is right, and if you are at the far end of long overhead lines, live next door to a welding company, or a guy who builds atom smashers in his basement then they can be a massive win, but nothing can cure a problem you do not have to start with.


Regards, Dan.

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Audiophiles use phono leads because they are unbalanced people!

Sometimes power regulation is needed-but when it is, it will be obvious. For example, lights dimming in an entire building! Also, I was in the habit for awhile of measuring mains voltage when recording remotely (location). I was very surprised to find RMS voltage as low as 95 in some buildings, and that was constant voltage, not a transient dip! Nominal was 120v. In the US, power companies have widely varying limits of acceptability, but generally they are reasonable, between 5 and 10 percent. When an "unreasonable" situation is found, however, it can take 4 to 8 weeks or more to fix. The fixes are usually not easy, and involve moving or adding outdoor transformers etc.

So, in the meantime, and in those pesky commercial buildings with 95 volts and more than a few volts measurable between neutral and ground, power conditioning is a nice thing to have!

In my case, I used (still have it but haven't needed it in my new city) a simple multi-tap transformer. It moves in steps of 8 volts. While this sounds very crude, it isn't! They've figured out how to get these thing to switch precisely at the 0 crossover, with absolutely no ill effects at all. You can watch what the thing is doing by viewing an attached RMS output voltage meter.

But if you need something like that, you'll know and it won't be subtle.

There are some pieces of professional and consumer gear that do subjectively sound different with some sort of power conditioning. Usually, though, that can be accomplished by adding a ferrite choke to the mains supply. If you can't hear a difference, there probably isn't one!

On the other hand, all of my AC supply boxes have toroidal transformers and other passive devices, and it's a bit unnerving to hear and sometimes feel all those transformers buzzing away-sometimes very loudly. And dimmers will definitely get those toroidal transformers singing!

When I did outdoor sound reinforcement, I'd generally try to get everything running off the same mains line. I would run the everything except the amp off the transformer. You'd be surprised at what a relatively modest (3-600 watts) amp can do to line voltage. This kind of thing would be very large but transient-swings in excess of 15 volts were common on a 120v system.

I wouldn't try to fix anything that's not broken, however....

Quote Alex A:

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Hey guys. The thing is, if I'm stuck with the CVT surely it's worth using, right?

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Well, if you've got it, you might as well use it... but on the other hand, if it is actually creating a big magnetic field that is causing unwanted noises then there is obviously no point -- it is doing more harm than good. At the very least, put it far away from the sensitive gear.

Quote:

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Won't the operation of these high-energy drawing devices cause interference and surges/spikes for the other equipment connected to my mains?

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Not really. You might occasionally get the odd click when a fridge turns on, or a very old and dirty switch arcs when operated, but it is rare. I've never had anything damaged by surges or spikes. The only thing I know that was in recent times was a computer modem taken out by a lightening strike at the end of the guy's road, straight into a power substation. And that modem was on the safe side of a supposedly 'surge protecting' mains plug!

Quote:

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Also, has no one ever come across the supposed benefits of powering your audio equipment from a perfect sine wave?

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I've never really found a need in the UK to justify the expenditure, other than in cases of outside broadcast vehicles where you never know what the mains supply will be like, and don't have time to get a bad one sorted out.

I can only think of two occasions in over twenty years where the local mains was nasty enough to cause some problems. It's just not that big a deal, and any properly designed mains supply will be able to cope perfectly well.

Hugh

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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Well, if you've got it, you might as well use it... but on the other hand, if it is actually creating a big magnetic field that is causing unwanted noises then there is obviously no point -- it is doing more harm than good. At the very least, put it far away from the sensitive gear.

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I do have my stuff separated by a wall and some distance (I'd say a good 30 feet from the CVT to the amps).

I think that I'm going to pursue Advance to rectify this problem because it was sold to me on the basis that it would solve any power-related issues, not add to them!. Thus, I bought the 2500-Watt version, enough to power everything in my studio, including amps. If they can't figure out what's going on and the situation remains, I still feel protection for my API pre-amps, PMC monitors, G5, Hard Disk enclosures, etc, is probably a good thing, but I need nothing like the 2500 watts the CVT can provide if I'm not connecting my amps to it. Apparently it uses about 10% of the 2500-Watts just to run so I feel I am severely wasting energy. I only bought such a high capacity model to cover all my equipment *and* leave room to grow into. I didn't think I'd be going in the other direction!

It might be an idea for them to downgrade me to a lower capacity model and I'll just plug my amps into the mains straight and keep the CVT for the other bits.

Quote Steve Hill:

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I genuinely don't think you need this thing. Is it too late to get a refund?

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I've had it for a while now (I went away and then when I got back didn't start using it until I got the hole through to the adjacent room ready). At least if I put the ball in their court then if they can't fix the problem they might be willing to take it back or replace it with a lower wattage version that I won't power my amps from.

Thanks for all the advice guys. It is, as always, much appreciated.

Alex

Interesting thread.

One point - if your mains supply is seriously out of spec, then your electricity supply company are probably obliged to sort it out anyways.

I note that, here at Feline HQ, the transformers in my gear seem to buzz louder at night. This could just be psychological, cos its quieter outside at 3am anyways,
but I suspect its more cos a.c. mains frequency is going out of tolerance then, and the more rubbish bits of my gear don't like it.

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~~~ A weasel hath not such a deal of spleen as you are tossed with! www.feline1.co.uk ~~~

It's unlikely to be the mains frequency Feline, but the waveform. Have a read of this:

www.psaudio.com/articles/hum.asp

Specifically, "Mechanically induced hum is caused, almost entirely, by the transformer and is nearly impossible to get rid of. If you suffer from this noise problem, you've probably also noticed that it's intensity varies depending on the time of day, sometimes even the time of month. The reason it varies is due, in large part, to the quality of the AC line voltage and how much DC is on it."


Martin

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YewTreeMagic

Oh, I see.

Can I also, without appearing to be bonkers/RussAndrews, note that if you turn some of these troublesome devices around in their geographical oriention, vis-a-vis the geomagnetic field, ewe may see your mileage vary

Martin, that website has products to remove d.c. from yer mains, but they're for US supplies.....
Can I ask "Seeboard Energy" (or whatever they call themselves these days) to just bally well stop sending me d.c. in the first place, I wonder?

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~~~ A weasel hath not such a deal of spleen as you are tossed with! www.feline1.co.uk ~~~

Edited by feline1 (19/02/07 02:53 PM)

There is typically negligible DC component on the mains voltage, and DC current is heavily discouraged (It does really BAD things to the supply companies delta/star transformers).
What there is is just down to asymmetric loads (naughty, not supposed to do that), in combination with the DC resistance of the supply circuit.

If there was enough to worry about a simple series capacitor would remove it easily (It would need to be quite large to have near zero impedance at 50Hz, but would only need to be rated at a few volts).

I suspect that the real source of most transformer hum is manufacturers cheaping out on the core (or specifying for 60hz), and not vacuum impregnating the windings correctly.

A transformer that is just barely adequate on 60hz will run the core into saturation (And hum loudly, while getting very hot) when run on 50Hz at the same voltage.

Yet again, we see expensive attempts to fix cheap gear issues, when it would be better to spend the money on decant gear in the first place!

orientation in the geomag. field has no effect as the AC flux density in the core is sufficient to quickly remove any residual magnetism (Otherwise shutting down would be a critical activity so as not to leave the core magnetized).

The buzzing is probably down to a core on the edge of saturation (small changes in line voltage will make a big difference to this), and harmonics on the supply - most mains power has bad flat topping due to crude switchmode supplies).

A correctly sized core and vacuum impregnated windings will make this whole problem go away.

To be honest that psaudio web site trips my serpent lubricant detector (But then most 'high end' audio web sites do that these days).

Regards, Dan.

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Audiophiles use phono leads because they are unbalanced people!

It's all very well admonishing us musicians to "buy good gear in the first place",
but the two bits of gear at Feline HQ which produce the most mechanical humming from their transformers are:
my Roland TR-808 and my Kurzweil MIDIboard.

The former sounds fantastic and feck all else really sounds like it - I couldn't get a better more expensive replacement -
and the MIDIboard remains one of the best MIDI master keyboards ever - there's nowt else out there with Note Off Velocity and Polyphonic Aftertouch.

So harrumph! :-/

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~~~ A weasel hath not such a deal of spleen as you are tossed with! www.feline1.co.uk ~~~

In that case, open them up and fix the bleedin' power supplies.
Or put the supplies in the rack room where the noise doesn't matter, or just live with it.

In no case will buggering about with mains conditioning help this problem (Running at a slightly lower line voltage may however).

I cannot be the only one to have a rack box with 5,9,12V AC & DC setup to multiple output connections precisely to cut out this sort of crap.

Regards, Dan.

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Audiophiles use phono leads because they are unbalanced people!

I am most certainly not qualified to start opening up power supplies and tinkering with them, I fear.

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~~~ A weasel hath not such a deal of spleen as you are tossed with! www.feline1.co.uk ~~~

I have removed DAN B's new post from this thread as it wasn't really related to the original, and it warranted a new thread all of its own to avoid confusion.

You can find it here

hugh

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Technical Editor, Sound On Sound