AC converter for an expensive stereo

I brought my high-end stereo over from America and have it plugged into two AC 500 watt current converters. Both of which give off a very low hum that is a bit distracting. Is there any alternative that might be more quiet? I read that something called a "true" transformer might work. Any opinions?

Other facts:

My tube amp is listed as 400 VA maximum, and is plugged into a 500 current converter. I never turn the volume up beyond the 9 o'clock position, but I wonder if its safe. the current converter never heats up, but sometimes makes a brief crackling noise when I turn it off.

I also sometimes get brief bits of crackling noise in one of the speakers and wonder if the current converter causes that.

Further Wisdom:

Do not bring a subwoofer over here, no matter what they tell you in the stereo store back in the states. Even a 1500 watt current converter is insufficient. Anyone going back to the states want a 5-star subwoofer very cheap? It's just taking up floor space at the moment.

Hi Melvinx

I used to really really enjoy my audio systems, was a sub dealer for a few Car hifi dealers and had some good contacts for the home stuff. Lately just no time for it all!

As you've an high end Valve amp, a couple things spring to mind -
1. does the manufacturer have a UK presence? if so, it may be worthwhile getting a PSU from them that will fit your amp.
2. Is there not already a switch to change input voltages on the back of the unit? (bit of a stab in the dark that one!)

If none of these work, you'll need to look into getting those 'clean' power supplies meant for Audio use. I've no idea more on those as I've only ever skim read anything about them. I suspect the current transformers you have are general purpose ones

I'm 'slightly' surprised at the subwoofer aspect though, I'd have guessed you'd need the same 'clean' audio PSU items to plug it into, and check of course if it has a voltage selector. As for 'cracking' sounds, this could be a number of elements,

1. Power supply issues - 'dirty' supply, spikes and surges etc
2. Distortion on one channel of your amp
3. possible problem/issues with the internals of the amp (dry solder joint? bad valve?) on one channel
4. Loose connection in the speaker itself?

Check out the hifi forums (google or yahoo) and pop you're questions there as someone may give you more specifics as to what is (or isnt!) available here!

Hope this helps a bit!

Dennis! West London & Slough UK!

thanks for the google and yahoo group idea's.

Just for any  stereo-heads reading from the USA,  reliable information is almost impossible to find prior to your move. I bought the subwoofer from Stereo Exchange in Manhattan, one of the best stores in the USA. They assured me that a simple travel-style converter from radio shack for $5 would do the trick! They simply didn't know the issues involved and spoke off the top of their heads. Likewise all the power converter people that show up on Google who assured me that converter was completely silent.

Most people do not bring expensive stereo's overseas and so I hope that my contribution here can be a resource for anyone who does. If I find a suitable answer, I will come back and post it.

Meanwhile, I do in fact use a "powerline conditioner" as a component in the system which supposedly "cleans" the electricity going into the components. There is some controversy as to whether or not these actually do improve sound quality, or are more stereo voodoo-hype like buying expensive speaker wire when the cheap kind works just as well. My impression is that it does improve the sound, maybe 5-10%, mostly by making it sound a little bit more dimensional. I got a top of the line one cheap on ebay. People interested in trying one could get one even cheaper and just as good by using one for medical machinery. Let's face it; electricity is electricity; no need to buy the audiophile model in a pretty casing.

Meanwhile, I have checked all connections and tested the amp. I suspect that high end stereo's are a bit like high end cars. They need a little tweaking and are sensitive to their enviroments. If I had it all over to do again, I'd have sold it stateside and bought something over here.

That said, with the humming converters tucked inaudibly away in the fireplace, I notice no fall-off in sound quality. If you absolutely cannot bear to part with your system, it will work over here. How this affects the longevity of the system is something I am trying to research.

Hi Melvin,

Is there any alternative that might be more quiet? I read that something called a "true" transformer might work. Any opinions?

Technically, it's either a transformer or it isn't, but I suspect this is a reference to the switched-mode converters which are becoming quite common these days.  Switched-mode (also called "chopper" supplies) work out cheaper than a transformer for higher-power applications, but most of them have an output which does not emulate the true sinewave of A.C. line power.   At best it's a rough approximation, and at worst it can be just a squarewave which is full of harmonics and transients.  The waveform from such a converter will tend to be "smoothed off" to a degree by the main power transformer in the amplifier, but those high-frequency components could still get through and cause noise.    If your converters are of this type, then that could be what's causing the problem, and changing to a "proper" transformer might be the solution.    

My tube amp is listed as 400 VA maximum, and is plugged into a 500 current converter. I never turn the volume up beyond the 9 o'clock position, but I wonder if its safe. the current converter never heats up, but sometimes makes a brief crackling noise when I turn it off.

It's hard to be specific without having more details about the converter, but some of the units on sale are rather liberally rated.  They'll just about supply the stated maximum power, but often not for sustained periods.    The crackling sound on switching off suggests to me that you do have something in the converter other than just a plain transformer.

By the way, tube amplifiers do not necessarily draw more power as you increase the volume like most modern semiconductor amps do.   If the output stage is class A push-pull (as is the case on many of the modern high-end tube amps), then you won't notice an appreciable increase in power consumption.   If it's class AB (or class B, although that's unlikely) then there will be an increase in power consumption at higher volumes.

I also sometimes get brief bits of crackling noise in one of the speakers and wonder if the current converter causes that.

Possibly, but if it's only on one channel it may well be something within the amplifier or on the interconnections, as Dennis suggested.   I'd be inclined to check the soundness of all connections, looking particularly for loose ground connections on cables.   Sometimes it can even be the result of something as simple as a little oxidation on the valve/tube pin contacts, so pulling the tube out and re-inserting it can cure the problem.

Do not bring a subwoofer over here, no matter what they tell you in the stereo store back in the states. Even a 1500 watt current converter is insufficient.

One of the problems you get as power increases is the source impedance of the supply.  If it's too high, then you get a drop in the power when the amp tries to draw a sudden pulse of current  (i.e. just when you need it -- but note my comments about class A vs. class AB/B).    I'd try looking at a nice hefty toroidal transformer for such an application.  They don't come cheap, but are ideally suited.

1. Power supply issues - 'dirty' supply, spikes and surges etc

To expand upon this point that Dennis made, the "cleanness" of a supply can really vary considerably from one neighborhood to another.  If you're in a residential area which is served by the same big power transformer as an industrial estate, for example, you can even notice considerable difference between the daytime when all the "dirty" commercial loads are running and night when it's quiet.  

no need to buy the audiophile model in a pretty casing.

Like the gold-plated, snake-oil enhanced "audio grade" receptacles advertised as replacements for your regular outlets -- A mere $150 a pop!  

I'd love to hear the explanation on how replacing just one component in the power chain like that makes such a vast improvement.  Or maybe they've also convinced the power company to use "audio grade" generators, and "audio grade" transmission lines, not to mention "audio grade" pole transformers.