strange constant buzzing from my pre amp

hey, i recently got a studio projects vtb1 preamp but have found it makes an incredibly annoying noise, theres like a buzzing noise which im sure it didnt use to do. ive tried changing loads of the settings and unplug various things incase they were causing it but had no effect.
this is a clip of the noise, i did turn up the pre amp to give u a better idea of the sound, so it isnt quite as bad as this. also that is even without a mic plugged in.
link the the file
thanks a lot!

It’s 50Hz hum with distinct spikes right after each zero-crossing.
There’s probably something wrong in the power supply electronics.

the product only came with an american plug, and because i live in england, ive been using a shaving adapter to plug it in until i can get a proper plug. does that sound like its the problem then?
thanks.

Quote (Yubious @ Jan. 23 2006,14:55)
the product only came with an american plug, and because i live in england, ive been using a shaving adapter to plug it in until i can get a proper plug. does that sound like its the problem then?
thanks.

yes, most likely.

If the preamp can’t be properly set or converted for your voltage (220v?), then you’d need a TRANSFORMER (can’t be just any old “converter”) that converts the UK voltage to “US” voltage of around 110 V.

A pro-audio, music or “hi-fi” store should be able to help you select the proper unit.

Hmmm. It’s a wallwart psu on these?

What does it say on it?.. input voltage… and output voltage & current.

The VTB-1 can be had for £69 inc. delivery on ebay.co.uk btw

my uncle is good with electrics and has been trying to find a plug for it, ill see him next week and i think he has found one, so hopefully that works and gets rid of the buzzing.
thanks a lot for your speedy replies.

hey mark, i did originally get my pre amp on ebay for the same price, must be the same seller, except i wasnt expecting it to come with a us power supply! wot do u mean by wallwart psu?? im not gd at electronics so ill just write wot it says on the plug!
PRI.: 230V~50Hz 15VA
SEC .: 12V~Max 12VA

:cool:

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hey mark, i did originally get my pre amp on ebay for the same price, must be the same seller, except i wasnt expecting it to come with a us power supply! wot do u mean by wallwart psu??


Wallwart… one of those black lumps that houses the power supply and the plug that sticks out of the wall like a wart.

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PRI.: 230V~50Hz 15VA
SEC .: 12V~Max 12VA


Well that should have been fine. Sounds more like a European power supply than a US.

Can only assume that something has gone faulty.


Mark

If your shaving adapter has a transformer inside, that could be the problem. If the adapter is just a plug to mate the wall wart PSU to the proper receptacle… you may have other problems. Find an adapter plug with NO transformer in between the in and out and see what happens.

D

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PRI.: 230V~50Hz 15VA
SEC .: 12V~Max 12VA

Is that secondary AC or DC? That matters. Some boxes will actually work (though with lots of buzzing or noise) if AC is supplied and DC is required, as hard as it is to believe. They may have a failsafe rectifier onboard to block reverse polarity.

The other thought is that the box (you preamp) may require fully regulated DC and it’s getting nothing more than rectified power (always positive or negative but NO smoothing or filtering of the waveform to make it a good clean DC power source) from the PS you have. THAT is most likely what’s happening.

The spec on the VTB-1 itself says 12VAC. I think he has the right power supply. Just the wrong connector maybe?

D

Just a shot in the dark here but have you placed a fluorescent light near any of the equipment recently. The spiky waveform sounds just like the hash produced by a ballast in a fluorescent light. I had to replace a large four foot light fixture in my studio because my electric bass guitar was picking up the noise. I guess the pickups are not “humbucker” type.???