jaycee Posted September 17, 2010 Report Share Posted September 17, 2010 A mate of mine has just got one of these http://www.biyang.com.cn/Products.php?id=68 When plugged in, it emits a high pitched noise which increases as the volume on the pedal is turned up but is drowned out when the guitar is played.....very annoying, any suggestions? Quote Link to comment Share on other sites More sharing options...
Ripthorn Posted September 17, 2010 Report Share Posted September 17, 2010 Is his guitar plugged straight in to the pedal? Also, are there any high gain amps or other things in the area? Possible causes are oscillation (though in a tube screamer circuit that seems unlikely unless something is really screwe up), wrong power supply voltage, EMI from radio stations, etc., to name a few. What you describe sounds like oscillation, but there is not anywhere near the kind of gain in that circuit where you tend to see oscillation, though it is possible. If it's oscillation, he would have to open the pedal and replace the unshielded cable with shielded and pray that that works. It's a nice looking pedal, though. Quote Link to comment Share on other sites More sharing options...
jaycee Posted September 20, 2010 Author Report Share Posted September 20, 2010 He gave the pedal to me to try before he used it. When we tried it on his gear it was fine, even my guitar was fine with it. So it's not really a problem but I would like to find out what caused the noise. I will go through a process of elimination to find out. I'm no expert in pedals but this one does sound very nice. Quote Link to comment Share on other sites More sharing options...
jaycee Posted September 20, 2010 Author Report Share Posted September 20, 2010 (edited) Found the problem, it's the power supply unit, for some reason it causes interference with the pedal Edited September 20, 2010 by jaycee Quote Link to comment Share on other sites More sharing options...
Paul Marossy Posted September 23, 2010 Report Share Posted September 23, 2010 Found the problem, it's the power supply unit, for some reason it causes interference with the pedal Was it a "switching" type power supply? Those use an IC chip which can inject a whining noise into your audio system via the power supply. Quote Link to comment Share on other sites More sharing options...
jaycee Posted September 24, 2010 Author Report Share Posted September 24, 2010 Found the problem, it's the power supply unit, for some reason it causes interference with the pedal Was it a "switching" type power supply? Those use an IC chip which can inject a whining noise into your audio system via the power supply. It's one where you can select the voltages from 1 to 12 Quote Link to comment Share on other sites More sharing options...
Mender Posted September 24, 2010 Report Share Posted September 24, 2010 Found the problem, it's the power supply unit, for some reason it causes interference with the pedal Was it a "switching" type power supply? Those use an IC chip which can inject a whining noise into your audio system via the power supply. It's one where you can select the voltages from 1 to 12 Ah. That is your problem. It is more than likely the power supply is not regulated. Most of the switchable 1.5 to 12 volt ones are simple designs with no rectification or smoothing at all. If you set it to 9 volts and without it being plugged into anything, check the voltage with a meter, I can pretty well guarantee the voltage will be up around 16 volts or even higher. If you check the output with a scope, you will see horrendous ripples and spikes. I would never use one of those types of power supply without putting a regulator circuit with smoothing capacitors between the supply and the equipment. Quote Link to comment Share on other sites More sharing options...
jaycee Posted September 25, 2010 Author Report Share Posted September 25, 2010 OK. I will check the voltage output with a meter and report back. Cheers guys Quote Link to comment Share on other sites More sharing options...
Paul Marossy Posted September 28, 2010 Report Share Posted September 28, 2010 Ah. That is your problem. It is more than likely the power supply is not regulated. Most of the switchable 1.5 to 12 volt ones are simple designs with no rectification or smoothing at all. If you set it to 9 volts and without it being plugged into anything, check the voltage with a meter, I can pretty well guarantee the voltage will be up around 16 volts or even higher. If you check the output with a scope, you will see horrendous ripples and spikes. I would never use one of those types of power supply without putting a regulator circuit with smoothing capacitors between the supply and the equipment. Yeah, if it does massive buzzing, then I agree, it's probably a non-regulated, or poorly regulated wall wart unit. If the noise is a high pitched whining, that often comes from one of those "switched" power supplies. The other thing to keep in mind is if the wall wart is designed to put out 500mA at a range between 1.5 and 12 volts, and you set it at 9V but your current needed is only 10mA, it will put out quite a bit higher voltage than 9V because it's not loaded. It wouldn't surprise me if it was putting out 16V or more with no load on it. Quote Link to comment Share on other sites More sharing options...
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