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> Massive Hum With Ac Adapter!
Sean_1234
post Jan 29 2011, 02:58 PM
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Hello GMC!

Lateley I've been trying to incorporate some stomp boxes when playing a song with our band. I didn't want to use batteries, since they're expensive and I don't like running out of power during a song sad.gif

I bought an AC adapter with a Daisy Chain, but now it's mega humming! I use a reverb channel on the FX loop of a Peavey Valve King and a Bos DS-1 between the guitar and the amp's input. They're both powered by an adapter with a daisy chain. The DS-1 hummed so bad! I had to play without, because it was really anoying when we were talking. Turning off the pedal didn't resolve the hum, same result with turning down the guitar's volume knob to 0. Playing over the clean channel did result in zero hum wink.gif

Any one has a clue on why this happens? I'm afraid it's because of the adapter, but maybe anything else? It could also be the pedal ofcourse...

Sean
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Hardtail
post Jan 29 2011, 07:26 PM
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Try batteries with no adapters and see if it hums. If so, it's probably a cable problem.

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Sean_1234
post Jan 29 2011, 07:48 PM
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QUOTE (Hardtail @ Jan 29 2011, 07:26 PM) *
Try batteries with no adapters and see if it hums. If so, it's probably a cable problem.

Hardtail

If it works with batteries, could it also be a problem with the adapter? I've heard stories about adapters giving a hum when for some reason the electricityis out of phase or something like that.... I read an online solution: I should connect the first input jack and the last output jack with eachother with some wire, but no luch there sad.gif I did notice one cable hummed a bit less when I touched the iron part, maybe some groundng issue in the cable?
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Hardtail
post Jan 30 2011, 06:36 AM
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Use a process of elimination first. By using all batteries and no adapters you can determine for sure if the adapter is the problem or not.

If the adapter isn't the problem, start with a basic setup... remove all pedals and other cables. Then add things one at a time until you get the hum. Once you get the hum remove the pedal you added with a different pedal but keep the same cables. If it hums after you swap the pedal then it's definitely the cables. If it stops then it's the pedal itself.

By using the scientific method you can determine for sure what your problem is. Good luck bud!

Hardtail


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macseamus
post Jan 30 2011, 09:19 PM
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Did you get anywhere with this?

The coil in your ac adapter will generate a hum at the frequency of your mains supply. keep your audio cables away from it. try wrapping your guitar cable around the ac adapter, or even just place it close and you should hear this induced hum. then try moving all you audio cable well away from mains cable to see if you are getting induced hum.

another this to be aware of is that switching transistor regulated power supplies will generate a lof of noise and are not always suitable for audio applications. they are generally a lot lighter than the unregulated types, especially if they are rated at 1A or more.


interesting how your non fx channel is clean though.
I don't know the peavey walve king, but you say it's powered also by the ac adapter?
is that right?
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Sollesnes
post Jan 30 2011, 10:34 PM
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After trying all the above, go to a store and try a proper powering unit, like a VooDoo Lab Pedal Power or something similar, and see if that eliminates the hum.
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Bogdan Radovic
post Jan 30 2011, 11:26 PM
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Which power adapter do you use? It has to be regulated and "stabilized" in order not to have too much hum. All adapters have hum, though some less the others. You should try running your setup on batteries and see if the hum is gone.


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Sean_1234
post Jan 31 2011, 04:35 PM
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QUOTE (macseamus @ Jan 30 2011, 09:19 PM) *
interesting how your non fx channel is clean though.
I don't know the peavey walve king, but you say it's powered also by the ac adapter?
is that right?

No, it's powered the normal way, power chord into the wall wink.gif
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Ivan Milenkovic
post Jan 31 2011, 11:27 PM
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You need to have special kind of power adapter that produces no hum. Regular adapter won't do. What adapter did you buy?


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Sean_1234
post Feb 2 2011, 07:30 PM
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QUOTE (Ivan Milenkovic @ Jan 31 2011, 11:27 PM) *
You need to have special kind of power adapter that produces no hum. Regular adapter won't do. What adapter did you buy?

It's an adapter for pedal use, but it's not very specia and it was 20 euros tongue.gif The brand is Stagg, so it is music like tongue.gif This one:

Stagg writes:
QUOTE
9V/1.7A DC power adapter, reverse polarity - Compact, ultra lightweight design - Compatible with all popular brands of effect pedals and other 9V adapter-powered accessories - Optimized and stabilized output - High-quality electronic components - Durable 1.5m power cable with reinforced connector - Linear power supply: will adapt automatically to any input voltage between 100V and 240V AC (+/- 10%) - Can power up to 8 effect pedals simultaneously if paired with Stagg SPS-DC5 multi-cable (available separately)


Hum seems to be less on my own practice amp, it was terrible on the peavey tongue.gif But that also might be because the volume was way higher during the rehearsel then it is when I use my practice amp...

This post has been edited by Sean_1234: Feb 2 2011, 07:33 PM
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Ivan Milenkovic
post Feb 27 2011, 02:33 PM
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There is a way to check it your adapter is indeed good. Try it on some other wall outlet on some other installation. It could be that your wall outlet is not grounded. If you experience problems on another location, then you would need another quality adapter. Go to store and try to A/B yours with Boss PSA-120S for example, that adapter is 100% quiet and suitable for pedals. (and it costs 17$ online).


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sbt1977
post Mar 19 2011, 11:56 PM
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Hi,

I have pedals where the "male" part of the socket is negative and some where it is positive. The same goes for power supplies.

A pedal connected to a power supply with wrong +/- can work but might generate some noise.

Just a thought.
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maharzan
post Mar 20 2011, 06:54 AM
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As regards to hum, I just got it fixed on my guitar as well. We don't have earthing system and not sure these days, I am getting electricity that seems to be 'more' than usual, Everything has this strange current, even on laptops. I had the bridge connected the volume pot ground (wired) and got rid of the hum. smile.gif Might be the same for you.


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