Can I use a 9V power supply with a 7.5V pedal...?

[zindra]

Can I use a 9V power supply with a 7.5V pedal...? What could happen to the pedal for feeding it with those 1.5V more? Tragic? 
Thank you.

[anchovie]

No idea. Name the pedal and someone might know what's inside. Some circuits are fine with a higher voltage, others will die.

[petemoore]

Can I use a 9V power supply with a 7.5V pedal...?
  You don't see many of these around.
  What could happen to the pedal for feeding it with those 1.5V more?
  Anything from sounds worse to sounds different to...
  Tragic? 
  PRetty much, if a component gets over-volted.
  Most effects have 16v or better caps and the rest of the components rated for voltages greater than that, this isn't like most pedals though.
Thank you.

[zindra]

It is a pedal by Electro Harmonix called "Hum Debugger". The manual says you can only use the EHX's supplied transformer. Inside I can only see two 47uf 45V caps. In the enclosure it says it's rated for 7.5VAC/200mA, but inside the circuit is printed 7.5VAC/400mA.  Here is a picture of the circuit: http://picasaweb.google.es/ohwowmail/HUMDEBUGGER#5400031863495970162

[MarcoMike]

AC... ! that's quite a different thing... but still, I have no idea what's in that circuit, so I am not able to tell you wether it would be fine or fatal... sorry!

[aziltz]

those new EHX pedals have all kinds of different power requirements.

I would only use the supplied adapter.

[petemoore]

  Does it hum-de-bug ?

[petemoore]

  7.5 AC has to be converted to DC, which is the average of the AC, iow's, the DC power supplied to the audio circuit is some other voltage, maybe 1.414 x 7.5v = 10.65...@@Rate I wouldn't mess with it if it's working.

[zindra]

Yes, it does get rid of the hum, and to my ears, it doesn't suck big tone. How it works is a mistery to me. Very bad wiring around here, this has saved me a few times, but carrying different power adapters on the pedalboard is a hassle. Why won't they stick to the regular 9V....?

[anchovie]

So that you have to buy their PSUs - more cash for them!

[zindra]

More cash for them = no more hum for me. Fair deal. Can you build something like this...? Please do it with a standard 9V power and I'll give more cash for you. Best.

[David]

More cash for them = no more hum for me. Fair deal. Can you build something like this...? Please do it with a standard 9V power and I'll give more cash for you. Best.

Actually, Zindra, you can do an awful lot of hum elimination on your own.  You are stuck with this pedal, but for other pedals you may build or have built, if you insert a 100R resistor right at the +9V input, followed by a large (I've used 1000MFD) capacitor across both power inputs,  this will filter out most if not all of the audible crap.

[petemoore]

  How does it humbug ?
  Maybe I'll study it some.
  ..two typical ways are break a ground loop or noisegate.
  If you break all the ground loops [see Spyder Power supply at GEO], use good shielding most everywhere [some small portions of unshielded you can sometimes get away with like in plastic pedals] the main cause of noise can have a look at the source [pickups are often a good source for noise].
  Isolating where the noise comes from is a good first step to reducing it.
  Not to say that tossing in a noise bug box or other noise reducing devices won't work, there may be other ways to approach noise which don't require the box or the plugs or the power supply.

[slideman82]

  7.5 AC has to be converted to DC, which is the average of the AC, iow's, the DC power supplied to the audio circuit is some other voltage, maybe 1.414 x 7.5v = 10.65...@@Rate I wouldn't mess with it if it's working.

I think the multiplying factor is 1.3333 or 1.27, more convinced is 1.3333 so... 7.5 x 4/3 = 10 ... OH! I thought it was 9V exactly!

[petemoore]

  Between this page and the Spyder, a great reference for helping to better understand about any 'conventional' power supply.
  http://geofex.com/Article_Folders/Power-supplies/powersup.htm

[blueduck577]

i forget where but I think I read the hum debugger requires the AC supply because it actually derives the noise-reduction from the AC power supply itself, rather than filtering/gating the guitar signal