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Higher-than-normal supply voltage: safe?

Discussion in 'Effects [BG]' started by Peter McFerrin, May 2, 2006.

  1. I have four stompboxes currently sitting on my PS-25 pedalboard/power supply: an Akai tuner and phaser, and a Guyatone chorus and tube distortion. The tube distortion sounds awesome but it needs a 12V power supply; I would prefer not to run it at 9V because I don't want to be changing out tubes on a regular basis. I'm currently running the PS-25 on a 12V supply.

    My question is, would any of the other effects be damaged by running at a higher supply voltage? I'm not so much worried about the chorus and phaser, which are both analog, as I am about the tuner. I was half-asleep through most of my introductory EE courses in college (prior to switching to economics, obviously :smug: ) so I don't remember if digital circuits are especially friendly with higher-than-normal supply voltages.
  2. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    I'm going to over-generalize and say that digital circuits are especially UNfriendly with higher-than-normal supply voltages.
    The digi chips in your pedal may or may not be rated for a higher voltage over an extended period of time. It's kind of a "ratings roulette"- you don't know how high a voltage all of the chips are rated for until you burn one of them out. Note that this is equally true for analog effects, especially ones that use ICs. Although the passive components (resistors, diodes, etc.) are almost certainly rated higher than 12V.
  3. It largely depends on the circuit and you couldn't really give a broad, generalised indication one way or the other.

    Often a digital circuit will incorporate a voltage regulator that keeps the supply to the chips at a constant level - so the chips themselves are not likely to be at risk from a moderate increase in supply voltage. The result of running the device at a higher supply voltage would be that the voltage regulator runs hotter than normal. Whether this is likely to be a problem is best answered by the people who designed the circuit. Try emailing Akai.

    Many circuits (such as most Boss pedals) have 10V rated capacitors in them. However, very few of them are placed across the full supply voltage. A simple upgrade of the power supply filter capacitors would make such a pedal more or less compatible with the higher voltage. Having said that, the older Boss units were designed to run from unregulated supplies, and as such, they actually fail to operate correctly when fed with exactly 9V. I have three such pedals, and they have served me well for a long time being run from a regulated 12V supply.

    Which brings me to an interesting point. If you were to go with a 12V supply, I would highly recommend a regulated 12V supply. An unregulated 12V supply may actually be putting out as much as 20V depending on it's power rating.

    Not being a tube expert, your comment about changing tubes more often because of a lower supply voltage doesn't really gel with me, but I cannot say whether it's right or wrong because I just don't know.

    Perhaps a compromise between 9 and 12V is in order?
  4. Well, maybe I could run the BB-X (tube distortion box) at below-normal voltage. It's my understanding that running tubes at below their normal plate voltage can produce a more pleasing tone, but at the cost of shortening their life considerably. Eddie Van Halen used to run his EL34-powered Marshalls at 90 volts for more saturation, but had to change tubes every night!
  5. EricF

    EricF Habitual User

    Sep 26, 2005
    Pasadena, CA
    How about just using a battery in the tuner?

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