Using higher voltage supplies to a 4558-based overdrive

[Carl]

Hi just wondering.

I heard that some people prefer running their 9v pedals with 18v. Fulltone is even meantioning it at the website.

Will a SD-1 perform differently with 12 or 18v or would the higher than 9v voltage damage it?

/Carl

[Ge_Whiz]

I wouldn't risk it. If there are any 10V electrolytics in there...POP.

[Mark Hammer]

GE-W makes a good point.

Although a great many semiconductors CAN operate at supply voltages greater than 9vdc, you have to distinguish between what the semiconductors are spec'd for, and what any of the components are spec'd for.  For reasons of size, cost, etc., many pedal manufacturers will use electrolytics with lower voltage ratings, assuming that the consumer will either stick to 9v batteries or else use the wallwart supply indicated in the manual.  To be able to use a higher supply voltage, ALL of the components would need to be able to support that voltage, including any electrolytic caps or other components that are voltage-sensitive/dependent.

For an SD-1, the transistors will be fine, the diodes will be fine, and the resistors will obviously be fine.  The chip can take a surprisingly large supply voltage, and the nonpolarized caps are likely spec'd to 35-50v or so, but as noted, the electrolytics will probably be off spec if you go much above 10v in some instances.  Change those caps to 25v-rated units (making sure to adhere to orientation) and you should be fine.

The larger question is whether there is any audible benefit to goosing the supply voltage.  In the case of a pedal like the SD-1, the answer is "not likely".  There ARE instances where boosting the supply voltage has a beneficial impact on some voltage-sensitive parts of the circuit, or provides greater headroom for transient peaks, etc.  The goal of the SD-1, however, is to clip, which means that improving headroom works against the "mission" of the pedal/circuit....unless you like using it as a clean booster.

On the other hand again, if a person wants to use a slightly higher supply voltage from a single power supply (e.g., 12vdc) to power a whole pedal board, and wants to know if such a thing is feasible, the answer is generally "yes", with only a few exceptions.  The performance of something like an SD-1 will not be degraded, and the performance of a compressor or EQ pedal or clean booster may even be improved.  Other pedals, such as FET-based phasers, MAY need some internal adjustments to bias voltage to perform optimally, though following such adjustments they should perform well.

[Carl]

Well I have several reasons for asking.

1. A friend of mine has a good 12VDC PS which which he built and designed for a studio console. He has sold the console and doesn't need the PS anymore. So I can use it for my pedal board if I want. I know that my old 20 year old Boss pedals will do fine with 12v DC. But I am not sure about my brand new guineapig Boss SD-1 would like it or the 2½ channel TS808/FD/SD-1 inspired overdrive which I am working on would like it.

2. Some people say that they like their FD2s better when they run them on 18v and it looks like F******* supports this idea too, so I thought I should as you guys about it because there is so much pedal knowledge and experience here.

I doubt that the clipping section of an OD pedal would benefit from the higher voltage. But maybe the buffers and the volume/tone section could.

I use my SD-1 to push a good amp (a Cornford Harlequin BTW). Sometimes without drive and sometimes with. Sometimes I use it a bit like treble booster with the "Level" and "Tone" up and the "Drive" low. The amp itself sounds fantastic without any pedal. I am just using the SD-1 to spice its sound to suit different songs or to change the sound or level during the song.

/Carl

[niftydog]

Fulltone talk about it in regard to three of their pedals only. They loose points from me for saying stupid stuff like;

"The FD2 gets... more articulate, more amp-like, with more of the strings coming through....very nice!."

More of the strings coming through?  More "amp-like"?  WTF?!!!? Also, apparently the FD2 comes to life and starts talking to you, impressing you with it's vocabulary range! I mean, I sort of know what they're trying to say, but I hate such flowery words. What exactly does it mean when a pedal becomes more "articulate"? Can anyone describe it to me in specific, meaningful words?

Anywho...

With guitar levels, we're talking quite small voltages here, I doubt (except in the case of a pedal with a lot of gain) that raising the supply voltage would have much of an effect on the sonic qualities when the pedal is used in a conventional way. Buffers have no gain and they are generally dealing with small voltages, often far less than 1VACp-p. 9VDC is already heaps of headroom, adding more headroom, while not disadvantageous would seem unnecessary.

Volume and tone stages are often passive so they would not show any benefit.

[Mark Hammer]

There are probably cases (though I wouldn't/couldn't say which ones), where the op-amps used for a given application are sufficiently restricted in voltage swing between rails that increasing the potential voltage swing by changing supply voltage CAN have a tonal impact (positive or negative would depend on your tastes and the pedal's purpose/design).  

Again, as Nifty accurately points out, the amount of gain applied may be negligible enough that the voltage swing available with THAT op-amp and 9vdc is more than enough, but there can also be cases where the gain applied exceeds what that op-amp can deliver with that supply voltage.  Case in point is the Dist+, where the amount of gain requested from that puny little 741 and a 9v battery is well above what the chip is able to provide.  In that case, exceeding the available voltage swing may be part of the pedal's "sound".  Of course, where distortion is deliberately avoided, rather than sought out, increasing supply voltage CAN be helpful...but as Nifty points out, if you don't really need it there is no advantage, only the potential for advantage.

[Carl]

Thanks guys! That was intresting and makes sense.

/Carl

[Ge_Whiz]

If you have a good 12V supply, use it. It's a no-brainer to add a 7809 regulator and two capacitors to give a separate +9V supply.

[Carl]

I am buying it from him so he is rebuilding it to 9v and I will modify my two old ACA-style Boss Phasers to PSA-spec (9VDC) and run all my pedals on 9VDC.