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There are two types of O/D pedals. Ones that run from your wall wart or 9V standard supply (Klon Centaur,Tube Screamer) and ones that run from 120V line (Blackstar HT Drive etc).
Which do you prefer. Is it a problem using a pedal (overdrive or something else) that runs from the AC line.
I'm curious only because I'm playing around with tube overdrive and am not sure which way to go with this for power.
 

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I don't think there's that many pedals that run off wall power (vintage MXR/EHX excepted). Never tried a wall powered OD, but I did have a vintage Memory Man with a 2 prong cord and there were no real issues with that (doesn't mess with the rest of yer stuff like a PNP fuzz) it's just a matter of getting a second cable to the wall power (i.e. in addition tom your daisy chain or pedalboard power supply). One nice option here is that some pedal power supplies (thinking Cioks Link series specifically, but maybe others too) have a mains thru jack (ostensibly to daisy chain a second Cioks power supply off of, but you could use it to feed the mains powered OD pedal instead.

Basically, at worst it is a minimal hassle, if the pedal is good (your thing) then go for it.

Now if you're looking at tube driven pedals specifically, it matters not in the current times if wall or DC. The only thing that matters is that the tubes are driven at proper plate voltages vs starved. Wall power's advantage is only that you know this will be the case, but with modern tech and design, there are some very good charge pump chips out there that can give you the 200-300 V you need to power tubes properly from a standard 9V DC supply. Check and verify this is the case (should not be too hard if your google foo is reasonably strong).

There are also a number of pretty good DIY projects/kits for full power tube drive pedals. ... maybe not as a first project tho; start simpler.
 

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I avoid pedals that aren't able to be powered off a power supply, or wall wart.

Anything with an attatched cord, is an automatic pass for me.
 

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1) The fundamental trait of any overdrive is that it runs out of headroom. So, in some respects, larger supply voltage from the wall is not what a person wants. Well, maybe a little more, but not much.

2) I was given an Eleca tube overdrive earlier this year, and it would seem to be a clone of the old BK Butler tube driver. Like a number of such units, there is a single 12AX7 to power, and it is operated in "starved plate" mode (i.e., sorely under-powered) via an external wallwart. The use of a proprietary wallwart is simply to give a sturdy-enough 12VDC. In that sense, it is not so much AC-powered, any more than the various mini-pedals that have no room inside for a battery are AC-powered by an external supply.

3) Some older units that ARE provided with a power cord stem from before the era of power bricks. For instance, the EHX Hot Tubes was an entirely solid-state inverter-based overdrive (very similar to the Way Huge Red Llama) that was provided with anexternal cordand power transformer. But in truth, it CAN be run off a 9V battery. I know because I've built a few. The battery doesn't last a long time, so the transformer power assures you can leave it plugged in for hours without running out of juice. Again, remember a lot of pedals from that era lacked external power jacks, so the choices were either battery, constantly replacing battery, or wall power.

4) Some wall-powered pedals simply want a bipolar +/-9v supply and a single battery won't do it, or at least couldn't in the old days, so an on-board power transformer and fully regulated supply was provided to offer that. These days, we have charge-pump chips that can take +9v and either increase the supply voltage by 2x , 3x or more, or else turn a single-ended supply into a double-ended. F'rinstance, I used such a chip to provide my Craig Anderton ring modulator with +/-9v from a standard Boss-type power jack being fed with +9v, the Klon Centaur uses one, and the Visual Sound Truetone booster uses one to turn 9v into just under 26V.

5) Although some tube-based overdrives that use external supplies do use fairly low supply voltages, and only require wall-warts because they need more than 100ma (one of the more standard power-brick outputs), some may well aim for a little more dynamic range by applying higher supply voltages. In those instances, the inconvenience is counterbalanced by what one might assume is greater touch-sensitivity and dynamics afforded by a higher supply voltage.

6) Ultimately the quality of the overdrive, and dynamics, are not dictated strictly by the supply voltage, but by the gain structure, and the manner in which headroom limitations are imposed. So, a JFET-based overdrive can be run off 18V, but if it is deliberately biased to swing only 3V in one direction and 15v in the other, then there will be heavy clipping for one half-cycle. Similarly, the Timmy runs off a measly +9V, but sets its clipping threshold high, by means of using additional diodes.
 

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I think if your OD pedal requires its own power source, its probably a preamp in reality.
 

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I think if your OD pedal requires its own power source, its probably a preamp in reality.
Yes and no. It will depend on the period of production. Keep in mind that it is only in recent years that "full-service" power bricks have been providing supply voltages other than +9V, and more than 100ma current per output. Some pedals that would have required their own supply to function, 5 years ago, are now easily accommodated by current- production power bricks that can deliver voltages higher than +9V and currents greater than 100ma.
 

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Im thinking verellen skyhammer versus a fulldrive-3.
 

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1) The fundamental trait of any overdrive is that it runs out of headroom. So, in some respects, larger supply voltage from the wall is not what a person wants. Well, maybe a little more, but not much.
I always assumed (incorrectly?) that a higher supply voltage would allow for a greater dynamic range of the overdrive, like an old school tube amp tends to give you.
 

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I always assumed (incorrectly?) that a higher supply voltage would allow for a greater dynamic range of the overdrive, like an old school tube amp tends to give you.
Yes and no. It would depend on the means of clipping. If we are talking about diode-based clipping, you could feed the op-amp in a Tube Screamer with +/-18V and those diodes are still going to cut off the signal at +/-500mv. The point of clipping is absolute, and a function of the diodes, rather than the power supply.

If the means of clipping is of a relative form - i.e., the cumulative effect of running out of headroom over multiple stages, as occurs in tube amps but also in some FET-based overdrives - then yes, you are correct in your inference that higher supply voltage yields greater dynamic responsiveness.

The positive influence of increments to supply voltage is context-dependant. So folks are not wrong to wonder if maybe using the 12, 15, or 18V output of a powerbrick will make something sound better or different, but they need to keep the particulas of the circuit in mind.

As an addendum, note that electrolytic capacitors are rated for a given voltage. It is standard good bench practice than one wants to use caps rated at 50% or more above the anticipated supply voltage just to be certain that the caps adhere to their spec. So, if a pedal expects a 9V supply, it will not likely have any caps rated below 16V.

Once upon a time, higher-voltage caps tended to be much larger, and certainly more expensive. So they wouldn't be used unless absolutely necessary, because they would demand a bigger board and increase production costs. In more recent decades, they have gotten much smaller and much cheaper, essentially negating the price difference, and board-size penalty. So where an older pedal might only use 16V caps, it is not uncommon to see more recent pedals using 25V and 35V-rated caps throughout, even where not really required.

I mention this because the wisdom of using higher supply voltages to extract greater dynamic responsiveness from a pedal depends not only on whether the design itself will do what you think, but also whether the components themselves will behave on-spec. Folks wishing to use higher supply voltages from their power brick are always encouraged to open up the pedal and look on the side of all electrolytic caps to see what their "comfortable" operating voltage is.
 

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I always assumed (incorrectly?) that a higher supply voltage would allow for a greater dynamic range of the overdrive, like an old school tube amp tends to give you.
That is correct. That's why a lot of pedals (not just dirt pedals fyi), even ones that take a 9V supply, either allow you to run them off 18v (built to handle it and advertised as such, 9V being the min power requirement) or use an internal charge punp to up the voltage internally. This is why the first mixing consoles were 48V (where phantom power standard comes from), and the classics are all at least 24V; to keep that headroom through the summing amps. The current Neve 5088 console runs 90V.

Edit: yeah as regards mhammer's caveat, but, that is not an issue when the pedal is designed to take/run on a higher voltage - never give any pedal not explicitly approved for higher voltages a higher voltage not just because of the fixed thresholds of diode clipping stages, but also because you're probably going to blow it (if you're lucky just the input filter cap or pull down resistor, but it could be worse than that - e.g. this is what happens when you feed 24V AC into a Big Muff: (Search results for: big muff-) surprised it wasn't worse, because caps stop DC but not AC; the resistor blew instantly - it actually may have been worse if the voltage was a bit lower and the resistor didn't act as a fuse).

Yes and no. It will depend on the period of production. Keep in mind that it is only in recent years that "full-service" power bricks have been providing supply voltages other than +9V, and more than 100ma current per output. Some pedals that would have required their own supply to function, 5 years ago, are now easily accommodated by current- production power bricks that can deliver voltages higher than +9V and currents greater than 100ma.
Even now you can only get 18-24V max out of a power brick. Tubes need 200 and up. 18-24 V supplies have been around for a while, but it's only recently that switching type power supplies became stable enough for critical audio use (used in pedals for ages, but only recently acceptable in higher end pro studio gear) and that charge pump ICs that can give enough voltage and be small enough to fit in a pedal with just a single smoothing capacitor (before that you needed a bunch of large caps and multiple transistor stages) have hit the market.
 

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Considering pickups put out a volt or two, P-to-P, max, I never really saw the point in doubling the input voltage of a SS pedal. The pedal is feeding a circuit that is expecting a pickup's output, how much more voltage swing do you want to hit it with?

I've tried a couple pedals at 18 volts and the difference is minimal, at best. At least for the way I set them up. Wasn't worth the extra power supply requirements. YMMV.

Of course tube pedals are a different beast, as Mark pointed out. Tubes, being a high voltage device, need a certain level of voltage well above transistors to work at their optimum.


This is why the first mixing consoles were 48V (where phantom power standard comes from), and the classics are all at least 24V; to keep that headroom through the summing amps. The current Neve 5088 console runs 90V.
Actually, 48V is the standard set by the first electronics/networking business - telephones. All telecom equipment still runs at 48V DC - and usually positive ground, for noise reasons and just to screw up electricians installing it. I've had them more than once short the 'hot' negative bus of a charger to ground. Mucho sparkiness and surprised looks.
 

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1) Again, yes and no. Where some tube-amp preamps in a floor pedal will try and emulate the typical plate voltages found in a tube amp head, many tube-based overdrives will still use a "starved plate", feeding the tube much less than what they might get in an amp head, in order to reach headroom limits easily and yield the desired overdrive. The presence of a power cord does not reliably indicate which of those two approaches is being used.

2) Yes, a great many op-amps are quite comfortable with +/-18V supplies (which can also be +36V split in half), and many discrete transistor circuits are comfortable with supply voltages even greater than that. The use of 9V is simply a convenience, given the historic availability of that voltage in a compact package. There is not very much that absolutely compels use of that voltage. I might note that one can often find 12V batteries in the dollar store that are about 2/3 the size of a single AAA battery. You may have a harder time finding battery-holders for them, and they certainly won't last as long as a 9V battery, at typical current-drain rates, given their smaller size, but they're out there.

3) As for charge-pump chips, the more common ones are limited in how much current they can supply....not that most solid-state overdrives require much current to begin with. But it is still a consideration.

4) Some pedals will insert a resistor in series with the power source (whether battery or external supply) to impose a limit on the current drawn for the circuit. But that resistor value is predicated on the voltage of the anticipated supply. So yeah, feeding the pedal with a much higher supply voltage runs the risk of making that resistor behave like a fuse; especially given that so many of them are going to be 1/4W or lower rating. Having said that, the pedal could be adapted by installing a higher-value and higher wattage resistor in that position, such that the circuit gets the current it expects, albeit at a higher voltage. There is some math and soldering chops involved.
 

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Considering pickups put out a volt or two, P-to-P, max, I never really saw the point in doubling the input voltage of a SS pedal. The pedal is feeding a circuit that is expecting a pickup's output, how much more voltage swing do you want to hit it with?

I've tried a couple pedals at 18 volts and the difference is minimal, at best. At least for the way I set them up. Wasn't worth the extra power supply requirements. YMMV.
In some instances, the intrinsic sound of a given pedal comes from deliberately exceeding the headroom and voltage swing of the op-amp at 9V.
For the uninitiated, a great many op-amps are able to "swing" within a volt to a volt and a half of the supply voltage.. For a 9V pedal, as an example, that would mean that the input signal could be cleanly amplified from whatever it was originally, to a maximum of +/-3.5V (i.e., 2 volts less than 9). If the input signal is +/-100mv (and the reputed 1V P-P is really only there for a moment, when hitting a power chord; it comes down PDQ after that), that means it can be amplified roughly 35x before it runs out of headroom in that circuit at that supply voltage. If the gain in an overdrive pedal is set to 50x (which is low, given how many pedals can include gains of >1000x), then in addition to whatever diodes or similar elements are being used to clip the signal, the chip itself is contributing on top of that. That's why some "classic" overdrives only yield their magic when using 1st/2nd generation (now considered lower quality) op-amps like the LM741, LM308, LM1458, etc., which can often have limits to how much clean gain they can provide across the frequency spectrum. Higher supply voltage may still work, but they may not sound like the pedal is expected to sound.
 

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There are two types of O/D pedals. Ones that run from your wall wart or 9V standard supply (Klon Centaur,Tube Screamer) and ones that run from 120V line (Blackstar HT Drive etc). Which do you prefer.
Back to the original question about which you prefer, I do like the tubes in general. But as pointed out, it doesn't seem to matter much these days how the pedal is powered. The best comparison I can think of between these two types of pedals are the Plush Drive and Valve Job by Fuchs. They are basically the same pedal, except the Valve Job has a tube. I did like the feel of the tube pedal and the overdrive seemed a little "smoother" to me. I think the Valve Job runs at full plate voltage, but I don't know for sure.

However, like any pedal, just because it has tubes doesn't make it great. I had an Effectrode Tube Drive once, and I liked the feel of playing the pedal and the warmth, but it was actually really hard for me to dial in a range of tones that I enjoyed. Without swapping tubes, it was kind of a "one trick pony" for me. It also had strange power adaptor requirements.

The Kingsley stuff looks pretty great, with some of the smaller pedals drawing only 500 mA at 9V. With power supplies from Stymon and the like, they are well within getting real tube feel without needing a separate power supply or AC connection.
 

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It's modifying a low level wave-form signal.
How much power does it need?
Seriously
 
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