# Powering pedals with different voltage



## The Usual (May 14, 2008)

So I tried something tonight. I have an adapter from a phone or something that reads DC 6V @ 200 MA or 7.5V @ 100 MA on the back. It is center negative. 

I tried it with a couple of pedals. First my Bad Monkey. It sounds pretty good. I A/Bd it with my Boss adapter. It is a different sound. 
Then I tried it with my vintage RAT, using the proper coversion tip of course. After a couple of seconds the pedal just dies, at which point, I immediately pulled the adapter out. If I fried this pedal, I would have to shoot myself.

I know that the PP2 has outputs that you can sag, which I think is just lowering the voltage. So I guess my question is where can I, and can't I be safe using a lower voltage adapter?
Will it harm my Bad Monkey? Or anything else?


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## Jim DaddyO (Mar 20, 2009)

I had a TS-9 and used a universal adapter on it. I set the voltage at 7.5 volts and it sounded great! I got the idea from an Eric Johnson interview where he talks about using black cat carbon batteries and liked the sound when the batteries are about to die. When you are using less voltage, the power requirements of the effect is still the same, so it will draw more current (amps). The adapter you were using may not have been beefy enough for that, and your pedal dieing may have actually been the adapter being overloaded. 

Jim


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## mhammer (Nov 30, 2007)

1) Pedals which are intended to produce a "clean" sound (e.g., compressors, noise gates, equalizers) rarely, if ever, benefit from using a lower voltage, and often benefit from using a higher supply voltage.

2) Pedals intended to distort, CAN, though not always, benefit from using a lower supply voltage. Nine volts is simply a convenient package that permits one to achieve an acceptable supply voltage at low cost/size. There is nothing particularly "magical" about that voltage. Do note, however, that there is a difference between a so-called "dying battery", and a robust stable supply. An adaptor that provides 1A of well-regulated power at 8v, or 6v or whatever, is not the same thing as a carbon-zinc battery that started out life around 9.4v and has now faded to 8v, with much less instantaneous current-delivery capacity.

3) Analog time-based pedals (flangers, chorus, delay, etc.) should generally be operated at the designated supply voltage, though in some instances you can exceed that voltage. All bucket-brigade chips require a bias voltage being set just right in order to pass audio signal. That bias is generally set by taking a fraction of the expected supply voltage (e.g., 14/15 of 9v = 8.4v). If the supply provided is different than that expected, the "fraction" results in the wrong bias voltage and the pedal might not function well/properly. In some instances, manufacturers have used "low-voltage" delay chips, and provided an internal regulator on the circuit board that drops the battery voltage down to a stable 5v, and it derives the bias from *that*. In those instances, you could possibly use a supply voltage as low as maybe 7.5v without disturbing the functioning, and can probably safely go up to around 14-15v in a number of cases. Sometimes, it wors the other way. I have a couple of Boss BF-1 flangers that require an external supply. While the chassis says "9v" by the jack, the service notes indicate 12v, and by gum, the sweep is much wider and more pleasing when powered by 12v.

4) Many pedals, especially DOD, use CMOS chips for electronic switching. Those chips will fry at supply voltages above 15v, and may not provide the appropriate logical functioning if operated at 6v or below.


Overall, if it was just transistors or op-amps in our pedals as the active devices, we could power them with a VERY wide range of supply voltages. Certainly there have been older fuzzes that ran off 1.5v, and many members here are familiar with pedals that require 24v supplies. However, a great many pedals use other sorts of devices, like CMOS, or chips/FETs that have to be biased juuuuuuuuust right to function well, and in those circumstances, the designated supply voltage is the one to use.


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## The Usual (May 14, 2008)

Thanks. Great explanation. I intend to keep using the Monkey with the new adapter, because it sounds great, but I don't think I'll mess with the RAT anymore. I assume that if there's an issue, the adapter dies before the pedal? Do I risk damaging a pedal with too low that is too low? Or will I just fry the adapter? I wonder, because I'd like to try messing around with other pedals, but I don't want to damage them.


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## mhammer (Nov 30, 2007)

Frying adaptors is generally a case of the device being powered demanding more current than the adaptor can deliver without overheating. Unless we're talking about powering something like a Line 6 Delay Modeller with a 50ma supply, this generally will not happen.

The pedal being powered will not be provided with more current than it can take, unless there is no means to limit current draw. Generally, manufacturers who suspect that their pedal could suffer damage if it draws more than it should will have current-limiting resistors built in. They don't want the aggravation any more than you do.

Where it gets weird with adaptors is when:

a) It's "DC", of a sort, but not really that regulated. This will show up as constant hum from the pedal.

b) The adaptor is really AC, and not DC. If you see two parallel squiggly lines, that means it puts out AC not DC.

c) The polarity is opposite to what you thought. Again, many pedals have protection diodes built in to avoid damage via the "wrong" adaptor.

d) There is a slight mismatch between pin and hole. barel plugs/jacks are spec'd in terms of the diameter of the pin/hole. You can often stick a 2.5mm plug into a 2.1mm jack, but the pin will be slightly smaller than the hole provided for it in the plug, resulting in intermittent or even no contact.


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## The Usual (May 14, 2008)

More great info. Well, I am pretty sure all my bases are covered so far. But very good to know.

The thing I take from this, is that you can find some great stuff cleaning out your house! I was debating springing for a PP2, just so I could play with voltage on my grit boxes. Now for free, I found out that there is a difference, and I like it. Saves the expensive trial and error.


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## Guest (May 13, 2009)

You definitely don't need to pay the outrageous price for a PP2+ to experiment with sagging voltages. A $5 potentiometer from Radio Shack, a 9V battery clip and a 2.1 mm or 2.5 mm (whatever your pedals use) plug is all you need.

Battery -> battery clip -> potentiometer acting as a voltage divider -> 2.1 mm plug.

Plug goes in to your pedal. Sag the voltage with the pot. You can get fancy and put some probe points in to hook up a volt meter so you can read the voltage you're sagging too. When you find something you like it's easy to move from the potentiometer to a trimming resistor and package up a little sag unit that sits between your power supply and your pedal.

I have a sag control on my protoboard:



Here's Beavis Audio's Dying Battery Simulator that explains it all. Very, very straight forward stuff to build. Great place to start if you're green with soldering iron: http://www.beavisaudio.com/Projects/DBS/


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## The Usual (May 14, 2008)

Sweet. Definately potential here. So can I do the same trick with a 9V adapter instead of a battery? Just put the pot there instead? I could likely find a way to house that pot, and just add it to my board, correct?


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## Guest (May 13, 2009)

The Usual said:


> Sweet. Definately potential here. So can I do the same trick with a 9V adapter instead of a battery? Just put the pot there instead? I could likely find a way to house that pot, and just add it to my board, correct?


Absolutely. You have to be a little more careful with adapters. Anything that plugs directly into the wall requires a little more attention when dealing with. But you can see in my picture: I'm powering my protoboard off a wall wart. I think I was using a 1Spot in that picture. And Dano's page I linked to deals with how to incorporate the sagger idea into a daisy chain setup run off a wall wart. He also shows you nice ways to box it up. It's quite ridiculously easy.


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## mhammer (Nov 30, 2007)

As useful as the Beavis adaptor is, it does not capture the true "dying battery" phenomenon AFAIC. It provides fixed voltage and/or current reduction. That can provide useful change to tone, but the thing with dying 9v batteries is the manner in which they respond to sudden transients. 

I hasten to mention that this is a property of 9v batteries, and is not replicated by either alkaline 9v (only carbon-zinc, specifically) or by a 6-pack of AA or AAA cells.

The basis is found by taking a 9V battery apart. If you disassemble a 9v alkaline, you will find 6 little sub-AAA cells inside, each one with a tab spot welded to the next cell. Since they are linked by that little metal strip, all current must flow through there. Take apart a carbon-zinc battery, and you'll find 6 stacked ugly "slugs" with a surface area between them that is essentially the same size as the bottom footprint of the battery. 

The amount of instantaneous current that can be provided by each cell is partly a function of the surface area linking them. Alkaline batteries are known to provide longer life, but they differ from carbon-zinc i the amount of instaneous currenthtey can deliver over their lifespan. As they get older, they drop voltage, just like carbon-zinc, but are better able to provide a relatively constant amount of current over fluctuating demands. And therein lies the difference.

Years ago, in the heyday of Polaroid cameras, Polaroid used to include a "Pola-pulse" battery in each film cartridge. After reading an article about them in Popular Electronics, I started scavenging them from the folks at work who used Polaroids until they went digital. The thing with the Pola-pulse batteries is that they were really thin, essentially the thickness of a quarter or loonie, but with a huge surface area (for a battery anyway) between the stacked cells. It could provide a big whomping instantaneous current for the flash and motor movement required to take a picture and feed it through the self-developing mechanism, but could not keep the current up for very long.

The "sag" that people experience with aging carbon zinc batteries comes from the battery trying to respond to a sudden demand for current, and essentially failing after a couple of milliseconds, providing a unique kind of compression. You can't duplicate that very dynamic phenomenon using a robust stable supply (whether wallwart or brand new 9v alkaline) with a fixed resistor in front of it.

Now, if you had a current-limiting resistance that varied dynamically with input signal level, then maybe you'd be a little closer. But the Beavis thing essentially mimics the difference between a 9v battery and other imaginary batteries that might come in voltages between 6v and 9v. That,s not a reason to avoid it, just a reason to keep one's expectations realistic.


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## Guest (May 13, 2009)

mhammer said:


> As useful as the Beavis adaptor is, it does not capture the true "dying battery" phenomenon AFAIC.


Mark, did you see Dano's answer to this question at the bottom of his page. Funny guy. 



> Now, if you had a current-limiting resistance that varied dynamically with input signal level, then maybe you'd be a little closer.


I'm starting to envision a small incandescent bulb modification to the unit now...


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## mhammer (Nov 30, 2007)

iaresee said:


> Mark, did you see Dano's answer to this question at the bottom of his page. Funny guy.


You mean the Z-Vex reference? Well, as much as I respect Zach, make note that this guy makes a point of having his effects draw a pittance of current, so he may not be the guy to give the definitive judgment on the degree to which a series resistor "nails" a dying battery. Does the series resistor do *something*? Yes, which is why you should try it. But like I say, don't expect miracles.

Just for the record, I suspect that "the dying battery phenomenon" is likely something relegated to some select designs with some specific current requirements. DO NOT expect an overdrive that requires a constant influx of 15ma to work to respond favourably to a tuckered out carbon-zinc 9V. That pedal will either work, or it won't. As you approach the zone where the battery starts to behave more interestingly with, say, a Tone Bender, the pedal will simply crap out on you. I certainly can't say for certain, but my gut sense is that the pedal really needs to require somewhere around 3-6ma to benefit aesthetically from a battery that tries and gives up on peaks.


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## whammybar (May 7, 2008)

I hardly fit in with this thread as you are all sooooo out of my league I have to read each post two or three times just to understand it. Thing is I remember this being discussed on TGP some time ago and a guy mentioned that he used a voltage regulator to drop the power to his FD II to around 4.5 volts and said his tone improved enormously. I guess between the dying battery and the voltage regulators you'll get different reactions. I'm trying something with a Zener diode voltage regulator circuit to see if I can get some similar results with sag and tonal improvement.

www.reuk.co.uk/Zener-Diode-Voltage-Regulator.htm


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