I decided today to try a tip I read on the BYOC forum of using 18 volts to power my DIY pedals for more headroom. I must say that there is a noticeable difference and that is a good thing. My DC Brick only has three 18 volts slots so I have settled on powering my compressor, OD and Shredmaster that way. The chorus sounds almost the same on 9 volts. I'm digging my pedals even more now.
For those of you who have pedals compatible with the higher voltage, I suggest you give it a shot if you have 18 volts available.
Keebo,
thanks for the report. It's interesting what it does to different pedals. Most mod pedals won't benefit from it. Your OD/Boosts is where you want to try it. Depending how how an OD works, it does different things to them that may or may not be desirable, or may create "18V is better for one thing, 9V for another" scenarios. Some people have done 3V increments and found the sweet spot for them and their setup might be at 12V or 15V.
A "GENERAL" expectation from an overdrive or distortion when running at more voltage (and again, this depends completely on pedal design and HOW it is clipping) is, the more voltage you have, the more level, and the more headroom, but less gain or distortion. Many people think the opposite will happen, and that applying more voltage will add gain. Well, with certain designs, it might, but with most it wont. Also, with boosts, it again can add more clean headroom. A good example of when NOT to use more voltage is with a Fulltone Fatboost or similar "Fat" boost type pedal. The "Fat" comes from the signal hitting the power rails, and thus "compressing" the leading edge of the note transients. When you apply more voltage, it doesn't hit the rails, it has the headroom to let the transient fully develop, and then you just have a regular "clean boost," not a "fat boost."
Also, some ODs have lower voltage clipping sections (example: 1n34 germanium diodes) and adding more voltage won't really open up any headroom at most gain levels, because they germs are already compressing a lot at 9V.
I want to build a clean regulated power supply that puts out 9-12-15-18V. Then you can test each pedal, and determine what voltage is best for your use and your gear.
That is some good information to learn from, Howie. I haven't heard it from those angles. Thanks for sharing.
I wasn't extremely happy with my compressor to begin with because it suffered from a bit too much distortion for my tastes. There were some suggestions for replacing a component (can't recall which off hand) or powering it with more volts. I had to make a few adjustments to the knob settings that were different from the 9 volt settings but I am now much more satisfied with this pedal.
I am not very good at explaining the differences in tone that I have gotten from my OD and Shredmaster so all I can say is that they both seem fuller and less fizzy. Not that they were bad with 9 volts, just more pleasing now. It may be the placebo effect going on but it is definetly not worse sounding.
I can see where a different value of volts could make a difference but I don't have that option at this time. I am quite interested in what you come up with in a multi-volt power supply. Do you have any kits or schematics that you have in mind?
Keebo,
There's a nice 4 output regulated power supply board at GGG. It comes stock with 9V regulators, but you can change just the regulator and get 12V, 15V and 18V. Some guys I've seen built all 18V outs. Another did 2-9s and 2-18s. Then I asked about trying other voltages since some guys (buy buying individual supplies at 12V and 15V had discovered that most pedals sound different at each voltage) and some said that mouser carries the 12V and 15V regulators. So, you could build one supply with a 9,12,15 and 18V tap, and experiment. Then you could A) build another that suited the preferred voltages for the four pedals you use it with or B) change the regulators in the first one to do so. Only downside to B is it would prohibit future testing with new pedals that come along.
Um, just butting in where I don't belong, but couldn't you use those Radio Shaft adjustable power units/wall warts for each pedal and then just switch the voltages whenever you feel on a pedal by pedal basis?
For even more fun, since you're building custom stuff, how about making the voltage adjustable using a dial? :D
Craig,
Actually, if they make one it's a very good point. I have a variable voltage unit from Radio Shack, and it has about 6 choices, but they are all between 1V and 9V. If they make one with higher voltage and the right tip, it would be a killer way to experiment.
As to your second question. I had the same question, and I have seen ideas on what would be needed to do that, but for a multi output unit, it would get expensive fast. I estimated that something like a pedal power, with all variable voltage outputs would probably cost $300 or so. And be larger. I might ask a few questions though. That concept has always interested me.
Regulation is not as important on a variable output, IMO. The reason that regulation is important, is to always have the same voltage, no matter what it's being fed. Have you ever noticed that your amp sounds better some days than others? This can be nothing more than different voltages from that wall at different times.
I'll put in my few cents worth, here, to kind of add to this topic and why 3V vs. 9V vs. 18V makes a difference and, sometimes, does not. Please note, my comments, on this particular board, will be few and far between, these days. I have, somehow, found a "real" job where they actually expect me to accomplish something during my work day. The bastards! ;D I haven't had a job, like this, since about 2002, so I'm still trying to get used to the routine of progressive accomplishment!
First, let's take a look at a standard "gain" stage. In the olden days (tubes, if you remember what those were), the first stage of any preamp/amp, was ALWAYS a low voltage, lower current stage! WHY? Because, that's why! Actually, the logic and reasoning was simple. A) You don't need the headroom in this stage, supplied by the higher voltage. The input signal is small and, even though the gain of the stage might be large, the output signal swing is still going to be small. B) And this is probably more "practically" important, or pragmatic, higher first-stage voltage = higher first stage current = higher noise! Yep, noise is a direct result of current/voltage flowing through an active device. If you generate noise, in this first stage, it's level is MULTIPLIED by every subsequent stage after that. If the first stage is quiet the rest of the amp/preamp will be quiet, too.
So, a guitar signal, by itself, is about 40mV (0.040V). That's pretty tiny. Let's say the op-amp is setup for 9VDC (single battery). That means the voltage rails, of the op-amp, are "split" to about 4.5V. That's the theoretical maximum signal swing. In reality, the cheap op-amps that folks use in these DIY projects - especially those crappy 4558's that everyone loves (I'm being tongue in cheek, in a way, but in pure specmanship, those op-amps truly do suck), your TRUE signal "rails" will be about 70% of theoretical maximum, or 3.2V.
Let's say the first stage amplifies the signal 100 times (that's a LOT of gain for a DIY first-stage). The output voltage will be roughly 4.0V RMS! You've got approximately 6.4V peak-to-peak and RMS voltage is, roughly, 70% of peak-to-peak - which means you have .25V, on each peak, to spare. If you drive this right into another gain stage, with zero loss between them, you're going to end up hitting the op-amp rails and distorting the op-amp.
So, in stage 2, let's assume the gain was, again, 100 - and that's a LOT of gain for a DIY-stage, you start with 4V RMS input, you'll end up with 400V RMS output. So, to make this work your rails, for the signal, would need to be about 200V each, with a power supply voltage of about 575V, split, to handle this.
So, what gives, here? Most op-amp stages, in pedals, run at a gain of about 30-70, not 100. A good deal of the signal is "lost" between the stages (via capacitor coupling filters, voltage dividers, poor design, etc). Let's say we have a stage gain of 30, this time. We start out with a 40mV signal input x 30 (gain) = 1.2V RMS, or roughly, .85V peak. Amplify that, again, by 30 = 25V peak, which would be a LOT more than the 9V rails supplied by our 18V power supply.
That said, though, we're going to lose a bunch of signal in the interstage coupling (voltage dividers and filters), and other things. So, the 18V supply, with 9V supply rails, will provide us with a bit more "clean gain" and "headroom" in the pedal.
In "clean" pedals, such as a "Boost" pedal, which provide, say, 25dB of gain. 25dB of gain equates to a physical multiplier of about 17.78. (Equation is: 20 * log (vout / vin) = dB gain. 25dB / 20 = 1.25. 10^1.25 = 17.78. If Vin is 1V and Vout is 17.78V, that's 25dB of gain.
So, at 40mV input (guitar level), 25dB/17.78x = .71V RMS output! WHAT???? Yeah, that's it. That's WELL below the 4.5V rails supplied by the gain stages internal to the product, or even the more practical 3.2V rails. First, the 40mV, of guitar signal, is an RMS value. RMS = Root Mean Square. RMS is created using a complex calculus process called "integration." We, more simple people, know this process as "averaging".
When all is said and done, and the calculus folks have had their time, we find out that there are several areas to be reckoned with. First, RMS values take into account both positive and negative signal swings. Secondarily, there are "peak values" and "peak-to-peak" values, and a "crest factor" to take into account.
So, RMS, for the most part, works out to about 70% of peak-to-peak values. Peak-to-peak is the TOTAL positive PLUS TOTAL negative swing of the signal. So, the peak-to-peak value, then, would be at 40mV / .70 = 57mV. 57mV * 17.78 = 1.01V (MUCH closer to the voltage rails). The "peak" value = 1/2 peak-to-peak, or about 28.5mV.
So, what we're seeing, here, is the fact that peak swings can, indeed, come in at a rate that may cause the op-amp, especially if it's higher gain with coupling losses between stages, to nearly reach the rail limits. Another factor, here, is what is often referred to as the "slew rate". This is the gain stages ability to track rapid changes in signal (either rising, as in initial pick attack) or falling (quite mutes).
The slew rate, of the op-amp, is largely determined by voltage gain NOT by supply voltage. So a higher supply voltage SHOULD NOT make the op-amp track any better/faster. HOWEVER! A slower slew rate (the op-amps rise/fall is SLOWER THAN the rise/fall of the input signal) will cause the resultant output to be "warmer" as the initial, and relatively harsh, transients are "subdued" or "compressed" by the gain stages inability to actually track the fast-rising transients.
Slew rates are expressed in volts / second, or volts per micro-second, etc. The higher the gain, the higher the voltage rails, etc. will then require the op-amp to "slew" further from 0 to the maximum in one direction, change and slew the other way. NOW, another thing, is that higher voltages charge the capacitances, in the circuit (op-amp and surrounding) higher. This causes "resistance" to voltage changes and will cause the slew rate to drop, some, too, resulting in greater inability to "track" rapid changes in input voltage.
The other issue is that, especially with the lower-end op-amps, when the output signals begin to approach the rails, the internal components actually force a bit of "compression" on the signal which increases as the signal gets closer to the rails. When you increase the voltage you're getting away from this effect, as well, but then mucking with the slew rate - though the latter doesn't impact that signal as much, IMHO, as does the former. The former sounds a bit more "muddy" in comparison, to my ears - especially, again, on the lower-quality op-amps.
Anyway... there you have it, a relatively technical explanation for the things that go on, inside the op-amps in the DIY pedals.
With regards to distortion pedals, you shouldn't have to worry so much about these things, overall! Most of the time, the distortion gain stages are lower, as they're only using diodes to distort, anyway. The signal levels don't need to be quite as high and, consequently, neither does the stage gain, unless you're trying to replicate the Digitech Death Metal pedal. Otherwise, moderate gains are in order. Who wants a "clean" and "crisp" distortion? LMAO.
I need to run. Got work to do... have fun. Ask questions if you have them.
Dar
couple other things to remember (and I won't get as technical as Dr. K! ;) )
Not all OD/Distortion pedals these days use op-amps. The latest trend is going away from them to cascaded FET gain stages, which more closely replicate the design of a tube amps gain stages. The effect of more voltage on them is a bit different.
Also, even with op-amp driven pedals, there are several design types. Some actually rely on the op-amp itself to clip. Another type (the most popular) uses clipping diodes in the feedback loop of the op-amp. The type and number of diodes used here, or the choice of other clipping devices such as LEDs, Germaniums, and even FETs used as diodes, can change the effect that more voltage has on the pedal. If we simplifed and said that clipping option A was the standard Tube Screamer like diodes, option B was LEDs, and option C was 1N34A germaniums. These three clipping choices all clip at different voltages. The LEDs have the highest clipping threshold, and the 1N34As the lowest. All other things being equal, if you had these three options on one switch, the 1N34As would clip at the lowest level, and have the lowest volume output, the standard diodes next, and the LEDs would require the most volume (level) to clip and would have the loudest output (more voltage gets through, blah blah).
Applying more voltage to this bench pedal will show varying results. The 1N34s clip early with 9V, so jacking 18V through them won't give a big boost in volume. They'll clip even earlier on the gain knob. At the other end, you'll see some volume increase with the LEDs because they have the most headroom (highest voltage before clipping) to start with.
Now, if you had a clipping bypass option as well, where the signal didn't go through any of the diodes, THERE you would hear a HUGE volume increase between 9V and 18V because with no clipping, you are doubling the output signal. With the others, your putting more in, but clipping more off.
I took the liberty of some generalization there, and some standardization. :)
Here's some more fun... Boost A is a Fulltone Fatboost or equivalent design. Boost B is a Mosfet boost. When you go from 9V to 18V, the mosfet boost will have a big jump in headroom and output, and not much else to note. With the fatboost though, when you go to 18V you'll get a big increase in headroom and volume. But you will also make it no longer BE a "Fat" boost. Because the "Fat" comes from the natural compression that occurs in the circuit when, by design, compresses the peaks of the voltage swings because it's hitting the supply rails limit. When you double the input voltage, you double the rail voltage and the circuit (as designed) will no longer swing more voltage than the rails can supply, which =no compression of peaks, aka, no "FAT"
I tried to control myself, but Dar makes me talk all crazy like this! :D
That said, many pedal designers prefer their pedals at 9V because sometimes the added headroom defeats the purpose. You want the OD character of the pedal, and jacking up the voltage may give you more headroom but that means less of the OD that you paid for. . . Prompting one boutique pedal maker, when asked about using 18V with his OD, he said " If you just want a boost, get a boost. " ;D Sometimes 12V or 15V is perfect. Sometimes 18V is better for what you want.... just don't assume it's "across the board improvement" for all ODs to run more voltage.