18 Volt Power Supplies

[robotboy]

I was checking out the fulltone website the other day, and I saw a blurb on the tech tips page about running the OCD, Fulldrive2, Bassdrive and FatBoost on 18 volts DC with the following warning.

Do NOT try this on any other pedals by any other manufacturers without first determining whether they have components with high enough tolerances or the result may be fire and/or serious injury to you and perhaps your pedal. The FD2, Bassdrive,  and Fat Boost are over-engineered to withstand the higher Voltage.

So, do pedals really have to be over-engineered to accomodate an 18-volt supply? If so, is it worth doing so? What kind of modifications are generally necessary? Seems interesting, but  it leaves me wondering if this is just hype or if it really requires "over-engineering".

[niftydog]

fulltones use of "over-engineered" is in my opinion mojo-speak; it's not "over-engineered" at all! What they mean is that they design it at 18VDC...

...but it just happens they make sure that it works on 9VDC as well.

Other manufacturers look for ways to reduce manufacturing costs due to the large number of units they ship. Boss therefore try to get away with the bare minimum spec components - that is to say 10V rated caps.

So, with some exceptions, a boss pedal could probably be beefed up to accept 18V, provided you can replace all the relevant caps with 25V rated ones, as well as some other considerations perhaps, like maybe some of the resistors.

This topic has come up before, and my opinion was that it seemed pretty unnecessary. Think about the voltage levels required and the power available: Guitar signals, even really really loud ones are less than 1V. A well designed circuit running from 9VDC should be able to produce signals of around 7V peak to peak - easily!

That's already a LOT of headroom. But, it is also a simplistic view of things. Digital chips is a whole other ball game and there are other factors that might come into play.

Also keep this in mind; in most cases you can equate "over-engineered" with "needlessly expensive".

[seanm]

I doubt it is "overdesigned". A lot of my designs will work at 18V even though they where designed for 9V. For example the B. Blender.

Why? I use TL072 opamps. They are designed to work at +/- 18V. NE5532? +/- 22V. J201s can hande 40V. I use 25V caps because they are the cheapest.

That is not to say all effects will work at 18V. Anything with carefully biased transistors will not.

Is it worth it? In the B. Blender, maybe. I have distorted the opamps with a hot effect. 18V would give more headroom. I have tried the B. Blender at 12V and it works. However, I tried my Fulltone Bassdrive at 12V. I lost almost all of the overdrive! It became a clean boost, with a lot of sparkle.

I bet many Boss pedals would work at 18V. I wouldn't try it though without checking very carefully. And even then, would it be worth it? Probably not.

Note I am not knocking Fulltone. I think it is great that they admit the pedals run at 18V. A Fatboost at 18v could be the cats meow for some people. Tons of clean boost!

[MartyMart]

I agree, all my builds will run at 18v ( apart from Ge FF's bias of course)
I have always used 25v caps ( and above ) but some commercial pedals
like Boss etc have only 10v/16v caps so BE WARNED !!

I just ran a few yesterday at 18v with interesting results, some circuits
get a great "clean" improvement and are louder/beefier than on 9v
others sounded a touch "mis-biased" , even if they were not a fuzz ... !

I guess it depends on the specific design, whether or not the voltage
doubling has a benefit or not......... opinions ?

Marty.

[robotboy]

My most recent build (a blackfire) was done using all 50V caps, so theoretically, it could run at 18V, right? I understand that bias will probably be a problem, but the chance of damage would be negligible, correct? Did you just use 2 9V in series, or an 18V supply? Anyway, thanks for the helpful replies.

[seanm]

My most recent build (a blackfire) was done using all 50V caps, so theoretically, it could run at 18V, right? I understand that bias will probably be a problem, but the chance of damage would be negligible, correct? Did you just use 2 9V in series, or an 18V supply? Anyway, thanks for the helpful replies.

Theoretically, but your biasing will be way off. You may push too much current and blow the transistors, or at least weaken them. Note that the circuits we are talking about are opamps and jfets, not BJT.

It probably also won't do much good. The Blackfire works by having the early stages overdrive the later stages. If you give them tons of headroom you will reduce the distortion. Remember, your input signal is still the same.

[MartyMart]

sean is correct, if you mean the "Blackfire" then I wouldn't run that above
9 volts as it's setup with the 5089's for a certain gain structure/bias.
Circuits which sound "better" at 18volts (PSU BTW) are :
( I use the term "better" loosely! some clean up a bit too much)
DIY TS-9
DIY Boss OD-1
Boosters
`liquid drive
A couple of silicon FF's

Blackfire and Vulcan sounded "miss-biased" as do several other ic/transistor circuits.
My guess is that going to 18v rather than 12v should work better as its
2X the supply of a 9v circuit, so some bias/gain structures will still be
in proportion ..... or am I going mad here ??
Hope that makes some sense......

Marty.

[robotboy]

sean is correct, if you mean the "Blackfire" then I wouldn't run that above
9 volts as it's setup with the 5089's for a certain gain structure/bias.
Circuits which sound "better" at 18volts (PSU BTW) are :
( I use the term "better" loosely! some clean up a bit too much)
DIY TS-9
DIY Boss OD-1
Boosters
`liquid drive
A couple of silicon FF's

Blackfire and Vulcan sounded "miss-biased" as do several other ic/transistor circuits.
My guess is that going to 18v rather than 12v should work better as its
2X the supply of a 9v circuit, so some bias/gain structures will still be
in proportion ..... or am I going mad here ??
Hope that makes some sense......

Marty.

I figured that it might reduce gain on the blackfire since higher voltage seems to mean more headroom. The only reason I even considered the blackfire is because besdies my BSIAB II, it's the only pedal I've got (since I've given away every other pedal I've made...). OT, but I've got an SM57 microphone coming in the mail today, so I'll be posting some clips of my latest builds in the near future   I've been planning on building a rangemaster in the near future, so maybe I'll try it at 18 volts to see the difference. Would that require a rebias as well? If so, maybe I could use a trimpot above the collector to make life easier.

[MartyMart]

If you mean a Germanium PNP rangemaster then I dont think that would work.
All the "FF's" etc that I tried that with ( including a brian may treble booster) just wouldn;t sound "right" at higher voltages, but you may be
able to hit a "sweet spot" with the bias, depends on the particular tranny .... ?

Cheers,
Marty.

[seanm]

I figured that it might reduce gain on the blackfire since higher voltage seems to mean more headroom. The only reason I even considered the blackfire is because besdies my BSIAB II, it's the only pedal I've got (since I've given away every other pedal I've made...). OT, but I've got an SM57 microphone coming in the mail today, so I'll be posting some clips of my latest builds in the near future   I've been planning on building a rangemaster in the near future, so maybe I'll try it at 18 volts to see the difference. Would that require a rebias as well? If so, maybe I could use a trimpot above the collector to make life easier.

The rangemaster would be a bad choice. You need to change more than just the collector resistor When I say rebias I don't mean just trimming the bias, most of the resistors would have to change.

If you want to try something at 18V, build a mini-booster or a TS. Almost anything opamp based should work fine. An MXR Distortion+ or DOD 250 would be a good simple one to try.

[Ben N]

I can't see why there would ever be a bias issue in any opamp circuit with the standard votage divider for 1/2 V+ bias.  Then the only consideration is having suitably rated caps.  I would think that the more sensitive the bias, the bigger the issue, as in germs and fets.

FWIW, Barber also advertises that most of his pedals (which are all opamp-based) will run fine at 18v.  I tried my Direct Drive for a while at 18v--not much difference, really, a little more max volume and headroom.  It only mattered when I pushed the front end of the pedal with another boost, and then I did not like the extra headroom.  He also has the Launchpad, intended to be a super-clean booster/splitter, which runs internally on 24v for max headroom.  

Doug Hammond had designed a high voltage Shaka Brada variant called the Sweet 16 a while back.  I'm not sure what the point was.

Ben

[robotboy]

I figured that it might reduce gain on the blackfire since higher voltage seems to mean more headroom. The only reason I even considered the blackfire is because besdies my BSIAB II, it's the only pedal I've got (since I've given away every other pedal I've made...). OT, but I've got an SM57 microphone coming in the mail today, so I'll be posting some clips of my latest builds in the near future   I've been planning on building a rangemaster in the near future, so maybe I'll try it at 18 volts to see the difference. Would that require a rebias as well? If so, maybe I could use a trimpot above the collector to make life easier.

The rangemaster would be a bad choice. You need to change more than just the collector resistor When I say rebias I don't mean just trimming the bias, most of the resistors would have to change.

If you want to try something at 18V, build a mini-booster or a TS. Almost anything opamp based should work fine. An MXR Distortion+ or DOD 250 would be a good simple one to try.

Mini-booster has been on my list for a while, so I might try it... Then again maybe 18V isn't that big a deal, and I should just proceed onto the build I've been planning for a while, the Phase-45 w/ univibe mod.

[analog kid]

Was UP??!! Noone I have seen even mentions the Tyco Octavia in this thread.  Isn't it originally designed as an 18-24v crkt??
I have long been wanting to try running it like that but does anyone know if the crkt AS MOST of us know it IS the original the way RM would've designed it to run at 18v? aside from the vltg handing of the electro's etc....??
 Reason is MOST of the Tyco 's I've ever built (just 3) have sounding crappy!! and a little misbiased when volume or boost is turned down much.
Thought this may produce a stronger sounding Octave/Fuzz.
(Also a dumb ??>>> how do you typically run two 9's in series . ?? I mean if both -9vlt went to ground and both +9v went to the power bar , then that would be in Parallel wouldn't it?? Any schem for how that's easiest done?)

[niftydog]

I mean if both -9vlt went to ground and both +9v went to the power bar , then that would be in Parallel wouldn't it??

yes.

For series, you connect one batterys negative to ground, then that same batterys positive to the other batterys negative, then that batterys positive to the supply rail.

[petemoore]

What the heck, I'll come right out and say it.
  What better way [plenty of other ways that have been explored for this], to help 'curve' a distortion or cleanup a sound that needs it.
 I'm running my Splitter Blend at 18v and it likes it there. Batteries last longer, takes two of 'em. BMP, Si Booster don't seem to mind 18v at all.
 FF's like 1X 9v battery AFAIKTell.
 Mu Amp is mu favorite voltage staver as may you know, they're self biasing and have made headway to PB use.
 Starving Opamps was a waste of time for me so far.
 Single Jfets, bipolars, [didn't mess with Ge's Hmm] can sound cool starved, but some R adjustmentS are necessary, for 'optimal, wider ranged Voltage use.
 LM317's are easy to do.

[sevenisthenumber]

What would a LPB1 do at 18volts? Could it easily work with no adjustment?

[anchovie]

What would a LPB1 do at 18volts? Could it easily work with no adjustment?

Set it up on the breadboard and find out - the parts list isn't exactly huge!

[drk]

you would need to do some adjustments

[sevenisthenumber]

is there such thing as a simple boost circuit that will run at 9v or 18v with no adjustment? Thanks

[MartyMart]

is there such thing as a simple boost circuit that will run at 9v or 18v with no adjustment? Thanks

There's a few things such as Jfet and Mosfet boost's that will be happy at 18v, check out AMZ

They are clean anyway and would just be "super clean" and have more headroom, perhaps useful on an active
bass / guitar's output.
I built a few "Hamptone" preamps that are very nice, can be used for mic mostly but running two together for
guitar was a good noise !

MM.