I wanna starve my fuzz pedals. What parts will I need?

[zenpeace69]

I wanna make a small pedal that I can throw between my One Spot power supply and my fuzz pedal.  Basically, I guess I need to know what parts I need and where I can get them.

I know I will need a standard 9v dc jack that will take a boss style power supply.  Then, I will need a male jack to put on the other end to plug into thepower supply of my fuzz.  Between, I am not sure what I need, but I know it will need a pot to control the amount of power I am feeding my pedals.  I have plans of putting them on a starvation diet to get the killer fuzz-tones that are in my head.

Thanks for any help!

[zenpeace69]

Someone mentioned something about a voltage regulator?  Does a voltage regulator have a pot? I dunno... I'm new to this stuff.

[niftydog]

an LM317 adjustable voltage regulator CAN have a pot and will do what you're after.

There's a sort of generic circuit  and and important equation in the data sheet for an adjustable supply.

[bwanasonic]

Someone mentioned something about a voltage regulator?  Does a voltage regulator have a pot? I dunno... I'm new to this stuff.

From what I recall, a voltage regulator is a little fancier than what you need. I'm pretty sure all that is involved is a pot and maybe a resistor between the battery and the rest of the FF circuit. The details are here somewhere, I'm sure. Not sure this will get "what is in your head", but it is the way to cop the dying battery sound with a fresh battery.

Kerry M

[Paul Perry (Frostwave)]

A simple pot wired as a variable resistor in series with the power input might get you what you want, but it doesn't cover ALL possible flat battery situations. For that, you need a variable power supply (as suggested above) and a series adjustable pot after it. Be careful, because you might make a power supply that supplies too high a voltage at maximum. You won't hurt a fuzz face (I thnk) but, you might damage some otehr units. Of course, if your algebra is good, you can set the max voltage wherever you want, following the regulator data sheets.

[axr]

another is try adding a pot on the V+ of the fuzz pedal, and put it in the enclosure.

[RedHouse]

Simplest is to use a diode in series with your power supply or battery.

One 1N4001 will give you a 1.1v drop which will land you in the 7.9v dying battery zone and carry 1A of current.

One 1N4148 will give you a 1.0v drop which will land you in the 8v dying battery zone while carrying a max of 200mA.

One 1N914 will give you a .73v drop which will land you in the 8.2v dying battery zone while carrying a max of 200mA.

[zenpeace69]

Simplest is to use a diode in series with your power supply or battery.

One 1N4001 will give you a 1.1v drop which will land you in the 7.9v dying battery zone and carry 1A of current.

One 1N4148 will give you a 1.0v drop which will land you in the 8v dying battery zone while carrying a max of 200mA.

One 1N914 will give you a .73v drop which will land you in the 8.2v dying battery zone while carrying a max of 200mA.

What if I want to make it adjustable with a pot to find the sweet spot?  I guess I can try the LM317 Voltage regulator, but can I just attach a pot to the adjustable pin of the LM317?  If I try different value pots can I get it down to a zone of say 3 volts to 9 volts?  

thanks for all the input guys.  Any more clarification of how to use the LM317 would be appreciated.

[Mark Hammer]

Two things happen to batteries as they "die".  One is that  they are only able to deliver a lesser voltage, and the other is that they are only able to deliver less current (current delivery is partly a function of the surface area and contact quality separating the 1.5V cells that make up a 9v battery; older batteries have higher internal resistance separating the cells).  The latter can be mimicked by simply sticking a variable resistor in series between the battery and where the V+ normally connects to (or V- if its a positive ground pedal like some Ge-based ones).

In my experience, silicon diodes like the 914 or 4148 can chop anywhere between .400v and .700v off whatever DC voltage you feed them, depending on the batch.  If you measure them with your meter, perhaps you can identify some that will let you shave off small amounts of supply voltage.  For instance, a trio of diodes in series with individual voltage drops of 400mv, will give you 1.2v less than what you feed it.  Using a toggle to shunt 1 or two of those diodes will give you 0.8 and 0.4v less than max battery supply.

Alternatively, poke around JD Sleep's www.generalguitargadgets.com website and find the schematic for the late Charles R. Fischers "EM Fuzz".  What Chuck did was to use a variable current regulator to starve the CMOS invertor section he used for clipping.  Supposedly, it is capable of some Neil Young style "splat" at extreme settings.

Certainly, no self-respecting brand new Duracell with a couple of diodes and a 470R resistor in series is going to sound like its as new as you know it to be.  On the other hand, part of the "dying battery" thing is the instability of the voltage/current supplied under different gain and input signal conditions.  You need to imagine a battery with bags under its eyes, asked to amplify the initial attack of a note by 200 times.  It says "You want me to do WHAT?", and as the note fades away, the battery pipes up in a raspy voice and says "Well, I suppose I could boost THAT, but that other stuff you asked me to do before? Fuggedaboudit".  A battery that can reliably supply 4ma at 8v irrespective of signal conditions, is NOT a dying battery, merely a constrained one.

If anybody knows how to create battery-operated supplies that have the "spongy" quality of tube rectifier circuits, now we're talking!

[RDV]

Just give your address to us & we'll send you a bunch of dead batteries! :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  :wink:  

RDV

[niftydog]

Any more clarification of how to use the LM317 would be appreciated.

it's all in the data sheet that I posted.  goto page 4 & run the equation that's there.  It's easy, trust me!

Keep in mind that R2, which is your adjustment pot, will be a particular value, depending on which value pots you have available.  You may wish to add a resistor in series with R2 that will limit the maximum voltage to a fixed value.

Quick and greasy: try R1 = 220ohms, R2 = 1kohm with a 1kohm pot in series with it.  Should give you about 7-13VDC.  The datasheet says that Iadj is such a small value, that the error is negligible.  So I have ignored it for this demo.

Code Select Expand


from data sheet;
Vout = 1.25V (1+R2/R1) + IadjR2

R1 = 220
R2max = 2kohm
Vout max = 12.6V

R2min = 1kohm
Vout min = 6.9V


Also, consider that the output configured in the form shown on the data sheet is adjustable from 1.2V to 37V - dependant on the input voltage.  Be careful not to over cook it if you're swapping resistors around!

Also try here, and the FAQs listed at the top of this page.

[Hal]

RDV - yea!!! my work desk has about 5 batteries of varying life on them...

[Paul Perry (Frostwave)]

If you are making an adjustable voltage power supply, don't forget the 'headroom' for the 3 terminal regulator, if you are wanting a max of 9v from it, you neeed to send it at least 12v from memory (check the data sheet, it is all ther including the schematic).

[RedHouse]

I'd recommend the LM78xx series over the LM317 for effects boxes, the heat sink (mounting tab) on the LM78xx is at ground ...unlike the LM317 where the heat sink is internally connected to it output.

For more experienced tech's this is not a big deal, but for the regular-guy hobbyist the LM317 can short if it makes contact with stuff within the enclosure (pot casings, enclosure itself etc).

Just use the same schematic as calculations recommended above and you will get the same variable supply regulator, but a little more DIY (user) friendly.