How to build an effect pedal into a really big enclosure?

[vanessa]

A guitar amp! 

What would be the best way to build an effect (or mutable effects) into a guitar amp using its power source? I've thought of two ways so far but I'm not sure if they would work (well one anyway).

1.) Install a small stepdown transformer tapped off the main wall power source to get 9V DC?
2.) Tap off the heater source (usually 6.3V) and use a charge pump to get another 3V (9.3V)?

[The Tone God]

I personally like option one just for noise and isolation purposes. It would be easier to reverse later down the road too.

Andrew

[Mark Hammer]

Given that the Visual Sound Workhorse amps do this very deed (i.e., supplying regulated 9v for pedals), and given that it was designed/intended to be a robust build that did proper justice to pedals, the logical choice is to ask Mr. Keen how he/they did it.  Not a schematic ( ), but simply a here's-why-this-is-the-right-fork-in-the-road-to-take-when-you-balance-it-all-out response.  The math is optional. 

[Steben]

A guitar amp! 

What would be the best way to build an effect (or mutable effects) into a guitar amp using its power source? I've thought of two ways so far but I'm not sure if they would work (well one anyway).

1.) Install a small stepdown transformer tapped off the main wall power source to get 9V DC?
2.) Tap off the heater source (usually 6.3V) and use a charge pump to get another 3V (9.3V)?

-I guess it is really important to know what amp it is. At first I didn't read the 6.3V, so I wasn't sure about the tube part.
-The second thing: why stick to 9V? it is only 9V for most, because of the battery standards, you know. Distortion effects for example will do fine on 6V.
-If you tap off 6.3V into a germanium rectifier (full wave) (or even an opamp one) you'l have about 6V. But don't forget the pump of a ripple cap: you'll have about 8V for sure. It can be even several 100mvolts more. That seems pretty close to me. The magic of this passive circuitry is the full use of transformer power. The filament heating will suck up many times more than your effects, so don't be afraid of voltage drops. Charge pumps are not "strong".

[petemoore]

  Here's how I did that.
  Stuck an AC supply jack right at the back of the amp, solidly mounted and wired to the AC input. I used a 'two same prong back of amp' type [I don't know if you call an old wall socket like 110v outlet a 'jack']...an AC output thing came out of the back of a stereo. It's made to be mounted to a metal ''dock'', I did it with a couple screws, some glue/2nails in ~drilled holes and two <1x1 blocks.
  Plugged a VS1-SPOT in that.

[Meanderthal]

Given that the Visual Sound Workhorse amps do this very deed (i.e., supplying regulated 9v for pedals)

Whoa, I didn't know that! That's a great idea! Now I'm gonna hafta go look up if they have a bass version... (G.A.S... here we go again...)

Edit: Apparently not. Actually, I'm relieved... I didn't need to be wanting yet another amp... and now that I think about it, I wouldn't wind up using that feature unless I was in a pickle... cord would have to be be... long. Oh well...

[Processaurus]

Given that the Visual Sound Workhorse amps do this very deed (i.e., supplying regulated 9v for pedals)

Wonder if they just stuck the guts from their 1spot switching power supply in there?

I've wanted to leech power off of my other equipment (18v EH pedals, amps, guitar synth, keyboards) with +/-15 supplies,  to power pedals, would it be reasonable to stick a robust 6v zener diode in series with the +15v to create a 9v tap for some pedals?

[Ronsonic]

Try to not use the heater supply of a tube amp for anything else. If you want to rectify for the preamp tubes, sure. But, there are a number of failure modes that involve high voltages being shorted to the heater supply. It's best if there's nothing else on that supply that could be damaged by severe power surges. It isn't uncommon to find the 2W carbon comps (a resistor type used for its surge resistance) that Fender used between the heater string and ground severely burned. Any solid state effect unit powered from that supply would've been fried. We also see more problems in the switching circuits of amps that get their supply from the heaters.

Even a seperate winding would be subject to voltage sag when the amp was cranking. You could design your supply to accomodate that.

I say keep it simple and plug your supply into the courtesy outlet on the back. Or, bolt a power strip to the inside of a combo amp.

Ron

[Mark Hammer]

Given that the Visual Sound Workhorse amps do this very deed (i.e., supplying regulated 9v for pedals)

Wonder if they just stuck the guts from their 1spot switching power supply in there?

I've wanted to leech power off of my other equipment (18v EH pedals, amps, guitar synth, keyboards) with +/-15 supplies,  to power pedals, would it be reasonable to stick a robust 6v zener diode in series with the +15v to create a 9v tap for some pedals?

Well, I certainly didn't want to force anyone to divulge what the specific circuit was.  Rather, if it does make a difference how one arranges for the second power source, that's worth knowing.  If it doesn't make a difference, that's worth knowing too.

[R.G.]

The nice thing about design for reliability is that it's as hard to copy as it was to do in the first place. The secret is not some magic circuit trick - it's that the thing is solid. It's not easy to fake solid.

I remember Gordon Liddy's %^&*tail party trick. He'd take a lighted cigarette and calmly lay it in the palm of his hand. And leave it there. The smell of burning flesh would permeate the air. When asked "What's the trick?" he'd say "The trick? The trick is not caring." 

Right. Copy that one. 

Since I got to specify the power transformer, there's a low voltage winding on it that supplies low voltage DC to a garden variety voltage regulator to make 9V. Putting a switching power supply inside a tube amplifier is a prescription for trouble that I didn't even want to consider. In fact, putting a line frequency power supply inside a tube amplifier is not all that easy - but you got to get DC from somewhere. 

In reply to Vanessa - option 1 is by far preferable. You can make the power supply and signal ground connect to the amp signal ground at one and only one place so you can get the ground hum down to zip. Tapping a heater supply can be done, but it's very fiddly to get everything right and have it be both noise free and interference free.