JHS AT 18v

[Marbles]

Hi there,

A friend asked me to build him a JHS AT (recommended a crunchbox). So I thought about the Turnaround. I'm just confused about the 18v.. I know I can add a charge pump, which will then convert 9v to 18v.

As long as my caps are ok (above 18v), it wouldn't hurt to use an external 18v supply right? He wants to keep his pedalboard small, and with 4 knobs and a switch, i'm not feeling putting a chargepump inside..

[Travis]

You should use caps rated 25V or higher

It would be easy to fit the turnaround with a charge pump and top mounted jacks in a 125B. The 125B with top jacks tends to take up a hair less space than a 1590B with side jacks depending on how your board is setup.

I built a 9V-18V charge pump in a little 1590LB which is handy for trying out different pedals at 18V, and also compact for the tiny pedalboard freaks. This was Mark's idea btw :)

[Sensei Tim]

confirmed. There is plenty of room in a 1590b for a charge pump. there's no reason why it wouldn't fit in a 125b

[Marbles]

Oh that's neat! Great idea, thanks!

I should be fine then. Thanks guys!

[Marbles]

So.. maybe a stupid question too, but.. On the vero, there is a wire to the led as well.. So That would be 18v, then a resistor and then the LED.

Wouldnt that be a problem? Or do I just don't get it? :D

[Beaker]

It depends on the exact specs of the LEDs you are using, but the minimum resistor value is usually far lower than the values we tend to use, so you should be absolutely fine. The LED will be a bit brighter at 18V than at 9V, so you may want to increase the resistor value to compensate. Even if you don't, you are not going to blow it.

LEDs typically have a minimum value of approx. 500 Ohm at 9V. Raise that to maybe 750 Ohm for 18V operation.

Most guys tend to use something more like 2.4k for diffused, and 10k or over for super-bright waterclear LEDs at 9V simply to prevent scorched eyeballs, You can see that is over the minimum limit by a country mile.

[Marbles]

Ah great! Thanks for your quick reply!

I like it when the LED comes from the board. Saves thw awkward wiring of the resistor at the powersupply or LED. My builds are messy enough without the ugly use of heatshrink :D

I was affraid because of the 18v I still had to wire it from the powersupply.

Thanks!