You are here

powering pedals - electronics question

For all things relating to guitars, basses, amps, pedals & accessories.

powering pedals - electronics question

Postby AllyB » Wed May 07, 2008 2:10 pm

Hey

So i have a trex fueltank junior to power all my 9v pedals and a doubler cable to power the 18v...

i have bought a trex juicy lucy (12v, 300ma each output) to power my bigger pedals...

so trex room mate works fine with the amp doubling cable (12v, 600ma)

I want to power my cornell custom distortion which is 9v 30-300ma... so what do i put on the lead to pull back the current and V a bit? 5k resistor?

Also i want to power a exh HOG the supply with that says 9v 500ma.. so i can use another current doubler cable to bring up to 600ma.. then i just need to pull it back a bit... or i heard somewhere that ehx pedals internally regulate?

Cheers
AllyB
Regular
Posts: 220
Joined: Sun Mar 07, 2004 1:00 am

Re: powering pedals - electronics question

Postby Teleute » Wed May 07, 2008 7:11 pm

Your confusing current with voltage. you can stick in as much current as you want, a pedal will only take what it needs.

a psu that delivers 9v 1000 ma will power a pedal that requires 9v 10 ma without causing any damage to the pedal or the psu.

Using the double cable will double the voltage and this will destroy your pedal. A double lead on the Lucy will give 24v, 600 ma not 12v, 600ma.

If your Cornell will run off 30ma then you the T-rex junior will be fine as it is. If it needs 300 ma which is more than the junior can deliver then you need a separate psu. An analogue distortion pedal is very unlikely to need over 30 ma.

If the HOG requires 9v 500 ma then use separate PSU, I assume one came with it anyway. You could in theory use the double cable as you suggest. solder on 2 equal value resistors in series and then tap the 9 volts found at the center of the 2, but i don't think its worth the hassle / risk. Plus off the top of my head I have no idea what values to use or how it would affect the MA level

The junior wont have enough amps and the Lucy's 12v will destroy it.
User avatar
Teleute
Regular
Posts: 55
Joined: Sun Aug 17, 2003 12:00 am

Re: powering pedals - electronics question

Postby AllyB » Wed May 07, 2008 11:56 pm

hey thanks for that..yeh i double checked for the distortion 30ma was cool, the junior is only supplying 24 tho... but its working now..

in the end i actually bought a multimeter.. and tested the luicy.. it comes with two cables, one doubles voltage and one doubles current..the amp doubler cable still runs 12v... im running my memory lane off the voltage doubler cable on the junior..

i wanted to keep plugs to a minimum...my boards already big enough!

i tested the '9v 500ma' adapter that came with the hog.. it was actually kicking out 15v!.. so i just reversed the polarity and all is cool..

Cheers
AllyB
Regular
Posts: 220
Joined: Sun Mar 07, 2004 1:00 am

Re: powering pedals - electronics question

Postby cfb4 » Thu May 08, 2008 12:07 am

Sometimes those meter readings can be misleading - a 'wall wart' will typically read higher *unloaded* - unless it has a voltage regulator onboard. When the PSU is presented with a load, it will give a DC reading that is much closer to 9 volts. The ones with the voltage regulators onboard will give a steady voltage
regardless of load (within reason) - there is circuitry in there that carries out this task.
User avatar
cfb4
Regular
Posts: 326
Joined: Wed Jan 14, 2004 1:00 am

Re: powering pedals - electronics question

Postby AllyB » Thu May 08, 2008 12:32 am

ok cheers, so if the wall wart was givin 15v unloaded and the trex juicy 12v... i should be safe with the HOG? It seems to be working ok, had it on for a few hours and the hog wasnt hot... the trex luicy was gettin pretty hot.. but not sure if thats normal or not?

the ehx guy did say that it regulates internally...and said not to put more than 9v in, but seemed weird to me the one supplied gave out 15....
AllyB
Regular
Posts: 220
Joined: Sun Mar 07, 2004 1:00 am

Re: powering pedals - electronics question

Postby cfb4 » Thu May 08, 2008 1:17 am

I'd say the TRex should probably get warm as it has several regulated outputs. Each regulator chip has a heatsink, and this thermal energy is radiated away through the box. BTW I was impressed with this PSU solution and plan on making my own pretty soon.

According to the EHX HOG manual, one should only use the supply that came with it. If this is the one that you are metering 15 VDC unloaded, then carry on using it - I'll bet it drops closer to 9V DC under load. As far as internal regulation goes - chances are the HOG uses ICs that have precise power requirements. These voltages will be derived from your wall wart voltage - within the pedal using additional regulation. All a regulator does is guarantee a precise (as determined by the designer) output DC voltage
from a less precise input DC voltage. The 9V battery - USB converter doofer is a good consumer example. In this device, 9 Volts is regulated down to a precise 5 Volts, and the output will not vary until the input goes below 5V (like when the battery dies). The additional energy is radiated in the form of heat - Newtonian physics & all that.
Ideally a regulated supply is better as it gives a reliable, steady, filtered DC voltage. Makers tend to avoid them as it adds costs into the production run - they opt for the 'tested wall-wart' option - they design a wall wart that will work with their unit and then ship this model with the unit - with the disclaimer that it is the only one you should use. Is it? Well, for users without technical training or horse sense, yes! And there are also safety and warranty issues to be concerned about.
User avatar
cfb4
Regular
Posts: 326
Joined: Wed Jan 14, 2004 1:00 am


Who is online

Users browsing this forum: ef37a