EHX Deluxe Electric Mistress Power Question

[jhamnett]

Hi guys, I'm a newb at building effects.  So far I've modded my Boss OD-2r and Crybaby and caught the DIY bug.  I'm working on the BYOC Octafuzz and the GGG Distortion+ as my first 2 builds and wanted a real challenge for my third project, so I ordered the EXH Deluxe Electric Mistress PCB for my third build.

What confuses me is the type of mains to 18V transformer I need for the job.  I searched the forum and didn't exactly come up with the cut and dry answer I was looking for.  I read that one could use a charge pump, so I ordered 2 MAX1044 samples from Maxim -- hopefully that will make my life easier.  Could someone who's done this build spell out for me what is the best option for powering the mistress?  I have a PS with both 9V and 18V outputs, so I can run either, but would prefer a 9V option so I can run off batteries in case I need to (should've just got the tonepad PCB, too late now).

Also any good build stories associated with this project would be excellent  .

Thanks,

JH

[jhamnett]

A thought...

Since my PS will be providing 18V, maybe I just need to hook up the PS to the pedal through a power jack and wire the +18V to the pink pads on the PCB (green wires from transformer) and the ground to the gray pad (black wire from transformer)?  I'm referring to the layout on the GGG website: http://www.generalguitargadgets.com/diagrams/dmistlo.gif.

Can someone validate this?

Also, how much luck have people had with switching out the trimpots for actual pots?  I've heard the clock has been switched with success, how about gain, feedback, and bias?

Thanks,

JH

[boogietube]

I think that Jim Dunlop sells an 18V power supply adapter
Here it is:
http://www.musictoyz.com/guitar/pedals/dunlopps.php

[boogietube]

You should also read about the MAXX 1044 - they have been known to induce noise in pedals -cant remember which pedal, but if you search you'll find it here

[jhamnett]

Thanks for the words of caution about MAXX1044, I'll read up about potential problems.

Currently I have a power supply (Gator's G-BUS-8) that has 18V outputs.  In the DEM layout on GGG, it shows a 18V transformer with 3 wires going to the PCB.  I want to use this to power the pedal, so I guess a DC jack would work.  The only problem is that the 3 wires going from the DC jack to the PCB instead of the normal 2, it's confusing me a bit.  If someone has experience with this, could you check out the layout and give me some advice?

Thanks,

JH

[Toney]

Or you could opt for the (reportedly) fabulous sounding 9volt Electric Mistress.

http://www.aronnelson.com/DIYFiles/up/9V_Mistress_project_file_v11_update.pdf

[jhamnett]

I wish I could, but I already ponied up the $19 for the PCB (OK, I can still scrap the project and go with the 9V, but where's the fun in that?).  Maybe when I have some more time (aka, get out of work) I'll compare the two PCBs and see how similar they are.  If it's an issue of a couple jumpers and changed component values, then I'm good to go 9V.

[slacker]

If you don't want to or can't get a transformer then you should be able to power it with your 18 volt power supply.
To do this remove D2, replace D1 with a wire jumper then connect the +18 from your supply to D1's input pad and connect the ground of your power supply to the grey pad.
I'm not sure how much different the 9 volt version is, but to power it off 9 volts might be as simple as removing the 7815 regulator and connecting 9 volts to the pad where it says Q2. That possibly wont work though.

[jhamnett]

Ian -- fantastic!!  Exactly the response I was looking for! 

I will do that and add a couple battery snaps in series for battery power.

[Uma Floresta]

If you don't want to or can't get a transformer then you should be able to power it with your 18 volt power supply.
To do this remove D2, replace D1 with a wire jumper then connect the +18 from your supply to D1's input pad and connect the ground of your power supply to the grey pad.
I'm not sure how much different the 9 volt version is, but to power it off 9 volts might be as simple as removing the 7815 regulator and connecting 9 volts to the pad where it says Q2. That possibly wont work though.

Sorry to bump an old thread, but some time ago I had correspondence with someone who removed a DEM transformer and replaced it with a wall wart input. The only difference is, he said it was 24 volts. His worked successfully, so I assume 24v won't fry a Mistress, but which is the correct voltage, actually?

Here was information he sent me:

Hey Ben.

It's not too difficult. The transformer supplies 24 volts DC. Electro-Harmonix sells an adapter for their modern effects: http://elderly.com/accessories/items/EH24DC.htm

That's not the one I used but it'll work just fine. The barrel is the negative which is what gets connected to ground.

You'll want to get an adapter that will allow for negative ground. Something like this: http://www.smallbearelec.com/Detail.bok?no=92. Again, not the part I used but I think it'll do the trick. I think I actually got something at Radio Shack. The point is that the barrel is ground and that contacts the chassis of the effect and grounds it. On mine, I ripped out the power cord and the adapter jack fit into the hole with just a little bit of persuasion.

Making the connection to the PCB isn't too hard. On my board it was a little weird because I recall there were two spots to connect the hot (positive). Not sure why but everything worked okay. Just remember that the trace running around the outside of the board is negative so that's where you want to connect the negative from the power supply.

I didn't find any resources online but there might be something there. I wish I could take a pic of the guts of my DEM for you but it's no longer in my possession unfortunately.

Good luck.

[george]

but to power it off 9 volts might be as simple as removing the 7815 regulator and connecting 9 volts to the pad where it says Q2. That possibly wont work though.

wortks for me .... I built the GGG DEM and didn't have a 7815, so I used an adjustable PS set to 15V so I could test my build.

Out of curiousity I reduced the power supply to 9V to see if I could still get it to work.

After twiddling the BBD bias trimmers it seems to sound as good on 9V as 15V - the only possible issue may be reduced headroom which may result in unwanted distortion with high output pickups, but it sounded fine with my strat ...

[StephenGiles]

but to power it off 9 volts might be as simple as removing the 7815 regulator and connecting 9 volts to the pad where it says Q2. That possibly wont work though.

wortks for me .... I built the GGG DEM and didn't have a 7815, so I used an adjustable PS set to 15V so I could test my build.

Out of curiousity I reduced the power supply to 9V to see if I could still get it to work.

After twiddling the BBD bias trimmers it seems to sound as good on 9V as 15V - the only possible issue may be reduced headroom which may result in unwanted distortion with high output pickups, but it sounded fine with my strat ...

Correct, that is exactly what the electronics specialist at Eh UK told me in 1980!

[george]

did he tell you that your warranty would be null and void ....? :-)

[StephenGiles]

Well now, that depended upon whether you knew him or not!

[george]

all right!!!!!!

did it work for you? Even if you had humbuckers?

Cheers George

[birt]

you can just buy a 24V EH power supply.

this page has UK, european and USA versions: http://www.banzaieffects.com/Other-Voltage-Power-Supplies-c-939.html