12 volt 18 volt what????

[Pbadness]

Hi folks,
I am not building my own stompbox here but I need someone's help.
Truly sorry if this is not the right place to put this question, but It seemed like the best place.

Here's the situation... I have a Yamaha DG Stomp floor effects unit. It uses a 12 volt power adapter. (Wall Wart)
I have a DC Brick regulated power supply for my effects pedals. I use it for my TU-2 Tuner, My Homemade A/B Box (Thanks guys), my Dimebag Wah, my Jekyll & Hyde, and my ISP Decimator Noise Gate. All of these are 9 volts, and I use the 9 volt spots on my DC Brick.
The DC Brick also has 3 separate 18 volt jacks. Is it possible for me to do away with my 12 volt adapter, and use one of the 18 volt connectors for the Yamaha? Would that fry my effects unit, or is it okay to do that. I guess I am just wondering if I can use the 18 volt power section for what normally uses a 12 volt adapter? Does anyone know the answer to this. Of course, Yamaha says to only use their adapter, but will I fry it if I use the DC Brick?

Thanks for any and all help for anyone.
Peace-
Jon

[Mark Hammer]

It would depend entirely on what sort of on-board regulation the DG Stomp has.  Is its 12v wall wart AC or DC?  If AC, then we know there will be SOME regulation on board.  Will that regulation accommodate 18vdc?  We don't know.

There IS a remote possibility it will, since the DG has digital circuitry on board and that will require some sort of onboard regulation to drop 12v down to 5v.  But we still don't know what it needs to be fed in order to do that, so I wouldn't risk it without further info.

The good news is that if the unit NEEDS to be fed 12vdc, you can always insert an additional stage of regulation between the brick and the DG's wallwart jack and regulate 18v down to 12v.  Those spiffy 3-pin regulator chips only need 2VDC more on the input than they put out (so minimum of 14vdc to get 12vdc), and they don't need many additional components to do their job.  You could easily make yourself an adaptor board and stick it into a little black plastic box.  All you'd need beyond that might be a 16-25v cap (say, between 220uf and 1000uf), a small value cap like 0.1uf, and an LM7812 regulator (the 1A size that looks like a power transistor).

[Transmogrifox]

building on what MH said...
You can also open your DC brick and change the 18 Volt regulated section to 12V.  If it just uses a 78xx series regulator, this would be really easy to do (assuming the opening the box and accessing the circuitboard is really easy to do).

It may also use a Zener diode.  In that case you could also change the diode to a lower voltage value.

MH's recommendation is the least invasive to both the DC brick and the pedal, yet still a very simple solution since you could fit the circuit into an Altoids Sours sized can.

[Pbadness]

Wow,
thanks for the help guys. Uhh, I'm kind of not worth a crap at most of this terminology. I did build my own A/B Box, but that was only jacks, power, and led's. That much I can do. It does sound like I could do the step down converter thing. I would like to do away with the giant wall wart. Here is a link to the parts manual for the DG stomp. It may tell you some information that helps? I don't know.

http://www.yamaha.com/yamahavgn/Documents/Guitars/dgstomp_1.pdf

The service and parts manual

http://www.yamaha.com/yamahavgn/Documents/Guitars/DG-Stomp_E.pdf

Of course, they say DON'T use any other adapter.
I think I could probably build a converter for one of the 18v spots on the DC Brick. I am a little bit lost as far as how to do it, though. Can anyone show me a parts list, and a wiring diagram for this? I am terrible at reading symbols, so if it could be in layman's terms, that would be awesome. I am mechanically inclined, and can solder halfway decent, so if I get some direction, I think I could do this. Please help if you can. Thanks-

*curses at Giant 12v Wall wart crammed in pedal board beside nice tidy neat DC Brick with it's space saving plug*

Oh yeah, and I love Altoids, so I have some of the metal tins already available, haha...

[Paul Perry (Frostwave)]

It's 12V AC. And looking at the circuit, it's half-wave rectified to give + and - which is then regulated to give the +-15V analog rails.
You are out of luck, you will have to live with the 12v AC wart. But if you ever have to replace it, here's a tip... it will be cheaper from www.jameco.com !

[Pbadness]

OK, so I don't understand any of that last post except "you're out of luck" 
So, does that mean I can't make a Tin Can voltage divider with a Zener Diode Thingy or something???
I apologize, but I am not very familiar with this type of electronics.
Thanks for your posts people!

[Doug_H]

OK, so I don't understand any of that last post except "you're out of luck" 
So, does that mean I can't make a Tin Can voltage divider with a Zener Diode Thingy or something???
I apologize, but I am not very familiar with this type of electronics.
Thanks for your posts people!

Your Brick is DC (direct-current) and the Yamaha box requires 12v AC (alternating current). So you will have to use the AC wall-wart that Yamaha provided. Evidently the Yamaha box takes the AC supply voltage and converts it to DC internally. As Paul mentioned, you can get 12v AC wall-warts real cheap if you ever need to replace the one that came with the pedal. They have them at mouser too.

One of my next projects is to build a power supply for my pedalboard. In addition to various DC voltages (other than 9v) I'm going to include a couple utility AC receptacles on it to accomodate the occasional oddball pedal that requires a 'speshul' wall-wart.

Doug

[Transmogrifox]

Yeah, I took a look at the schematic for the power supply input.  The only way to fit your remedy into an Altoids can is if you knew how to program a microcontroller.  You could have the uC convert your 18VDC into a 12VAC via MOSFET switch.

What may be easier at this point would be to see if you could find a service manual for the DC brick that has a schematic.  Then one of us may be able to guide you through the steps necessary to mod the DC brick so you can get 12VAC to your 18VDC jack.  It's possible that this is a very simple solution.   It appears from the Yamaha schematic that it would not be an issue if you were a little more or less than 12VAC on the input.

I think they make such a point of stressing the use of THEIR power supply to cover their butts in waranty cases.  If something goes faulty on the pedal, and it happened because somebody plugged some piece of junk wallwart into the pedal that had a short to the mains voltage and roasted their pedal...then Yamaha doesn't get stuck with replacing a product that was damaged from stupidity.  If THEIR power supply faults, then it's THEIR responsibility.  Anyway...sorry it's not so easy.  A DC-AC converter (called and inverter) is possible to make with analog circuits, but it's not so practical in this case as it may not be easy to keep it any more low profile than an ugly wallwart.

[Paul Perry (Frostwave)]

Transmogrifox, that's a damn good idea, working backwards & running the whole show off an AC transformer! The only difficulty is that to get 18V DC regulated you will need about 15V AC, which will increase the dissapation on the + and - !% and 5v regs in the Yamaha unit. And check the rating of the input filter cap in the Yamaha.
I'm not a guitarist myself, gigging or otherwise.. but if I were, and I had a need for a mix of warts, I think I'd attach them inside a box with labelled leads coming out. Plus, I would seriously thing about changing the sockets on the different FX boxes, so that it was IMPOSSIBLE to fry anything by plugging the wrong lead in! (OK lets be honest, I'd THINK about it, I wouldn't actually DO it..)

[Mark Hammer]

OK, so I don't understand any of that last post except "you're out of luck" 
So, does that mean I can't make a Tin Can voltage divider with a Zener Diode Thingy or something???
I apologize, but I am not very familiar with this type of electronics.
Thanks for your posts people!

Your standard "wallwart" used for pedals will typically do three things: a) it will drop the voltage down from what comes out of the wall socket (110VAC or something else, depending on where you live) to something more appropriate for the thing it will be powering, b) it will rectify that alternating voltage so that it is a single positive voltage with a ground, and c) it will smooth out any remaining ripple or mini-variation in that rectified voltage so that it approximates having the steady smooth DC of a battery...only with greater capacity.

The approach used for the DG Stomp, and in a lot of other commercial boxes, is essentially to divide those duties up.  The transformer yiou need only does part A above.  Parts B and C are accomplished within the DG Stomp itself.  One advantage that provides is that the main unit can be made smaller if the transformer is situated outside.  A second advantage is that the transformer is a source of hum that ups the design and layout complexity/requirements for producing a noise free pedal, so moving it outside the main unit removes that source of noise-risk.  A third advantage is that since AC has no real V+ and ground (it alternates, hence AC), the risk of plugging in the "wrong" DC adaptor hastily borrowed from someone or bought somewhere (with V+and gnd on the "wrong" contacts) is removed.

The good news is that 12VAC/700ma adaptors are cheap like borscht.  They sell them for $5 where I live, and I wouldn't doubt for a moment that places like Jameco or Parts Express would have them on sale.  Happily, since they are NOT DC adaptors, you don't have to worry about whether one from this place includes as much regulation as the one from THAT place....because your pedal does the regulation.

[Pbadness]

Dayum, you's guys is smart...
I not so smart. Thank you all for your help and suggestions. I appreciate it immensely.
Move on now, nothing to see here...hahaha

[Mark Hammer]

Anyone can look smart if they read the dictionary, newspaper, and encyclopedia on a daily basis for years and years.  You'll be just as "smart" if you hang around here for another 10 years.

[Pbadness]

Sounds like fun. Count me in.