Ultra Clean Power Supply - Transformer question

[danielhawkes]

I have read all the instructions, but still have a few questions:

What rating should the transformer be?

How many pedals can I run from the one circuit?

If I do need more than one circuit, can I just use a single 50v transformer, rather than two 25v ones?

Any help would be greatly appreciated.

[Aharon]

If you are refering to the Ultra Clean PS at GGG,I would use a 500mA or more PT(power transformer).
The PCB shows 4 connections for effects.
Hope that helps a little
Aharon

[David]

If you are refering to the Ultra Clean PS at GGG,I would use a 500mA or more PT(power transformer).
The PCB shows 4 connections for effects.
Hope that helps a little
Aharon

Aharon:

Did you build it?  If you did, did you use the split transformer?  I've got one I'm about ready to test.  It's not split, though, and the outputs are in parallel.  Think this will be quiet, or have I created a noise problem?

[RDV]

I'm building 1 with a 300ma tranny, but I bought 2 in case that's not enough. I'm not running any juice-hogs really anyways. I just gonna parallel 3 jacks.

RDV

[Aharon]

If you are refering to the Ultra Clean PS at GGG,I would use a 500mA or more PT(power transformer).
The PCB shows 4 connections for effects.
Hope that helps a little
Aharon

Aharon:

Did you build it?  If you did, did you use the split transformer?  I've got one I'm about ready to test.  It's not split, though, and the outputs are in parallel.  Think this will be quiet, or have I created a noise problem?

I built one similar to the Ultra Clean.
By "split transformer" you mean one with a center tap(CT)?.
Aharon

[David]

If you are refering to the Ultra Clean PS at GGG,I would use a 500mA or more PT(power transformer).
The PCB shows 4 connections for effects.
Hope that helps a little
Aharon

Aharon:

Did you build it?  If you did, did you use the split transformer?  I've got one I'm about ready to test.  It's not split, though, and the outputs are in parallel.  Think this will be quiet, or have I created a noise problem?

I built one similar to the Ultra Clean.
By "split transformer" you mean one with a center tap(CT)?.
Aharon

No, Scott specified a multiple-secondary-coil type of transformer.  I'm using a center-tap for mine, but it's 12V on the outsides.  The center is 6V.
I wanted to allow enough input to cover the losses on the diode bridge and the rectifier.

[niftydog]

can I just use a single 50v transformer, rather than two 25v ones?

it's 12V on the outsides. The center is 6V.

Que?!? Which is it?! Can you link us to where you're taking the instructions from because I don't see anything like this at GGG?

How many pedals can I run from the one circuit?

Depends entirely on WHICH pedals you're running.

If I do need more than one circuit, can I just use a single 50v transformer, rather than two 25v ones?

I think I understand what you're asking. Provided the 50V tranny is centre tapped, yes you can.

I dunno though, does anyone else think that a 25VAC tranny is a little high to make a 9VDC supply?!?!?

[David]

Nifty:

Easy, man!  Sorry for the weaving in the thread.  Aharon just mentioned he built Scott Swartz' four-output power supply from GGG.  What I did was just a design hack, that's all.  Scott used a transformer that had four independent secondaries on it, like the one R.G. specified for the Spyder.  Anyway, wanting to avoid waiting, I...  uhh...  cheated.  I used a standard transformer with 3 wires on the secondary.  The "outside" wires yield nominally 12VAC (I don't remember the exact amount).  All I did really was borrow Scott's diode bridge and rectifier stage and graft it onto this transformer.  My outputs come off the rectifier in parallel.  I had done this once before with a liberated wall-wart and it worked fairly well, although it had insufficient filtering and no regulation that I could tell.  Hence the new model.  Anyway, it puts out a nice, steady 8.96 volts on each output.  I haven't tried it with any pedals yet.  My electric is at church.  I hope to bring it home Wednesday night and do some testing!   :twisted:  :twisted:

[Aharon]

No, Scott specified a multiple-secondary-coil type of transformer. I'm using a center-tap for mine, but it's 12V on the outsides. The center is 6V.
I wanted to allow enough input to cover the losses on the diode bridge and the rectifier.
David


Ok,this is the way I see it now.
The transformer is a 12V with a center tap.If you read the voltage from the two outside wires is 12V but one outside plus the center tap yields 6V ....right?


Aharon

[niftydog]

Nifty:

Easy, man!

I'm cool!  

So sounds like you've got it sorted then?

I can't say I've done any testing on this whole parallel vs. multiple secondary thing, but I did wind my own transformer with 12 secondaries for powering my pedal board!!!!  :twisted:

Anywho... 25VAC is a little high, you could get away with a smaller tranny, just so you know.

BTW, there's nothing particularly special about any of the supplies at GGG, they're almost vanilla circuits straight from the datasheets, just with a few minor bells and whistles. For my money, scotts filtering is adequate, but I would go for bigger caps. That's just me!

[David]

I can't say I've done any testing on this whole parallel vs. multiple secondary thing, but I did wind my own transformer with 12 secondaries for powering my pedal board!!!!  :twisted:

12 secondaries?!?!?!

Holy seven-grand potentiometer, Batman!!!  How long did that take?  Can you write up what you had to do?  R.G.'s writeup pretty much scared me off the wind-your-own idea.

[David]

No, Scott specified a multiple-secondary-coil type of transformer. I'm using a center-tap for mine, but it's 12V on the outsides. The center is 6V.
I wanted to allow enough input to cover the losses on the diode bridge and the rectifier.
David


Ok,this is the way I see it now.
The transformer is a 12V with a center tap.If you read the voltage from the two outside wires is 12V but one outside plus the center tap yields 6V ....right?
Aharon

Bingo!

[Aharon]

You can use the two outside wires and safely shrink-wrap and stow away the CT.
25V IS a little more than needed but as long as it's within the voltage limit of the regulator you are safe.
Aharon

[David]

Kewl!  Just what I figured!  Actually, mine is 12V outside-to-outside.  I clipped the center wire.

[niftydog]

12 secondaries?!?!?!

Holy seven-grand potentiometer, Batman!!! How long did that take? Can you write up what you had to do? R.G.'s writeup pretty much scared me off the wind-your-own idea.

Ah yeah, well it did take a while, and it was bloody boring, but it wasn't hard at all. Power trannys are easy... audio output trannies are a whole other story! All you do is this;

DISCLAIMER/WARNING: This is incredibly dangerous and should not be attempted by someone unfamiliar with proper electrical safety procedures!

- find a suitable transformer with an adequate VA rating, sufficient size and a primary rated for the mains voltage you intend to use.

- hook it up (using an isolation transformer and an RCD to be safe) and measure the voltage of the secondary(s) and make a note

- disconnect the trannie and carefully disassemble it. (note that it must be of a disassemble-able type! E-I laminations are easy to get apart, provided they're not welded like some I encountered!)

- now you're left with the bobbin. Take off the coverings on the secondary and start unwinding. CRUCIAL POINT: You must count how many turns you unwind. [you could also cut the secondaries out and do a quick wind-and-test to ascertain the volts/turn]

- now, you work out the voltage per turn by simply dividing the secondary voltage you measured by the number of turn you counted.

- now, you work backwards. Using the volts/turn you just calculated you work out how many turns you need to get the secondary voltage that you want. (I added some just to be sure... you can deal with too much voltage, but not enough voltage is a disaster!)

- then, you buy some suitably rated copper winding wire and get ready for some mind-numbing, hand-cramping action!!!

- wind exactly the number of turns you calculated for each secondary, separating each winding with electricians tape of similar. It's best to try and be fairly neat, otherwise you won't get as much wire on there as you can. This is where it gets annoying; laying up each turn next to the last for ever and a day is quite stupefyingly frustrating.

- obviously you need a system to keep track of the ends of the windings and also you must take care not to damage the wire. That copper winding wire will break if stressed too much.

- then, hook it up to mains (again, read the warnings!)and measure the secondaries to make sure you got it right.

So, once I'd done all of this I designed a generic LM317 circuit that I duplicated and hooked across all but one of the windings. The odd one out was left as AC to power a dBx compressor that I had on my board at the time.

The trannie I used was way overrated (6.3V TV tube heater trannie from the 60's), but to get that many secondaries on you need a large bobbin. In the end it meant that I could have ultra-low ripple (massive filter caps) without worrying about anything over heating.

[Aharon]

Kewl!  Just what I figured!  Actually, mine is 12V outside-to-outside.  I clipped the center wire.

Ahhhhh.............never clip,one day you may want to make a bipolar + - 9V supply.
Take care
Aharon

[David]

Kewl!  Just what I figured!  Actually, mine is 12V outside-to-outside.  I clipped the center wire.

Ahhhhh.............never clip,one day you may want to make a bipolar + - 9V supply.
Take care
Aharon

It's too late to turn back now...

[danielhawkes]

Hi. Thanks everyone for the help.

Btw, the instructions I was referring to in case anyone wants them were on www.generalguitargadgets.com.