I need at least 24v for my Deluxe Memory Man from a Weber X-former...

[guitylerham]

My multipedal is going to be using two of the Weber transformers with the  8-11v and one 9v 2-amp outputs. I am trying to power my DMM clone using one of the taps. My question is should I regulate three 11v down to 9v and then stack three of them together to make 27vdc or should I stack 3 unregulated 11v taps together and regulate that down to something closer to 24vdc? Or should I go with another transformer for this particular pedal? I will be using all or most of the secondaries for the other 10 effect onboard so I'm going to have several available taps to potentially use for my DMM. Any help or direction for me to look into would be awesome. Thank you!

[amptramp]

It is probably easier to put three 11 VDC supplies in series and regulate it down since only low dropout regulators will provide full rated current going from 11 to 9 VDC.  Also, there are issues with putting separately regulated power supplies in parallel if you ever accidentally trip the current limit.  A single 33 VDC supply regulated down to 27 VDC would be the most efficient choice since you don't have as many diode drops or capacitors.

[kurtlives]

Put two 11V AC taps in series to get 22V AC. Rectify to get 31.1V DC and regulate down to 24V DC. Don't forget to filter! 

[PRR]

[guitylerham]

I am doing my best to learn with all of this. So this schematic above will rectify one 11vac secondary to 30vdc with just two diodes capacitors? Where does the middle leg of the 24v regulator go to?

Would you guys recommend this over putting the two 11vac taps in series, rectifying, then regulating down to 24vdc? This is really fascinating! Thanks for these cool ideas!

[njkmonty]

Where does the middle leg of the 24v regulator go to?

doesnt it go to ground?

[kurtlives]

What PRR posed is a bridge voltage doubler circuit. It will do everything you want with just the 11V AC tap.

[PRR]

> Where does the middle leg of the 24v regulator go to?

Whatever it normally goes to.

There's two common kinds: 24V-specific and a general 1.25V job which is programmed-up with two resistors to any voltage 1.25V-35V. I dunno which type guitylerham favors, so I left that part vague.

[guitylerham]

Ah, I see. The LM317 for example would utilize two specific resistor values to get the desired voltage. I was just surprised that the 11vac would rectify to 30vdc is all. I think I'd go with a 24v regulator. I can't imagine I'd need anything else for my DMM. Thank you so much guys!

[PRR]

> surprised that the 11vac would rectify to 30vdc

Do not believe anything you read on the interwebs.

Get two diodes and two 5-10uFd caps, twist them up, try it.

With no load you'll get something over 30V DC.

One diode one cap makes a half-wave rectifier which will make 15VDC.

You can rig another half-wave to also make 15VDC.

You can stack them to get 30VDC.

The total action is true full-wave. The drawback is twice the current in the winding (no free power) and significant sag. However this plan is as efficient as any other.

Note that this needs a dedicated winding. If you connect this winding to any other rectifier, you almost always make a sneak-path which shorts the winding.

[guitylerham]

Awesome. I do plan on dedicating one 11vac secondary of that Weber transformer for this memory man power supply and nothing else. Is that what you mean?

Also, with twice the current through the coil, is there a lot of extra heat generated? And will sag effect too much performance-wise? The secondaries put out 300mA and I'm pretty sure the original EH power supply was only 100mA, so plenty left over even when the current is doubled (or the capacity halved, I guess?).


Does anyone know how hot a weber transformer gets with, say, up to half of all the secondaries being in use at any given time? The reason I ask is I'm putting TWO transformers and effect circuits in a 30" x 8" x 4" aluminum box and haven't considered air flow yet...

Thank you guys for all your expertise. My goal is to finish this by one month's end!