Anyone have experience with a 10-stage voltage multiplier circuit ?

[joesatch]

I have a nice little beefy PT but the secondary taps are 40V and 25V.  I would like to multiply this 40V to around 400v.  I am not worried about the low current in the result as I'm only driving 3 or 4 preamp tubes (preamp build) .  What would this circuit look like?

[thetragichero]

i used to be silly with those type of power transformers out of old organs. i saved em for repairing solid state amps
you'd need a filament transformer to run some tubes anyway. that's 20-30 bucks. something like the power transformer for the fender standalone reverb units (hammond's is 290wx) is like 50 bucks and has filament and ht taps. if this is for a preamp you probably don't want to weigh the unit down with a bunch of beefy transformers

[joesatch]

I ask because this is a 2 space rack signal processor i am repurposing. i pulled the PCB's out and i am left with a nice PT , switches, indicator light, fusing etc. and a good amount of space to work with. I already have a DC heater board that will take the 25V tap from the PT so filaments not an issue. I would like to take this 40V from the PT and bump it up to say 380-400vdc.  Bad idea?

[tubeswell]

I already have a DC heater board that will take the 25V tap from the PT so filaments not an issue.

The heater supply will still need to provide the right amount of current demanded by the filaments (which means this current has to come from the PT, so as long as you’re satisfied the 25V tap can deliver enough current for the filaments, this might work, or not, depending on how robust your DC heater board is)

[joesatch]

I already have a DC heater board that will take the 25V tap from the PT so filaments not an issue.

The heater supply will still need to provide the right amount of current demanded by the filaments (which means this current has to come from the PT)

it will come from the 25V tap from the PT.  The heater board has it's own rectifier, Regulator and filtering to deliver the 12vdc.

[shooter]

If you have a couple hundred foot of bailin wire, make an electric fence for the annoying neighbors   

[uki]

That is a cool chassis Joe !!

take a look at those links, maybe this is what you looking for !
http://rawfire.torche.com/~opcom/psu/4x8_power_supply.html
https://www.electronics-tutorials.ws/blog/voltage-multiplier-circuit.html

[joesatch]

I do have a donut PT that i might throw in, would be cool to use this PT it looks modest but it is a heavy little piece of iron like 3 lbs These chassis are loaded with PCB boards with tons of removable IC's and you can buy these MM-8840 cheap!. They dont have any holes on the face so they can be drilled for anything. I think i will turn this thing into an X88 or SP77.  These units are under $50 used all over the net

[nandrewjackson]

+1 for the fender standalone reverb PT. It fits inside a 2 space rack, I've done it to make a preamp.

[trobbins]

If you want to stick with 60Hz rectification then you may get close to your target B+ with what would be called a full-wave tripler. 

An example of a full-wave doubler (from a quick internet grab) is
http://www.augustica.com/ElectronicsTutorialsImages/Tubes/Full%20Wave%20Voltage%20Quadrupler.jpg 

With 40Vac, that may get you to over 300V with a full-wave tripler, etc....

[SoundmasterG]

Any voltage multiplier circuit won't regulate as well as more normal type of circuits used in power supplies, so you will get sag, especially with transients when you are demanding a lot from the amplifier. Voltage multiplying with 10 stages will likely have pretty bad sag. You can simulate it with Spice to see. But that said, try it and see if it meets your needs.

Greg

[kagliostro]

Only remember that you require 10 times the DC current consumption of your circuit as AC current disposable at your PT

If the circuit consumption Is 100 mA the AC current disposable at the PT must be 1 A

If the AC current Is more than required, your B+ will not SAG

My preferted multiplier Is the Crockcroft Walton


https://josepheoff.github.io/posts/diode-capacitors-volts-pt4





Copy the unit stage the number of times you want
2 times = a doubler
4 times = a quadrupler
10 times = a decupler

I forgot

Each e-cap must be 2000/3000 uF for each A of DC current your circuit requires

200/300 uF if the circuit consumption Is 100 mA

Franco

[trobbins]

Franco, it appears that the transformer secondary is a single 40Vac winding.

[joesatch]

two secondaries.  a 25v and a 40v. 25v will drive my heater supply. the 40v i would love to get it up to 375v

[kagliostro]

OK, so you have two secondaries

Use the 25V winding to supply the heaters

Use the 40V winding to feed this version of the Crockcroft-Walton
(Remember, do the PT has enough AC current disposable ?)


https://en.wikipedia.org/wiki/Voltage_multiplier

Can this solve ?

The kind of single long cascade of the same voltage to which they refer is this




--

Some time ago, an australian friend, at https://www.aggh.net, had a similar problem that he solved this way



His problem was a little different, he had a 50V with CT PT and the way he used it result in a different consumption from the two half windings, however it worked also if not perfectly elegant as a solution


One other australian friend solved his problem this way




In Australia is difficult to have PT for tube amps at a good price, so our friends are very experienced on this argument


--


The use of big capacitors and a PT with extra current will help you but only  trying will give you an answer

Franco


p.s.: I'm thinking to something .... a bit different, not so much different from what was did
        but at the moment is only an idea, not sure it is feasible

        Which is the current available at the 40V winding and which is the current available at the 25V winding ??

[joesatch]

many thanks for the diagrams. it looks like i will need $50 worth of caps to get this done. Let me work this out

[kagliostro]

50 Dollars in e-caps .... oh, I was thinking you had a capacitors factory, isn't so ?

 

Sorry, this Is the other side of the medal

Franco

[trobbins]

Franco, my link in an earlier post to the fullwave doubler is somewhat similar to the first schematic in your recent post.  One side of the transformer winding passes through to be the mid-point voltage of the output B+, which can be useful as it provides a cheap and stiff screen supply at 50% B+ if needed.


Joesatch, note that the voltage rating of the e-caps don't all have to be for full-rated B+ voltage.  Typically the first step of rectification would use 100V rated caps to cover 40Vac being rectified to circa +/- 55V from the mid-point.

[kagliostro]

Ciao trobbins

In one of the link I posted (the first ?) there are explanations about e-cap voltage rating

At the moment I'm not so good in healt and am not able to go deep on the argument

Franco