Voltage Multipliers (for our tube projects...)

[g.]

Or can I hack a DC one and get rid of the rect. bridge!? I guess there's AC just before it, am I right?!

yes !

[Renegadrian]

40106 is another cheap IC that can be used to multiply voltage - here is a VERO LAYOUT I made - verified, it works so good with a valvy!!! 

[g.]

40106 is another cheap IC that can be used to multiply voltage - here is a VERO LAYOUT I made - verified, it works so good with a valvy!!! 

Hi can you point me the schem of this one ?

[Renegadrian]

[g.]

Thanks !

only small caps with this one, can be a really small B+ provider,  i 've some 40106, will test it shortly, and 2,5 mA are enough for some circuits

[gtudoran]

My lil' NIXE SMSP with a redesigned pcb and some Oscope shoots with DC ripple (the load was 4 triodes).






Best regards,
Gabriel Tudoran
Analog Sound

[BarnyardBill]

I was wondering, at what voltage does the 12AU7 begin to go from "starved plate" to non-starved plate.  I want to make a supply, but I was wondering if there is a low voltage that works, or does the sound change linearly with an increase in voltage?  I know all tubes are different, but I have a number of multipliers with 80V as the B+ voltage.  What voltage do tube amps use?  Do they use the maximum voltage? 

thanks,

Curious Geroge

[Renegadrian]

Voltages running inside an amp are usually between 250 and 350. Usually anodes of a standard double triode get 250-280 if memory serves well...

[zambo]

yeah thats about right as far as I know. depends on what amp too. 240 is a good ball park for 12ax7 it seems. You can go down to 125 or lower and still get good sound though. Less voltage causes more clipping which is good in our case. the tone suffers at low voltage and the clipping is fizzy and doesnt sustain as well as it could in my opinion. 80 volts could be very cool though. Cascading two tubes together at 80v would make a heck of a overdrive

[merlinb]

I was wondering, at what voltage does the 12AU7 begin to go from "starved plate" to non-starved plate. 

There's no exact point. As you say, there is a gradual change. However, in working with cascodes I have observed that most preamp valves show a more rapid increase in gm when you get to... you guessed it, 80V! For this reason I assume 80V to be the 'transistion zone', at least for the ECC81/2/3.

[BarnyardBill]

thanks for all the help, I think I'm ready to order some parts for the multiplier now.  I didn't realize how much I have gotten used to the valvey until I switched it off.  Since I only have a solid state Peavy Amp, the valvecaster really shines through.  I might make one and just set in on top of my amp since I leave it on all the time anyway.

-Bill

[Earthscum]

I wanna yank the step-up transformer out of my supply (it only steps up to 104V). I was wondering, can I sub a IRF730 for the 740? It's 5.5A, 400V, 1Ohm on resistance, where the 740 is showing 10A, 400V, 0.5Ohm. It's mainly the voltage handling we're after, correct? Does 1/2 ohm on-resistance matter much in these multipliers? And, I assume even the 5.5A rating is still way over-safe for these. I have a couple 730's I don't have anything else to do with, and they both have neat little heat sink clip-ons.

[gtudoran]

I wanna yank the step-up transformer out of my supply (it only steps up to 104V). I was wondering, can I sub a IRF730 for the 740? It's 5.5A, 400V, 1Ohm on resistance, where the 740 is showing 10A, 400V, 0.5Ohm. It's mainly the voltage handling we're after, correct? Does 1/2 ohm on-resistance matter much in these multipliers? And, I assume even the 5.5A rating is still way over-safe for these. I have a couple 730's I don't have anything else to do with, and they both have neat little heat sink clip-ons.

You can use 730 but you may find that it will be a little more hot (less resistance = less voltage drop across channel => less power to dissipate). You wanna do a flyback SMPS? if so you will need a Xformer that will support the switching freq. (a ferrite core wich will go up to 30-40kHz). But if you don't wanna do a flyback why do you wanna complicate things with xformers... use a small inductor and that shoud be it.

Best regards,
Gabriel Tudoran
Analog Sound

[casiomax]

Hi all,

i just recently try to build the nixie supply, after a smoke test, i get HV output definitely, but the IRF740 gets very HOT!.

Here's the different thing i had on my build:

a. 100uH using FT37-43 toroid 17 turn, according to its spec, it would make 100uH.
b. UF4004 replaced by UF4007
c. 2.2uF output cap, replace with 10uF 400V cap

i suspect using FT37-43 100uH coil and 10uF 400V is BAD, will get the correct parts as soon as i have time to go to the local store . and BTW, i use 12V input supply.

here's a photo of my build, i would really appreciate if you guys could help. thank you.

[frequencycentral]

Yeah, I think your inductor is the problem. The 10uF reservoir cap should be fine, better even, although with this type of supply it's easy to exceed the maximum rating of the cap (and smoke it) if you're not careful. I always use a small heatsink on the MOSFET, with a little thermal gel for heat dissipation.

[gtudoran]

Do NOT ever ever ever use a thoroid inductor in this kind of PS! Use either a ferrite bar or a standard inductor (experiment with values from 60 to 150uH and you will find a point where the ballance is right), the variable voltage output is made by varying the Frq. and not the DC (and this is a lil' bit tricky), you can also change the 2n2 oscilator cap to 1.2-1.8 nF. and if you feel that you need a smaller PS i can give you the SMD version.

Best regards,
Gabriel Tudoran
Analog Sound

[casiomax]

Yeah, I think your inductor is the problem. The 10uF reservoir cap should be fine, better even, although with this type of supply it's easy to exceed the maximum rating of the cap (and smoke it) if you're not careful. I always use a small heatsink on the MOSFET, with a little thermal gel for heat dissipation.

Do NOT ever ever ever use a thoroid inductor in this kind of PS! Use either a ferrite bar or a standard inductor (experiment with values from 60 to 150uH and you will find a point where the ballance is right), the variable voltage output is made by varying the Frq. and not the DC (and this is a lil' bit tricky), you can also change the 2n2 oscilator cap to 1.2-1.8 nF. and if you feel that you need a smaller PS i can give you the SMD version.

Best regards,
Gabriel Tudoran
Analog Sound

thanks for the answer, i plan to put a small heatsink to the mosfet. also, i do have a couple of ferrite bar, kind of a tubular shape, 4mm diameter, 15mm length, but i do not know how to calculate the value needed. i'll experiment later on this one.

thanks again.
julius

[casiomax]

ok, i got my ps working very well just by replacing the inductor. IRF740 definitely cool down.

is there any way to pump the output voltage within 200-300V range? i am trying to build P1 amp from AX84, its a 2x12AX7 and a EL84. would this PS provide enough current?

thx.

[gtudoran]

Hey casiomax,

You can't supply an output stage tube with this SMPS - don't think that this PSU will supply enough current for a EL84 outputstage. As far as the voltage output goes i was able to sqeez 280v from it (275v with load) - i've changed the oscillation capacitor with 1.5nF as fara as i remember, all the other parts are the same, i also recomand you tu use pcb and a ground plane for this PSU.

Best regards,
Gabriel Tudoran
Analog Sound

ok, i got my ps working very well just by replacing the inductor. IRF740 definitely cool down.

is there any way to pump the output voltage within 200-300V range? i am trying to build P1 amp from AX84, its a 2x12AX7 and a EL84. would this PS provide enough current?

thx.

[casiomax]

Hi Gabriel,

again, thx for the input. I know not much about SMPS, but i understand a bit now, changing the oscilator cap means changing the frequency in result different desired output voltage, like you have mentioned before.

I read the EL84 datasheet, if i am not mistaken it requires more than 60mA to operate, as for 12AX7, it only requires less than 5mA, this means firefly project will be able to use SMPS. cmiiw.

Hey casiomax,

You can't supply an output stage tube with this SMPS - don't think that this PSU will supply enough current for a EL84 outputstage. As far as the voltage output goes i was able to sqeez 280v from it (275v with load) - i've changed the oscillation capacitor with 1.5nF as fara as i remember, all the other parts are the same, i also recomand you tu use pcb and a ground plane for this PSU.

Best regards,
Gabriel Tudoran
Analog Sound