Voltage Multipliers (for our tube projects...)

[Ice-9]

Rick the inductor is rated at 2A so should be ok. I now need to be testing with some valves but it will be a few days before i can do that.

[earthtonesaudio]

My only switched inductor power supply experiment so far has been a simplified version of the one frequencycentral posted, but with a BS170 ( ) as the MOSFET.  Small changes in the circuit can make big changes at the output.  I over-volted the output cap for the split-second it took the voltmeter to show what was going on!  Luckily, no explosions. 

The thing I noticed though is the switching frequency spewed all over the place.  I could just hold my scope probe near (1-2cm) the inductor and get large (many mV) current spikes.  I think that may be a good argument for using shielded inductors/transformers. 

For comparison purposes, the near-field HF radiation was not much better with a %^&*roft-Walton supply, which was somewhat surprising (but may have had something to do with long leads on the breadboard acting as antennae).


The best lesson I learned from these experiments is that if you have multiple high frequency oscillators in close proximity, it's nearly impossible to avoid problems.  In the future, all my projects will have a single HF clock source.

[Ice-9]

The thing I noticed though is the switching frequency spewed all over the place.  I could just hold my scope probe near (1-2cm) the inductor and get large (many mV) current spikes.  I think that may be a good argument for using shielded inductors/transformers. 

Shielding would help but the problem this would pose is shielding the inductor would drop the efficiency, by how much i'm not sure.

[Darkness, Darkness]

Yet another proposal for a  'not so high' high power supply for our tubes project ? Be carefull, it is NOT tested yet... just want your opinion on the design and components values (And as usual be carefull with high voltage...)

I was preparing my next parts orders and thought it would be nice to experiments with higher voltage tube experimentations  I plan to get the high voltage from a 12V AC / 1A EHX power adapter. I would like to be able to power up to 3 X12AX7 tubes in the 230V areas... with good filtering and with being isolated from power supply (thus the 12V EHX power adapter)

I took the inspiration from http://www.electricwestern.com/diytubes.html and from our king of the tubes (Frequency Central) designs 

Here is what I would like to try. Any comments ? I am not sure if I really need the inductor/ caps filtering on the LM317 part of the schematic
http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply.png.html

Thanks !

[frequencycentral]

You flatter me sir! I'm no expert on transformers and power supplies, but it does strike me that you could simplify the heater supply by using a 7806 instead of the LM317. 6 volts is within the tolerance of the heaters, and you'll eliminate the trimmer, which could eventually fail or drift. One less thing to worry about! For my dual 6111 pedals I'm running the heaters at 6 volts (ok - two in series from 12 volts), it's fine. Though I understand why you might want the precision of 6.3v exactly.

[Darkness, Darkness]

You're welcome Rick ! It's always a pleasure to read from your tube projects ! 

I was also thinking of just using the LM7806 for the power supply... but I was fearing that it would shorten up the tube life... but don't know how much  Indeed, powering up/off the unit might be more harmefull for the tube life than the 0,3V difference In first instance I might just try the LM7806 instaed of the LM317.

Thanks !

[frequencycentral]

I don't think it should shorten their lives, it's within the spec. As I understand it, it's only heater voltages higher than the rated spec that will shorten their lives - in the long run. I can personally confirm that you can put 12 volts through the heater of a 6111 (oops) without killing it. They are tough little @#$%ers after all, designed to be shot up to 30,000ft in missiles......!!

[ClinchFX]

Yet another proposal for a  'not so high' high power supply for our tubes project ? Be carefull, it is NOT tested yet... just want your opinion on the design and components values (And as usual be carefull with high voltage...)

I was preparing my next parts orders and thought it would be nice to experiments with higher voltage tube experimentations  I plan to get the high voltage from a 12V AC / 1A EHX power adapter. I would like to be able to power up to 3 X12AX7 tubes in the 230V areas... with good filtering and with being isolated from power supply (thus the 12V EHX power adapter)

I took the inspiration from http://www.electricwestern.com/diytubes.html and from our king of the tubes (Frequency Central) designs 

Here is what I would like to try. Any comments ? I am not sure if I really need the inductor/ caps filtering on the LM317 part of the schematic
http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply.png.html

Thanks !

There have been a number of power supply schematics around the net recently, using a power transformer in reverse to obtain high voltage.

Please be aware that, unless the transformer is chosen very carefully, this format can be a recipe for Fire.

While audio transformers can usually be used in either direction, power transformers are usually designed differently, depending on intended use as either step-up or step-down.  When AC is connected to a winding that was originally designed as a step-down secondary, core saturation will often occur.  When core saturation happens, the winding will no longer appear as an inductor.  The input current will increase and the power will be dissipated in the DC resistance of the winding.  The winding will begin to heat up, even if there is no load on the other winding.  The heating can happen at quite low currents supplied by an AC plugpack.  Some transformers have a thermal fuse built in to the mains (original primary) winding, but, when the original secondary is being used as a primary, the thermal fuse can not give any protection.  If ambient room temperature is already high, the transformer can, over a number of hours, become hot enough to cause combustion.

The other, less serious, disadvantage of this practice is that, when core saturation occurs, the output waveform from the high voltage winding will be clipped and will therefore contain harmonics which will interfere with other circuitry, sometimes worse than a switch mode supply.

[objectx]

Guess you guys may have seen this, but weber has been selling this trafo for a while:

https://taweber.powweb.com/store/pdlptsch.jpg

specifically designed for tube pedals... not cheap though at $20

[Gus]

Google "Royer mxl2001 mod"
Look at the power supply section.
  Can be adjusted and changed.
  I have posted about this in the past IIRC.

[Darkness, Darkness]

Thanks for the feedback guys ! That's very interesting 

I really like the idea of the Weber transformer specially desigend for that purpose 

So here is an update of the design (I have delete the previous version) http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply+3.png.html If you have remarks...

At the moment size/cost is not an issue for me on this project (still working on Marshall like tube preamp ). I would prefer to use transformer solution as it seems less complex to build and should allow higher voltage and maybe a few more mA to power a few more preamp valves

Thx again !

[ClinchFX]

Guess you guys may have seen this, but weber has been selling this trafo for a while:

https://taweber.powweb.com/store/pdlptsch.jpg

specifically designed for tube pedals... not cheap though at $20

Thanks for posting that   I hadn't seen it before.

I really like the idea of the Weber transformer specially desigend for that purpose 

So here is an update of the design (I have delete the previous version) http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply+3.png.html If you have remarks...

That looks neat and simple.  It should work well.

[bassmannate]

Could a voltage multiplier like these be used to turn a Valvy into an amplifier since more voltage on the plates means more boost?

[frequencycentral]

Could a voltage multiplier like these be used to turn a Valvy into an amplifier since more voltage on the plates means more boost?

Yup: http://www.diystompboxes.com/smfforum/index.php?topic=73317.0

[Darkness, Darkness]

Thanks for the feedback guys ! That's very interesting 

I really like the idea of the Weber transformer specially desigend for that purpose 

So here is an update of the design (I have delete the previous version) http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply+3.png.html If you have remarks...

At the moment size/cost is not an issue for me on this project (still working on Marshall like tube preamp ). I would prefer to use transformer solution as it seems less complex to build and should allow higher voltage and maybe a few more mA to power a few more preamp valves

Thx again !

There is not much details on weber website about the characteristics of this transformer, but I wander if I should not have to power the heaters separately (=not from the same EHX 12VAC 1A power supply) :

-> if output is 260VAC 40 mA, then the transformer is 10VA. Then, if I am not wrong, the 12VAC input would then draw around 870mA... Am I right ? In that case there is not enough mA left for powering 3 tubes heaters from that power supply as I intend to, and I have to adapt the input fuse value too

[ClinchFX]

-> if output is 260VAC 40 mA, then the transformer is 10VA. Then, if I am not wrong, the 12VAC input would then draw around 870mA... Am I right ? In that case there is not enough mA left for powering 3 tubes heaters from that power supply as I intend to, and I have to adapt the input fuse value too

The quoted 40mA is the maximum that the secondary can supply, however, it will supply only what is drawn from it by the load.  Each half of a 12AX7 will probably be drawing less than 2mA, therefore the total load on the secondary with 3 x 12AX7 will be 12mA, a total of 3.12VA or a primary current of 260mA.

Unfortunately, the heaters and the 6V linear regulator will consume more than 11VA because linear regulators are very inefficient.  I don't understand why you want to regulate to 6V (or 6.3V) when the 12AX7 is designed for 12.6V heater supply.  Alternatively, if you really want to run the heaters at 6V, you will need either a 12VAC 2A adaptor or use a switching regulator such as the LM2575T-ADJ for the 6V supply instead of the linear regulator.

[Darkness, Darkness]

Thanks a lot ClinchFX 

You're right about the heaters at 12V... For the heaters I was still stuck with my 6111 tube tests...12AX7 have different heaters value

[ClinchFX]

Thanks a lot ClinchFX 

You're right about the heaters at 12V... For the heaters I was still stuck with my 6111 tube tests...12AX7 have different heaters value

Thanks.  Re-reading my post, I apologize if I sounded like a smartass.  I didn't mean it that way.  At times I become very involved in the technicalities and forget to be human

I'm just glad to help.

Peter.

[Darkness, Darkness]

No matter  You've been very helpfull. Thanks again 

Fabien.

[frequencycentral]

I found this over at AX84 forum, thought it may be useful to some folks:

PDF: http://ricktone.rickcampbell.org/cgi-bin/getimg.cgi/PedalPowerSupplyLayout.pdf

Link to thread: http://www.ax84.com/bbs/index.php?id=385353