High Voltage Circuits

[raulgrell]

Having recently developed a crush for upping the voltage supply of pedals from 9V to 12V, I would like to take it a step further... Well, 12 steps further, really...

Anyone have any 24V+ ish designs to share?

I've looked at several circuits designed for higher voltages already - the Shaka HV, Sweet 16, and that russian valve emulation thing that went round a while back... I'm just curious to see some more schems particularly if anyone has a copy of the Obsidian HV... The original pedal sounds so bloody awesome, I can only imagine what it sounds like in HV...

Sound clips to follow 

[petemoore]

  Tube Amps...they need high voltage for 'optimal' performance.
  Other than that check your data sheets and put 24v to a circuit.
  Check that the components can handle at least the voltage'd be applied [+ 10% is good idea]. Mostly capacitors...transistors and resistors etc. mostly can handle 24v, check data sheet when in doubt.
  Moving from 9v to 12v may make a more noticable difference when boosting say a guitar signal because there may be a lack of headroom at 9v. Once your'e over the voltage in which limited headroom occurs, differences should be smaller or harder to discern.

[Minion]

Well any Pedal that uses standard opamps can be upped to 32v+ as long as the other components can handle this voltage , Transistor based pedals would probably need re-biasing to get them to work properly .....

Cheers

[Gus]

Raising the power supply voltage might make it sound worse.  Think about how a gain stage without diodes clips.
Try it and find out.  Some circuits will need values adjusted also be mindful of the drain or collector etc current  changes.

[raulgrell]

Raising the power supply voltage might make it sound worse.  Think about how a gain stage without diodes clips.
Try it and find out.  Some circuits will need values adjusted also be mindful of the drain or collector etc current  changes.

That's exactly why I'm looking at purposefully high voltage circuits, I'm looking for patterns in their designs... those that are based on lower voltage pedals are a godsend - you can see what they did to make it sound better in HV... are there any established 'rules'?

About the biasing issue - any transistor circuit, especcially JFET will have some sort of biasing quirk when upping the voltage, that's a given... It's just awesome when it does work well with little to no tweaking! I really liked Rick's Murder One, it's amazing... really gonna look into tube circuits after seeing that.

Will post again with results...

[mac]

I'm taking fets to their max voltage, using 2sk117 and 2sk246 at 45v.
Recentrly I posted the Fet Junior, a clone of the Valve Junior at 45v.
At 9v it has little in common with the VJ, but at 45v it begins to sound more similar to the real thing. I want to get 300v fets but no luck.

mac

[davidallancole]

mac

Just to let you know, Supertex makes depletion mode MOSFETS that work similar to JFETS.  They self bias like JFETS and have voltages up to 700V.

http://www.supertex.com/pdf/misc/d_mode_mosfets_SG_device.pdf

[raulgrell]

I'm taking fets to their max voltage, using 2sk117 and 2sk246 at 45v.
Recentrly I posted the Fet Junior, a clone of the Valve Junior at 45v.
At 9v it has little in common with the VJ, but at 45v it begins to sound more similar to the real thing. I want to get 300v fets but no luck.

mac

I live in portugal, and the only (small signal) JFETs I can find in my local electronics store is the 2SK117 - Sounds amaaaazing... If their max voltage is 45V, could I run two in a mu-amp configuration at 90V, or that me over-simplifying the voltage distribution thing?

[brett]

or that me over-simplifying the voltage distribution thing?

yes

But go ahead anyway, coz many devices can easily exceed their rated values, and some devices act differently (e.g. many tubes sound better when run harder than their specified plate wattage).

[Renegadrian]

Any tube-submini tube project you can find here works better with some extra V...I have a voltage multiplier going to +-50V and it adds a lot of headroom when applied to the Valvy-Pentaboost-Tube Star and so on...Without going HIGH voltage, a MIDDLE voltage won't kill you and it's easy to get with common parts...

[davidallancole]

raulgrell

If you run the two in a MU amp, you may blow them up.  When the signal goes positive at the output the voltage across the bottom fet will increase towards the 90V rail putting it far above the 45V rating.  But like brett said, give it a try anyways.  If they blow up, at least you would know why then.

[mac]

2sk117 have more gain than j201 and low Vgsoff.

mac