VVR - Variable Voltage Regulators - GuitarTalk Community

VVR - Variable Voltage Regulators

Nicholas-L

I know there are two types of VVR's. 1 for Cathode Biased and 1 for Fixed biased amps. Who of you have done these kind of mods t your amps? Did you find schematics to it or bought a unit? I kind of like the whole D.I.Y thing, but at the moment I just don't quite feel like going into the math of it ??? ... The main reason I brought this up is because I have a 100W SLO-100 Clone that I finished the other day, but it's highly unlikely that I'll ever be able to fully utilize it's potential.

Come to think of it would the whole amps voltage need to be adjusted or can it be done on just the power tubes? and what about the PI tube?

ezietsman

You are going to need a MASSIVE mosfet and resistors to tame that one. Mine is an 18 watt, cathode biased 2x EL84 pushpull. The schematic I used included the VVR and it only works on the Power tubes and Phase inverter.

Here's the schematic.

http://rh-tech.org/public/18-Watt/18_Watt_LiteIIb_Superlite_VVR_PA_PI_162.gif

Here's the VVR bitsie

http://bp0.blogger.com/_4u9l5q2yFBA/SHLiQ2AZTOI/AAAAAAAAAbg/Eprac9awqoI/s1600-h/VVR+in+18watt+schem.gif

VellaJ

I'll be watching this eagerly... I've been wondering about doing something similar.

Also, what would the price difference be between having these mods done and buying a smaller amp, such as the Vox AC4?

Nicholas-L

Thanks EZ. At least now I have some sort of starting place. I'll Look into the pricing of this mod and let you all know.

ezietsman

VellaJ wrote: I'll be watching this eagerly... I've been wondering about doing something similar.

Also, what would the price difference be between having these mods done and buying a smaller amp, such as the Vox AC4?

That depends on a few things. If you have a factory amp, installing Power amp and Phase inverter scaling only, will be tough as you need to modify the power supply too that may make it more expensive, esp on an amp with pc boards. Scaling the whole amp is cheap and easy but doesn't sound as good. Look at London Power and Hall for VVR Kits. Mostly pretty easy to install (cathode biased amps) and cheap.

When building an amp from scratch and you should consider adding VVR unless its only 10 watts or less. My 18 would have been impossible to play properly without it. Depends what you you want out of an amp. I wanted lots of drive and I've got it.

makepeace

VellaJ wrote: I'll be watching this eagerly... I've been wondering about doing something similar.

Also, what would the price difference be between having these mods done and buying a smaller amp, such as the Vox AC4?

Uh.. a mosfet, some diodes and the needed resistors and possibly caps would probably come to a sum total of under R150 bucks if you're unlucky.

AC4 is in the range of R2000 to R4000.. soooooo, make your choice ?

Nicholas-L

Here's a schematic I found earlier today that has the sub section to adjust bias level if like me you have a fixed bias amp.

http://www.el34world.com/Forum/index.php?PHPSESSID=1e9940cb33254a046516c5aa26c13221&action=dlattach;topic=10918.0;attach=21519

lol I forgot I had it. :-[ :sorry: