Question for VVR users

[Tonegeek]

For those of you who have installed the VVR circuit, have you had to add extra supply filtering? I scaled an 18 watt amp (power tubes only) and it hummed until I put an extra 16uF cap on the node right after diode2 (see setup). My setup was tube recto > 33uf > 2 diodes.
diode1 > VVR > OT + 2k2R > 33uF > Screens.
diode2 > 2k7R > 16uF > 8k2R > 16uF > 4 triode plates (V1 & PI). I am wondering if I could have just rearranged the existing supply to avoid having to add extra components.

I want to use the VVR in other circuits but would love to know how much extra filtering to factor in for the VVR addition or if it is even needed. The Marshall 18 watt amp uses 16uF for 2 tubes so maybe on other amps that use 20uF per tube I won't need it.

[Cliff Schecht]

Did you try a much smaller capacitor (say 0.1-1uF)? What about using a low ESR film cap instead of an electrolytic?

[Tonegeek]

Did you try a much smaller capacitor (say 0.1-1uF)? What about using a low ESR film cap instead of an electrolytic?

I don't remember what all i tried as it was a year ago. I can't imagine 1uF would make any difference though. If I was a real engineer I could figure out what I need for filtering based on how much current the VVR itself draws but I assumed (incorrectly at least on the 18 watt) it wasn't enough to warrant extra filtering. Maybe I had some other issue but the amp is dead quiet with that extra filter now. I am revisiting this topic as I am planning another build and want to incorporate a VVR/LarMar again.

[10thTx]

There is some information about Dana's VVR in cathode biased amps
here: http://www.el34world.com/Forum/index.php?topic=6899.0

I like his product and YES, I had to add extra filtering which reduced the hum/noise. I think his VVR is a great system.

With respect, 10thtx

[Tonegeek]

There is some information about Dana's VVR in cathode biased amps
here: http://www.el34world.com/Forum/index.php?topic=6899.0

Good link. lots of 18 watt vvr schematics. Mine was similar but I did not scale the PI, just the EL-84 tubes. I don't quite understand scaling the PI unless you want it to break up. I thought the point was to break up the outputs. I can sort of see that in a non vvr application the PI may break up along with the power tubes when really pushed so maybe it makes sense to scale it too. I suppose I should try it. I did try scaling the whole amp and did not care for that sound.

I like his product and YES, I had to add extra filtering which reduced the hum/noise. I think his VVR is a great system.
With respect, 10thtx

Yes it is which is why I want to put it in my next higher wattage build.