Tube Amp Archive

I would like to hear how bcmatt installed VVR on his DC30-clone or if Dana has some experience with VVR on DC30, but I haven't seen them here in a while.

I think if I were to move the VVR again it would be to scale the power section and leave the preamp at full voltage. But then I would need to install a PPIMV, which translates to reinstalling the master volume circuit I removed (I guess). Maybe I can try first without reinstalling the master volume....

Now I've AB'd the VVR against a Weber MASS: VVR 100% and MASS at high attenuation against VVR 20% and no attenuation to compare at the same volume, no changes in other settings. There's much less overdrive/grit/crunch with the VVR compared to the MASS. Tone is much better with VVR though, but the de...

...and one small detail: The DC30 sounds much better (IMHO)

As explained as the power amp is dialed down, the loading is reduced allowing the voltages to rise. Are you using the VVR on all supplies or only the power tubes? If only the power tubes, measure your pre amp voltages and you will see an increase in them too as the voltage to your power tubes is de...

Not that I recall. Maybe you are getting less speaker break up as you dial down the VVR pot. You are no longer pushing the speaker as hard, so less dirt, maybe. I don't think so, because I used to get more break up at this setting with a cab sim and load. Not pushing the speakers so hard would not ...

The amps that I have with VVR either has 2 knobs (volume and tone) or 1 knob (volume). Sorry no gain knob. :) I just turn volume to get the dirt I want and then dial down the VVR to the level I want. Oh. Well the Matchless is simular... Volume and tone at the EF86 channel. I always mix volume and g...

Thank you for your explaination. Seems that it works as it should then

Does your VVR amps give less overdrive at low settings? I mean, do you have to compensate by increasing the preamp gain knob?

I did some measuring of B+(in) and B+(out) just for the fun of it and found something interesting: VVR 100%: B+ in: 325V B+ out: 319V VVR 50%: B+ in: 343V B+ out: 196V VVR 0%: B+ in: 376V B+out: 29V So the 6 DCV difference in B+ in and out at 100% is expected (I've read that the VVR circuit drops a ...

I've installed VVR after the first filter cap on my Matchless, and it works without any hum now :) I had to buy a 60W soldering iron, and next is to solder permanent wiring. Now it doesn't sound quite as good as I hoped as it looses quite some crunch at the low settings but the sound is much warmer ...

I will try to get better grounding, and if routing and better grounding fails I will try to move the VVR to after the first filter cap.

Another youtube-clip: http://www.youtube.com/watch?v=ZiqWoCA7hoQ

What can you make of this? Is this oscillating? Poor grounding? Poor cables?

I would put the the VVR after the 1st filter cap, but before the the choke. The output of the VVR should drive the choke and the plates of the power tubes if you are scaling the whole amp. Thank you for your help. If I move the VVR between the 1st filter cap and choke, the output tranny will run at...

I inserted it right after pin 8 at the rectifier tube, see the schematic. Haven't measured the voltages yet. VVR grounding is soldered to a point that is mounted directly to the chassis.

A picture says more than thousand words; I've made a recording with my cell phone and uploaded to youtube:

http://www.youtube.com/watch?v=hao2A4M08CM

See how the noise kicks in and then disappears without touching the knob...

No I used a different board and parts in this amp. Dana said that cap/resistor mods aren't needed if changing the resistor on the VVR so the minimum voltage gets higher. I would try this first as I would like to keep the Matchless as original as possible. I wonder if the noise is some kind of oscill...