VVR Voltage Drop

[alerich]

I have the Dana Hall VVR installed on my cathode biased 2 6V6 push pull Marshall Studio 15 clone. Before the installation my DC voltage at the output of the rectifier to the first filter capacitor was 315 VDC. The VVR is installed immediately after the rectifier tube and before the first filter capacitor. With the VVR I am reading about 295 VDC at the output of the rectifier (input to the VVR) and a few volts less (292 VDC) after the VVR at the first filter capacitor. It's really not a big difference particularly since my B+ was on the low side to start with for what we commonly see these days for 6V6 amps. Was just wondering if others who use a VVR (and in particular the Hall cathode bias VVR) notice a similar voltage drop across the circuit.

[FYL]

That's pretty normal: you've got a mosfet and a series 10R. Both drop voltage.

[phsyconoodler]

Those voltages can be different if the wall voltage fluctuates at peak times.To be sure,you need to check wall voltage before and after to verify your discovery.

[tubesornothing]

Those voltages can be different if the wall voltage fluctuates at peak times.To be sure,you need to check wall voltage before and after to verify your discovery.

+1

I have had wall voltages vary +/- 5VAC within 20mins

[alerich]

The particulars aren't terribly important to me. I was wondering more about the phenomenon. I suppose I should have guessed beforehand that those devices would drop some voltage but I never saw anyone mention it before I ordered and installed. No matter - it sounds great anyway.

[kagliostro]

In order to prevent the voltage drop

you can use a bypass switch

so when you don't use the VVR the amp conditions are like if it isn't installed

Kagliostro

[alerich]

I considered the bypass switch idea. I'm going to try some A/B tests next time I have an opportunity to play it at stage levels (apartment dweller) to compare. If it makes a noticeable improvement I may go for it. I am almost out of real estate on the chassis to add another switch.

[phsyconoodler]

I highly doubt it will make any difference at all.That small a voltage drop is insignificant in a tube amp.Especially a cathode biased one.A fixed bias amp will make a small bias change but not a bunch.