VVR3 enhanced TW

[stink]

I recently installed a VVR3 in my TW and am getting some "interesting" results. It's wired using the fixed bias diagram but it acts like a variable standby control. The more I dial it down, the sound "flubbs" out - kinda sounds like it does when you're playing loudly then flip the amp to standby....fizzles out like that...

Could I have blown one of the MOSFETS during the install?
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Chrysler Royal

[sliberty]

Measure your voltages. When maxed, you should see approximately full B+ coming out of the VVR, and approximately full bias voltage coming out of the bias portion as well. When minimized, you should see 10% of B+ and 10% of bias voltage (assuming you made no value substitutions on the board).

If the main voltage is not behaving as expected, replace the large MOSFET and the associated Zener. Don't just replace the MOSFET, as a bad Zener will blow a new MOSFET.

Similarly, if the bias voltage is not behaving as expected, replace the smaller MOSFET and associated Zener.

My guess is that if you did blow anything, it will be the B+ components, not the bias components.

[stink]

Measure your voltages. When maxed, you should see approximately full B+ coming out of the VVR, and approximately full bias voltage coming out of the bias portion as well. When minimized, you should see 10% of B+ and 10% of bias voltage (assuming you made no value substitutions on the board).

The B+ is about +375 full tilt, +200 half way and +31 fully CCW - working as advertised!

Similarly, if the bias voltage is not behaving as expected, replace the smaller MOSFET and associated Zener.

Ah-Ha! full bias = 41.5mV while half power = 0 and of course full CCW = 0 (using a 1W resistor to measure current) - all the while, the voltage at pin 5 remains at about -30...it never changes...

Thank you very much for the tip Sliberty - very much appreciated...

-Steve
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NEW JERSEY MEDICAL MARIJUANA DISPENSARIES

[stoo]

VVR 3 ??

[stink]

Si...

http://hallamplification.com/main.html?src=%2F#2,0
________
Ford Flathead Engine

[stoo]

Ah! thanks for the link. Dual pots eh!? some kinda' bias control?
Stew

[sliberty]

When used on a fixed bias amp, the VVR must control both B+ and bias voltage. So the dual pot controls them together. On a cathode bias amp, only the B+ must be controlled, so a single pot is used.

With the VVR2, the same board was used for both, and the board was simply populated accordingly. With the newer VVR3, seperate boards exist to optimize the space needed for installation (the boards are really small!).

[stoo]

When used on a fixed bias amp, the VVR must control both B+ and bias voltage. So the dual pot controls them together. On a cathode bias amp, only the B+ must be controlled, so a single pot is used.

With the VVR2, the same board was used for both, and the board was simply populated accordingly. With the newer VVR3, seperate boards exist to optimize the space needed for installation (the boards are really small!).

Thankyou Sir!
Sorry for the short hyjack
Stew

[guitarsnguns04]

i have been considering trying these for a while...any sonic differences to speak of?

[sliberty]

When you turn the pot down, the amop is not as loud

Generally, in my opinion, the VVR is the best alternative when trying to get lower volumes without impact on tone. Is it exactly the same tone when played lower? I don't think that is possible. But it is the closest I have heard. Much better than a MV or an attenuator.

[Colossal]

i have been considering trying these for a while...any sonic differences to speak of?

Guns,

I think the VVR is a great option. I have one wired on a plexi amp and often use it to control the overall sound pressure. As you dial back the voltage, it maintains the tone and character of the amp very well up to the point where you are no longer really moving the speakers. The tone does lose some of its quality and oomph at that point. I added a KF style PPIMV to the same amp to compare it to the VVR. Hands down the VVR is *far* more effective in actually reducing volume but preserving tone, no question about it. The PPIMV reduces volume somewhat but inherently changes the tonal quality immediately. I would not bother with a MV if using a VVR, at least for a plexi style amp. The amp still gets loud with the VVR at about 12 o'clock, not bedroom level mind you unless you take it way down (my wife always winces when coming into the room) but the VVR takes the "painful" edge off the amp when used in close quarters. Another great thing about it is that you can dime the amp to get glorious amp distortion and then dial back the overall voltage to get cranked tone at less than window breaking levels. The one caveat is that it is only currently available for amps up to 50W. The fixed bias design has a dual pot and tracks the bias along with the overall voltage. I chose to control the voltage throughout the whole amp but you can just do the power section should you desire.

Hope that helps you out.

[harryk]

I have installed both fixed bias and cathode bias VVRs to many amps by now and fixed bias version to two Plexi Lead clones. In the other version the whole amp has been scaled and the other has only power tubes scaled. With this experience I personally prefer scaling power tubes only. Only in the case when you go to B+ voltage of 30-40 volts and your PI is hitting power tubes with some 20-30 volts AC swing, you get some really nasty distorted sounds related to very low B+ voltage. VVR is not the best tool for bed room levels, but as Colossal mentioned, it can decrease big amp noise level to the point where you can live with. If you are interested in to hear some sound clips of my Plexi Lead with VVR only in power tubes, go to my website www.bluetone.fi and listen to Bluetone Plexi Lead clips. There are three different versions. One using amp without VVR, one with VVR in 12 o`clock and one VVR in 9 o`clock. Harry

[leleduke]

I have installed both fixed bias and cathode bias VVRs to many amps by now and fixed bias version to two Plexi Lead clones. In the other version the whole amp has been scaled and the other has only power tubes scaled. With this experience I personally prefer scaling power tubes only. Only in the case when you go to B+ voltage of 30-40 volts and your PI is hitting power tubes with some 20-30 volts AC swing, you get some really nasty distorted sounds related to very low B+ voltage. VVR is not the best tool for bed room levels, but as Colossal mentioned, it can decrease big amp noise level to the point where you can live with. If you are interested in to hear some sound clips of my Plexi Lead with VVR only in power tubes, go to my website www.bluetone.fi and listen to Bluetone Plexi Lead clips. There are three different versions. One using amp without VVR, one with VVR in 12 o`clock and one VVR in 9 o`clock. Harry

I just listend to your clips. Are you using a master volume also with the VVR? It looks like you mention a master volume at 5:00???

Sounds great

[leleduke]

double

[leleduke]

i have been considering trying these for a while...any sonic differences to speak of?

Guns,

I think the VVR is a great option. I have one wired on a plexi amp and often use it to control the overall sound pressure. As you dial back the voltage, it maintains the tone and character of the amp very well up to the point where you are no longer really moving the speakers. The tone does lose some of its quality and oomph at that point. I added a KF style PPIMV to the same amp to compare it to the VVR. Hands down the VVR is *far* more effective in actually reducing volume but preserving tone, no question about it. The PPIMV reduces volume somewhat but inherently changes the tonal quality immediately. I would not bother with a MV if using a VVR, at least for a plexi style amp. The amp still gets loud with the VVR at about 12 o'clock, not bedroom level mind you unless you take it way down (my wife always winces when coming into the room) but the VVR takes the "painful" edge off the amp when used in close quarters. Another great thing about it is that you can dime the amp to get glorious amp distortion and then dial back the overall voltage to get cranked tone at less than window breaking levels. The one caveat is that it is only currently available for amps up to 50W. The fixed bias design has a dual pot and tracks the bias along with the overall voltage. I chose to control the voltage throughout the whole amp but you can just do the power section should you desire.

Hope that helps you out.

Have you tried scaling the output only