Power Scaling

[pete.young]

Hi Dave,

Have you ever come across Power Scaling, from London Power [url="http://www.londonpower.com/pscaling.htm"]http://www.londonpower.com/pscaling.htm[/url] ?

I was wondering if it might make my Burman guitar combo a bit more useable.

[DHA]

[quote name='pete.young' post='90761' date='Nov 19 2007, 12:12 PM']Hi Dave,

Have you ever come across Power Scaling, from London Power [url="http://www.londonpower.com/pscaling.htm"]http://www.londonpower.com/pscaling.htm[/url] ?

I was wondering if it might make my Burman guitar combo a bit more useable.[/quote]

They don't give a lot away as to how they do it but reading between the lines I think they may be reducing the plate voltage but keeping the current the same by dumping the power or 'power sharing' if you like between the load and output valves.

I run my valve pedals at lower plate voltages and it's fine, I believe this is what they may be doing as well. I just can't work out how they control the bias but I am sure they must have fixed this or it would not work at all.

Looks neat and could be a good solution for your Burman.

Dave

[pete.young]

Thanks Dave, that makes sense. They have different kits depending on whether it's cathode bias or fixed bias, and there's another add-on for amps with a separate supply for the screen. I dont have schematics for the Burman but I guess it takes the screen voltage off the plate.

It's probably time for me to go and find someone locally who can poke about in the amp innards and confirm this!

[DHA]

[quote name='pete.young' post='91504' date='Nov 20 2007, 02:38 PM']Thanks Dave, that makes sense. They have different kits depending on whether it's cathode bias or fixed bias, and there's another add-on for amps with a separate supply for the screen. I dont have schematics for the Burman but I guess it takes the screen voltage off the plate.

It's probably time for me to go and find someone locally who can poke about in the amp innards and confirm this![/quote]

Hi,

The different kits for different bias tells me that they must change it depending on the plate voltage, neat trick.

I have worked on an old Burman and I am 99% sure it's just a fixed bias and the screen voltage is just taken via a resistor from the plate. It's really only hi-fi amps that have separate transformer taps for the screen as it's too costly for distorted guitar amps!

Let me know if you go for this as it sounds very interesting

Dave