pentode/triode switch...a good idea!

[Matt72]

Due to the full power Express being so loud people can hear me half a mile from the house (seriously!) I thought I'd try a half power switch.

I have to say it's a great idea! It sounds really good. And now between the different tubes (6v6s or EL34s) and the switch I have the choice of 8, 17, or 34 watts.

Pretty handy. Just an FYI.

[txbluesboy]

How is that connected?

[ampdoc1]

Attached is a schematic of a TW variation I built a couple of years ago for a friend. It includes switching to allow six levels of output power. A pentode/triode switch is included. Also, note the output tube complement.

ampdoc

[Matt72]

TxBB,
Here's link to a layout (of a Marshall) that uses the switch. The one wire from the switch that doesn't go to the power tubes goes to the screen supply. DPDT switch. Use a BIG one.

Ampdoc,
sounds cool, but unfortunately, I can't open it. But sounds wild.

[txbluesboy]

This is probably great information your trying to give me,and its probably me doing something wrong, but when I click on Ampdoc1's schematic all I get is a blank page with that little x up in the left corner. Nor do I see Matt 72"s link????? Computers just don"t like me!

[FUCHSAUDIO]

Try adding an extra screen resistor to the wire feeding from the output transformer to the switch. You can use a few ohm (470 to 1.5-K is fine), and this will tend to minimize switch popping, and can be used to get the screen voltages approximately the same in either pentode or triode mode. If the switch is close to the power tubes, a resistor from the plate pin to the switch is as easy as a wire would be anyway.

Enjoy,

[Matt72]

SOrry, I forgot the link in my post!
http://forum.metroamp.com/viewtopic.php ... wer+switch

And thanks Fuchs for the info regarding the resitors!