amp head switcher that only uses one cabinet?

[sevenisthenumber]

I want to build myself a switcher to use one cab but two different heads for clean and dirty? Anybody know of anything out there?

[Br4d13y]

radial tonebone makes one i believe, search musicians friend

[Paul Marossy]

I want to build myself a switcher to use one cab but two different heads for clean and dirty? Anybody know of anything out there?

The only bad thing about that idea is that it could leave one of the amps with an unloaded output transformer. I've read that you should never under any circumstances operate a tube amp with no speakers hooked up to it because that can fry the output transformer.

I suppose that you could possibly use some high wattage resistors to keep some kind of a load on the unused amp, though...

[BAARON]

I want to build myself a switcher to use one cab but two different heads for clean and dirty? Anybody know of anything out there?

The only bad thing about that idea is that it could leave one of the amps with an unloaded output transformer. I've read that you should never under any circumstances operate a tube amp with no speakers hooked up to it because that can fry the output transformer.

I suppose that you could possibly use some high wattage resistors to keep some kind of a load on the unused amp, though...

This is true.  My amp has a pair of 25 watt 470 ohm resistors in parallel across the speaker jacks (235 ohms, 50 watts overall) to make sure that there's always a load on the output transformer, regardless of whether or not there's anything plugged in, and they're a high enough impedance that they don't affect the performance of the speaker when it's actually in operation.

[Paul Marossy]

This is true.  My amp has a pair of 25 watt 470 ohm resistors in parallel across the speaker jacks (235 ohms, 50 watts overall) to make sure that there's always a load on the output transformer, regardless of whether or not there's anything plugged in, and they're a high enough impedance that they don't affect the performance of the speaker when it's actually in operation.

That's a good idea.

[BAARON]

You bet it is!  I can't take credit for it, though.  I got the idea from the AX84.com power amp designs.  (They have a lot of good ideas over there!)

[Paul Marossy]

You bet it is!  I can't take credit for it, though.  I got the idea from the AX84.com power amp designs.  (They have a lot of good ideas over there!)

Well, it's still a great idea. 

[MikeH]

The easiest way to go would probably be building (or buying) an attenuator and have a sort of "path switcher" built in.  Set the attenuator to zero (no output) and switch the paths of the heads.  On one setting head A will go to the attenuator, and head B will go to the cab.  And then you step on a switch and they flip flop.  Switching noise might be an issue though.  So might smoking amps... heh heh.  I'd say buy the head bone.

[DougH]

From the wayback machine archive of Aiken Amplification:

http://web.archive.org/web/20001003171545/www.aikenamps.com/TI_diy.htm

http://web.archive.org/web/20030812220539/www.aikenamps.com/HeadSwitch.pdf

[Gus]

At Ampage years go Steve Conner (scopeboy) did some tests.

http://archive.ampage.org/articles/1/gagd/002413/Re_OT_protection_tests.html

http://archive.ampage.org/threads/1/gagd/002249/Re_OT_protection_tests-1.html

http://archive.ampage.org/threads/1/gagd/037880/Re_pedantic_verbage_on_OPT_loads-1.html

Look at the dates and names.

[DougH]

Wow, Ken Gilbert... I miss that guy...

And I miss the good ol' days of Ampage. What a great discussion.

A lot of this stuff seems to parallel the idea that the reason Vox amps can be so  touchy is because they abuse the screens so bad. There's a guy in Australia that published a really cool paper on how screen grids work that explains this but I can't find the link right now.

[Paul Marossy]

And I miss the good ol' days of Ampage.

I learned a lot from hanging out there in "the good old days".