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Benny wrote:and you need to do some extra adjustments or it just work this way?

You have to divide the impedance in half. E.g., if you use an 8 ohm cabinet, set the selector to 4 ohms.

japmn wrote:

steve wrote:You can also try the Ice Cube mod, which uses the reverb circuit driver as an overdrive. A crude version of it is to just jump the reverb send and return jacks with an RCA cable, and then you can use the reverb knob to adjust the gain of the overdrive and switch it in with the reverb footswitch.

Are you taking the piss or serious. That sounds like nonsense or total genius.

It's a little of both. I remember they used to sell those "ice cube" sustain overdrive whatever things for Fender amps in the back of Guitar Player. They were little blocks you plugged into the back of the amp, I suppose joining the reverb send and return. I always figured they would make my Fender sound like ass, so I never bought one.

I still dont imagine it sounds very good, but it certainly would be easy to try it out. In my experience, the only reliable way to get decent overdrive with a Twin is by using an overdrive pedal.

I think it can be done more elegantly with a resistor divider to match the impedance of the two circuits and a cap to block any DC component (that's what was in the marketed Ice Cube), but it works and won't hurt anything if you just jump the two jacks.

steve wrote:You can also try the Ice Cube mod, which uses the reverb circuit driver as an overdrive. A crude version of it is to just jump the reverb send and return jacks with an RCA cable, and then you can use the reverb knob to adjust the gain of the overdrive and switch it in with the reverb footswitch.

does this only work with a twin, or would it work with other amps also?

Can someone explain what is going on with the pull-out Master volume?

It is almost an overdrive but not quite, more of a even more brittle than the bright switch type of high boost. It has always confused me and has always sounded like total unusable shit.

It works as a overdrive. You have to crank the regular volume into a low master volume setting 2-6. As well the tone knobs of the twin cut the volume as well as the eq of indicated tones. Try turning all the tone knobs down and you will not get as much volume as you think you should get. Put all tone on or near 10 the volume on or near 10 pull the master and adjust. If it is too treble orented use the bass switch on the channel or reduce the treble tone knob.

This is if you want it really overdrive. Put any volume booster box now you got a lot of overdrive.

megadan wrote:

Benny wrote:and you need to do some extra adjustments or it just work this way?

You have to divide the impedance in half. E.g., if you use an 8 ohm cabinet, set the selector to 4 ohms.

for an amp with an impedance selector, you can set the impedance selector to half of what the cab's impedance is. for an amp with no output impedance selector, you can use a cabinet with double what the normal impedance is.

you don't *have* to make any change to the impedance selector or speaker impedance or whatever. being off by having half or double what you're "supposed" to have should not be a problem for a healthy amp. it will just affect the frequency response in a way that is not necessarily very audible to begin with.

Just got in horribly late after work to find all these replies ... thanks v. much guys. tempted to try the ice cube right now but don't want to wake the kids.

japmn wrote:Is that the the way a basic half power switch works? just shuts down 2 tubes?

Actually no, the half power switch turns changes the wiring of your output tubes (usually a pentode) into a triode, which produces less power, as well as changing the sonic characteristics of the amp, and gives you a slightly looser, less dampened sound. Of course, if you have a 100 watt amp that has pentode/triode mode selection, you can bring the wattage down even further to 25 watts via pulling the two outer tubes. --I've done this with my Seymour Duncan Convertables, which not only alters the damping/headroom characteristics of the amp, but also makes it much more manageable in either a studio or home practice setting. --Seymour Duncan amps might not be the greatest amps made, but they were one of the first to have variable damping controls as well as pentode/triode switching.

--Benny, you may possibly want to look into getting a pentode/triode mod done to your amp at some point, and using that in conjunction with the removal of the two outermost power tubes.

japmn wrote:Is that the the way a basic half power switch works? just shuts down 2 tubes?

It varies. Often pentode output stages are switched into triode mode to reduce power.

Pulling two tubes from a Twin is probably worth while to see how it goes.