Using a multieffect together with a distorted amp is no problem as long as the amp distortion comes from a preamp only. Things become more complicated if you want some of your distortion from the power amp, if your amp has no effect loop, or if you want some effects placed before the preamp.
Tube amps are often thought to sound best when both pre- and power amps are overdriven, but to overdrive power tubes the amp must be played very loud. This also means that you can't change from distorted to clean power amp sounds unless you turn down the out level, making it unpractical to use the same amp for both clean and distorted sounds (when you change between clean and overdrive channels on a typical tube amp, you're only changing the preamp settings; the power amp is not meant to be overdriven if you want a clean sound).
Effect processors are normally placed between a pre- and power amp (or in the amp's effect loop, which is basically the same thing), but time based effects like delay or reverb will often sound unnatural if distorted by an overdriven tube power.
If you want tube power amp distortion despite the above disadvantages it makes sense to use a small power amp, because the required sound level to make it distort will not need to be so high then. Even a small tube amp will be very loud, though, but there are a few other possibilities:
If smaller power amps are easier to overdrive, why do amp manufacturers still design guitar tube amps with 50, 100, even 300W ratings? Here's my theory: in the beginning PA systems were used for singers only. Guitar players had to rely on their amps in order to be heard at all. But as some bands started playing in increasingly larger consert halls they needed more and more powerful amps in order to make themselves heard. Finally guitarists began miking up their guitar speakers to the PA systems, just like the singers. From that point there has been no need for huge guitar amps any more, but due to image reasons or conservatism amp manufacturers still offer them.
You may also prefer a big power amp if you want a loud but clean sound. Old tube amps were actually designed to sound clean; tube amp distortion sounds good despite these attempts, not because of them. Big tube amps are not that much louder than small ones (a 100W amp is not twice as loud as a 50W), the important distinction is that a small amp begins to distort earlier, while a big power amp must be played much louder before anything happens. But even if you want a clean power amp sound you can still use a reasonably small amp at low level, and mike it to a PA to increase the sound level more.
By connecting a tube power amp to an artificial load instead of a speaker you can connect an effect after the load, and that way get the benefit of power tube distortion at line level (never connect an effect processor directly after a power amp -always use an artificial load between or you may damage both amp and effect processor). This will also be a good idea if your amp lacks an effect loop. From the effect's output you can feed the signal to another power amp (that doesn't need to use tubes) and finally into guitar speakers:
Guitar --> Amp --> Load --> Effect --> Amp --> Speaker
When using a power amp like above you can't easily switch between clean and distorted sounds, since in order to reduce the power amp distortion you must turn down the signal level entering the power amp. If you don't use effects (see below) you can just switch between two amps; one for clean sounds and one for distorted. The clean one must then be "larger" in order to stay clean at the same sound level that made the small one distort:
/--> Big clean amp ---> Speaker
/
Guitar --> Small distorted amp --> Speaker
You can also insert a distorted power amp and artificial load in the effect loop of another amp or effect processor. By bypassing the effect loop you'll get a clean sound.
Guitar | Clean amp with effect loop --> Speaker | | Distorted amp | | | Load ----->------/
Another idea might be to split the signal from a distorted preamp and send one part to an overdriven tube power amp, followed by a speaker, while the other part goes to an effect processor followed by a (stereo) power amp and speaker(s). Three-way setups are also discussed on the killdry page.
/--------------> Distorted power amp --> Middle speaker
/
Preamp -- > Stereo effect -----> Clean power amp ---> Left speaker
\
\-> Clean power amp --> Right speaker
According to amptone.com, Brian May (Queen) used different tube power amps for the dry signal and delay effects, in order to distort each of them separately. I guess this might work at least for delay and pitch shifted harmony effects (but propably not for reverb).
Copyright © 1999-2016 Christian Jacobsson.