hifi VS instrument amp

hi .. what s excatly diffrence between an instrument amp and a hifi amp ???
why a guitar sound on a hifi amp is not so good and its so flat and somehow artificial .. lol !!!???
and can i use a hi-fi amp w a guitar pre amp for a guitar combo and have a sound like a real guitar amp ??? ( ex : a guitar pre amp w a stk amp )
 
Ahmad_tbp said:
hi .. what s excatly diffrence between an instrument amp and a hifi amp ???
why a guitar sound on a hifi amp is not so good and its so flat and somehow artificial .. lol !!!???
and can i use a hi-fi amp w a guitar pre amp for a guitar combo and have a sound like a real guitar amp ??? ( ex : a guitar pre amp w a stk amp )

Well, speaking in generalities (with all the pitfalls that entails) , an audio amp tries to be "transparent", but a guitar amp tries to impart a tone of its own to the instrument, by a combination of preamp, power stage, and speaker characteristics. This is true of buth tube and transistor guitar amps.

Yes, you can get good sound by combining a guitar preamp/processor with a chip amp. In fact, this is what commercial DSP guitar amps are like. The amp consists of a DSP stage where the sound is modified, and then the power stage is just a neutral sounding chip stage and a more neutral guitar speaker (e.g. Eminence Modeling12).
 
An instrument amp is also usually designed to be bombproof through all sorts of nasty things that a hifi/domestic amplifier would die horribly from. For example, shorted outputs, excessive driving into clipping, use with low impedance loads...

The output stage is usually "exaggerated" ie more transistors than actually needed and a larger heatsink, to increase reliability, especially as these amplifiers are usually used on stage where ambient temperatures can easily get up to 40 degrees C.
 
Assuming the power amp has enough headroom and clean power, it is probably the least of your worries if you are going to use it as a rig. The preamp is critical, and also the speakers or cabinet. Hi-Fi or PA speakers will give that flat, lifeless tone you mentioned. And a digital signal processor, while probably quite good, is only going to get you so far: everyone I know prefers tubes in at least the preamp section.
Very generally, the overall frequency response of a guitar amp is perhaps like the back of a two-humped camel!. You want some low end between 90 and 200, and some smooth upper range around 1.9 kHz to 4 kHz. Guitar sounds best with just the right amount of high end, usually cutting off drastically around 5 to 7 kHz. Very strong amounts of this type of EQ should exist somewhere within a guitar amp as compared to full range Hi-Fi.
I hope this helps!
 
To add to the other good answers, there is nothing flat about a guitar amp. I prefer a tube amp, but it doesn't matter really. The underlying principal is the same. The guitar amp is part of your instrument. The hifi is not.

The guitar amp typically is well rolled of by 5kHz. The speaker is a large part of this. Connecting a guitar amp to a hifi speaker will sound thin.