thanks for your answer.
do i need this radial x-amp no matter what or could i just run play back the recorded signal from any source, most likely the board?
you mentionen phasing issues? i don't know what that does?
also, why is it important to have an instrument level signal?
i'm just exploring this so please excuse my lack of general knowledge about these things.
thanks
no, the radial x-amp is a great device, but a luxury one, it makes re-amping very easy, but isn't needed by any means.
it is important to have an instrument level signal because thats what amps are designed to 'receive' ie a low level signal with a very high impedance. its not necessary to understand impedance to use the technique but its useful to know so worth a google. A line output from a desk is going to be, put basically, way too loud and the wrong 'sort' of signal for a guitar amp. it would still make sound, of course, so if it sounds good, go for it! but it wouldn't be the same as just plugging your bass straight in, which is what you want if you want the amp to respond how it normally does.
a passive DI box normally turns a high impedance guitar/bass etc. signal to low impedance to plug straight into a mic pre. if you come out of a line output into the OUTPUT of the DI the signal goes through the circuit 'the wrong way' and has the opposite effect, ie turns it back into the 'sort' of signal a guitar amp expects. You can then plug the INPUT of the DI into the amp. as Nick says, you will also need to attenuate this signal somehow so that the amps not shredding when volume is on 1!
this will not work with an active DI, they have additional circuitry which can't be simply reversed in this way.
Its worth noting that the way a guitars pickups interact with an amps circuitary is also a part of the sound you get, ie even a perfectly re amped setup will not sound IDENTICAL to plugging the same guitar directly into the amp, but this isn't a make or break issue.
phasing is, simply put, when more than one audio track from the same 'source' ie a drum, or bass or guitar, is used, and one is slightly out of line, time wise. for example, when DIing and micing an amp, the DI normaly gets to the board a bit quicker than the mic on the amp, shorter circuit, you see. often people leave this as is, it becomes a part of the tone of the bass but good effect can be had by moving them back in line with each other so the waves line up.
If they are completely out of phase, ie the DI track is showing a peak on the waveform while the mic track is showing a trough, the sounds will be badly out of phase and sound awful. in this case lining them up manually or flipping the phase of one of the signals will work.
when passing a signal out of the computer into an amp then micing it up it is inevitable that the returning signal will end up later than the original. if you will only be using the re-amped track then no biggie but if you plan to combine it with the original tracks then you will want to align this new track with the old.
sometimes when distorting a sound quite a lot it can be hard to see how the waves should line up, in this case I like to send a 'timing click' through the amp. at the begining of the original bass track put in a tiny super short click sound. after recording the re amp pass you can see where the re amped click has ended up in relation to the original and just line them up, easy! then you can delete the clicks and you have a nice, phase matched bass track!
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