guitar signal vs line input

[squidsquad]

Just picked up an 30 watt, stereo, auto radio chip....for a buck & a quarter!
Thinkin of makin a practice amp.
Assumig it wants to see a *line outut* level at the inputs.
How different is a guitar's signal?
Just plug in, or do I need a pre-amp or anything?
(there are pre-amps in the chip).

[Mark Hammer]

You'll want something in between the guitar and amp.  Not only does the amp expect to see something in the 1 volt range, but it expects to see it from something with somewhere around a 600 ohm output impedance.  That doesn't need to be complicated.  hell, it could even be a suitable matching transformer (e.g., 10k primary, 600R seocndary).

[d95err]

As with any poweramp, the powersupply is the first issue you need to think about. What transformer do you intend to use? It needs to be able to put out over 30W of power. This will also require a big heatsink for the chip.

Once you get that sorted out, start worrying about the preamp...