Mensur,
(The following is my humble opinion, that and $5.00 will get you a cup of coffee almost anywhere.)
As with any chip amp, I believe you can use this as the power amp stage of a guitar amplifier. However, with a closed loop gain of 30-35 dB (per spec sheet) you will need a pre-amplifier for this unit. I do recommend putting a 10k Log pot right up front of the power amplifer stage to allow for easy adjustment of amplifer level. I am unfamiliar with the pre-amp mentioned, but in my little world - an electron is an electron is an electron.
Couple-three of things to be aware of:
1) The rated power will only be developed across the rated speaker load (in this case, 2.7 ohms)
2) Be certain and have more than sufficient heat sinking on the chip - or it's "fried chip time".
3) The rated power can only be achieved with the rated power supply voltage (in this case +/- 40 volts)
4) Make certain that power supply can supply at least 2 times the necessary current needed to run the amplifier at full rated output. (100 watts out, 80 volts (+/-40), is about 1.25 ADC - I would not try to run this circuit with less than a supply that can produce +/- 40VDC at a current level of 3 amps minimum - try for 5).
5) I do recommend a voltage regulated supply for this - ABSOLUTE maximum voltage for the chip is +/- 50 volts.
The data sheet for the chip can be found here:
http://www.st.com/stonline/books/pdf/docs/1057.pdfFinally, below you will find a suggested schematic to interface the output of the pre-amp to the TDA7924
Hope this helps!