Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Hello,
For my A level engineering project I am attempting to build a guitar amp. However I am experiencing a major problem which I cannot resolve. I have both halves of a TL072 op amp set up as simple non inverting amplifiers running off +/- 12V with a simple tone control between the two. This forms my preamp. When I put a low voltage sine wave into the input and connect an oscilloscope to the output it works fine, just as it should. But when I connect an 8ohm speaker to the output the oscilloscope shows a much lower voltage and hugely distorted waveform, and it sounds very distorted as well. Any help would be much appreciated.
Thanks

that's because the pre-amp shouldn't be connected directly to a speaker - driving a speaker is a job of power-amp.

a lot of op-amps (especially TL072) aren't suitable for driving low impedance loads, I think that around 1k the TL07x start limiting the current, which results in distortion. At 8 ohms it's probably pretty awful.

If you want to keep it simple, you can add a simple LM386 straight-out-of-the-datasheet power amp after the pre-amp section. If you want more power than half a watt or so, you can use a more powerful chipamp like tda2040 or similar.

LM386 is fine, but needs a separate 9V supply; you may go up one step and build this 14W power amp which will happily run from +/- 12V and drive your speaker .
(http://1.bp.blogspot.com/-LPfTPtO_fmU/VfxRq_CQwKI/AAAAAAAAFFU/p7Jbw-o-JZo/s1600/10W-audio-amplifier-circuit-by-TDA2030.png)
http://www.circuitstune.com/2012/02/10w-audio-amplifier-circuit-tda2030.html