Hi everyone! First post on this fine forum as well as my first problem with a solid state amp build 

I've put together an amp from pieces around the web. The schematics are below. The first is the preamp and the second the power amp and power supply. The power amp is based on a TDA2005R chip. The FC+ and FC- are for an offboard cap, two 1000uF caps in parallel for 2000u for filtering. Left them offboard for space. Diodes are 1N4001 rather than 7's. Speaker is a 25W 8ohm Jensen.




TDA2005 datasheet: http://www.paia.com/KRUKits/K143/tda2005_datasheet.pdf

The LM317 was initially running at 17V, but I've turned to it down to 12V to see if it would help - no dice. Both 2005 and 317 are heat sinked and isolated.

The problem:

The presence control causes loud crackling when turned and the signal is always strangely distorted (as you can hear in the sound clip below) even when preamp volume is low.

Sound clip: http://snd.sc/13Ui8O8   Ephiphone Casino right into the amp.

0:00 - 0:19 presence all the way down
0:20 - 0:35 presence up a bit
0:35 - 0:49 you can really hear the crackle when the presence knob is turned up
0:50 presence knob full up and stays that way until the end of the clip.

Voltages:

Q1
D - 11.06V
S - 0.24V
G - 0.00V

Q2
D - 12.41V
S - 2.18V
G - 1.76B

Q3 - presence full down
D - 0
S - 0
G - 0

:loco

Q3 - presence full up
D - 6.93V and decreases as probe is held on
S - 1.51V
G - 0.47V also decreases as probe is applied.

TDA2005
1 - 1.16V
2 - 0.76V
3 - 7.68V
4 - 0.72V
5 - 1.14V
6 - 0V
7 - 12.18V
8 - 6.62V
9 - 12.62V
10 - 6.27V
11 -12.17V

LM317
1 - 19.62
2 - 12.62
3 - 11.33V

Something is clearly going on with Q3 but I'm not sure how to go about debugging! Thanks for any help, I look forward to exploring the forum.