Thought I'd share this thread here: ***Official thread here: http://acapella.harmony-central.com/showthread.php?p=40404857#post40404857 - It will be updated more often at that link, and will eventually have video clips*** ** Disclaimer: Do this at your own risk. Do not attempt it if you do not know what a filter capacitor is, looks like, and how to drain them. If you absolutely need these mods and cannot perform them, a competent tech should be able to execute this quite easily. ** To get into the amp, unscrew all these: Inside: Mod 1 - Bright cap mod: This mod will allow you to use a much larger spectrum of pedals in front of your amp. 1. Remove C67 - 10pf ground (Reads 100) It is located near the Top Boost volume knob. It is used to kill high end harshness. It is there to counteract the harshness which is brought on by the 120p cap, but is no longer needed when removing the 120p. This 10p capacitor was not part of the original AC15/30 schematic either. 2. Remove C8 - 120p high pass (Bright cap - Reads 121) It is right next to C67. It is the capacitor that adds tons of sparkle when the top boost volume is low, and the master is high. It is a nice touch, but also kills any chance of most pedals sounding good in front of the top boost. Mod 2 - AC30 tonestack mod: (Original vintage tonestack setup for AC15/30) This one is a little tricky, since there are no spaces on the board to solder a jumper wire off the bass tone pot. I improvised something that works well. The sound difference is night and day. It provides a much bigger spectrum of tones. The treble and bass become much more "extreme". You will notice a boost of low end in your sound as well. I keep my bass around 3-4. The biggest difference for the bass control is from 0 to 4 - then there is not much difference between 5 and 10. The biggest difference for the treble control is between 5 and 10. From 0 to 4 only changes the mid range response slightly. 1. Remove capacitor C67 10p. You will be using the lug where there is no trace leading anywhere, which is ground. To verify, use multimeter on "beep" mode and verify ground once capacitor is removed. 2. Cut about 8" of 22awg hookup wire - do not use bare wire. Start by bending one end (crimped) and stick it in the tiny hole under the bass tone pot. If standing behind all the pots, its the first lug on the left - it is the lug that DOESNT have a trace going to the treble pot. You will notice a tiny hole where the wire will fit. Its a bit crowded, but its possible to solder there. 3. Cut the wire so it has a bit of slack to reach the C67 ground lug - I suggest more slack if you plan on adding a switch. Crimp it, and bend it so it doesnt flick out of the grounded hole. If uncertain, verify its the proper hole by checking ground with the big green ground wire/nut. *OPTIONAL - Not shown in picture* *4. Add an SPST switch near the tone controls. Once the AC30 tonestack mod is completed, as long as you have plenty of slack left, you can cut the wire in the middle and attach each end to an SPST switch to toggle between standard and custom.