First of all, I replaced the Gain pot with a Push-Pull DPDT and put the Bright caps on the switch (caps C6 and C20). The amp, due to its size and design, can sound very harsh especially with pedals, so this was a must.
Additionally, the O.T. was replaced with a Hammond 125DSE. That was done for multiple reasons. First of all, I was interested in having an 8 Ohm tap (I use a Two Notes Torpedo Live at home), so I implemented a 3-way rotary switch to select between 4, 8 or 16 Ohm O.T. secondary. I was also interested to see if the sound would improve by using a high quality replacement by a reputed manufacturer like Hammond (as the sound of single-ended amps relies a lot on the quality of the O.T.). But most importantly, I wanted to have the option of a 5K primary, as per the original AC4 design (the stock reissue O.T. has a 10K primary). Seeing how the Hammond 125DSE offers both these primary values, I decided to implement a switch to be able to switch between the two (hint: I leave it almost always on 5K).
At the same time I replaced the Vox VX12 (Celestion Seventy 80) speaker that came stock with the amp, initially with a Celestion G12-35XC and lastly with a Celestion G12M, as the G12-35XC was a bit of an overkill and maybe a tad too bright for this amp.
This has been my small-gigs and grab-n-go amp since some time now and I am very happy with it.
