I just put in a pair of Black Gate capacitors as the coupling cap in the ASL MG Head OTL headphone amp. Wow, what a difference. Much more natural sounding, with great detail and HUGE bass response. This a really easy mod to do... the hardest part is paying the big bucks for BGs (about $35/pair). If anyone has the Antique Sound Labs MG Head OTL headphone amp, you should consider doing this mod.
Next mod that I do will be putting in FREDs in the diode bridge, but that will be a little bit more involved because of having the lift the circuit board to solder. Ugh...
