Here's one for yah - in examining the schematic for my new Traynor YBA100 "tube" amp I found it had a fixed third order 30Hz HPF 
. I put quotes around "tube" because it has several op amps in the signal path - many tube amps only have op amps in the DI or FX loop that are not in the normal signal path. This amp even uses op amps as the phase splitter .
. I put quotes around "tube" because it has several op amps in the signal path - many tube amps only have op amps in the DI or FX loop that are not in the normal signal path. This amp even uses op amps as the phase splitter .