This amp was built by P&H Electronics in Lafayette Indiana in 1956..It
used four 1625 tubes or 837 tubes in GG...The manual says that the
1625 tubes are modified ..Doesn`t say what sort of modifications they
have..Tube Manual shows same pin-out ,same socket ,same connections
etc..Anyone know what the modifcations might be...They both seem to
operate all OK with about the same power out..I seem to remember an
article some years back about removing the socket from the tube and
changing some pin connections or whatever...any help appreciated..