Is this a stock 68 12 series build?
If so it should not be oscillating like this, need to examine your lead dress and layout.
Tweaked amps can of course and the fixes are well doucumented (5k6 swamps for output section) and grid swamps on sockets (33k on each pin is the same as 68k pair) but using screened wire grounded on one end (bus rail end) or even hot shielding or small value ceramic caps across the plate resistors or between plates etc etc (oh and the one Dave F mentioned).
But I would be concerned why a well put together stock 12 series is oscillating like that............
12 Series Build
Moderator: VelvetGeorge
-
neikeel
- Senior Member
- Posts: 7231
- Joined: Tue Dec 06, 2005 8:31 am
- Location: Suffolk, England
Re: 12 Series Build
Neil
-
shakti
- Senior Member
- Posts: 2053
- Joined: Tue Apr 05, 2005 9:06 am
- Just the numbers in order: 7
- Location: Ramnes, Norway
Re: 12 Series Build
Sure it's not unshielded pickups causing this?
JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103