Posted by Sam P. on March 01, 2003 at 13:27:26

Well, I've rewired it a second time, due to EXCESS HUM. Converted the input jack wiring to a star ground, where all the shield leads run to the ground point of the B+ supply. THe HF outputs to the MC-240 are now pretty quiet, and seems appropiately "squeaky" to make me believe the HP filter sections are fine.
The LF amp, an adcom 555 is humming/buzzing pretty good, but the sound coming thru is all bass, so the LP filters are working fine too. Touching various jack shells affects the hum, so ground loop problems still remain...for some reason putting my finger on the jack shell for the LP out at the xover connection knocks the hum down to "almost" acceptable. This same amp will "buzz" loud enough to hear across the room if "rack mounted", but is dead quiet sitting ungrounded on a shelf...ARRGGG, that's probably the trouble, it DOES NOT WANT to see a "chassis ground" coming in on it's inputs shield leads.
Time to try another amp, report to follow soon. Sam

• Re: tube active xover update - Wayne Parham 13:46:10 03/01/03 (5)
  • do "bottle heads" use 3 wire power cords? - Sam P. 14:21:30 03/01/03 (4)
    • Ground loops - Wayne Parham 19:40:52 03/01/03 (3)
      • TEMPORARILY lifted the green wire from chassis - Sam P. 21:08:06 03/01/03 (2)
        • You found it! - Wayne Parham 22:04:30 03/01/03 (1)
          • heater-cathode hum? - Sam P. 17:21:19 03/02/03 (0)