isolating switchcraft jacks

[tubelovin]

any thoughts on isolating switchcraft jacks on the input of a 5E3 or any other amp? I've got a hum problem in my 5E3 clone and was wondering if that might help. The hum gets louder when volume is turned up. I used a star ground and twisted heater wires. Any experience good or bad on any amp is helpfull.

[Joe6v6]

Ive built several (6) 5e3's both ways & ive managed to make them all dead quite , The one I just finished has isolated jacks, input & speaker, I used cliff jacks on this one & just 1 buss wire along the top of the board. there is only 1 ground point with a total of 3 wires attached to it. this one didnt require any modification, it was dead quite from the time I turned it on. I will post a picture of the inside when I get home. . Several things to look for in a 5e3, First is your build in a traditional 5e3 chassis? If so you can most likely get away without sheilded wire from the inputs, I make all my own chassis's & every one is diffrent so I always use sheilded wire from the inputs just to lessen that source of humm right from the start. . Does your power trans have a center tap for the 6v heater supply? Or did you use a virtuial CT - 100 ohm resistors to ground? if you used 100 ohm resistors where did you reference them to ground? I have been attaching these resistors to the cathodes of the power tubes which makes the filiment positive with respect to the cathode (30-40v or so) I know Bruces layout shows it this way and thats good enough for me. I have personaly tested this on an amp where I attached a jumper wire to the resistors & tried diffrent ground points & the cathode method was always at least as quiet as the best ground point I could find & usually quieter. . . . The wire from the volume control can inject noise, try moving it around.. see if you can post a pic of the inside so others can look and see if there is anything obvious . . most importintly - patience & persistence. JOE

[Enzo]

Is there a tip grounding contact on the jack? Or is it a simple #11? Or put another way, with nothing plugged into it, does putting your fingers next to the jack increase the hum? Does the hum remaon when a guitar is plugged in?

Demount the jack and let it hang by the wires not touching anything. Does the hum change?

[tubelovin]

It's got the switching type inputs. There isn't any increase in hum when I touch the jack and there isn't any change when anything is plugged in. On some grid wires there is an increase in hum but its a different hum. The hum I have a problem with is a lower freq. I've used a mojo chassis and board and layed it out like the original except for the heater wires and the grounding. I grounded the power cord pt center taps and filters on the chassis bolt and cathodes on the bright input jack. Also I wired the cap on the tone to the volume ground terminal then to the other volume and the to the input ground. I wired another just like that and it worked fine. I used CTS pots if that makes any difference. I've obviously tried different tubes both pre and output. The ones Iv'e got now are NOS RCA 6V6, 12ay7 5y3 and a 12ax7eh. Transformers are mercury magnetics. I'll try to get some pics up soon.

[lil bubba]

hey,
try this : unsolder the ground wire that goes from the last volume to the input, solder the tone cap on the back of the tone pot with the ground of the third filter cap then wire tone and chan1 volume grounds.
cheers