Massive hum - B-15N

[Steve Conner]

12AX7 type tubes have spiral wound heaters for low hum. Do 6SL7s?

Maybe they don't. In which case, elevating the heaters with DC, or going over to DC heaters, would probably help.

If I'm seeing your picture correctly, you have the speaker jacks directly next to the preamp tubes. This was a really bad idea.

[txstrat]

12AX7 type tubes have spiral wound heaters for low hum. Do 6SL7s?

Maybe they don't. In which case, elevating the heaters with DC, or going over to DC heaters, would probably help.

Indeed, I elevated the heaters and the 60hz hum disapppeared. Cant't believe it. Didn't know this was so much of a cure for heater hum.

If I'm seeing your picture correctly, you have the speaker jacks directly next to the preamp tubes. This was a really bad idea.

Yeah, that's right. When I planned the chassis and made the faceplates, I didn't take too much care of that. After I drilled the holes for the speaker jacks I found'em too close to the preamp tube. I'm gonna fix that.

What's left now is a 120hz ripple (at least I think so, cause it's higher pitched than the hum that's now gone) that disappears when I fully turn up the volume pot. Truning up the treble pot more than half makes it worse.
All input wires to the first gain stage are shielded.

BTW thanks guys for your interest in helping me.

[txstrat]

Well, just wanted to let you all know.
Took the amp to a rehearsal yesterday. The buzz wasn't as bad as I had in my memory. Probably partly because the treble pot didn't need to be turned up that far.
Anyway, for an amp thrown together in a couple days it sounds amazing (and it's pretty darn loud for it's 60W OT).
Bass player's satisfied as the whole band (of three).
Thank's to all.

[tubeswell]

Good news. Post some sounds?

[txstrat]

Unfortunately the next rehearsal is in a week (well short of a week) in our drummers house which is 40 km from my place. I'll see what I can manage to record some clips. IMHO definitely worth of hearing.

[txstrat]

Here we go.
Had a chance to record some tones of the amp yesterday night.
No high end device for recording, just an mp3 player with a microphone.
Bass is a '78 Fender precision bass. The cab is a selfmade 2x12 guitar cab with two Celestion 50w speakers (15ohm speakers from somewhere in the 70s). The sound might be improvable with a 4x10 cab (my favorite for bass) and decent bass speakers. But for now...
What you say?

[tubeswell]

(making allowance for the hokey recording setup ) the tone hints at promise with the right speakers - I love that punchy-middy bass tone coming through in a band mix, but I don't think the 12" speakers do it justice.

[txstrat]

(making allowance for the hokey recording setup ) the tone hints at promise with the right speakers - I love that punchy-middy bass tone coming through in a band mix, but I don't think the 12" speakers do it justice.

Yeah, the bass player's already talking about a new (used) 4x10 cab.
Great tone to come, for the most part due to the help of the nice guys of this forum.
Thanks again to all.