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noise pickup on gigs

9/20/1999 1:20 AM
Andy Fuchs
noise pickup on gigs
I've built a Dumble OD-50 based on Steve Aholas website schematic. It uses a Dynaco Mk-3 power transformer,a Marshall 50 W output trans and (this is the kicker) is built into a Fender Champ cabinet with a Jensen P10 reissue. I managed to squeek in a reverb too (is this sick enough ?).  
ANyway, at home (and on some gigs) it sounds awesome, but on some gigs the noise pickup is unbearable ! I'm using a computer style AC IEC socket with built-in filtering and a three prong cord. The top of the cabinet is covered in copper tape, which is tied to the chassis ground. Do I need a ground lift or polarity switch ? In my home it's silent. I even have DC filaments on the input tubes. Thoughts ?  
9/20/1999 3:57 AM

I would try the polarity switch.  
9/20/1999 4:40 AM
"I've built a Dumble OD-50...Dynaco Mk-3 PT,a Marshall 50 W OT...built into a Fender Champ cabinet...squeek in a reverb too..(is this sick enough?."
A. Your PSYCHO  
B. You seriously need help  
C. Answers A + B  
D. Your a much better man than I  
"even have DC filaments on the input tubes"
The answer is C and D. I'd love to see pictures of this little monster. Boy, what some people won't do for attention.  
my amps suck NOW  
9/20/1999 4:48 AM

Oopps--lost my cookie. that's what happens when your computer crashes. and all the post are marked unread--spend days rereading posts to find out what I haven't read.  
sorry about the anon  
9/20/1999 12:02 PM
Andy Fuchs

Pictures soon. Thanks. It's not as impossible as it sounds.  
I had a trophy shop male a faceplate. I have P-Former in bottom of box, reverb (short tank) next-to it. OPTrans is on chassis. It's an OD-50 w/ a homebrew reverb (1-12AX7). 2 X EL34s., plus fan. Sounds very nice, but there is a practical limit to how loud a box that small can be played before things begin to vibrate and the sound 'chokes up'. Now into a 2 X 12, hmmmm theres a thought....
9/20/1999 5:39 AM
Ted Matsumura

OK, this sounds wild. Are there any builders out there ready to turn my SF Champ into a Dumble OD? Assuming the -xx is watts, I'd be pleased with an OD-12 or OD-20.  
Prefer not to use the Dynaco or Marshall transformers though, would make the champ way too heavy.  
email me if anyone wants to take this most exciting project on.
9/20/1999 7:30 AM
Steve A.

    I've heard of a few Deluxes turned into Dumble Overdrive Specials, but not a Champ yet. Does your Champ use the single output tube or a p-p pair? (The s.e. Champ design typically doesn't have enough gain to handle a "real" tone stack, which throws away a lot of the signal so if it has a tone control at all it is usually of the simple treble-cut/treble-variety. I think you'd have to add in another 12AX7 tube stage to bring the signal back up after the tone stack and I don't know if the PT heater windings could handle it.)  
Good luck!  
Steve Ahola
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