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Vintage threads from the first ten years

7/6/1999 4:03 PM
Bill Costello	Re: "Marshall tone mods" Doc, the OT is huge! The combined weight of the xfrmrs and chassis feels like about 40 lbs! The cabinet is 5/8" wood and together with the 12" Celestion I'm seriously considering a bolt-on "dolly", a la early 70/s Traynor. I suspect the amp was designed for a low bass cutoff. The coupling caps to the finals were giant round .47 uf at 600v. The plate voltage is only slightly over 800v no laod. When I draw current it drops about 60-70v. Somebody had replacted the 5R4 rect with a solid state module - I chucked that out in a hurry and plugged a tube back in! I'm using the 1 ohm cathode resistor measuring method and set the reading to 25 ma. Since I'm also seeing screen current I'm running kinda light but I don't seem to hear any crossover distortion. R G 's FAQ says the sweet spot is rather broad so I'm hoping I've got a reasonable compromise, considering the price of tubes. Thanks to Dave and the rest for the preamp suggestions. I'll post my findings. Might help someone esle in a similar situation some day...

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