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Sundown amp tone-anyone?

8/12/2004 12:38 AM
John S.
Sundown amp tone-anyone?
I have a SUndown 100W combo and would like to smooth out its red channel gain. At this point, the channel has a fairly narrow usability range otherwise its pure buzz/mud. I guess I'm looking for a marshally tone and tone controls that have more effect/range on the tone.  
I plan on posting any and all usable results to a site when and if successful.  
These amps are scarce and not many people seem to have messed with them. Reaching the original designer, Dennis Kager, is difficult and more difficult for some tech info on tweaks and mods.  
I'd love to do the mods myself, I just don't know enough about the tone stack/gain stages.  
Schematic is available at a few places readily, here's one site that has it:  
My guitar uses two 6550's, not the 6L6's shown.  
Any help appreciated.  
8/12/2004 6:14 PM
Ray Ivers

I was only able to download the top half of the schematic, but the preamp circuitry looks like a tweaked Marshall MV. I would try eliminating the 1M resistor after V3a, changing the first .02uF coupling cap (below the 'V3') to a .004uF, adding a 22K grid stopper to pin 7 of the V3 socket, lose the .001uF cap on the Gain 2 pot and the 270pF across the 470K resistor following it, and rebuild the tone stack with standard Fender values which can then be tweaked to taste. The tone stack is a Marshall topology, just (intentionally?) drawn weird. I would also replace the .001uF 'mud cap' across the MV with the 270pF you removed earlier.  
If this is one of the 'Governor'-equipped amps, I would keep that control set to "not governing at all".  
8/13/2004 3:14 AM
John S.

Thanks much for your help. I can email a full schematic if that would help with the rest.  
I've saved this and will implement it and "tweak to taste".  
Results will be posted here.  
8/20/2004 6:44 PM
I just worked on one of those. Make sure the RMS knob is full up as well, and check the tubes and bias. Huge diff on that amp.

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