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I have the schematic for the regular Lone Star but was looking for a schematic for the lower powered Lone Star Special. I just got a Maverick head and was interested to see how they switch from 30w to 15w to 7.5w. I read in another post here that the 30w mode uses ss rectifier while the other modes use a rectifier tube.
Without knowing how Mesa Boogie accomplishes the power switching I would probably first want to disconnect two of the output tubes. Would cutting the signal to the grids of two of the tubes work for that? I have also heard of disconnecting the screen grids but I would rather not run a high voltage to an added panel switch.
Disconnecting two tubes should cut the power down from 30w to 15w. To bring the wattage down even lower there is the Carr Amps trick discussed over at the Hoffman forum- basically running individual cathode resistors to each power tube and then switching around the connection at the minus end of the individual cathode resistor bypass caps. With both caps connected to ground you would have full power. If you disconnect both caps from ground you reduce the output a little bit. However if you connect the minus ends of the two caps together you get a considerable reduction in power (it has to do with the phasing of the two power tubes). You can also hook up a pot to the minus ends of the caps for a variable reduction in wattage.
The Maverick has a single shared cathode resistor and bypass cap for all 4 EL84's and I haven't even looked inside to see if any of that would be feasible. (Disconnecting the grids to two of the power tubes should be easier to accomplish.)
Thanks!
Steve Ahola
P.S. I have been drooling over the Maverick since it first came out- I was going to take out a loan against my condo to pay for one along with a $2500 PRS guitar but the salesman talked me out of it. Who ever heard of that happening?
In any case the OD channel is really really nice. If you look at the design there is a "virtual" tone stack after the first gain stage- basically a tone stack but with fixed resistors simulating the settings of the 3 controls. The front panel controls are connected to the second tone stack which is after the 3rd gain stage. Two tone stacks- not unlike the HRM Dumble ODS which has a second tone stack as internal trim pots after the OD stages (although with the HRM mod you would normally have the preamp boost engaged which pretty much bypasses the first tone stack). It seems like a neat trick that more amp builders might want to use: I would wire up the virtual tone stack after the first gain stage to trim pots which would be adjusted until you got the desired tone (I would also replace the slope resistor with a trim pot to determine the value that you prefer). Once you have the 4 trim pots set exactly as you like them you would measure the resistances and replace them with fixed resistors. Or just leave the trim pots in...
Without knowing how Mesa Boogie accomplishes the power switching I would probably first want to disconnect two of the output tubes. Would cutting the signal to the grids of two of the tubes work for that? I have also heard of disconnecting the screen grids but I would rather not run a high voltage to an added panel switch.
Disconnecting two tubes should cut the power down from 30w to 15w. To bring the wattage down even lower there is the Carr Amps trick discussed over at the Hoffman forum- basically running individual cathode resistors to each power tube and then switching around the connection at the minus end of the individual cathode resistor bypass caps. With both caps connected to ground you would have full power. If you disconnect both caps from ground you reduce the output a little bit. However if you connect the minus ends of the two caps together you get a considerable reduction in power (it has to do with the phasing of the two power tubes). You can also hook up a pot to the minus ends of the caps for a variable reduction in wattage.
The Maverick has a single shared cathode resistor and bypass cap for all 4 EL84's and I haven't even looked inside to see if any of that would be feasible. (Disconnecting the grids to two of the power tubes should be easier to accomplish.)
Thanks!
Steve Ahola
P.S. I have been drooling over the Maverick since it first came out- I was going to take out a loan against my condo to pay for one along with a $2500 PRS guitar but the salesman talked me out of it. Who ever heard of that happening?
In any case the OD channel is really really nice. If you look at the design there is a "virtual" tone stack after the first gain stage- basically a tone stack but with fixed resistors simulating the settings of the 3 controls. The front panel controls are connected to the second tone stack which is after the 3rd gain stage. Two tone stacks- not unlike the HRM Dumble ODS which has a second tone stack as internal trim pots after the OD stages (although with the HRM mod you would normally have the preamp boost engaged which pretty much bypasses the first tone stack). It seems like a neat trick that more amp builders might want to use: I would wire up the virtual tone stack after the first gain stage to trim pots which would be adjusted until you got the desired tone (I would also replace the slope resistor with a trim pot to determine the value that you prefer). Once you have the 4 trim pots set exactly as you like them you would measure the resistances and replace them with fixed resistors. Or just leave the trim pots in...