Marshall PT 100W to 50W, possible?

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eanderso22193
Junior tube assistant
Posts: 99
(4/9/04 7:13 am)
 Marshall PT 100W to 50W, possible?
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 I have a 100W Marshall power transformer(the MPT100 that Doug sells) and I want to make a 50 watt amp with EL34's. Can I wire the 100 Watt PT up for 50 Watt operation? Its got that extra bias winding, and all the 50 Watt schematics I've seen don't have that, and the HT rating on the 50 Watt PT is almost double that of the 100 Watt. Should I just wire it up like I would the 100 Watt power amp using the bias winding and all but just use two tubes instead of four, or is there another trick to it? Thanks.

Eric
 
Tiny Daddy
I will work on all amps
Posts: 601
(4/9/04 7:41 am)
 Re: Marshall PT 100W to 50W, possible?
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 Just use 2 tubes instead of 4. Power out depends on speaker loading.
 
eanderso22193
Junior tube assistant
Posts: 100
(4/9/04 12:05 pm)
 Cool
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 Cool. I just wasn't sure if the voltages and bias schemes needed to be different. Thanks.

Eric
 
jbrew73
Junior tube assistant
Posts: 115
(4/9/04 5:31 pm)
 50/100watt
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 eanderso
just to make sure you are clear on the wiring, you would have to use the 100 watt wiring schematic not the 50 watt. because the transformers use different rectifier and bias circuit designs.
let me know if you would like to swap trade or sell the 100 watt for a 50. i need a 100 watt PT for a project and have a 50 watt to get rid of.
j_brew "AT" earthlink "DOT" net
 
cbevans
Junior tube assistant
Posts: 4
(4/11/04 2:27 pm)
 Re: Marshall PT 100W to 50W, possible?
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 I have used a 100-watt power transformer in a 50-watt plexi-style amp. I had to bridge the rectifier and then adjust the bias range resistor to accomodate the bias tap.
 
 
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