100 to 50 Watt Conversion

[StuntDouble]

Hey guys,

I've got two 100 watt Plexi clones, and the more I've been listening to 50 watters, I really like the sound of the smoother compression, and warmer midrange. There seems to be a little less headroom and more of a softness to the breakup as opposed to the harder, clearer grind of a 100 watt.

Both of my 100 watt amps just flat out smoke, but I'd like to convert one over to a 50 watt power section. Would there be a significant difference tonewise, if I were to leave the stock 100 watt power transformer and just change out the mains, filter caps and the OT. Would this cause any potential problems.

thanks, Ben

[flemingmras]

Hey guys,

I've got two 100 watt Plexi clones, and the more I've been listening to 50 watters, I really like the sound of the smoother compression, and warmer midrange. There seems to be a little less headroom and more of a softness to the breakup as opposed to the harder, clearer grind of a 100 watt.

Both of my 100 watt amps just flat out smoke, but I'd like to convert one over to a 50 watt power section. Would there be a significant difference tonewise, if I were to leave the stock 100 watt power transformer and just change out the mains, filter caps and the OT. Would this cause any potential problems.

thanks, Ben

Depending on the voltage that your current PT kicks out I would seriously consider changing it. Some of these Marshalls run too high a plate voltage for the OT load impedance they run, but lots get away with it because the power supply can sag enough to allow for it. With a 100 watt PT in a 50 watt amp you won't hardly sag at all since you'll only be pulling 1/2 the current from it. This may cause you to have redplating issues running it at full tilt...especially if you're seeing plate voltages in the 470-490 range.

[StuntDouble]

thanks for the tip; I was reffering to using a 50 watt OT in a 100 watt amp, and just pulling two tubes.

[shakti]

As flemingmras points out, you'd still only be halfway there...the 100W power transformers deliver significantly higher B+ to the tubes. And if you use only two tubes, the B+ will even increase (at idle), probably to over 500V. Factor in less sag, and you could well be in trouble as far as redplating. It won't sound the same as a 50W either, with the much higher B+. A typical 50W is in the 420-440V region (minus the appropriate sag under load).

I honestly think you'd be much better off with going for a "real" 50W.