Mesa Mark 4 Output Tranny swap ?

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Mesa Mark 4 Output Tranny swap ?

Post by stav92 » Sun Jan 12, 2020 6:30 am

I'm thinking of swapping out my Mark 4 output transformer for a different transformer that also has a 16 Ohm speaker out tap AND installing an impedance selector switch. I hate using impedance mismatches as the amp gets duller and muddy so I'm not interested in using the 8 Ohm out with my 16 ohm 4x12 .

I'm not bothered about resale value as I will be keeping this amp until the day it dies. I'm no stranger to amp modding & circuit tweaks but I always prefer to be careful when dabbling with an amps power section.

All I want to know, is theoretically, could I whack a completely different output transformer in here such as a marshall plexi style transformer etc. without frying the amp ? The only thing that concerns me is the fact the amp is 6L6 and Simul-class ... I would also be happy to have the amp fully operating in AB Pentode so if the Simul class is the only thing affecting output tranny choices (+/- 16 ohm outs) then I'll happily ditch it.

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Re: Mesa Mark 4 Output Tranny swap ?

Post by danman » Sun Jan 12, 2020 6:07 pm

If the OT came from an amp with the same type and quantity of power tubes, there would not be an issue. The amp may sound slightly different with a Plexi style transformer though.

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