taking tubes out of marshall plexi

[dreamer]

Hi, I am wondering which two tubes to take out of my 1959 slp to halve the wattage. I know this does not make it half as loud but its a start. I have been looking for a fender deluxe or similar to trade but for now I just need this thing quieter! I know I have to change the impedance too, I think from 16 to 8 ohm. Any advice would be appreciated.

[Chuck H]

Take out the two inner power tubes or the two outer power tubes. When running two tubes in a four tube amp you should should set the impedance switch one lower than the speaker load, ie: when using a 16 ohm speaker you would set the impedance switch for 8 ohms. When using an 8 ohm speaker set the impedance switch to 4 ohms.

I ran my 1959 this way for over a decade. Just to be anal about it I would swap the four power tubes from the set in pairs. Also alternating from the inner to the outer sockets and vice versa about once a month under the belief that this would help maintain even tube and component wear/ aging if I ever decided to use all four tubes again.

Your amp will be quieter. There seems to be some magic 3dB drop from 100 watts to 50 watts that seems larger than the 3dB drop from 50 watts to 25 watts. But what can really help quet you down would be lower efficiency speakers. Find out about the speakers your using and find a similar sounding speaker (possibly even a better sounding speaker, who knows) that is lower in efficiency. A 3dB drop due to speaker efficiency is the same as a 3dB drop due to lower wattage as far as your ears are concearned. So, if you pull two tubes AND change to a speaker that has 3dB less efficiency it will be like your amp was just reduced to 25 watts.

Chuck