Fourth valve on a 1959with Power control?

[Mats A]

Do you have to install a fourth preamp valve on a 1959 Marshall even of you just install the Power control like on the YJM100?

[surfnorthwest]

A 1959 will only need three preamp tubes. Just having the powerscaling does not mean you need this fourth tube. Santiago said the fourth tube was to compensate for volume lost when using the reverb. It is not used for extra gain.

[SteveD]

The fourth preamp valve is used as buffers to compensate for the loading of the reverb circuit on the signal path. Remember it still has to behave exactly like a 1959 which traditionally didn't have a reverb in its signal path.

[Mats A]

OK i see. Thanks for telling me.
I want a straight 1959 just with power scaling and self biasing. Don´t need that extra stuff. If i only knew if this will be the only 1959 type amp marshall will build with the power volume control. Then i think i would wait for that.