Marshall Valvestates are as the name implies: valve (tube) preamp into solid state power amp.

One ECC83 (aka 12AX7). Replacing it may help.

"Buzz" can come from many different sources. Take pstring's advice and bring it to a qualified tech.


Here's a link form the Marshall website:

http://www.marshallamps.com/images/extra/lifeofvalves/valvelife.html