Used Amp Quality

When I am looking at used amps I notice most(99%) buzz, even at very low volumes with the guitar not plugged in. What is causing this??Does it mean you would have to replace the tubes?Or is it the speaker? Or what could it be, how much would it cost to repair it?

I take it you are asking about tube amps, probably the buzz you are hearing is hum from the AC cycle, this normally comes from one or any combination of the following, Filter Capacitors, they degrade with age and get noisy, Pre-amp Tubes, cheap or failing tubes can be noisy even though pre-amp tubes are humbucking by design, Power Tubes, which are not humbucking by design, can be noisy for a variety of reasons, the DC heating element circuit in most amps will cause this, for one reason being that 50% of the time they are wired wrong from the factory, some amps ( Like Fender Silverfaces ) have a bias-balance circuit that bring alot of noise into the tubes, and cheap power tubes can be noisy too. The good news is that all of the above and more can be fixed by the normal maintenance that a tube amp should given to keep it healthy...................

this could explain the buzz on my marshall vs100 that I just bought used.

How difficult is it to replace the valve? I know the lad I bought it off said it hadn't had anything done to it whilst he owned it.

Matt

To my knowledge the Marshall Valvestate amps are all solid state, no valves at all, a simple rule to follow is that if you can't see a tube or valve from the back side of the amp, it is a 99.9% surety that it has none. Word to the Wise, playing around in the back of amps can be hazardous to your health and has been known to cause death in laboratory test guitarists, Be safe, take your amp to a reputable shop.....................

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