A Marshall update...

[FretlessJazz]

I have a Marshall Valvestate 100watt combo amp. I got it from a pawn shop in WV. It is in nice shape, it's from 1996. I run a Digitech 55 in front of it on the clean channel. The backs on these are wide open, so i cut a piece of wood and enclosed the cabinet behind the speaker up to about 2 inches below the back of head. I replaced the tube in it with a Groove Tube. I love the sound of this amp, power and clarity. The problem is about 3 hours into practice I notice it doesn't have the same punch as it does in the begining. It doesn't seem to be getting hot or anything and the speaker seems fine. It did this before I enclosed the speaker so I don't believe that's the problem. Is this normal? Would replacing the speaker fix this?

The sound it's making sounds the same as breathing in a mic. Like wind hiting a mic and coming thru a PA. What could be causing this? It's not all the time, alot when you first fire it up. Then it happens off and on after that.

[jai]

i'd make sure the bias is in the proper range first of all, also it still may be a heat issue. i have a tsl-122 and if i dont run a fan on it all the time it will cut out

[BloodyFingers]

You r amp was open back which means it was designed to used that way. Closing it up could cause issues with heating up to much......

[The Shadow]

i'd make sure the bias is in the proper range first of all,

The valvestate amps have a solid state power section, hence the moniker valve-state. You can't bias a solid state amplifier, no matter how hard you try.

As a side note the TSL can be fixed by changeing the bridge rectifier, which is undersized.

[Jasaoke]

ear fatigue
everything sounds different after 3 hours

[FretlessJazz]

The amp was doing this before I enclosed the speaker. It actually took the amp alot longer to get muddy after I did this, before I enclosed the speaker the amp would go only about a half hour before losing clarity. And I did not cover the enclose the top half of the amp so it would be vented well and air could move. At the end of a four hour practice I reached into the back of the amp and put my hand on the bottom of the amp head and felt all around and nothing felt even slightly warm. I'm not sure that a basically solid state amp will over heat.

Could the speaker be doing this?

[jai]

well excuuuuuuuuuuuuuse me lol.

[FretlessJazz]

ear fatigue... That actually makes sense. At a show you have the momentum of the show to not notice such things. Rehearsals can be wearing.

[FretlessJazz]

Sorry... didn't mean to sound like an ass.

[FretlessJazz]

any thoughts?

[lonewolf]

you say its sounds like air hitting a mic and it loses a lot of output power?

Listen closely, is is making any other sounds like popping or crackling?

[FretlessJazz]

It doesn't lose power, after a few hours it gets a bit muddy at high volume. It makes noise for a little bit when you first turn it on, while its warming up.