Amph T00b Questions

[Robert****]

The tube covers are safe to remove.

"Tube shields are those little metal cylinders you find over the small tubes in your amplifier. They're used to reduce the chance of picking up hum and noise. Sometimes they're also used to hold the tubes securely into the tube sockets. Tube shields have an adverse affect on the tone of most amps. Here's the reason why. The tube has an element called a "cathode" which gives off electrons. Electrons are attracted to a positive charge and repelled by a negative charge. The cathode is in the center of the tube element called the "plate". The plate has a positive charge which it uses to attract electrons. OK, so now we have a cathode flowing electrons to the positive plate and all is well. Then we install a tube shield that connects to the chassis which is negative in relationship to the plate. Confused? So are the electrons that see this negative charge past the positive plate. Also the plate and the shield form a small value capacitor.

To test this for yourself, start with the tube shields off. That way you won't be dealing with hot tube shields later in this test. Warm up the amp and play, listening to the tone with a critical ear. Next put the tube shields back on. Be careful, the tube shields will be cool but the tubes will be hot. Do not change any settings on the amp or guitar and listen to the tone again. I rest my case. If your amp makes too much noise or does any nasty tricks with the tube shields off, do put them back on."

[marnold***]

"To test this for yourself, start with the tube shields off. That way you won't be dealing with hot tube shields later in this test. Warm up the amp and play, listening to the tone with a critical ear. Next put the tube shields back on. Be careful, the tube shields will be cool but the tubes will be hot. Do not change any settings on the amp or guitar and listen to the tone again. I rest my case. If your amp makes too much noise or does any nasty tricks with the tube shields off, do put them back on."

Thanks for the info, Robert. I think I'll try this some time. I assume that since you have this in quotes that you got the information from someone else?

I ended up ordering preamp tubes from Tube Depot today. They had JJ 12AX7s for $9.95 which is the cheapest I've seen them anywhere. I got five of them, one is balanced. Don't know if that's necessary or not but for $2, I wasn't too concerned. I also got a JJ 5751 which I'm going to try in V1. If nothing else, at least I'll have a spare 12AX7.

In the future, I intend to pick up some random 12AX7s as I have opportunity and trying them in V1 and V2. I know I really liked JJs in my old JCA20H so I suspect it will be the same story here. Unfortunately, it's almost impossible to find tubes around here.

[Robert****]

Thanks for the info, Robert. I think I'll try this some time. I assume that since you have this in quotes that you got the information from someone else?

I ended up ordering preamp tubes from Tube Depot today. They had JJ 12AX7s for $9.95 which is the cheapest I've seen them anywhere. I got five of them, one is balanced. Don't know if that's necessary or not but for $2, I wasn't too concerned. I also got a JJ 5751 which I'm going to try in V1. If nothing else, at least I'll have a spare 12AX7.

In the future, I intend to pick up some random 12AX7s as I have opportunity and trying them in V1 and V2. I know I really liked JJs in my old JCA20H so I suspect it will be the same story here. Unfortunately, it's almost impossible to find tubes around here.

Yeah I found that info somewhere online... I think it is correct though.