Whistling Sound in Express

[Guitar Adjuster]

I have been getting a whistling/high pitched sound when I turn my Express volume past 12/1, as I increase the volume the whistling does not seem to get any worse, but stays the same. There is no shielding plate inside the head cabinet. I have tried to change out pre-amp tubes but it's still present. The amp is an EL34 express, ceritone layout, Moose trannies. Has anyone else experienced this problem?

[Elcabong]

I have experienced that to some extent with another amp I built before. I spent some time with a chopstick moving and rearranging wires and it fixed my problem.

So basically I tried to keep high voltages wires down close to the chassis, signal wires higher. And have wires that intersect at 90 degrees as much as possible.

Good luck and take care!

[Guitar Adjuster]

Installed a shielding plate in the bottom (ala Marshall) of the head cab and moved some pre-amp wires around and that seem to do the trick, nice and quiet now.

[hot_tube_tone]

Installed a shielding plate in the bottom (ala Marshall) of the head cab and moved some pre-amp wires around and that seem to do the trick, nice and quiet now.

What did you use for your shielding plate, and how big did you make it?

[straycat]

I used a .090 aluminum that was used for traffic signs that we make at our garage. I made mine longer than the chassis so I could drill holes in the extra length for mounting the chassis in a cabinet. The plate must cover the complete bottom of chassis to provide shielding.

[Guitar Adjuster]

I bought a piece of aluminum at Lowes that would fit the width of the chassis then cut it to length. I then used small brads or nails to secure it to the bottom of the head cab. Here is a photo of my Marshall head cab which you can see shielding inside the head cab.