The Yamaha THR10, THR10X and THR10C are fantastic little practice amps, but they have a design flaw. When some of the wires inside get too close together, their signals interfere and a nasty high-pitched whining, squealing or ringing sound results. This may be constant, or only when you play, or only when the noise gate is off. It sounds like this:
Nowhere does there seem to be a guide to fixing this. When my THR10X showed up with this squealing issue, I opened it up, turned it on, and poked around with a pencil to find out what was happening. Turns out it’s a five minute fix. Follow this short tutorial and you’ll be whine free.
Caution: Amps and humans are fragile. Don’t touch anything you don’t have to. Static electricity stored in your body could zap a microchip, rendering your amp useless. Power stored in a capacitor could zap you, making you useless. Proceed at your own risk. I will not buy you a new amp or new hands.
1. Open Up
With the amp off and unplugged, remove all screws holding on the metal casing, including the four chrome hex bolts on the front, and open as shown.
These thick cables with the gray foam insulation are for the speakers. We’ll leave them alone.
We’re interested in this mess of smaller wires at the right edge of the board.
2. Fix It
The problem is that when cable A gets close to the bundle of wires at connector B, the interference generates a nasty squealing feedback sound.
Separating them even this much makes the sound disappear. Yamaha should not have designed the THR10 series with these wires so close to each other, and their flappy little piece of silver shielding between the two is apparently insufficient!
To keep cable A away from connector B permanently, and enjoy quiet, whine-free shredding forever more, secure cable A to this little circuit board with a cable tie.
It’s now impossible for the wires to get near each other. Carefully reassemble the amp and you are done with the repair for the cost of a cable tie.