I bought a Yamaha GA15 II.

Disappointed when I plugged in my Yamaha acoustic guitar to hear the hissing sound. Got worse when I switched on the Drive mode.

A. Reasons for the hissing sound?

B. How can I do to fix this annoying sound?

Is this problem common in most budgetary amplifiers?

Thanks.

The power supply is dirty ..try getting power conditioner .

Did your amplifier produce hissing sound when there is no cable plugged in? If nothing connected, then it can be grounding problem.

If the hissing sound only become loud when you plug in your guitar, it can be the wire problem.

The power supply noise usually produces humming sound.

I have no idea what kind of pick-up you use for your acoustic guitar. Built-in or separate purchase. See this article if it helps

https://joneruizguitar.com/guitar-amp-hissi...-you-must-know/

Thanks.

Mine is a Yamaha FJX730SC with built-in pickup.

This post has been edited by plumberly: Mar 6 2024, 07:40 PM

Since both guitar and amplifier are Yamaha, I think it is not about cheap amplifier.

The signal from guitar is very small and the amplifier does have high gain to pick-up the signal. The cable itself can pick up signal from surrounding. Maybe there are other devices nearby that produce noise. That is why you need to avoid long cable. If you still need to have long cable, then try to use pre-amp. This way the cable from guitar can be short. The signal from pre-amp to main amp is no longer weak signal. It is amplified high enough to be above ground noise level.

an update

got a new replacement from the seller. No more hissing sound.

by the way, how long does a 9V battery last for an acoustic guitar with built in pickup? Surprised that mine lasted for about a week. Cannot be.

There is no switch for me to switch it off, thought it is an auto on/off type.

Maybe I should take the battery out when not using the guitar. Troublesome.