Fender Frontman 65R - hiss when cable plugged in

[bleuguitar]

Hello,
I have a Fender Frontman 65R, and i have a bit of a sound problem.
If i don't plug in any cables, i can roll the volume knobs all the way up and i can't hear a thing, but if i plug in a guitar cable, i get a hiss noise. I tried with all kinds of cables, effect pedals, without effect pedals, different guitars. With the guitar volume down, i still get the hiss.

Also, it does not matter if i use the first or second input, i have the same hiss sound. If i use the pwr in input, all sounds great, but i really need the preamp settings.

Is there a fix for this?

Thanks

[Robert M. Martinelli]

Hi, and welcome to the forum!

In a nutshell:

The "problem" you're reporting actually sounds to me as a "normal" behavior. The input jack sockets possess a built-in grounding switch, so that, when nothing is plugged in, the signal input is shunted to GND, in these conditions, whatever little hiss you hear is simply thermal ( AKA Johnson-Nyquist ) noise generated by the amp's electronic components ( resistors, seminconductors etc. ). When you plug something in, the input is no longer shorted to GND, so whatever noise/hiss/hum coming from outside the amp gets amplified by the amp's circuitry together with the "useful" signal (when present ).

FWIW, it's pretty normal for a cheap amp like that to exhibit a certain amount of "hiss" ( the technical term actually being "white noise" ), as the components used are "standard grade" ones e.g. 4558 (dual) op-amps ( IIRC ).

Noise is an "inevitable" companion, you can only try to minimize it ( you'd need to mod the amp,though ), but, honestly, I would ask myself if that amp is worth the effort...

Hope this helps

Best regards

Bob

[bleuguitar]

Thank you for your answer ...
I was afraid there is something wrong with my amp, but as you say is normal, i will just live with it ..
Thanks again