Princeton RI has a “dial tone” like background noise in Input 1?

[BenTobith]

It’s hard to describe this sound, but it’s like a faint “dial tone” background noise. It shows up as soon as you turn the amp on and the tubes begin to warm up. It only seems to be audible when I’m plugged in to Input 1. When I plugged in to Input 2, it went away. The tone gets louder if you turn the Volume up on Input 1.

Any ideas to isolate/troubleshoot further?

I should note this started happening a week or two ago. It wasn’t occurring before this point.

 

[donepearce]

Does it go away if you turn the guitar volume to zero?

 

[donepearce]

Just looked at the schematic, and 1 and 2 are essentially connected together. If they re behaving differently, it sounds like something mechanical has happened at the sockets

 

[BenTobith]

Does it go away if you turn the guitar volume to zero?

Yes. It happens whether a guitar is plugged in or not. Whenever a lead/cable is plugged in to Input 1, guitar included or not, that’s when it happens.

 

[donepearce]

Is the guitar sound on inputs 1 and 2 identical otherwise? And I was asking about guitar plugged in with volume control at zero.

 

[Skulltula]

Hopefully you got to the bottom of this, but I had issues when I first got my 1974x where channel 1 would make sound a bit like a petrol mower chugging along. Did it whenever a cable was in channel 1, even if I dropped volume on the guitar to 0, no matter what guitar it was etc. It did so straight out of the box, so spoke to retailer and it went back and I got another sent...same thing. Did more google searching and somehow ran into the idea of RF interference, so I started turning everything off nearby one device at a time. As soon as I turned the internet router off the next room over? Bingo.

 

[Huntroll]

I would put that router on a power strip.
And leave it OFF as much as possible.

 

[Skulltula]

I would put that router on a power strip.
And leave it OFF as much as possible.

Turning a router off and on a lot is how you end up with slower internet speeds on ADSL and such. From the exchange side it sees line instability and prioritises stability over bandwidth.

My amp lives in another room of the house now, further away from the router.

 

[Huntroll]

My wifi modem sits next to my bed.
When I'm done using the computer and the phone, I switch it off.
Minimizes exposure to the RF of others routed and repeated by its wifi functionality.