high frequency intermittent noise

As sure as I am that it's cell phone noise, I'm almost certain it's not that tower. That tower is serving dozens or hundreds of clients at any one time. If it was the tower it would be practically constant. Something in the building is the source, and it's close. Last night I played around. I got my phone steaming videos last night and put it INSIDE my F5 right up against the left amp board. I could barely hear it. It was strongest when I placed the phone on top of the toroidal and right next to the power cord. Even then I had to be inches from the speaker. 

james1969 OP286 posts11-16-2017 1:35pmI thought it was my interconnects.  I turned off everything except my amps, then I disconnected the interconnects, the noise disappears for a while...but reappeared.  Maybe my speaker cables are suspect too...

You need the RCA shorting plugs for the amps inputs.

James, searching at eBay for "RCA shorting plugs" (without the quotes) will lead you to a number of sellers offering them at low cost.

Good point by Ralph (Atmasphere) re the possibility that the amp doesn't provide grid stopper resistors in its design.  If that proves to be the case, James, I would think that if you explained the situation to Vladimir he could have them installed at modest cost.  It would just involve the addition of a physically small low power resistor in series with the grid of each tube.

Good luck.  Best regards,
-- Al
 

@kosst_amojan,

As sure as I am that it’s cell phone noise, I’m almost certain it’s not that tower.

Re: On-site Cell Tower Interference
« Reply #2 on: October 03, 2012, 10:03:56 pm »

It’s highly unlikely the cell site will induce RFI problems with any properly designed audio equipment, or any other system inside the building.

First, cellular/PCS sector antennas are highly directional. Directly below the antenna is a major null with signal levels easily being 50-70dB below on axis carrier level (based on antenna type and design) before building attenuation is considered.

First, cellular/PCS sector antennas are highly directional. Directly below the antenna is a major null with signal levels easily being 50-70dB below on axis carrier level

@kosst_amojan,

So for cell phone reception in the apartment building there may be equipment to compensate for the "null zone"? If so, would you expect the equipment, or antenna, placed on each floor?

Also if james1969 placed his cell phone in areas on his audio system as you did on yours he should pick up the same RFI noise as you did, correct?

Another question.
What if the apartment building has some type of building automation system that is remote controlled by a digital transmitted signal? Could that cause the same type of RFI noise?

That is GSM noise-your (or someone nearby) cellphone is being "polled" or is polling the basestation nearby....earthing(use copper pipe in bathroom or kitchen) may well fix...if not then chokes on power cables is another avenue to explore...and of course keep mobiles charger off hifi circuit.