Backup Generator transfer switch

I have a whole house Koehler generator that I had installed when we built our house four years ago. I cannot comment on on the transfer switch as my stereo room was the last major indoor project I did after occupying the house. Since moving in  we have unfortunately had numerous outages with the longest being 6 days. I have tried playing music with the generator running and even though I get a spot on 120V there is a constant annoying low level hum like a bee coming out of each speaker so I don’t play music on my system during outages. 

Where is @jea48 when you need him?
Bob

I have been following M. Fremer's problem in Stereophile closely as well.   As I mentioned before in other posts, I am Director of Engineering at a green energy company and we bought that exact same transfer switch to reverse engineer.   As you might guess, his problem certainly hit close to home.

One possible problem is the ATS isn't "just a switch".  The problem with any ATS is UL108 which applies to all ATS units.   There is no relay company on the planet that can make a relay meet the requirements of UL108, rather it is left up to the manufacturer of the ATS to build enough logic and microprocessor power around a solid relay to handle the requirements.   That stuff is running full time, so expect it to bleed EMI into the lines and into your gear.   

A solid EMI brick wall filter or power regeneration system like the PS Audio one that M. Fremer installed would do the job.   The fact is, the power lines and house wiring make excellent EMI antennas, so expect some EMI to bleed into your system, and cause some havoc at some level.   

There are only two ways to eliminate the ATS and still be code compliant.   One is a manual switch, which you have to operate yourself.   The other is an ATS that has a five+ minute lag between grid failure and switch over to generator power.   That is a long time to be in the dark!  

M. Fremer also mentioned in the latest issue of Stereophile that he had a "flat topped" waveform, I assume he meant he has a clipped sine wave, for AC power.   If that is the case, he really has some serious problems there that go beyond the ATS.   
We have a customer that has the top level of his 60 Hz power waveform clipped at the transformer at the street.  His power company won't replace the transformer, since he is the only one who complained about the noise in his high end audio system.   For him, running off the solar, batteries, and inverter was the best solution.  

A manual switch will work. And all the power line and house wires are an antenna bringing EMI into the system. 

Man, that sounds so familiar. Could swear I have heard it all before somewhere. But, where? We only have one Director of Engineering around here. Who else could possibly have such advanced detailed knowledge of electricity and electrical circuits?

The last time I went through this I left gear off that needed a week to warm up.

If Fremer is seeing flat topped wave forms though, as noted above, that’s bad, and a properly installed switch should not do this.