AC/Generac Transfer Switch

The contacts are passive.  They are no more / less noisy than a main breaker otherwise.

A better consideration really is, do you want your generator sized up to include your stereo when it's running?

I cannot speak for Generac but I have a whole house Kohler unit and when it is running I have learned not to even bother to listen to my stereo due to the amount of very noticeable background noise. The voltage is spot on but the noise coming through my normally dead quiet system makes listening intolerable to me.

I also had the electrician pull a separate earth ground specifically for the 2 circuits not tied to the main panel.

That makes me question your electrician’s qualifications...

As for your question.

Feed the power for the audio room audio equipment ahead of the Generac ATS

There are a few methods for doing this that will meet the 2020 NEC code.

Texas has adopted the 2020 NEC, (National Electrical Code).

Worth checking;

2020 NEC:

230.71 (B)

230.85 Emergency Disconnects.

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@lwin When you speak of this noise, is it safe to assume that it's electrical noise (hums, buzzes, etc) that you're hearing through your audio system itself, and not mechanical generator noise that you're hearing through walls or windows (mechanical noise that's interfering and mixing with your ability to cleanly hear your audio system)? 

All switches put noise on the line when they break contact. The transfer switch won't be a problem when closed against utility power.

You cannot use a subpanel at the service anymore if your local building department uses the 2020 NEC. That panel will have to be a service entrance rated panel (load center) with a main breaker disconnect or a switch in a separate enclosure ahead of the panel if it's not a load center. 

I would say talk with your electrician, but if he installed more than one ground at your house I doubt he's got a license.

I have a 200 amp service and a 100 sub panel and they both share the same ground. Did your electrician say why you needed a second one?  Did he charge you for the second one?

Several of us are very curious.

@dpop It is an electrical noise. It is a steady buzzing sound like an electronic bee. Music playing will obscure it but it is very annoying between tracks.

I also learned the hard way that I should not have placed the generator outside our bedroom. The mechanical noise is irritating especially when it cycles under load.

Friends installed their generator out of site on the side. Prevailing winds blew CO into the house. The wife ended up in the hospital.

Ensure the install cannot kill you. Electrically or otherwise.

+1 on the multiple ground question. It's generally a bad idea.

See Ground Rod Theory Installation

Here is one method for feeding the audio room audio equipment power outlets ahead of the ATS.

A Combo meter socket / with main breaker with a small circuit breaker load center. The bus has feed-thru lugs that would feed the normal, (Utility Power), to the ATS.

A breaker would be installed in the panel to feed a sub panel in the house for the audio room audio equipment outlets.

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There must be a solution here. Over decades, I was Chief Engineer for numerous radio stations that were many times on generator power. This transfer of power always involved an automatic transfer switch. There was never any new buzzing or humming when on generator power (which sometimes involved 5 radio stations and many radio station studios on the same generator). That simply would not work with radio stations. And some of you actually want to bypass this generator power, when you can actually still listen to your audio system when you lose utility power?! Sorry, that doesn’t make sense to me.

If it were possible, I would love to investigate every one of these situations where a generator is creating electrical noise in a home audio system. One thing that comes to mind is long unbalanced RCA cables. These *can* pickup electrical EMI & RFI noise. It’s possible that the alternator portion of the generator (the portion that generates the AC) is emitting this interference, and being picked up by the RCA cabling. It’s very possible if the home audio system was interconnected using balanced analog, this interference would not be heard, as it would be canceled out by the balanced design of the equipment and cabling.

Two things are critical to generator output (voltage and frequency), to replicate utility power (240 volts and 60 Hz for a typical US household). The goal is for the generator to reach full speed (resulting in the correct voltage and frequency) before it transfers this power to the house.

In my situation, to keep most microprocessor studio equipment powered up while this transfer of power takes place, UPS’ were incorporated in studios and equipment rack areas. The UPS’ would temporarily carry the load until the generator came up to speed and transferred power. All earth grounding and equipment bonding stayed the same.