Power to my Amps, AV gear and computers

mboddy

New member
I think I have my power requirements sorted but I am not an electrical engineer. Hoping you could comment Alan.

3 phase power to house and main board and breakers all new about a decade ago.

16 amp breaker, new 20amp dedicated circuit to double GPO (general power outlet).
Thor RF-11 rack mounted power board with surge protection and filtering dedicated to AV gear.
Circuit 2 has 4 IEC outlets serving 2 March Audio P422s and a P452 and P451.
Circuit 1 has 7 regular outlets serving other AV gear such as AV processor, disc players, media players, etc.

16 amp breaker, new 20amp dedicated circuit to 2 double GPOs.
Another Thor RF-11 for subwoofer, TV, my computer, NAS and router.
Thor A12BF with surge protection and filtering for wife computer, printer, scanner NBN router.
Jackson with surge protection for work computer.
 

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Hi @mboddy

Mains power practices and requirements are an interesting topic. Often people think they have a problem when they dont. People sometimes think they need a special "clean earth"", when in reality the real issue is they are using single ended RCA connections which somewhere have the shield connected to earth. This causes no end of potential problems.

So first rule is go XLR balanced if at all possible.

If you get clicks and pop noises from other mains appliances switching on and off (fridges etc) then having a dedicated line from the trip board for your hifi may be of some use in minimising the issue, but really you might want to get the offending appliance looked at.

Mains power is noisy. It is rarely a clean sine wave. Loads on the line leading to your house cause distortion, harmonics etc. The voltage will rise up and down. Its a given so a good hifi component should be designed to be immune (as far as possible) to this. Anybody who is claiming massive differences in sound quality with improved mains power supply may want to think about the quality of the design of their hifi components. 😉

Most hifi components use regulated power supplies inside. DACs, pre amps etc. What this means is the electronics power supplies are isolated from what's going on with the mains. The voltage is filtered and regulated. The isolation from this can easily be 80dB or more. A simplistic example.

240v supply gets a 10 voltage spike. The component transformer steps down the voltage from 240v to 24v (10:1). The spike is now no more than 2.4v and probably lower due to the response of the transformer. This is filtered by the resevoir caps. So 2.4 v is now reduced by 80dB by the voltage regulator, and is now only 0.24 mV.

Then the components the power supply is feeding (such as an op amp) also have a property call Power Supply Rejection Ratio, PSRR. This is how much they reject variations in the their power supply. This can again be another 80dB.

So 0.24mV is reduced to 0.024uV! So the component is massively isolated. This is way below the inherent noise in the system. It's a non issue.

Now, there is a component that is more susceptible, and that's a power amplifier. The reason being is that their output stages require a high power supply voltage and high supply current. For example in our P422 amp it's +- 65 volts. It is expensive to build A fully regulated high current power supply. As such most power amps use unregulated supplies as a result. This means they rely on the inherent PSRR of the amp circuit. This is still very high, but not as good.

A typical linear power amp PSU is very simple , a step down transformer followed by a bridge rectifier to turn the AC voltage to DC, followed by resevoir caps to smooth the voltage ripple.

Another issue with this design is that the psu output voltage will vary in sympathy with the mains input voltage. If it dips your amp may not give its full output power.

Now, our power amps don't use linear power supplies. We use switched mode psus. These operate in a different way. They rectify the incoming AC voltage to DC. This is then switched at a high frequency (typically around 100kHz) through a high frequency transformer and rectified and smoothed again. In our supplies feedback also keeps the output voltage controlled, not fully regulated by way better than a linear supply.

This means that the output voltage is massively isolated from what the mains is doing. The noise from the switching is way above audio frequencies, so it's a non issue. In a linear supply it's at 50Hz (60hz) and harmonics thereof, so that's an issue.

So this is a long winded way of saying that in your system with our amps, the mains is nothing to worry about.

So I can hear the next question, what about RF on the mains. Again very unlikely to have any impact. Far more likely if you are using single ended RCA with its shield connected to the chassis and mains earth.

Please, please don't spend money on mains cables as thick as your arm 😉

TBH mains issues are not a problem in 99.9% of systems.
 
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