Re: Large, 1500W RMS, audio amplifier ground.

[edbarx]

I would like to aks to which point on a large amplifier circuit the ground terminal is usually found. An amplifier that I am trying to understand with the aim of repairing has its ground connected to the audio power output. By the latter, I do not mean, the centre tap of the power transformer, as that, in my logic, should be where the ground should be connected.

The amplifier is powered by a large toroidal transformer, with two centre tapped secondaries connected to two bridge rectifiers with the centre taps to the point between two smoothing capacitors. This forms a DC power supply as follows:

-82V ---- 0V ---- +82V (both DC)

The about is replicated for both channel A and channel B.

I am completely perplexed as in my entire life (~51 years) I have never met a circuit with such weird earthing.

The amplifier is a professional public address amplifier.

I downloaded the service manual from:
https://elektrotanya.com/wharfedale_pro_s1500.pdf/download.html

 

[dave9]

If the center tap of the transformer has its own, locationally isolated lead to this point so it is a star ground config to avoid ground loops, that can work. If it does not, apparently they didn't care or tested and found negligible difference.