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

edbarx

Sep 28, 2017
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Sep 28, 2017
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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

Mar 5, 2017
1,188
Joined
Mar 5, 2017
Messages
1,188
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.
 
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