Thanks the response Paul - it has encouraged me to read for the 10th time my notes on grounding and having question to answer certainly helps learn something new. And I've just found an updated version of my main reference - seems clearer.
Even though this is an all DHT power amp, I'd like to use best practices where possible.
I will ground the input, using the noise blocking network. I grounded my last build at the input, connected to chassis close to the input without the network, and it sounded awful: lean, edgy. I've seen it recommended that the input be grounded by running a wire from the (isolated) input socket and connecting to the chassis close to the safety earth - is this what you would suggest?
I will earth the power transformer shields at the transformers - that is what I did with my last build.
Regarding the input and interstage transformer screens, I'm a bit at a loss with my limited understanding of how shields work and I need to read up on the screening behaviour of a chassis. A few thoughts and questions:
Even though this is an all DHT power amp, I'd like to use best practices where possible.
I will ground the input, using the noise blocking network. I grounded my last build at the input, connected to chassis close to the input without the network, and it sounded awful: lean, edgy. I've seen it recommended that the input be grounded by running a wire from the (isolated) input socket and connecting to the chassis close to the safety earth - is this what you would suggest?
I will earth the power transformer shields at the transformers - that is what I did with my last build.
Regarding the input and interstage transformer screens, I'm a bit at a loss with my limited understanding of how shields work and I need to read up on the screening behaviour of a chassis. A few thoughts and questions:
- Are screens susceptible to picking up noise from ground or chassis; does it even matter?
- Grounding the screens at the first PS capacitor seems wrong to me: there are strong current pulses (and noise) present in that location that I suspect could(?) contaminate the screens.
- I probably would not want to ground them to their local stage 0V ground either: although the current "pulsing" would be minimal, would I want even a small amount of noise from the screen in my 0V ground - probably not.
- So that leaves chassis, which I'm not entirely confident about either: can chassis noise contaminate the screens? My guess is to connect them to chassis at the same point as the input stage ground.
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