Installing ground busses in point to point amps

[goldear]

I believe that as a general rule of thumb, this is aways good idea from an electrical standpoint.

However I'm curios as to what kind of performance benefits (if any) one may expect from converting a point to point wired amp which connects everything to chassis ground plane to one which uses a ground-bus instead.

For example: My Eico HF89 connects everything to chassis ground. After recapping this unit, there is no hum at all, so ground loops certainly don't appear to be a problem with this construction technique. However, I can't help but wonder if this approach has compromised the sonics of this amp.

So can anybody tell me if converting an amp like this over to use a ground-buss is likely to make an audible improvement or not? And if so, what kind of subjective improvements should one expect?

 

[wa2ise]

The engineers probably did some work, combined with their experience, to make the amp without ground loop hum when using the chassis as a ground. One important place in the circuit to pay attention to is to connect the centertap from the high voltage power transformer secondary right at the same point the first filter cap's negative terminal is located. Also it helps to connect subsequent filter cap negative terminals to that same point as well. Also, do not pass any heater current thru the chassis.

Your amp's sonics should be fine as it is, and I doubt you'd get any improvement with a bus.

 

[goldear]

Thanks. I didn't do this originally for exactly the reason you state.

I'm just trying to determine what the biggest design weaknesses in that amp are, and that just happens to be one of my guesses.

Any contrary opinions?

 

[kward]

For a new scratch DIY build, it makes sense to start with a star or bus ground scheme, as I think you have a better chance of creating a hum free project. But if the Eico is already hum free, I don't think you will improve the sound one iota by converting the grounding scheme.

Preamps on the other hand, I think can benefit from star/bus grounds because the signals are so much smaller, it's easier for hum to creep in.

Some people might forget that there is current flowing into (or out of--depending on your convention) the ground. So the use of the same quality wiring of the same gauge as used on the high voltage lines for the ground wires is a good idea.