Earthing and how it effects sound.

[likeDIY]

Oops, it is 5mm, not 5cm for the PCB plates.

 

[MikeBettinger]

Hi all,
I was messing about with my latest amp over the past couple of days, mainly shifting earth wires. I noticed that quite small alterations had quite dramatic effects on the sound of the amp. It was possible to vary the sound from very thin to bloated to just neutral. Anyone care to comment on what is going on hear.

I'm quite surprised that there has been no response to this post describing the observation that the way that the circuit returns are implemented has an effect on the sound quality of an amplifier design. Judging from the attention to detail applied to many other aspects of audio design on this site, I would think that there would be a lot of experience to share on this topic.

If you consider that the performance of any circuit is only as good as the foundation that it is built on, the quality of the return path is one of the basic building blocks.

Consider what the effect would be of taking the world’s quietest voltage reference and attaching its ref/return to a noisy path back to the supply reference; essentially any variations present at this connection would be reflected in the reference's output. Any attempts to filter or bypass what appears to be noise in the voltage ref output will be useless or worse (if you could detect it at all, depending on where your scope is referenced to).

Or consider the effect a noisy ground might have on a feedback signal referenced to it; especially when the noise is signal related (or possibly RF)...

Since measuring this noise cannot be easily accomplished through normal means (and I'm not aware of any simulation approaches), hypothesizing and experimenting is a legal approach to controlling and understanding the effect; improving your circuit performance in the process.

To effectively experiment with this, one needs to think through the circuits, looking for places where the stages might interfere with each other, specifically: current paths and their magnitudes through the stages, the functional loops and their input and output characteristics, the signal path, feedback paths, etc. Essentially an understanding of the defining points between stages and the various loops that are present is a good place to start conceptualizing and experimenting. This information is used to map out a sensible return strategy and component layout.

The sonic effect of a good return network is audible in the noise floor and stability of the circuits. The best way to get there is to question what you do know and experiment. The attention to detail is definitely worth the effort.

Regards, Mike.

 

[KBK]

since ground means but does not cover the topic of current flow, but inherntly encompasses, and that in an audio device, also encompasses the idea of 'skin effect' due to the idea of 'modulation', then Reductio ad absurdum makes that a requirement for multiple ground lines, each of a nature that is less than 20ga. per wire, to avoid skin issues.

Try it, instead of really big single ground lines, multiple small ones. If I'm making a board, which I don't do much of now, I run everything mirror imaged, and in a star implementation, with short, clean pathways for power and grounds, the other half (50%) of the equation (other than the circuit). If you use negative feeback on a board, try to route it so the circuit is naturally situated so that the input (to the circuit) and return of the whole negative feedback implementation is as short as possible! The importance of the quality of the power, grounding, and layout of a NF circuit cannot be stressed enough.

The sound is more uhm..'balanced'.

For example, the larger part of the ST part in Bryston was Stu Tyler's grounding mods and a slightly different front end.

Another example, Nelson gave Adcom a great design with the 585 model. It's not his fault that Adcom implemented a POS. Man, in stock form, that amp is terrible. Or I'm spoiled. First time I've ever owned a Adcom, but not for long! On Ebay it goes! Get out of my house, you POS.