Grounding techniques

[flester]

This is amp.  https://imgur.com/gallery/0DvnHiX

Works fine with this ps. not much noise using pedals on battery. https://imgur.com/gallery/49d8gK3

The noise comes in when I use this.
http://imgur.com/gallery/02LCUTt

Works well with a friend's  amp and



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[flester]

Problem solved. I changed the mains adaptor supplying the pedal power supply. Noise now much at unacceptable level. Thanks again for your input. it stopped me going off om a fruitless and maybe expensive tangent! All for the price of four 9v batteries.

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[flester]

The mains adapter that worked has now died. Any tips on how to buy a new one that is not noisy?

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[electrucio]

Hi everyone,

I'm new here, pleased to join this forum! I'm picking my audio electronics hobby back up again after putting it aside for a really long time.

https://electrucio.substack.com/p/ground-loops

I would like to share a compilation of ideas I did about this topic, I hope it is useful for someone.

[aquataur]

Hi,
thanks for the great write-up.
I particularly like the section on ground planes, because people splash ground planes over all PCBs, thinking that this relieves them from a thoughtful routing.

For balanced inputs (and many other hum related subjects), there is a paper by Bill Whitlock from Jensen Transformers called Design of High-Performance Balanced Audio Interfaces, hosted by Rod Elliott. He explains in depth that the balance does not mean symmetric signals, but balanced impedances.
It would nicely fit your write-up.

You may also be interested in:

• Power and Grounding for Audio and Video Systems
  A White Paper for the Real World – International Version, Jim Brown, Audio Systems Group, Inc.
• TUTORIAL 5450 (Maxim) Successful PCB Grounding with Mixed-Signal Chips -
  Follow the Path of Least Impedance, By: Mark Fortunato
• A practical guide to high speed printed-circuit-board layout, by John Ardizzoni (Analog.com)

If anybody thinks - I only do audio stuff, that does not concern me... let me correct that: audio amplifiers love to oscillate in the MHz region. Once at least.
It is really a rabbit hole you are opening up here, but for serious design, it is inevitable to dive into.
I guess all amp designers did so.

[Kaz Kylheku]

He explains in depth that the balance does not mean symmetric signals, but balanced impedances.

Indeed, balanced transmission works even if you send signal only down one of the two equal-impedance conductors. (Of course, you must avoid sending identical signal of the same polarity down both.)

The noise is what is counted on to be symmetric: but then both lines have to face identical impedances, so that the noise is subject to identical transfer functions.

If identical but noises are filtered differently, they are no longer identical and do not subtract to zero.