does connecting mains ground with circuit ground create a ground loop?
Jun 25, 2003 at 9:44 PM Post #2 of 8
Hi,

Yes, in a sense. But not really what we call "ground loop."

It is a ground loop in a sense that it may form a ground loop through the AC outlet with another equipment (ie CDP). But then this isn't as critical as ground loop forming within your amplifier design itself. That will promote badness such as oscillation.

Many say that you must isolate, but in the end, you cannot really solve this particular problem completely unless you use signal transformers or/and convert to balanced signal system.

T
 
Jun 25, 2003 at 10:59 PM Post #4 of 8
Yujun -

It isn't all that bad. Sometimes it is unavoidable anyway. However, this could be the cause of badness when you use a headphone amplifiers with computer audio output. You never know what kinda junk runs in computer PSU ground.

In essence, this wouldn't cause improvements in sound quality. But it will provide less "susceptability" to oscillation. Note I quote. This is because it isn't necessarily only cause of problem. Usually, this becomes a "catalyst" to oscillation. So besure to build amp well. That should be the first thing in your mind.

In fact, one of my amp has signal ground connected to PSU ground, however, it has no problem whatsoever and has premium sound quality. I really put a thought into oscillation stuff when I built it.

Tomo
 
Jun 25, 2003 at 11:10 PM Post #5 of 8
Hello,

What I usually do is to use Mr. Jan Meier's Ground Breaker Circuit to connect signal ground to PSU ground.

This is, I believe, is important. All ground must be stabilized and must not be kept floating. No caps or regulators can really provide that. That is why signal ground must be connected to PSU ground. However, you shouldn't simply connect PSU ground to signal ground if you can avoid it. This is because some craps can be running in the ground. Generally, this is ~60Hz junk. Mr. Jan Meier's Circuit kills this.

It works quite well and goes highly recommended. Of course, this doesn't apply to battery operation. It is so not because batteries are better but you don't have a choice.

Tomo
 
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