Again fellas, I'm using a 2 prong wall wart and am not using safety ground in this instance. My circuit works fine with no connection of chassis to ground but when I connect chassis to ground a bit downstream from my PSU ground (where it's shown in diagram) noise floor drops by a few dB. What explains this? Is it coupling RF noise into the circuit and the op amp is rejecting it in it's CMRR?
It blows my mind that I cannot find any noise measurement data from actual experimentation on these different wiring schemes from forum members here. These debates on ground routing seem to pop up incessantly. Will no one step up and post actual data to put this issue to rest?
I agree with you, but I do not see a contradiction with what I said.
Can we summarize by saying that there are three different areas where one can work again the disturbance of the signal by parasitics : their sources, their propagation, and the susceptibility of the signal path to convert them into voltage ?
Inductance is an impedance. I am all in favour to reduce impedance in the ground path as much as possible.
Differences of potential between separate points can never be stricly null. But it is a realistic aim to make them negligible.
Without considerations from the greater simplicity of wiring when designing with the concept of equipotentiality in mind, we are looking for the best performances.
I can't claim there is a clear winner between way #1 and way #2 of the first post. Shredhead arrived to an unexpected result in favour of way #2. It puzzled some members because it is not currently the usual method to mount RCA sockets. It needs of course confirmation by many more measures. I encourage people to make their own experiences on sockets ground connection, it's an aspect of design which has been a bit neglected, I think.
100% agree. I will conduct this test again in more detail in about a week and post results in this thread. I urge everyone on this forum with measurement capabilities to do the same so that discussions like this can be resolved with cold hard data.
Ground path inductance is rarely an issue for audio. Controlling the current loops is far far more important.forr said:
If you are comparing 'floating chassis' with 'grounded chassis' then it is obvious that 'grounded chassis' will give less noise and interference. A floating chassis picks up any stray electric fields and passes them on to the circuit; a grounded chassis does not, at least not to the same extent.shredhead said:
I thought we were comparing 'audio grounded one way' versus 'audio grounded in a different way' all within a grounded chassis.
Current loops are annoying when they introduce voltage in the signal path.
A very instructing test is to deliberately introduce various ground loops in amps or preamps installed in their chassis.
Hello,
Interesting test.
I have to say that I use this method for at least 10 years without any problem.
All RCA input and output are connected directly to the chassis as well for amplifiers as for RIAA preamp.
All my circuits are double sided with a ground plane on top, strongly connected to the chassis with at least 4 brass spacers.
Speakers ground connections are also made directly to the chassis, and until now, I don't ear any hum, even if power is on.
Regards, Hervé.
Interesting test.
I have to say that I use this method for at least 10 years without any problem.
All RCA input and output are connected directly to the chassis as well for amplifiers as for RIAA preamp.
All my circuits are double sided with a ground plane on top, strongly connected to the chassis with at least 4 brass spacers.
Speakers ground connections are also made directly to the chassis, and until now, I don't ear any hum, even if power is on.
Regards, Hervé.
if indeed you are not getting any hum, then it's because you have very small loop areas.
One could for example ground al, the RCA input sockets.
Ground the output sockets
Make the central ground return (I.e star ground) in the middle between the input and output sockets.
The main thing, it to keep the loop areas small, and keep magnetic fields out of the way.
I agree that for analog audio, trace inductance is a secondary issue.
One could for example ground al, the RCA input sockets.
Ground the output sockets
Make the central ground return (I.e star ground) in the middle between the input and output sockets.
The main thing, it to keep the loop areas small, and keep magnetic fields out of the way.
I agree that for analog audio, trace inductance is a secondary issue.
That is why current loops need to be kept under control. That means designing the grounding, rather than following a recipe.forr said:
The "recipe" you think of is neither absolute nor definitive.
It just happened that, in my case, it has been preceded some thinking which led to a wiring method which turned out to be plainly satisfactory until today.
It just happened that, in my case, it has been preceded some thinking which led to a wiring method which turned out to be plainly satisfactory until today.
I think everybody agree on the fact that loop areas, formed by signal path, return path, have to be as small as possible. It is not specific to RCA ground connected to chassis method.
If you mean the points where the supply ground is connected, it is not the case.
Reservoir capacitors are connected to the chassis on 2 points. Chassis IS the star ground.
I know.
What do you think of bad ideas which works at least as well as excellent ideas ?
Each capacitor has its own rectifier bridge, there is no current coming from one connection to the other.
The dual rectifier fed from dual secondaries MUST connect to create the dual polarity supply. That connection is usually made just after the last capacitors in the smoothing capacitor bank.
Hello everyone!
I'm not a guru on the subject but I think the masses connect to the chassis is a bad idea and can not Take affected as hum problems. The chassis should only be connected to earth and thus make Faraday cage office.
I have always done so and never on the preamplifier, amplifier or corrective riaa the slightest background noise is appeared.
It is only my opinion! 😀
I'm not a guru on the subject but I think the masses connect to the chassis is a bad idea and can not Take affected as hum problems. The chassis should only be connected to earth and thus make Faraday cage office.
I have always done so and never on the preamplifier, amplifier or corrective riaa the slightest background noise is appeared.
It is only my opinion! 😀
You told me to "Design and build your circuit so that it works correctly as an audio circuit with no connection to the chassis." I was just telling you what happened when I connected it to the chassis.
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