weebeesdad said: 09-16-2017 7:54pm
Now that I have switched to a different power cord, there is no more buzzing or noise, and all grounding switches are set at "float".
I would say that rules out an interconnect/s causing the buzzing problem.
Audio system sounds fine now, no buzzing, same interconnects.
Through experimenting, listening, you found the power cord you were using on the preamp was causing the buzzing sound you were hearing.
Exactly why is still the unknown, imo.
What puzzled me you said, in an earlier post, when you closed the ground lift switch the buzzing would stop. If the integrity of the continuity of the equipment ground wire connection, of the power cord, was compromised somewhere from the male plug >>> through the IEC connector, >>> through the ground contact of the preamp IEC inlet connector, closing the ground lift switch would not make any difference. But you found closing the float ground switch did.....
What exactly could be the cause of the buzz? At one point I considered poor contact pressure between the hot and or neutral current carrying conductors between the IEC female connector, on the end of the power cord, and the male inlet connector on the back of the preamp. Even a slight arcing would induce RF noise into the preamp, imo. Sounds plausible to me.....
But why closing the ground lift switch would stop the buzzing sound?
When closed it connects the preamp’s audio circuitry, signal ground circuit, back to the chassis of the preamp.
This is where John Curl would say, this is where the test equipment is brought on board to measure and found out the why.
Something to throw into mix of thought for the why. Here is a response from Charles Hansen to a post of mine.
Close
< < The AC power wiring is double insulated. The case is floating.... > >
Actually the case is connected to the signal ground of the internal circuitry.
I think the main reason that most manufacturers use 3 wire power cords with a safety ground is ignorance. It’s the easiest way to ensure safety, and it’s also the method most commonly espoused in textbooks.
Kind of like FETs versus bipolar transistors. All the textbooks focus on bipolars. Not much is generally known about FETs. So designers follow the path of least resistance. It’s too much work to dig up all the stuff to learn about some other technology like FETs or double insulation.
And then his response to another post of mine.
RE: Thanks Charles for your response, but you left us, me, hanging.
The only way that the case can provide any shielding for the audio circuitry is if it is connected to the signal ground. In addition, if it is left unconnected from the signal ground, then it will create unwanted capacitive feedback loops (both positive and negative) between various parts of the circuitry. Refer to Morrison’s books for additional details.
https://db.audioasylum.com/mhtml/m.html?forum=general&n=525553&highlight=double+insulated+po...Now keep in mind the responses from Mr. Hansen are in response to my posts for audio equipment that have double insulated AC power wiring where the power cord is 2 wire with a 2 prong plug. AC mains equipment ground is not used.
So how does the above relate to your situation? Not really sure.
But what if the AC mains equipment ground is broken, open, somewhere in the bad power cord. No continuity, or sometimes intermittent continuity. With the ground lift set to float wouldn’t the chassis be acting exactly as Mr. Hansen said in his post?
All just conjuncture on my part.....
Al, (almarg),
If you are reading this post of mine what are your thoughts on the "why the buzz"
~ ~ ~ ~ ~
@weebeesdad,
Question.
What are you using for front end sources connected to the preamp? Do they use the AC mains safety equipment ground? There in, a 3 wire grounding type power cord and plug where the equipment grounding conductor, wire, in the power cord is connected to the chassis of the front end source/s ?
Jim
