To Float or not to Float...

Jim -
I have always used the preamp in the "float" position, whether it was with a solid state or tube (including the DeHavilland mono blocks) amp.  My impression was that sonically this was the preferred position, and as I mentioned the manual for the mono blocks even states a potential sonic improvement keeping the switches in the "float" position as long as there are no accompanying noises or buzzes (I can't seem to find the preamp manual to check, however it was planted in my head from somewhere (probably the manual) to keep that switch at "float").  Only recently did the buzzing begin which corresponded with some connectivity problems related to the preamp's power cord.  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". 

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

Posted by Charles Hansen (M) on August 26, 2008 at 21:40:33

In Reply to: RE: If you’re referring to the ’double insulated’ designation that allows manufacturers of small posted by jea48 on August 25, 2008 at 11:36:39:

< < 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.

Posted by Charles Hansen (M) on August 27, 2008 at 22:50:26

In Reply to: Thanks Charles for your response, but you left us, me, hanging. posted by jea48 on August 27, 2008 at 16:58:04:

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

Jim - My only front end source is a Resolution Audio Opus 21 cd player which uses a three prong power cord which presumably grounds it.  The cd player and preamp are both plugged into a power strip which I was told is recommended for use with Naim equipment and also utilizes a three prong cord and receptacles.  I initially thought the buzzing was caused by the interconnects between the pre and power amp, however swapping them out for different interconnects did not alleviate the problem.  I was have issues with the IEC female connector on the power cord making consistent contact, and, as I reported, changing that has seemingly solved the problem.  As to why the buzzing stopped when I switched to "ground" position, the technical answer is above my pay grade and I will let those of you with greater expertise ponder that...

I have so many things plugged into my system I'm amazed at how utterly quiet it is. There are bespoke DC buzz killing power supplies on the DAC and phono preamp, a PS Audio Humbuster III for the tube and SS amps, no ground pin was provided for the main preamp (Kavent S-33 dual mono masterpiece) weirdly, but doesn't seem to matter, and I did have to lift the ground via a small switch on a REL Q150e due to a small hum issue. Otherwise, although my SEP main power amp is working fairly hard in its Class A massive 12 watts (or something) per side, it is also dead quiet…blacker blacks, redder reds, more opaque opaqueness, you know what I mean.

Never lift grounds on power amplifiers. you don't want that to go live with the currents that can easily kill you. If however your house is correctly earthed the breaker should go before there is any damage done to the equipment or more importantly you. Unless as said above manufacturer has a ground lift capacity on the board " no "always leave grund in place. if you have a ground loop "buzzing" noise lift the earth on the pre amp as interconnects can more than likely handle that current going back to earth. But as said check connections are tight and that balanced connectors are wired the right way in phase etc. Pull the power amplifier as far away from the sensitive circuits in the preamplifier as some are oversensitive and away from central heating circuits , strip lighting. There are many noise sources that cause these issues. Often here is no need to jump to lifting mains earth on audio gear.