2. amps-preamps
  3. 131368-5044

To Float or not to Float...

I have a DeHavilland preamp which has a switch allowing one to "float" the ground.  I've always used it in the "float" position, however recently, perhaps due to some connectivity issues with my interconnects, there is a small buzz emanating from my speakers with the switch in this position.  The buzz disappears when I flip the preamp switch to the "ground" position.  Irrespective of the buzzing, is there any sonic advantage (or disadvantage) to "floating" the preamp ground in this situation??
Thanks for your informed opinions...

weebeesdad
georgehifi's avatar
georgehifi
10,312 posts
 
"Be sure your system installation is finished before you try moving the Ground Lift switch from its “Normal” to its “Lift” position."
This statement proves my point, that then the amp circuit will get it’s system ground reference from the next stage via the interconnects shield, and if the shield were disconnected it could have large amount of noise and maybe even damage the amp.

Cheers George
helomech
1,491 posts
 
The most quiet amps I've used "float" the ground.  
jea48
4,265 posts
 
weebeesdad OP
54 posts                                                                            09-12-2017 12:48pm

Thanks for all of your responses. Cleeds triggered the solution when he (or she) wrote "a properly grounded power cord", which reminded me that I was having intermittent problems with the connecting plug of the preamp’s power cord. Swapped out the power cord and problem solved. I also have a pair of DeHavilland mono block amps with the same ground/float switches, and in the manual it states that leaving the switch in the "float" position may result in a "cleaner sound". At any rate, a fully functioning grounded power cord has done the trick...
@weebeesdad,

I checked and was told the ground lift switch lifts the signal circuit from the chassis/AC mains safety equipment ground.
The AC mains safety equipment ground is always connected to the chassis of deHavilland audio equipment for electrical safety.
It is recommended the user "float" both deHavilland mono blocks and close the ground lift switch on the preamp.

The chassis of the power amps will still be grounded, connected, to the AC mains power outlet safety equipment ground.

Jim

weebeesdad OP
138 posts
 
Thanks, Jim.  I also use the preamp with a solid state amp that has no ground lifting switch, and keep the preamp switch in the "float" position.  Any danger in that?? 


jea48
4,265 posts
 
@weebeesdad ,

No danger at all. The switch only lifts the audio circuit from the chassis ground.
(The AC mains safety equipment ground)

The AC mains safety equipment ground remains connected to the chassis at all times. In the event of a Hot to chassis ground fault event the safety equipment ground wire in the power cord connected to the preamp will carry the fault current to the wall receptacle equipment ground contact.

Are you using the preamp with the SS amp at the present time with the switch on the preamp in the float position?
I also use the preamp with a solid state amp that has no ground lifting switch, and keep the preamp switch in the "float" position.

Jim

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