6N6P Heater and earth wiring advice - diyAudio
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Old 24th July 2011, 09:05 PM   #1
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Join Date: Jun 2008
Default 6N6P Heater and earth wiring advice


Building my first buffer using two 6N6P's.
It works well, I like the sound but I have a hum issue.

I have been addressing the silly mistakes I made in relation to earth and grounds and now have screened cables for input etc and tight twisting of the 6.3 heater cables.
This has helped a lot and the hum is not audible till after 12 on the volume pot.

I'm still addressing the earth issue as we speak, creating a better star and making the wiring as neat and as far away as possible from any potentially noisy cables - if you know what I mean ( away from signal carrying cables ).

One of the heater windings is referenced to gnd ( at chassis - near the transformer ) but I also have a centre tap between the 6.3v rails unused. Should I be using this instead and would this reduce some hum in any way ?

Am I expecting too much ? - I'd like it silent to maximum volume setting if it's possible.
Of course I don't listen at ' stupid ' loud levels but for peace of mind I'd like no hum.

I'm learning - this is not my arena at all so apologies in advance

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Old 24th July 2011, 11:13 PM   #2
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Is my post really this boring ?
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Old 24th July 2011, 11:17 PM   #3
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nigelwright7557's Avatar
Join Date: Apr 2008
Location: Carlisle, England
You could try setting the centre tap to about 50 volts DC using two resistors.

You can also get hum depending on which unit is earthed.
Multiple earths will give you hum.
I always have a switched zero volts to earth connection on my amps.
Murton-Pike Systems PCBCAD51 pcb design software. http://www.murtonpikesystems.co.uk
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