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Initial burn-in....

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Posted on February 10, 2016 at 03:24:48
6AS7_6SN7






To me it is amazing the agreement of LT Spice nominal bias prediction vs. actual measurements (i.e. I have found less than about 5% discrepancies w.r.t. sim world).

For burn in I am just using my cell phone (and no feedback, as I planned 6 dB of GNFB but, right now, I do not feel compelled to try).

There in no hum at all and even by switching on and off neon lamps in the room there is any click coming from the speakers.

This is my first time that I do not use any pot for bias adjustment: the fixed bias comes directly from the filtered dual output of the auxiliary small toroid and series PP topology of the output stage does the rest.

 

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RE: Initial burn-in...., posted on February 10, 2016 at 03:27:37
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 So it is a stereo amp? interesting layout of the tubes.

 

RE: Initial burn-in...., posted on February 10, 2016 at 04:04:39
91derlust
Audiophile

Posts: 1101
Joined: December 25, 2014
 Lookin' good - I like the wood. No doubt you have the ventilation sorted.

Tube layout to support efficient star-grounding?

Cheers,
91.


"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

 

RE: Initial burn-in...., posted on February 10, 2016 at 05:48:23
6AS7_6SN7



As there is no metal chassis there is no need for a safety connection to 'ground'.
I prefer to leave the 0V internal terminal floating (as it is insulated from both ground and live AC terminals by the toroids 'double 3KV insulation', as in a standard CD player).
In the case, the 0V terminal could be internally connected to the AC socket 'ground', but this usually leads to a somewhat impaired hum & EMI performance.

You may see in the picture that there is a sort of 'circular ring of wire' that constitutes the 0V internal terminal and it is connected to the input common terminal at the back of the rear panel.


 

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