Audio Note Kits Forum

RE: Kit1 HT voltage issue

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This Post Has Been Edited by the Author

In Reply to: RE: Kit1 HT voltage issue posted by Felice on July 13, 2010 at 02:19:08

After one year (yes, I didn't have much time to spend on Kit1 fixing) I can report results of my quest: having the Kit1 correctly, silently and reliably running with 2A3 tubes.

here how I fixed the issues:

1) mains voltage too high for 2A3 operation: I just added 2 resistors between mains transformer and rectifier tube so to have 60mA flowing into the 2A3 tubes, regardless to Anode voltage (just be sure is now exceeding max admitted value). I used 2x150R10W.
(Adding resistors after the rectifier had lead to higher temperatures in mains transformer, 5U4G shaking and electrical hum)

2) Filament residual hum - I had to add a third capacitor into filament supply board, this to have a slight increase of mean current and let the regulator be capable of providing a better SNR on output; so residual AC got from 10mA to 0,5mA and the Kit 1 become absolutely silent. Be aware that this change rises the current in filament rectifier... make your calculations based on AC frequency in your country.

3) bass howl added to bass frequencies during music reproduction - I didn't find anything better than lifting the groud, I do not recommend this solution as without earth connection you could be electrocuted by touching the kit (or better said: powered by the mains transformer!!!)

so I finally had a fixed 2A3 Kit1, and I am sure you are curious to read how does it sound against 300B version.... using a pair of 2A3 EH Gold:

- sweet and veiled midrange, strong tight and deep bass, focus on highs but not unbalanced, instrument tone closer to reality.
- soundscape confined between speakers and close to them in depth
- volume have to be set higher to have realistic dynamics but you can hear much more contrast in music.

I would say:
Kit 1 2A3 is the choice if you mainly listen to Opera, vocals and baroque
Kit 1 300B is the choice if you mainly listen to Symphonic, Jazz, Piano

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