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SET VT52 amplifier; 12-14mV hum noise is too high?

Posted by glc (A) on February 1, 2004 at 03:28:21

I have just ended to build and debug (thanks TriodeKingdon, Paul Joppa etc.) my new stereo E83CC+VT52 set amplifier.
I have solved a big mistake in the assembly of hum pots, and after a little mod to the new hum potentiometers (100ohm pot now with 100ohm Kiwame resistors from each pot end contact to wiper) I have the hum noise at each the Lundhal transformers 8 ohm output about 12-14 mV rms.
Take note that the filaments are 6,3V ac and I am using for the amplifier burn in tests Siemens ECC83 and Sovtek 6A3 (compatible with VT52).
I have tried some parts screening, to move wires etc. but I am unable to reduce hum noise below the actual 14mV.
I have read that somebody obtain less than 3-4mV noise on their amplifiers so I am afraid of my results.
Is my 14mV too bad? Take note that my speakers are 94dB/1watt Tannoy Edinburghs.
What do you think or want to suggest me?
Thanks
Gian Luca

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