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AlexBerger wrote:

Hello Romy, I just have build the postage used your "End of Live"  scheme and Altec step-up transformers. http://picasaweb.google.com/alex.berger73/Phonostage# I have original EAR. After of 100 hours of working, the new Phonostage  sounds more dynamic, transparent with much better separation. One problem is 100Hz hum. I did hitter supply filter with too weak ripple filtration: C-L-C (13200uF-3mH-6600uF). Now I going to rebuild  hitter supply. Is any difference in sound of semiconductor stabilization filtration, C-L-C-L-C or L-C-L-C filtration.

Alexander, are you sure that it is 100Hz hum but not 120Hz hum? Even I do not like and tend do not use CLC supply for filaments but your hum most likely is NOT due you your PS. The 13200uF-3mH-6600uF is enough to drive the ripples low and kill the hum.

It is VERY difficult to debug any devise “over the phone” in search of hum. Hum is most likely some kind of ground loop and you need to find it yourself. Pay extra attention to the wiring diagram of the old Altec step-up transformers. I have some of them (Altec and EV) and they are in my view need to use extra shielding and they are very difficult to make them to be quit.

What you need to do for sake of simplicity is take a wire of 2 feet long and begin to short different sections of your new pnonocorrector grounds. Soon on later you will find the location that after they were shorted minimize the hum. This will give you an answer where the hum comes from. I would do it separately for the pnonocorrector and then what I find the absolutely silent configuration, only then I would put the transformer to the game.

Also, considering the proximity of the air caps to the filaments I would VERY strongly advise to use twisted pair for filaments. The twisted pair is very singly but it is VERY effective as it is self-shielding. You can detect if the hum come from air caps by disconnecting them. Also use the “disconnecting trick” to see if the problem comes from the filaments. When you turn off the corrector off then it will be still a second or two operational. You will be able to hear how the hum will change in the moment of disconnection. Remember, what you disconnect the B+ still there and the tube is still hot but there is no filament voltage…

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