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In Reply to: RE: Audio Note Kit One =) Update!, the nightmare is over... posted by Acoustic-Dimension on May 18, 2015 at 00:55:03:
Hello Peter,
thanks so much for your words and I hope you had a very nice time on München, a very nice city, by the way.
Yes, you pointed exactly where the problem was! and Tre helped me to realize that I did not have the correct mains voltage, so now my amp is running at a very precise standard.
After doing almost a week of tests with different kind of music at different volume, with different preamp tubes, the noise in the output transformers still is there when I play very low frequencies at high volume...so I am returning to chapter 1, before I accidentally have caused the short circuit, while I was routing the wires on the filament board to eliminate a little hum, when I have installed a pair of rubber stripes down the output transformers to eliminate the vibration noise....then happens the well known history: the short circuit had damaged the regulators so I have replaced it but left them too tight, so one isolation washer was a bit damaged provoking a contact from the regulator to the chassis. Mine is not the regular filament pcb board, it is the hardwire version, so one have to be very careful to leave the regulators in perfect coincident length to the perforations on the heat sink in order to not stress the isolator washer...
One thing caught my attention; when this noise happens, there is a variation on the filament glow, the more the music is high volume/low fq, the more intense is the glow. I was noted this when the problem appears some years ago and now I can confirm as part of the analysis. Varies exactly in the same "rhythm" than the music intensity. The noise is like there something inside the tx that is hitting the tx shrouds. tiny hits on a rhythmic basis, directly related with the "over saturation" on the music.
Since a long time, I am doing a lot of research on the web and the more difficult task was to get the appropriate name to this phenomenon to search the appropriate posible solution. Buzzing, motorboating, oscillation, to name a few, but still I don't find the exact match and how to cure it. I believe that the rubber straps I put under the txs help in a small degree, by the way.
Since I don't know if the variation on the intensity of the filament glowing is normal when the music tends to sound full and complex at high volume, I can't discard that maybe the problem is some kind of gas leaking inside the output tubes or a mechanical problem inside them that is transported to the output transformers, etc.
One explaination I received earlier was "this is that there is some airgaps on lamination and the electromagentic flux generated by the current flow, activate this with vibrations"...but I'm sure that this was not there the 7 years before, so in some point this begins to happen.
At least I can hear music and sounds a little better than before and this noise is only happens with very low frequencies. Those frequencies are not present on orchestral, acoustic instruments music, traditional jazz, rock, blues, folk, etc, but there are some electroacoustic music, noise music, experimental music, etc that can have a huge degree if very low fq.
Any clue will be gratefully received.
The best for you,
Alberto
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- RE: Audio Note Kit One =) Update!, the nightmare is over...but chapter 1 again - beto1 08:35:32 05/18/15 (0)
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