MeloManiac Posted April 24, 2021 Share Posted April 24, 2021 41 minutes ago, Limberpine said: Welp, I turned off every circuit in the house except the one that the stereo system is on and the buzz still persists. What's weird is that my SET amp doesn't have the buzz, it has a dull hum up close, but all of my push pull amps have this same buzz. Video attached of the sound from 3ft away from the speaker. Headphones are helpful to hear it, because of taking the video from my phone. 20210423_194609_2.mp4 My Leben CS300 has a similar hum, though, I think, not as loud. I have learned to live with it, as it is caused by the 'topology' (the architecture, the way the components are laid out inside the amplifier.) This topology creates the 'magic' of the amp, but it is impossible to change, and it is also the reason why 'measuring' will not result in finding anomalies. Also, the more efficient the speakers are, the more you can hear the hum. Klipsch speakers are very efficient... The quote below is about the CS300 Leben, but I think your humming amp is having the same characteristics/topology. Here is my source and citation, I put the crucial phrases in bold lettertype. (...) I asked to check, why there is a slight mains hum audible (you can hear a 50Hz noise, and its multiplications 100Hz, 150Hz, especially in one channel). This was not the flaw of my unit – I heard something like that with all other CS-300 listened to. With normal use, with 89dB or less efficient loudspeakers, it was somewhere in the background, and did not interfere with music. The same thing was with headphones – AKG, which I used with all the Leben versions, have 62Ω impedance, quite low, so they did not pose any problems. But the HD800 are high impedance headphones - 600Ω – and they are not so forgiving, any error, any noise or hum can be heard immediately – just like with high efficiency loudspeakers. And with them, this hum was annoying. Mr. Waszczyszyn, like any scientist, systematically searched for the reason, and found out, that there is no choke in my unit, but only resistors, what increases noise slightly, and that the hum is a result of the chosen topology, with one channel closer to the power supply than the other. So it cannot be helped without reworking the whole amplifier. And I did not want to do that, because we could maybe improve on this one aspect, while destroying everything else, because architecture of elements is a part of the “magic” coming from years of experience. And I am sure Mr. Hyodo knew what he was doing. Well – this was probably a part of the compromise. There is nothing we can do with the loudspeaker output, but with the headphone output it is a different story. It was enough to solder a few resistors to the headphone socket, and that was it. Their values must be chosen experimentally, as it will depend on the impedance and efficiency of our headphones. At first the values were chosen too big, and needed to be adjusted, but now I can tell, that there is no hum at all! And no noise. This is the reason I recommend this simple trick to everyone – it is cheap and effective. Probably in the future I would like to see better resistors there, like Vishay, but for now, I am happy. source: http://highfidelity.pl/@main-135&lang=en 2 Quote Link to comment Share on other sites More sharing options...
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