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Bottlehead Forum Welcome! Need support, you got it. Or share you ideas and experiences. |
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Bottlehead Forum Welcome! Need support, you got it. Or share you ideas and experiences. |
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In Reply to: Hum and Sonics posted by Garland on September 23, 2005 at 10:09:50:
Yep. A recurring comment I picked up on from other people is how DC
filaments sound "dry", "washed out", "lifeless". Then a number of people figured out that if you use common mode chokes on DC filaments, the life comes back. Of course, whats happening is the CMC is killing all the rectification hash that is causing IM. Also, the CMC keeps the electrolytics on the DC side of the supply from interacting with the audio signal. Best thing is to not need DC filaments in the first place! This lets the filament suck electrons from the wall with no reactive components in the way of the signal.I'd take hum (60hz fundamental) over buzz ANY DAY. Buzz is nasty
because it has a whole series of harmonics of 120Hz. I think the
harmonics go like this: 90% 120Hz, 60% 240Hz, 5% 480Hz 3% 960 Hz
etc.All of that stuff in the midrange intermodulates with signal components producing a whole combination of intermodulation components. Christ, it reminds me of NMR and spin-spin coupling!
I was thinking it might be a FUN experiment to try to reproduce
some of these effects. One way to do this would be to take my signal generator and hook it into the grid of the power tube. Then, you could inject controlled amounts of crud ontop of signal. For instance, you could inject some ultrasonic square waves into the signal and then listen - A/B style - turning on and off the signal generator at will. That would be a FUN and EASY experiment. Another
option would be to insert some 60Hz sine and see if you can hear the effects of IM as you bounce the level up.I think these experiments might be more interesting than swapping one boutique capacitor for another, or worse yet, rolling used NOS tubes in and out of the same circuit.
Maybe later tonite I'll try dropping in 40MHz onto the grid of the
811A and see what happens. :)-- Jim
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Follow Ups
- Impedances, Intermodulation - Jim Doyle 09/23/0517:50:00 09/23/05 (0)
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