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In Reply to: RE: What sized grid stopper should he try? posted by Tre' on January 30, 2017 at 19:32:09
This brings up an interesting parallel to the HFAC filament discussions. Elsewhere it has been insisted that we cannot hear the effects of HFAC since the frequency is well above what humans can here. If this logic is to hold true then surely we cannot hear an oscillation in the mHz range yet people claim the effects of an oscillating tube as a bright or harsh sound.
what gives?
dave
Follow Ups:
Oscillation usually happens with grid current...and I once saw a 12BY7 LTP go singing away at a few tens of MHz...and the sonics were not very good at all...:) Now if it is a semi-regular oscillation, triggered by some of the program, getting harsh is quite likely, though you're not hearing the oscillation, it is the other side effects that present...:)
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Good point Dave, I'm curious if HFAC heating has any IM artifacts in the audio band...
Often the problem with RFI in a circuit is when it gets rectified. When that happens any modulations become audible.
Preventing the RFI in the first place is the better move...
If high frequency (above our hearing range) is just steady HF that's one thing.
If a circuit is falling in and out (parasitic) of oscillation at a rate that we can hear that's a different thing.
Just a thought.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I've seen that so many times. This is one of the reasons it's so silly when people say engineering is unimportant.
--------------------------
Buy Chinese. Bury freedom.
IMO/IME, in DIY projects, it's best to assume parasitic oscillation will be present and appropriate prophylactic measures taken, before a single connection is soldered into place.
Darned tootin, engineering matters. 1st, get the Physics right! Then, you know the field you're "playing" on. If Newton, Einstein, Maxwell, et al, say you are smoking loco weed, move on.
Eli D.
used to smoke loco weed in Newton...or was that eat Newtons after smoaking loco weed?
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Eli D.
IM distortion products inside the audio band are (IMO) a likely candidate.
Remember, IM distortion, even in small amounts, is highly irritating.
Eli D.
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