andy_c;693179 Wrote: > I think he's referring to a Cyril Bateman article in which Bateman > measured the THD of an electrolytic cap at about 22x that of a > low-distortion film cap. I have the Bateman articles, which he used to > provide for free at his web site, but that web site is gone now - it > was on geocities. I've provided an alternate link 'here' > (www.diy-audio-engineering.org/web_dl/papers/cap_dist.zip). > > The thing is, this distortion was measured with 1VRMS across the cap. > But this is a coupling application, and if the cap is chosen to be > large enough, the AC voltage across it is negligible. That's why the > Douglas Self excerpt I posted shows the distortion approaching zero as > the cap value is increased. > > Bateman did find that, for polar electrolytic caps, a reduction of > distortion could be had by DC biasing. But that technique is wasteful. > The absolute level of the second harmonic distortion component is > proportional to the square of the amplitude of the AC voltage across > the cap, while the absolute value of the third harmonic is proportional > to the amplitude cubed of the AC voltage component across the cap. So > decreasing that amplitude gives great benefits. I've attached a plot of > that relationship from Bateman's articles. That's the relationship that > Self is taking advantage of by limiting the AC voltage component across > the cap to tens of mV. > > Bateman also found that non-polar electrolytics had lower distortion > than polar ones, so they are a good choice.
Cool I'm not that kind of engineer so I can't really have a well grounded opinion on circuit specifics just thought the number was a bit out of context now you provided some more context great :) now I understand more. Any engineered opinion on how it applies to Touchs output stage , but you may need schematics to have an opinion on that ? -- Mnyb -------------------------------------------------------------------- Main hifi: Touch + CIA PS +MeridianG68J MeridianHD621 MeridianG98DH 2 x MeridianDSP5200 MeridianDSP5200HC 2 xMeridianDSP3100 +Rel Stadium 3 sub. Bedroom/Office: Boom Kitchen: Touch + powered Fostex PM0.4 Misc use: Radio (with battery) iPad 64gB wifi +3g with iPengHD & SqueezePad (in storage SB3, reciever ,controller ) ------------------------------------------------------------------------ Mnyb's Profile: http://forums.slimdevices.com/member.php?userid=4143 View this thread: http://forums.slimdevices.com/showthread.php?t=93875 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
