Anyone using a Class D amp w/ribbon tweeters?
dsycks15 posts08-25-2018 9:18amI ran BelCanto with Magnapan 1.6s for years.Yes, I can imagine it was, as in my first post about the Raven ribbon tweeter with the Belcanto M600’s, Maggies are also similar "usually" a nice smooth benign mainly resistive 4ohm load. Cheers George |
and I hear no top end sibilanceWhat I’ve heard is either two things in the upper/mid highs from Class-D, either sibilance as mapman mentions or an opaque whiteness. This to me comes from "high power the low order switching noise output filters" either "set too high" which lets through too much of the switching noise (sibilant) and some audio band phase shifts, or "set too low" which hacks out most of the switching noise but also hacks into the audio frequencies upper mids ,highs (opaqueness) and creates not only attenuation but even larger phase shifts than the "too high" filter does. The only way to fix this to me is to raise the switching frequencies much higher so the "high power low order output filter" can do it’s job properly without any effects down into the audio band. As Technics have started to do with the flagship SE-R1 with more twice the switching frequency of today, but at $30k aud and limited supply. BTW you can see this switching frequency noise on Class-D amps in Stereophile bench tests that sits on the 10khz square waves, like a buzz saw across the top of the square wave. https://www.stereo.net.au/forums/uploads/monthly_2016_12/583f6e91157f6_Class-Dsquarewaveringing..jpg... But last year or so Stereophile have introduced a special filter (Audio Precision’s AUX-0025 passive low-pass filter) that goes between the the Class-D amp and the test measuring equipment that gets rid of the buzz saw, just for Class-D tests purposes, they always say they use it somewhere slightly hidden in the bench test reports. ( Belcanto with AUX-0025 filter applied https://cdn.head-fi.org/a/1862061_thumb.jpg) Still to me a disgusting looking 10khz square wave, but better than the buzz saw with the special filter. This is what a proper Linear Class-A/B amp square wave looks like. https://cdn.head-fi.org/a/1862052.jpg Cheers George |
jackd135 posts08-24-2018 3:39pmGeorge Still the same switching frequency at around 600khz, to me it’s too low for the low order output filters filters to get rid of it all without having bad phase shifts (artifacts) down low into the audio band. That why in older tests you still see switching noise across the top of 10khz square waves. https://www.stereophile.com/images/1212AM1fig02.jpg ) (Unless lately, last year or so Stereophile have been filtering it out in testing, with "Audio Precision’s auxiliary AUX-0025 passive low-pass filter". a high order "but very low power handling filter" between the tested amp and the Oscilloscope picture https://www.stereophile.com/images/418BC600fig03.jpg just so you don’t see the switching noise on the 10khz square wave, which I believe is not the right thing to do, as that filter is not there when you listen because it can’t handle any power at all. Technics SE-R1 switching frequency is around 1.5mhz, better, because it’s phase effects are not into the audio band so much, but 2-3mhz would be best. Cheers George |
but particularly in improving the high end sibilance and listener . Apparently we are in the 3rd generation now (?) Yeah we’re getting close to me selling my hot, energy sucking, boat anchors. When future technology allows the switching frequency of Class-D to be taken from 600-800-khz to around 2-3mhz so the output filters can do their jobs properly. This is day the day my boat anchors will become obsolete. Technics with their $20k usd SE-R1 is on the right path with a switching frequency of 1.5mhz using the new limited gallium-nitride (GaN) semi conductors, who’s designers were the same guys who invented the Power Mosfet Here’s what one reviewer said about the SE-R1 " Listening to tracks that we’ve heard 100s of times — and on excellent systems at that — is now a revelation of once hidden nuance and detail. Not only are we hearing things we’d never heard before, we’re hearing it in a way we’ve never heard it before. A music system that sounds like a live performance is a tough goal to attain, but Technics’ flagship nails it." I don't know if this is real or a hoax, but there was one actually for sale on Audiogon https://www.audiogon.com/listings/lis8hiab-technics-se-r1-power-amplifier-solid-state Cheers George |
I’m not a big fan of Class-D yet, but the best one I heard was the Belcanto M600 monoblocks, and this was driving a two way speaker that had Ravens best ribbon tweeter, and it was I believe because the Raven tweeter was a very benign 8ohm constant load, compared to when I heard that same amp with normal dynamic drivers. Cheers George |
