Class-D amps - a different re view

Hello Kijanki.
Excellent review of the review. I would point out only that

"Have thermal dissipation limitations due to the small power module size which means that thermal dynamic variations are present in the performance with time"

has a lot of sense and if designers did not so proper and extensive thermodynamic analyses then this is exactly what is occuring...with time.

Don't measure tmeperature outside the amp - measure it inside the small power module size and at not in one point... Nobody cheated physics yet

Simon

Hello Art_t,

"To be perfectly honest, I have heard listeners say that our (switching) amps sound "very tube-like".

... and it is because in all probability they do. Most published measurments of switching amplifiers distortion patterns are very similar to....that of the tubes. Strong 2nd harmonics and strong even harmonics.

I personally love to read in Stereophile comments of reviewers on most of class D amps they review: "tube-like", warm, musical etc...and then glance to John Atkinson measurments with huuuuge 2nd harmonic distortion etc

I love expression "life-like" be it tubes, snakes or whatever...

All The best
Simon

Muralman1

ICE modules do not sample - they have analog sinewave oscillator/modulator converting input voltage to duty cycle and drive output switches (Mosfets). They resemble now more of sigma-delta modulator.
Hypex is also analog and probably most of the others.
(Hypex has half bridge output and sounds more like very good Class AB amp versus ICEPower with Full Bridge sounding more like very good tube amp)

Sampling is not even possible since to preserve 16bit resolution at for instance 1kHz - carrier frequency would have to be 65536*1kHz=65MHz. Just imagine bandwidth of my Rowland would require 65kHz*65536=4300MHz carrier. I wish it could be possible since one could take SPIDIF and run to PWM using just some DSP manipulations.

I heard claims of small amount of carrier residue causing intermodulation with audioband on the tweeter - which is only possible if tweeter can move membrane at this (0.5MHz)frequency.

Oversampling itself was created to allow filtering of the carrier with gentle filters with even group delays (Bessell) preventing wrong summing of harmonics in passband. My Benchmark DAC1 uses statistical manipulation to achieve equivalent of 1milion times oversampling and 24-bit resolution to drive output DAC at only 100kHz (audio DACs have lowest THD at around 100kHz).

Stereophile reviewed CODA S5 class A amplifier and compared findings to older Class D Bel Canto Evo amplifier. CODA was little bit better. In letter to Stereophile president od CODA expressed happiness that his amp came favorable in comparison with as he said "such great amplifier as Bel Canto Evo". There is no more honest praise of the product than one made by competition.

Interestingly Coda had more hiss at the tweeter than Bel Canto.

I chose Rowland since I heard That Jeff Rowland is classy guy and did not released bad or mediocre product in 20 years. He switched now his production to 100% Class D (Icepower). Rowland 102 is built nicer than Bel Canto and was cheaper at the time. I have heard a lot of very positive things about H2O.

Atmasphere

Peak current I mentioned is the current limit of the amplifier output to speaker. 20A means that my amp can put that much current on the speaker. Nothing unusual - many amps have similar spects. It is rated 100W at 8 Ohm and 200W at 4 OHm - both with 0.2% THD 10Hz-20kHz. As for impedance - amp can drive 3 Ohms min (larger ICE drives under 2 OHms).

Branimi

I'm not from Italy either - cannot understand a word.

My Icepower (200ASC) has DF=30 at 10kHz (nothing unusual about it). At 1khz DF=1000 and climbs to 4000 at 10Hz.