Class-D amps - a different re view

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.

Ar-t
I agree absolutely. Synergy is probably one of the most important things.

I respect people who can honestly say "I don't like it" even if it costs $500k, but I don't care much for blindsided people who try to present pseudo-sientific reasoning.

Being subscriber to Stereophile for many years I have a lot of respect for technical knowledge and integity of people there. They present detailed measurements but put more stress on impression with different co-equipment and different music pieces. Technical aspect is always interesting but is secondary to sonics.

Simontju

Amp is close to 95% efficient and does not have to be large to do so.

"thermal dynamic variations are present in performance" - thermal dynamic variations of what? This is still jibrish to me.

Let me place here results of test made by somebody to 1kW icepower and 100W Icepower (same as mine). Notice that he tests 1kW amp with no hestsinks at all. If you take into consideration that average power in music i very low (only few percent) statements about "Thermal dynamic variations" are complete nonsense. Read below:

"Originally posted by dmfraser
I operated a sample 1000ASP on the bench delivering 350W average of pink noise into a 4 ohm load for over one hour with no additional heatsink and the metal case stayed below 55°C.

However, higher levels would make the power supply voltage go down to act as a thermal compensation. Much nicer than just shutting down.

However, with 1214W of sine wave, partly into clipping, after about 35 seconds, the output level would drop to about 600W by the protection circuitry. Remember this is with no additional heatsink.

The 200ASC, I was able to operate with sine wave at 100W into 4 ohms continuously. Turning it up, with sine wave, the module would shut down at about 214W.

However, with pink noise at 100Waverage and a 6 db crest factor, the 200ASC would run all day without shut down, until I was tired of tying up one of my Audio Precisions with it. It would also run all day with music, driven hard where the output limiter was set to a peak limit of 210W maximum. That is, the limiter would allow small amounts of clipping. Driven so the limit light in our external optical limiter was on essentially continuously.

We're quite satisfied and will be ordering production quantities of the 200ASC shortly."