Originally Posted by echopraxia
How do they protect the speakers when they start clipping? Do they smooth over or attenuate their waveform somehow to prevent blowing out the tweeters? If so, I definitely can see the appeal. I’m just not sure how that’s possible without introducing some delay, which maybe they do?
... The AHB2 has a THD monitoring circuit that shuts the amplifier down if you overdrive it beyond 1 % THD. THD+N is < 0.0003 % at full output, but if you drive it into clipping, you can reach 1 % and this will trigger the shutdown. The speed of this shutdown is also adjusted according to the severity of the overload. The result is that the tweeters are fully protected from an over-driven AHB2.
One of the most common failures in an amplifier output stage is a short to one of the power rails. This type of failure will take out a speaker. The AHB2 has a DC detection circuit that will shut down the entire amplifier including the power supplies. A failed AHB2 would not damage speakers.
Best of all, the AHB2 has proven to be absolutely bullet proof in the field.
The amplifier will shut down if repetitive peak currents exceed 29 Amps or if the RMS current exceeds 20.5 Amps for more than a few seconds.
The TEMP lights will flash when peak currents exceed 29 Amps. This is a warning that the protection will kick in if the condition persists. The CLIP lights will flash whenever the amplifier is driven into voltage clipping causing the THD to exceed about 0.5%. If the CLIP and TEMP lights flash together, it indicates that you have simultaneously reached the voltage and current limits of the AHB2. Each channel has its own set of lights and has its own protection monitoring. If protection is triggered, both channel will mute. To protect your tweeters, the distortion monitoring will not allow sustained operation if the amplifier is driven into voltage clipping resulting in a sustained THD exceeding 1%.
The feed-forward correction keeps the AHB2 distortion free when driving very low impedances and difficult phase angles. The protection system in the AHB2 monitors output current, output voltage, distortion, temperature and other critical parameters. The AHB2 can cleanly drive a 1.4-Ohm resistive load to full output voltage on both channels for several seconds without triggering the protection circuits. This is much longer than any musical peaks. Load impedances below 1.4 Ohm (stereo mode) or 2.8 Ohms (mono mode) may flash the TEMP lights indicating that peak currents exceed 29 Amps. If the overload condition is severe enough, and persists for a long enough time, the over-current protection may trip. The amplifier remains distortion free until the protection system shuts it down.
There is no limiting or soft-clipping. I have tested driving the Salon2s full range and I can illuminate the clip indicators but not the temp indicators.
The amps were voltage clipping and not current clipping.
Current limiting causes voltage sag and reduced output.
For some reason, non-linear behavior is not considered "distortion" but, I would argue, that it is.
Most of the discussion around these amps circles around SOTA low noise and distortion but I wonder regulated power supply is part of what makes them great.
There seem to be quite few Salon2 owners have these amps. They are small, light, and are not something most will put on an amp stand, though I found cute ones on Amazon.
I have some great dealers but they don't carry these amps. The margins are not there.
EDIT: There is no delay, all protection and monitoring is performed by an FPGA.