Audio Excellence

Audio Excellence backing Bafana Bafana!

We have been told by many audiophiles that they dislike Class D amplifiers because they are digital and have a sterile sound compared to the warm quality of a class AB amplifier. Class D doesn’t mean digital, it simply refers to the next letter in the amplifier classification sequence after Class C.

Here’s difference:

* Class AB amplifiers use output transistors that operate in their linear region. The transistors act like variable valves, continuously adjusting the amount of current flowing to reproduce the audio waveform. This produces excellent sound quality, but the unused energy is dissipated as heat, making Class AB amplifiers relatively inefficient (typically around 50–70% efficient).
* Class D amplifiers work differently. Their output transistors operate almost exclusively as switches, turning fully on and fully off at very high frequencies. The audio signal is converted into a rapidly changing pulse pattern (usually using pulse-width modulation, or PWM). After passing through an output filter, the original analogue audio waveform is reconstructed at the speaker. Because the transistors spend very little time in their inefficient partially-on state, Class D amplifiers can exceed 90% efficiency and generate much less heat.

The important point is that the input and output of a Class D amplifier are still analogue audio signals. The switching process is an analogue power-conversion technique, not digital signal processing. A Class D amplifier may contain digital circuitry in some designs, just as a Class AB amplifier might, but Class D itself is not inherently digital—it’s simply a highly efficient analogue amplifier topology that uses high-speed switching instead of linear operation.

Get to know your speaker:

Tweeter - a loudspeaker driver which produces high-frequency sound. Typical response is from 2000 Hz to 20 kHz. In extreme high end audio they can extend to 50 kHz.

Tweeters are the most critical and delicate part of a loudspeaker. If poorly designed and or implemented music can range from sounding dull and lifeless to bright and fatiguing. Done correct, a nylon string guitar will sound smooth and mellow and a drum cymbal will sparkle. How to tell? Always audition before buying

At least they agree on the same team!

Sonny Rollins, jazz icon and saxophone colossus, has passed at 95.

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When your home cinema is so good it hurts!

NAD M28 – A masterclass in multi-channel amplification.

A recent installation of a NAD M28 reconfirmed what we’ve known for over 35 years – how to interpret specifications and what separates a good from a great audio performance.

For a multi-channel amplifier in a home theatre application how much power it can deliver when all its channels are driven simultaneously is a critical specification. Unfortunately, very few companies provide this spec. Common practice from them is to indicate when two or one channel/s are driven. In addition, they indicate at a specific frequency, not from 20Hz to 20kHz often with high THD.

From another highly regarded company’s website, the spec on one of their multi-channel amplifiers reads as follows:

Power Output (8 ohm, 1 kHz, 0.05% 2ch Drive) 200W

And when only 5 of its 12 channels driven the total harmonic distortion increases to 0.7%

Power Output (8 ohm, 1 kHz, 0.7% 5ch Drive) 200W

Spec on the NAD M28 is shown as such:

≥ 200 W (ref. rated THD, 8 Ohms , 20 Hz - 20 kHz, all channels driven) ≥ 340 W (ref. rated THD, 4 Ohms , 20 Hz - 20 kHz, all channels driven)

Rated THD ≤0.003 % (ref. 20 Hz - 20 kHz)


AND IT SOUNDS GREAT!

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