De versterker is het 'Hart' van uw installatie. Dat zeiden we in 1970 en dat is nog steeds zo. De versterker(s) bepaalt voor het allergrootste deel de uiteindelijke geluidskwaliteit. Dat geldt natuurlijk ook voor de geluidsbronnen waar altijd een versterkerdeel in zit.
De luidspreker is natuurlijk ook belangrijk. Maar een luidspreker kan het niet helpen als één (of meer) van de versterkerdelen iets weglaat of toevoegt. De kwaliteit van de versterker is van doorslaggevend belang bij de geluidsweergave. Zelfs met zeer eenvoudige luidsprekers kunt u al horen of de installatie kwaliteit heeft.
Nieuwe tijden brengen nieuwe uitdagingen. Hawk Audio speelt hier op in en we laten u hieronder onze overwegingen daarbij weten.
Energy consumption and pollution in audio equipment
In the 21st century we have some major challenges in order to survive on our planet. Almost any natural source for energy generation will be empty or not commercially explorable in the foreseeable future. We are developing a lot of new technologies such as solar power and wind to counter this problem.
The consumer is confronted with a rising price for his energy consumption and we have to find solutions in that area as well.
A different problem is the pollution of our world. A big problem there is the waste of used consumer goods. Another problem is electronic pollution.
This article concentrates on the problems and solutions in home audio equipment.
Audio reproduction
With the reproduction of musical audio signals we can enhance life quality. Although there’s no scientific cohesion about the mechanism and the psyche of our hearing system the common hypothesis is that man enjoys music if it is reproduced within a bandwidth from 20 Hz to 20 kHz. Within that bandwidth the amplitude should stay within a margin of maximum 1 dB and no phase deviation should occur. It is commonly accepted that a distortion level below 0,01 % is not detected by man, hence has no influence on the subjective experience of the audio quality.
Although this kind of quality “level” is accepted in the public as well as in the major part of the audio industry there are some developments which go further in improving the audio quality. The chip industry, i.e. Texas Instruments and Analog Devices, recently introduced using hearing sessions with experienced listeners in order to improve the behaviour of new audio operational amplifiers. The newest op amps now show distortion levels of around 0,0001%.
Also in the niche market of “High End” audio equipment there’s a continuing development of “better” circuitry.
Electronic pollution
This term covers a wide range of distortions; those are generated in free air as well as inside electronic equipment.
In “free air” or the “ether” we have to cope with an ever increasing amount of high frequency signal sources such as GSM, Wi-Fi, cordless phones, remote controls, electronic distribution in homes etcetera.
Most home audio equipment is connected to the mains distribution net as a source of energy. The mains distribution system forms an electric (and electronic) connection between all connected devices. A lot of those devices (magnetron, coffee machine, refrigerator, laundry machine, personal computer, lap top, printer) now are controlled by a microprocessor and those generate a “clock signal” at a high frequency. Also there’s a tendency in using “switch mode power supplies”. These also generate pulses at high frequencies. Some audio home distribution systems use a “digital connection” in-between the various devices using high frequency clock signals.
Inside audio equipment moreover a kind of “clocked” microprocessors are used in order to control the signal flow. Much of this applied technology has to do with the “ease” of the design work using integrated chips with multiple functions.
All these types of high frequency switching cause “pollution” which can interfere with the audio signal path. Often such a signal is “detected” hence converted into a DC signal and in this way the amplifying device shifts its’ working area causing an increase in distortion.
Which way to go in audio development?
In modern life we’re used to control audio equipment using some type of remote control. This control system can be developed using some type of high frequency carrier. This carrier holds the coded information instructing the device under control to act as wished by pushing a button. A different type of control uses (coded) frequencies just out of the audio band. Both types of remote control enhance the level of high frequency pollution and should be avoided.
A different way is using “invisible light” such as infrared. That method has the disadvantage of a relatively high noise level. Applying current technologies could solve that problem.
The various “functions” in audio equipment can be controlled by a programmed micro-processor. The clock needed for the processor to function can be switched off after the user has chosen the way the signal should be passing the circuits. The various chosen functions stay switched on by using a kind of “set-reset flip flops”. Such a circuit stays “set” until a reset pulse is applied. Some (high end) manufacturers already use such a circuit switching off the clock. When music is playing the clock signal will not interfere with the signal path.
Using a Switch Mode Power Supply (SMPS) has several advantages. There’s no need for a big transformer so the total weight is low. Also the mains voltage level and frequency is not important, any mains around the world will sufficiently feed the equipment.
But an SMPS supply is controlled by switching at a relative high frequency. In order to avoid that this switching signal interferes with the audio circuits the entire SMPS should be shielded. Also an adequate filter at the output is needed. This could be realized using a kind of Pi-filter consisting of a C-L-C circuit.
The SMPS also generates switching noise at its input. So in order to avoid pollution of the mains supply a filter should be applied between the mains and the SMPS.
Most audio amplifiers are configured at the output functioning in “class A/B” or “class-A”. Using transistors (semi-conductors) means having to do with a “step” or threshold before that transistor starts functioning. The solution, avoiding distortion from this step, is to run a constant current in that circuit. That energy is not used for the amplification so this energy is “wasted” (as is the energy needed for all other circuits, they all function in “class-A”).
A recent development is using a type of “class-D” circuit at the output of the amplifier. This technology hardly uses energy when no signal is flowing. Class-D implies using a kind of power switch which switches at around ten times the highest audio frequency to be amplified. This type of switching generates high frequency signals at the output and in the power supply. At the output mostly a kind of L-C filter is applied to avoid these signals to travel into the loudspeaker connection (with the loudspeaker cable functioning as a transmitting antennae). For this type of amplification better types of filtering should be developed.
Energy consumption
An easy way to lower energy consumption in audio equipment is lowering the (maximum) output power. This is possible if loudspeakers are developed with higher “efficiency”. Most current loudspeakers are specified as delivering a sound pressure of around 89 dB if a 1 Watt signal is applied. If a loudspeaker can be constructed with a sensitivity of 92 – 95 dB at 1 Watt the necessity for large amplifiers will be smaller.
Most loudspeakers are constructed with a kind of “bass reflex” opening, improving the sound pressure at low frequencies. The BR tuning has the disadvantage of creating a low impedance at low frequencies (where the amplitude of music is loudest). That low impedance can only be adequately be handled by the amplifier if that amplifier delivers enough current. This means that an amplifier delivering 10 Watts into 8 Ohms should be capable to deliver 20 Watts into 4 Ohms.
With current electronic components and class-D technology we now can develop an amplifier consuming around 3 Watt at “Stand By” and 5 Watt when switched “On”. When music is playing, using a 92 dB sensitive loudspeaker, the consumption will be around 15 Watt.
An “average” audio system with an amplifier in A/B delivering a maximum of 50 Watts will show a continue consumption of around 15 Watt without music and around 30 – 40 Watt when music is playing.
A “class-A” amplifier always, whether music is playing or not, consumes 100 Watts or more.
Considering 8-channel surround systems those figures should be multiplied with a factor four.
Now let's have a look at various audio amplifiers and their energy consumption.
Consumption in Watts
| brand |
type |
function |
stand by |
with music |
maximum |
| Harman Kardon |
HK3490 |
stereo |
1 |
60 |
310 |
| Harman Kardon |
AVR3550 |
surround |
118 |
150 |
890 |
| Sony |
STR-DH100 |
stereo |
? |
60 |
250 |
| Sony |
STR-DH-700 |
surround |
0,3 |
60 |
480 |
| Denon |
DRA-697 |
stereo |
? |
48 |
480 |
| Denon |
DHT-789 |
surround |
? |
84 |
1500 |
| Marantz |
SR-4023 |
stereo |
? |
60 |
220 |
| Marantz |
STR-5003 |
surround |
? |
84 |
600 |
| Hawk |
D-402 |
stereo |
4,6 |
26 |
220 |
| Hawk |
D-122 |
stereo |
4 |
8 |
50 |
| Hawk |
D-123 |
stereo |
6 |
10 |
80 |
| Hawk |
D-202 |
stereo |
6 |
15 |
100 |
| Hawk |
D-128 |
surround |
18 |
40 |
320 |
N.B. The specifications of the D-128 are preliminary
Milieuvriendelijk omgaan met audio producten
