1. ABOUT POWER MEASUREMENTS OF
DIGITAL AUDIO AMPLIFIERS
One of the main advantages of D-Amp Amplifiers is the
possibility to handle in a considerately more efficient
way the musical power with respect to conventional linear
amplifiers, taking in to account that music average power
energy is considerably lower with respect to continuous
sine wave signals of the same peak level. In few words
the main advantage of D-Amp Amplifiers is to underperform
the continuous signal power output (unusefull from the
musical point of view) in order to greatly enhance power
output of the useful musical signals. Therefore the Audio
Power outputs stated in D-Amp Specifications sheet must
be measured in the following conditions:
1. Power RMS x Channel (1kHz, 0.5%THD):
• Maximum
continuous output power delivered to the load for at least
15 minutes, then thermal limiting processor shut down
amplifier.
2. Power RMS x Channel in stereo working:
•
Maximum EIAJ standard test output power: average of RMS
output voltage squared divided by load impedance.
• Test signal 1kHz tone burst 8 cycles 0dB, 8 cycles
no signal, THD 1%. If the power measurements will follow
the above conditions there will be founded the power figures
very close to those stated in the data sheets. In the
case that measurement are done with the non significant
method of continuous sine wave input signals (applied
for more than 15 minute), the system is self-protected
from that unusefull signals, and shut down amplifier.
It is now possible to introduce a new approach in
designing Audio Amplifiers, especially when a very high
audio output power is required. In effect in the normal
operation the amplifier's useful output music usually
is limited by its short term power capabilities and
not by the heating that results from high continuous
power emission. Based o the above consideration, it
is possible to minimize the non realistic usual requirement
for continuous power rating, typical of conventional
analogue amplifiers, and to design much more efficient
Audio Amplifiers increasing their burst power capability
with respect to the continuous power rating.
For the correct design it is moreover necessary to define
as valid for any topologies of music two basic parameters
as: the ratio for the peak output power to continuous
power rating and the max. burst duration. About the first
parameter from specific research it results that in the
worst case of rock music compressed for FM broadcast the
ratio of r.m.s to peak power is around 8 dB. This means
that if an amplifiers volume control is set to place the
high peaks at the on set of clipping, the most severe
continuous power demand is less than 15% (usually under
10% ) of the amplifier's max. peak power.
About the second parameter - max. burst duration confirm
that for all the music types the burst peak power Is
always reducing with the increasing of the duration
of the bursts. This general rule is represented by the
following expression, and takes in to account all possible
music worst cases: 10 log p/pc =-0.16 Log t were 't'
is the toneburst in milliseconds and ' pc' is the power
level at 0 dB (the clipping point) This means that the
distribution of peak power bursts in function of duration
can be represented in the following table: • burst
duration max r.m.s level
• 3 ms 0 dB clipping
• 30 ms -2 dB
• 300 ms -3 dB
• 3 sec. -5 dB
• 30 sec. -7dB
Based on the above results D-Amp has been in the position
to define the basic requirements to design of an innovative
very efficient Audio Professional high power amplifier:
• To obtain extended duration of headroom, able
to delivery burst of 10 sec. or longer at substantially
higher level then normal linear amplifiers 'continuous
power rating. • To obtain an optimized thermal
design suitable to manage very high r.m.s output power
within 3 dB with respect to the peak power. This requirement
will allows a margin with respect of to above mentioned
experimental results. • To obtain an automated
gain control suitable to maintain for any input signal
level the full dynamic capability. This requirement
in order to avoid clipping distortion and ensure the
nominal r.m.s power. The right solution to the above
requirements was founded utilizing digital switching
technologies (based on the principle of PWM) with some
circuitry topologies solutions. In effect this PWM technology,
through a very high frequency sampling of audio input
signal (over 500 kHz) allows with the necessary accuracy
to process the signal in digital form and provides the
highest power outputs with extreme efficiency (near
to 97.5 %). A well designed output filtering and processing
solution provides output capabilities at the highest
level of quality in terms of low distortion, noise and
bandwidth . Based on the above, D-Amp has developed
a new generation of digital audio amplifiers branded
HVI Series. D-Amp series of Professional Audio Amplifiers
is a complete range of products from 4000 W to 12 000
W on 4 ohms load in 1 unit 19" rack size and 8.5
Kg weight.
The global audio result of such new generation of Audio
Amplifiers is that with such innovative design criteria
it was obtained a very cost-effective product with the
best adherence to the real music professional requirements.
2.Does your limiter indicator
represent true output clipping ?
No, the LED is driven only when the amplifier output
fails to track the input. This condition normally results
only from limited clipping (2%), which occurs when the
power amp reaches either its voltage or current limit.
Limiter LED is red and when light on you are at limit
of clipping. The amplifier have an internal compressor
circuitry to prevent excessive clipping, when the amplifier
clipping reaches the point that the compressor turn
on the limiter (red) and alert the operator that the
input signal is being compressed. 2 Level of limiter
is used, 1 at -2Db before clipping to minimise stress
to loudspeaker (when limiter LED ‘’flick’’
and enable blue LED stay on, and a distortion limiter
when limiter goes on and enable goes off. Limiter limit
to a maximum of 2% absolute amplifier distortion.
3.Is it possible to change the
input sensitivity within your amplifiers ?
In theory, yes, but only by changing certain resistor
values, which requires opening the covers and exposure
to dangerous voltages. This should be done only by qualified
service personnel, or under the guidance of D-Amp Technical
Services. See our support web page for more details
on how to perform this for D-Amp series amplifier.
4.Is possible to disable the
limiting circuit in the D-Amp amplifiers ?
This is not possible due to the philosophy Design.
5.The clip LED’s on my
amplifier flash upon power up before the muting cycle
ends. Is this normal?
During the muting cycle, the "front end" of
the amplifier is internally disconnected from the output
transistors, ensuring that they are fully turned off
in the event of overheating or during routine on/off
muting. When disconnected from the feedback loop, the
front end circuits may have enough stray signal to flash
the Clip LED's. This is perfectly normal, and will stop
as soon as the amp enters the normal "run"
state.
6.Which is the warranty on my
D-Amp amplifiers?
D-Amp provides a 3 year warranty from the date of purchase
of our Distributor. The warranty does not cover failures
due to damage and misuse of the equipment. The customer
is responsible for freight charges to D-Amp will repair
the product under warranty and return it to customer
free of charge.
7.When installing D-Amp amplifiers
in a rack should I leave spaces between ?
The answer is no and yes. The airflow technology that
we use in our amplifiers is designed such that it is
best to stack multiple amplifiers on top of each other,
with no space between. The amplifiers draw air into
the back of the amplifier and exhaust it out from the
front panel. If you choose to place the amplifiers with
space between them, then use solid panels between them,
not vented panels. It is not recomended to stack more
than 3 amplifier.
8.Which are loudspeaker protections
on D-Amp amplifiers ?
D-Amp series is equipped with an evaluation / processing
circuitry for output stage behaviour. All signals that
are feed to the load (i.e. loudspeakers ), are subjected
to a pre processing that allows the output stage of the
amplifier to deliver always non distorted and “loudspeaker
safe” signals. This specific feature lead to a dramatic
improvement of reliability of the complete installed system,
reducing loudspeaker failures even in case of incorrect
design. Another circuit track and detect speaker over
excurtion and limit the power to avoid to break the speaker.
9.What is mains current requirement
for D-Amp 8000HVI
Mains requirement is defined by the ratio between average
power consumption and mains voltage. For a D-Amp 8000HVI,
power consumption is 1200VA per channel on 1/8 Max power
@ minimum load impedance standard duty program, and
1800VA on ¼ Max power @ minimum load impedance
heavy duty program.
|
HOME
| PRODUCTS | SALES
& SUPPORT | REALISATION |
TECHNOLOGY | ABOUT
US