some interesting info from powersoft faq:
1. About power measurements of digital audio amplifiers As explained in the DIGAM Series data sheets , one of the main advantages of Digital Audio 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 Digital Audio Amplifiers is to underperform the continuous signal power output (unusefull from the musical point of view) in order to strongly protect the loudspeakers loads and greatly enhance power output of the useful
musical signals. To this regard, in order to have more clear picture about the scientific approach, please make also reference to the enclosed document "Design Criteria for an innovative professional high power audio amplifier".
Therefore the Audio Power outputs stated in Digam Series Catalog 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 5 seconds, then internal limiting processor reduces output
voltage swing to _ maximum output.
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, 24 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 5 seconds), the system is self-protected from that unusefull signals, and lower output values will be found.
2. Design criteria for DIGAM, the Powersoft innovative digital professional high power audio amplifier It is well known that the qualitative analysis of audio spectrum characteristics for different typologies of music is showing the presence of sequence of short burst with different peak power values and duration.
Taking in account these peculiar spectrum characteristics it is 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, our assumption was that 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 typologies 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 and analysis performed by DeMarinis (1) 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 - other studies and tests as been performed (2),(3), in the past and specific confirmations as been obtained in the Powersoft Co. Laboratory, confirming 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
• 1 ms 0 dB clipping
• 10 ms -2 dB
• 100 ms -3 dB
• 1 sec. -5 dB
• 10 sec. -7dB
Based on the above results Powersoft 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 1 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.
Moreover it was recognized necessary also to have a very high efficiency power supply system together with a power factor corrector to keep the system independent from variations of mains and to be also in full compliance with the new European regulations.
The right solution to the above requirements was founded utilizing digital switching technologies (based on the principle of PWM modulation ) with some patented circuitry topologies solutions.
In effect this PWM technology, through a very high frequency sampling of audio input signal (over 250 kHz) allows with the necessary accuracy to process the signal in digital form and provides the highest power outputs with extreme efficiency (near to 95 %).
A patented 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, Powersoft has developed a new generation of digital audio amplifiers branded DIGAM.
DIGAM series of Professional Audio Amplifiers is a complete range of products from 2000 W to 9000 W on 2 ohms load in 1 unit 19"
rack size and 9.5 Kg weight.
Other main features of DIGAM series are PFC (power factor correction); overheating power control and significant options in
professional applications as multiple remote control and pre-processing signal.
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.
• J.V. De Marinis: "How valid is the FTC Preconditioning Rule? " - Audio Sept 75.
• P.J. Mitchell: "A musically Appropriate Dynamic Headroom Test for Power Amplifiers. "A.E.S. Pre-print 2504, Oct. 87.
• A.E.S. Convention 7/10 Oct. 93 - Pre-print: "The Dynamics of Recorded Music". Presented by J.A. Mc. Manus, Chris Evans and
P. J. Mitchell.http://pro-audio.powersoft.it/faq_li...menu=325&obj=3