Audio Precision to Discuss Amplifier Measurements at our Trade Show Event

by September 12, 2008

As many of you are aware, I am not champion of the classic 1kHz instantaneous distortion vs power all channels driven test popularized by most of the major audio magazines as an accurate way of gauging amplifier performance.

In fact, I’ve written several articles on this topic which can be found here:

Thus I figured what better time than our 2008 SOTU Trade Show event this October 23rd and 24th at the Disney Dolphin Resort in Orlando Florida to invite Audio Precision – the world’s leading manufacturer of high end audio test equipment to talk about the measurements behind more meaningful multi channel amplifier standards.

Mcintosh AmplifierSpecifications are the bragging rights of gear manufacturers and owners alike. However, unlike a math test in high-school, there is no single score that can tell you which product is better. There are multiple specifications to deal with, many of which appear similar to the untrained eye. However, even a trained eye will raise questions as to which measurements and measurement techniques are most relevant. Nowhere is this more prevalent than in power measurements for home theater receivers and multi channel amplifiers.

Most power measurements in use today were designed for measuring two-channel stereo gear. Most audio analyzers in use today were designed for those tests. This model isn’t well suited for modern home theater receivers that feature at least 5 channels. This session will explore the challenges faced in testing home theater receivers/amplifiers and show sample results using new testing techniques that have recently become available.

Jonathan Novick, Director of Sales for Audio Precision, holds a B.S.E.E. from Rensselaer Polytechnic Institute in Troy, NY and is currently the chairman of the Los Angeles Section of the Audio Engineering Society. He will be joining us at our event to discuss this topic in detail and look at the first steps taken towards a more meaningful measurement standard that could be universally adapted by the audio industry as a better and more efficient way of gauging multi channel amplifier performance.

If you are an industry professional or manufacturer and wish to attend our event and participate in this seminar we will waive the registration FEE for up to two people from your organization which will also include all of our event amenities such as our 6 demo rooms, 2 days of breakfast, our semi formal dining event / Halloween costume party,  auction and door prizes.

The Registration deadline is September 29th and our event is nearly sold out so > REGISTER  NOW <.

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3db posts on September 15, 2008 05:57
mtrycrafts;455974
Yes, it is interesting
But, another but,, the way you are figuring is not the way it is rated.
Yes, each of those channels is capable of producing 120 watts continuous power BUT, not at the same instant since that event on recorded software has yet to be met. The front two channels are so rated in the calculations and the rest are rated at 1/8 power, plus the amp efficiency.

Go to your circuit panel in the house and add up all the breakers value. I bet it will exceed the main breaker value Why? Because no residential house will use all that full power at the same instant on each breaker


Unless you're a Griswald at Christmas
mtrycrafts posts on September 14, 2008 14:51
jliedeka;455720
My Marantz SR8002, according to the specifications on page 82 of the manual, is capable of 125 WPC at 8 ohms including Front L&R, Center, Surround L&R and Rear Surround L&R. At 6 ohms, they claim 160 WPC. Assuming 120V that means 7.3 Amps at 8 ohms and 9.3 Amps at 6 ohms. Yet, the power consumption is rated at 6.7 Amps.

I'll admit I'm not a math genius but I think 6.7 is less than both 7.3 and 9.3. If you figure 115 or 110 volts, the number of amps would be higher.

At least they rate the WPC 20-20kHz with THD 0.08% for both figures.

Jim


Yes, it is interesting
But, another but,, the way you are figuring is not the way it is rated.
Yes, each of those channels is capable of producing 120 watts continuous power BUT, not at the same instant since that event on recorded software has yet to be met. The front two channels are so rated in the calculations and the rest are rated at 1/8 power, plus the amp efficiency.

Go to your circuit panel in the house and add up all the breakers value. I bet it will exceed the main breaker value Why? Because no residential house will use all that full power at the same instant on each breaker
3db posts on September 14, 2008 08:00
jliedeka;455720
My Marantz SR8002, according to the specifications on page 82 of the manual, is capable of 125 WPC at 8 ohms including Front L&R, Center, Surround L&R and Rear Surround L&R. At 6 ohms, they claim 160 WPC. Assuming 120V that means 7.3 Amps at 8 ohms and 9.3 Amps at 6 ohms. Yet, the power consumption is rated at 6.7 Amps.

I'll admit I'm not a math genius but I think 6.7 is less than both 7.3 and 9.3. If you figure 115 or 110 volts, the number of amps would be higher.

At least they rate the WPC 20-20kHz with THD 0.08% for both figures.

Jim


You forgot to multiply in the cosine of the power factor angle. In AC, in a purely reactive circuit, voltage leads current by 90 degress in a capacitive circuit and lags current by 90 degrees in an inductive circuit. Throw the two together and resistance and your power factor angle reduces less than 90 degrees. In a purely resistive circuit, current and voltage are in phase.
jliedeka posts on September 13, 2008 19:58
My Marantz SR8002, according to the specifications on page 82 of the manual, is capable of 125 WPC at 8 ohms including Front L&R, Center, Surround L&R and Rear Surround L&R. At 6 ohms, they claim 160 WPC. Assuming 120V that means 7.3 Amps at 8 ohms and 9.3 Amps at 6 ohms. Yet, the power consumption is rated at 6.7 Amps.

I'll admit I'm not a math genius but I think 6.7 is less than both 7.3 and 9.3. If you figure 115 or 110 volts, the number of amps would be higher.

At least they rate the WPC 20-20kHz with THD 0.08% for both figures.

Jim
mtrycrafts posts on September 13, 2008 18:08
jliedeka;455545
That was an interesting read. I've noticed that the claimed WPC of my receiver adds up to more than the rated power of the transformer. I've also wondered why some amplifiers claim more power than you could get out of 15 amps. I wasn't even aware of the 12 amp limit and hadn't considered inefficiencies in the amplifier.

Jim


Is it? Or just adding up each channel's power is not what it is rated for And, it is not rated like that for a good enough reason. Never get full power demand from all channels at the same instant.
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