Laboratory Standard Amplifier

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#1
Dose anybody know what the significance of the nomenclature of "Laboratory Standard Amplifier" as apposed to the : "Four Hundred Wats RMS" on the early PL400?
 

mlucitt

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#2
Dose anybody know what the significance of the nomenclature of "Laboratory Standard Amplifier" as apposed to the : "Four Hundred Wats RMS" on the early PL400?
My memory tells me that the terminology you mention was partially marketing and partially referencing the ability of the PL400 to amplify DC to 20KHz for use in a lab where AC or DC amplification was necessary. Oh, and it was also an audio amplifier. That kind of thing.
 
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#8
I believe, that in order to meet the IHF preconditioning spec, the extra heat sinks were added. P/L took a shot at the standard by calling it Laboratory Standard. The standard required the unit under test to operate at 1/3 of rated output for 1 hour. 1/3 output of a linear amplifier produces the most heat in the output section. More than 2/3 or full power. I'm guessing the 4 fin heatsinks resulted in so much heat that the thermal switches activated before the 1 hour time limit. I can beleive it wouldn't make it past 15 minutes.
 

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#9
I think a lot would depend on what frequency was used for warmup... any spec in the IHF standard for that Don?
 

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#10
I'm think I am remembering that Blackwood said that the FCC made the Manufacturers quit using the power output of the amps as Model Numbers and hence deceptive trade practices of using false power out claims so instead of saying 700 Watts RMS they changed Lab Standard blah blah blah....

I could be wrong but I remember him documenting that here somewhere. You can call him... I'm sure he would love a chance to tell you what the deal was.
 

WOPL Sniffer

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#11
The earlier 700B's said "Seven Hundred Watts RMS" and the later ones said Laboratory Standard Amplifier..........
 

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#13
I believe, that in order to meet the IHF preconditioning spec, the extra heat sinks were added. P/L took a shot at the standard by calling it Laboratory Standard. The standard required the unit under test to operate at 1/3 of rated output for 1 hour. 1/3 output of a linear amplifier produces the most heat in the output section. More than 2/3 or full power. I'm guessing the 4 fin heatsinks resulted in so much heat that the thermal switches activated before the 1 hour time limit. I can beleive it wouldn't make it past 15 minutes.

CLOSE but no cigar


The FTC requires that the amplifier be pre-conditioned at one-eighth of rated total power output (for a multiple-output system, all channels are on) for one hour using a sine wave at a frequency of 1,000 Hz.


The power spectrum measurement is then collected with two channels at maximum rated power over the audio frequency range of 20 Hz to 20,000 Hz, in ambient still air of not less than 25°C, for the a duration of not less than 5 minutes.
 

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#14
This is from the Engineer at Texas Instruments, it also states the 1/8th rated output for 1 hour:



1.1 Power-Rating References and Basic Definitions
Application Report
SLEA047A–February 2005–Revised March 2005
Power Rating in Audio Amplifiers
Tuan Luu ............................................................................................... Digital Audio and Video Group
ABSTRACT
Average consumers often weigh heavily on cost versus power rating of audio amplifiers
as their basis for purchasing one. Depending on the marketing strategy, the power
rating methodology for audio amplifiers can vary from manufacturer to manufacturer.
The purpose of this document is to clarify three commonly used power ratings: average
power, peak power, and PMPO. The following Texas Instruments PurePath Digital™
power stages will be used for power measurement:
• TAS5142 – 4 half-bridges (2 BTL channels or 4 single-ended [SE] channels)
• TAS5152 – 4 half-bridges (2 BTL channels or 4 single-ended [SE] channels)
• TAS5186 – 6 half-bridges (6 single-ended [SE] channels)
There are a few standards that describe the power rating of an audio amplifier. The Federal Trade
Commission (FTC) establishes fair advertisement practices for home audio power ratings. This is
described in the FTC document 63FR37233, 16 CFR, Chapter 1, Part 432. Another standard is the
Electronic Industries Association (EIA) SE-101-A. For the car audio industry, some manufacturers accept
the Consumer Electronics Association CEA-2006-A standard. It defines how the amplifier should be tested
for power and signal distortion.
How can one tell a good power rating from a bad one? For a good power rating, all the specified reference
points are measurable.
Ohm’s law establishes the relationship of voltage, current and load, i.e., V = I × R, where V = voltage, I =
current in amperes and R = load resistance in ohms.
Power is energy per time and is derived as P = V × I = V2
/R = I
2
× R.
For an audio signal, the voltage is in Vrms (root-mean-square), the power is referenced to a frequency of
1,000 Hz, and the load is usually referenced to a resistive load. Thus, the power obtained is the average
power that the amplifier can sustain. The FTC requires further that the amplifier be pre-conditioned at
one-eighth of rated total power output (for a multiple-output system, all channels are on) for one hour
using a sinusoidal wave at a frequency of 1,000 Hz. The power spectrum measurement is then collected
with two channels at maximum rated power over the audio frequency range of 20 to 20,000 Hz, in ambient
still air of not less than 25°C, for the duration of not less than 5 minutes.
 

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#15
All the testing jargon may be interesting but when you get down to the bones, the FTC hammered the manufacturers and made them stop using the fake bullshit numbers on the front panels of their amps
 
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