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Amplifier bench tests

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Tonskulus View Drop Down
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    Posted: 31 October 2017 at 4:07pm
Share your bench results here!

I have recently made couple of uncertified dyno runs for different amplifiers. Especially those cheaper ones, claimed power outputs are sometimes a bit optimistic.  So let's see how they really perform. 

Setup: 40Hz sinewave signal, 8ohm resistive dummy load.  Measurements taken just before clipping led lights, confirmed w/ oscillosope that there is no signal clipping.

Alto mac 2.3

Claimed:  
2x285Wrms / 8ohm or 1x1000Wrms / 8ohm

Measured:
8ohm stereo:  48Vrms / 288Watts, single channel driven.
8ohm bridged:  82Vrms, 840Watts.   Not quite 1kW,  however input voltage dropped from 233V to 224V.   



T.amp TA-1400 mk2

Claimed: 
2x450Wrms/8ohm,  1x1200Wrms/8ohm

Measured:
8ohm stereo (one channel loaded), 61Vrms / 465Watts
8ohm bridged, 100Vrms / 1250Watts  (223Volt input at full power)

I will soon add more amplifiers and measure both channels loaded @ stereo as soon as I get another 8ohm dummy load :)









Edited by Tonskulus - 31 October 2017 at 4:08pm
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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 02 November 2017 at 9:56am
I have done quite a few. However, time is not what I have at the moment to post multiple figures.

Here is one out of the bunch:

Peavey CS 800X

 

Rated wattage: 400 watts per channel @ 4 ohms from 20 Hz – 20,000 kHz

 

Rated wattage before clipping @ 4 ohms

 

 125,347 kHz: 37.4 volts: 349.69 watts

 

 100,141 kHz: 41.0 volts: 420.25 watts

 

  75,128 kHz: 42.0 volts: 441.00 watts

 

  61,638 kHz: 42.9 volts: 460.10 watts

 

  50,274 kHz: 42.6 volts: 453.69 watts

 

  40,205 kHz: 42.9 volts: 460.10 watts

 

  30,370 kHz: 42.8 volts: 457.96 watts

 

  25,008 kHz: 42.9 volts: 460.10 watts

 

  19,992 kHz: 42.8 volts: 457.96 watts

 

  14,988 kHz: 42.8 volts: 457.96 watts

 

   9,994 kHz: 42.9 volts: 460.10 watts

 

   5,003 kHz: 42.9 volts: 460.10 watts

 

   2,498 kHz: 43.3 volts: 468.72 watts

 

   1,018 kHz: 43.4 volts: 470.89 watts

 

   509.28 Hz: 43.3 volts: 468.72 watts

 

   252.84 Hz: 43.5 volts: 473.06 watts

 

   100.36 Hz: 43.4 volts:  470.89 watts

 

    50.078 Hz: 42.8 volts: 457.96 watts

 

    40.016 Hz: 43.1 volts: 464.40 watts

 

    30.474 Hz: 42.0 volts: 441.00 watts

 

    25.125 Hz: 42.0 volts: 441.00 watts

 

    20.007 Hz: 41.5 volts: 430.56 watts

 

    14.908 Hz: 42.0 volts: 441.00 watts

 

      9.998 Hz: 31.4 volts: 246.49 watts

     (Amplifier ramps into DC Protect beyond 31.4 volts)

 

     Completely Squared Wave Form: 100.47 Hz:  56.6 volts: 800.89 watts

 

 

2 Ohm Load

 

Rated wattage: 600 watts per channel @ 2 ohms from 20 Hz – 20,000 kHz

 

 

Rated wattage before clipping @ 2 ohms

 

 

   100.765 Hz: 37.4 volts: 699.38 watts

 

   50.336 Hz: 37.1 volts: 688.20 watts

 

   40.101 Hz: 37.0 volts: 684.50 watts

 

   29.946 Hz: 37.0 volts: 684.50 watts

 

   20.674 Hz: 35.3 volts: 623.04 watts

 

   15.161 Hz: 35.5 volts: 630.13 watts

 

Completely Squared Wave Form: 101.64 Hz:  49.7 volts: 1235.05 watts

 

Completely Squared Wave Form: 101.64 Hz:  49.9 volts: 1245.01 watts (Regulated)


Best Regards,


Edited by Elliot Thompson - 02 November 2017 at 10:02am
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Tonskulus View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 02 November 2017 at 11:14am
As can be seen, heavy distortion (squarewave compared to clean sine wave) almost doubles the output power..thus, power dissipated by driver.  No wonder why heavy distortion can make voicecoils overheating quickly.




Edited by Tonskulus - 02 November 2017 at 11:15am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ReubGold Quote  Post ReplyReply Direct Link To This Post Posted: 02 November 2017 at 1:16pm
Some would argue, testing using load with inductive component, as opposed to purely resistive, is more realiststic..

E.g., segment of heating element.

However, the mere hint of bench testing amplifiers with 40hz sine waves, will send shudder down spine of many lightweight amp manufacturers, and distributors on SP.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote ReubGold Quote  Post ReplyReply Direct Link To This Post Posted: 02 November 2017 at 1:18pm
Also maybe tests, with both channels driven, are more reflective of real world use, PSU sturdiness !?
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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 03 November 2017 at 1:26am
Originally posted by Tonskulus Tonskulus wrote:

As can be seen, heavy distortion (squarewave compared to clean sine wave) almost doubles the output power..thus, power dissipated by driver.  No wonder why heavy distortion can make voicecoils overheating quickly.





Older amplifiers have the capability of doubling their output power when pushed beyond clipping. You won't find that type of behaviour with amplifiers offering burst ratings for the power supply is not robust enough to offer such results.

Best Regards,
Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 03 November 2017 at 5:44am
Originally posted by Elliot Thompson Elliot Thompson wrote:

Originally posted by Tonskulus Tonskulus wrote:

As can be seen, heavy distortion (squarewave compared to clean sine wave) almost doubles the output power..thus, power dissipated by driver.  No wonder why heavy distortion can make voicecoils overheating quickly.





Older amplifiers have the capability of doubling their output power when pushed beyond clipping. You won't find that type of behaviour with amplifiers offering burst ratings for the power supply is not robust enough to offer such results.

Best Regards,

True that. Many of those old "iron amps" had quite overrated transformers.  I have some big old QSC amps which will be soon measured. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 03 November 2017 at 10:21am
Here is an old Crown lightweight Switch-Mode Design

Crown XS 900

 

Rated Power: 900 watts per channel @ 1 kHz, under a 4 ohm load

 

 

Measured Results before Clipping Takes Place

 

  20.707 kHz, 72.1 volts, 4 ohm load: 1299.60 watts 

  

  14.991 kHz, 64.0 volts, 4 ohm load: 1024.00 watts

 

  10.004 kHz, 64.0 volts, 4 ohm load: 1024.00 watts

 

    5.003 kHz, 64.0 volts, 4 ohm load: 1024.00 watts

  

    2.083 kHz, 64.0 volts, 4 ohm load: 1024.00 watts

 

  999.282 Hz, 64.0 volts, 4 ohm load: 1024.00 watts

 

  500.995 Hz, 64.0 volts, 4 ohm load: 1024.00 watts

 

  200.939 Hz, 64.0 volts, 4 ohm load: 1024.00 watts

 

  100.882 Hz, 62.9 volts, 4 ohm load:   989.10 watts

 

    50.221 Hz, 62.5 volts, 4 ohm load:   976.56 watts

 

    39.903 Hz, 62.0 volts, 4 ohm load:   961.00 watts

 

    30.021 Hz, 62.9 volts, 4 ohm load:   989.10 watts

 

    20.746 Hz, 62.2 volts, 4 ohm load:   967.21 watts

 

      9.999 Hz, 62.2 volts, 4 ohm load:  967.21 watts

 

      4.939 Hz, 60.0 volts, 4 ohm load:  900.00 watts

     (Amplifier goes into DC Protect beyond 60 volts)

  

 

NOTE: Amplifier received a constant sine wave signal at various cycles for a period of one hour. The amplifier did not overheat nor thermal during the testing.

 

Best Regards,

Elliot Thompson
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