Measuring Amplifiers - Page 2 - AVS Forum
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post #31 of 1918 Old 06-09-2007, 01:04 PM - Thread Starter
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Here is the 2nd round of measurements completed at 4 ohms. Again, the high frequency is not up to par.

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post #32 of 1918 Old 06-09-2007, 01:33 PM - Thread Starter
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Just a note..... After finishing the measurements at 4 ohms, I used a non contact infra red thermometer to measure the temperature on the case where the heat sink is bolted to the cover. The thermometer was reading between 110 degrees and 115 degrees. This is with an unmodified fan system, BTW.
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post #33 of 1918 Old 06-09-2007, 01:35 PM
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Thanks for the tests so far Chuck, I'll be watching this thread closely.
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post #34 of 1918 Old 06-09-2007, 01:54 PM
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Has anyone used or even heard of Powersoft amps? The Q4004 (4x1000 @ 4 ohms) goes for about $550 plus shipping from Germany on Ebay. I've looked for some US retailers but couldn't find them.

-Robert
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post #35 of 1918 Old 06-09-2007, 01:55 PM
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Hi Chas,
When you find an amplifier that tests "out of bounds" for THD as you've indicated the EP1500 did, is it possible to find out at what frequency the distortion level starts to rise? Would that take up too much time?
Have you set an arbitrary limit as to what level of THD distortion you consider to be "out of bounds" and what is that limit?
Is there a way to run a high/max wattage (sweep) to test for THD levels?
The project you have started will be of very valuable interest to a lot of DIYers AND professionals.
Thank you for your time and expertise in assembling and building the test equipment. I will be patient in waiting for future results of your testing.
Phil
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post #36 of 1918 Old 06-09-2007, 01:59 PM
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Quote:
Originally Posted by rlj5242 View Post

Has anyone used or even heard of Powersoft amps? The Q4004 (4x1000 @ 4 ohms) goes for about $550 plus shipping from Germany on Ebay. I've looked for some US retailers but couldn't find them.

-Robert

Definitley. Mark Seaton would know more, as he's had some hands on experience with the Powersoft DIGAM K10.

And how much is shipping?
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post #37 of 1918 Old 06-09-2007, 02:26 PM
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Quote:
Originally Posted by Willd View Post

And how much is shipping?

Around $75.

-Robert
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post #38 of 1918 Old 06-09-2007, 02:41 PM - Thread Starter
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Quote:
Originally Posted by LINEARX View Post

Hi Chas,
When you find an amplifier that tests "out of bounds" for THD as you've indicated the EP1500 did, is it possible to find out at what frequency the distortion level starts to rise? Would that take up too much time?
Have you set an arbitrary limit as to what level of THD distortion you consider to be "out of bounds" and what is that limit?
Is there a way to run a high/max wattage (sweep) to test for THD levels?
The project you have started will be of very valuable interest to a lot of DIYers AND professionals.
Thank you for your time and expertise in assembling and building the test equipment. I will be patient in waiting for future results of your testing.
Phil

Phil:
There is no 'arbitrary' limit. It is based upon published manufacturers specifications. I consider the amp out of bounds when it will not meet the manufacturers specification. In this case the EP1500 should be able to do 260 watts into an 8 ohm load with less than .1% THD from 20 Hz to 20 KHz. I could make the amp do 260 watts at 20 KHz with outrageous unlistenable distortion or I could run the amp at .1% THD and measure the watts
As far as running a high/max wattage on amps, I have tried it on the EP1500 and it is barely worth noting. This unit barely meets factory specs much less outperforms the specs. I am sure on units like a QSC or a Crown you will see performance above and beyond the published specs.

If I had the time, I would 'play' with the amps all day long. As it is, it has taken me since 10 AM this morning to get 2 sets of measurements. Thats 6 hours. For an amp like the EP1500 I wil not go much farther than checking it for meeting specs. You can tell when you are setting up and testing if an amp is worth investigating any further and this one is not. I will probably go deeper with the EP2500 and the Crown K2 when I test them.

Chuck
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post #39 of 1918 Old 06-09-2007, 02:54 PM
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Since many people buy the ep's to run 2ohm loads, it would be neat to see what they do with that kind of impedance.
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post #40 of 1918 Old 06-09-2007, 03:07 PM - Thread Starter
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Just an update.............. I am in the process of testing at a 2 ohm load, both channels driven, at 1 KHz. In 20 minutes of test time, I have blown the dedicated 20 amp breaker 5 times attempting to get the amp up to clipping and just take a reading of voltage and distortion. In that time the case of the amp has registered 125 degrees fahrenheit on the top cover. So far it will only do approx 500 watts at .5% distortion. I am going to let it cool for a few hours and rerun the test to see if it will meet specs. Very disappointing so far.
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post #41 of 1918 Old 06-09-2007, 03:49 PM
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Any chance of seeing how much power the EP1500 is putting out in 4ohm bridged mono 20 Hz to 20 KHz @ .1%THD ?
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post #42 of 1918 Old 06-09-2007, 04:00 PM
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Considering the first harmonic of 20k is 40k, I wonder if this distortion is really that audible?

Will you being doing a "standard" test so that different amps can be compared to each other, not just their specs?

Are you doing a Buttkicker? I have one I may be able to send.
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post #43 of 1918 Old 06-09-2007, 04:01 PM - Thread Starter
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Quote:
Originally Posted by Jerm357 View Post

Any chance of seeing how much power the EP1500 is putting out in 4ohm bridged mono 20 Hz to 20 KHz @ .1%THD ?

It is on the menu. Have patience. I am still letting the amp cool down from the 2 ohm attempted test. After I get the 2 ohm results, i will get some bridged results.
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post #44 of 1918 Old 06-09-2007, 04:04 PM
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Cool thanks.
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post #45 of 1918 Old 06-09-2007, 04:40 PM - Thread Starter
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OK, here is the 2 ohm testing results for the EP1500 amplifier. I only did one test at 1 KHz full power, both channels driven. Behringer specifies that this unit will do 700 watts RMS at 0.1% THD both channels driven. I could not get the amp to go past 35 volts per channel before it would blow the circuit breaker on the amp itself. Here is the report. For the record, the amplifier is drawing 16.4 amps from the outlet at this power level. (BTW, the manual states that it will draw 6.7 amps at 120 VAC, the circuit breaker supplied on the amp is 15 amps!).



It took less than 30 seconds for the amp to go from 70 degrees fahrenheit to 110 degrees when under power. After the amp cools down, I wil perform some bridged mono tests.
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post #46 of 1918 Old 06-09-2007, 04:45 PM - Thread Starter
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Quote:
Originally Posted by augerpro View Post

Considering the first harmonic of 20k is 40k, I wonder if this distortion is really that audible?

Will you being doing a "standard" test so that different amps can be compared to each other, not just their specs?

Are you doing a Buttkicker? I have one I may be able to send.

All the tests I am doing will be in this format being presented so that you can compare apples to apples. Same frequencies, same loads, same methodology. One thing to realize is that to put the amps on the bench with a static load and a pure sine wave at high voltage and let them cook is far more punishment than they wil ever see when playing music in our homes. OTOH, the manufacturers publish the specifications that say what theses pieces of equipment are capable of.

If you want to send a Buttkicker, PM me and we can work out details. I will gladly put it on the bench and test it.
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post #47 of 1918 Old 06-09-2007, 05:42 PM
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Update your logsheet to show AC input voltage used

Do a 96VAC test like Bink did so we can correlate data. It's easy to get under 100VAC
using typical house wiring when you torture a high powered proamp using an rms test
method.

Don't fear, Behringer is not alone, many proamps get punished when they are tortured with an rms test method.



The storm was gone, but dark clouds still hung around
The perfect setting for things to come......

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post #48 of 1918 Old 06-09-2007, 05:53 PM - Thread Starter
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Quote:
Originally Posted by thylantyr View Post

Update your logsheet to show AC input voltage used

Do a 96VAC test like Bink did so we can correlate data. It's easy to get under 100VAC
using typical house wiring when you torture a high powered proamp using an rms test
method.

Don't fear, Behringer is not alone, many proamps get punished when they are tortured with an rms test method.

All AC voltage is 120 VAC as output by the variac. It has taken me 10 hours to get this far on 1 amp. I will have to investigate what it takes to add a '96 VAC' portion to the test. I will look at Bink's testing again so I can see what is common between our tests. Since this is my first test it is easier for me to change to follow Bink now than later down the road.

And actually, many proamps don't even care about running 20 Hz for an extended period of time with pure sine waves if they are designed well. Crown DCA, Yamaha P series, Crest, QSC, etc. I even remember a Phase Linear 700 able to passs 20 KHz without a sweat for an hour at a time!
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post #49 of 1918 Old 06-09-2007, 06:04 PM
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Binks test is 1% THD+N, 117VAC test and 96VAC Test. 20hz, 1khz, 20khz. Both channels
driven, 4 ohms per channel.

http://home.pacbell.net/lordpk/bink/bink.jpg

The 1% THD reference is fine if you ask me. This is still considered inaudible distortion levels and you can record a higher power figure.

He didn't do a 2 ohm/ch test though.. boo on bink

You don't have to mimmick his test but he has a nice database already that you
can add to it to make a bigger list.

Bink
http://binkster.net/



The storm was gone, but dark clouds still hung around
The perfect setting for things to come......

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post #50 of 1918 Old 06-09-2007, 06:31 PM - Thread Starter
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Here is the final test of the EP1500. I have tested both 8 & 4 ohms bridged mono. The 8 ohm test went well but the 4 ohm test did not fare too well even at 1 KHz so I did not even go any further with it. The circuit breaker on the amp kept blowing just as I would aproach ful power in 4 ohm bridge mono. Note the increased distortion at 4 ohms also.



Ok, that is it for the first amplifier in my tests. If you have comments, gripes, suggestions, or preferences for a format let me know now or forever hold your peace (yeah, right, on AVS ). I am going to try and fashion some tests to fit with Binks spreadsheet but that may be down the road.

Chuck
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post #51 of 1918 Old 06-09-2007, 06:32 PM - Thread Starter
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For those that have not seen it, here are Bink's tests.

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post #52 of 1918 Old 06-09-2007, 07:01 PM
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Excellent work Chas. I think we all expect the test figures to be somewhat disappointing compared to manufacturers claims but this particular amplifier seems to perform way under claims. Thanks for your success.
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post #53 of 1918 Old 06-10-2007, 12:11 AM
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Quote:
Originally Posted by LINEARX View Post

Excellent work Chas. I think we all expect the test figures to be somewhat disappointing compared to manufacturers claims but this particular amplifier seems to perform way under claims....

Especially as an amp for subs.
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post #54 of 1918 Old 06-10-2007, 02:13 AM
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Quote:
Originally Posted by chasw98 View Post

... You will notice that at 20 KHz the distortion is out of bounds. In order to get the distortion down to a reasonable level, I had to drop the voltage to 43.7 volts which equates out to 225.4 watts at this frequency. ... I do not believe that this amplifier likes to be tested with a 20 KHz sine wave, even for a short period of time. ...

Are any weighting curves being used by the Tektronix? I'm pretty sure Behringer uses A-weighting to get better numbers on their spec sheets. Harmonic distortion for 20 kHz happens at 40 kHz, 60 kHz, etc. If Behringer cheats and counts only the components under 20 kHz then they can get really good numbers for THD+N; you can't hear 20 kHz harmonic distortion directly anyway. Besides, the tweeters in most home speakers can't handle even a fraction of that kind of power.
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post #55 of 1918 Old 06-10-2007, 10:13 AM - Thread Starter
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No, no weighting curves are being used, but a 30 KHz LO PASS filter has been engaged for all tests. I did put an A weighting filter in this morning and checked the distortion. It dropped to .0002% at 20 KHz. Not very realistic. If you want to learn more about the quandry of amplifier measurement, especially as it applies to pro units, then read this article.

http://www.soundandcommunications.co...6_06_audio.htm
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post #56 of 1918 Old 06-10-2007, 11:19 AM - Thread Starter
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Here are the 8 ohm results for the EP2500 amplifier rated at 450 watts/channel 20-20KHz at <0.1%THD both channels driven.



If you are wondering how much more power this amplifier will give up before shutting down, it won't! This is the ragged edge for this amp. It will either go into oscillation or shutdown from thermals before giving more power.
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post #57 of 1918 Old 06-10-2007, 11:24 AM - Thread Starter
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Here are the 4 ohm results for the EP2500 amplifier rated at 650 watts/channel 20-20KHz at <0.1%THD both channels driven.



Some interesting notes. The digital ammeter connected to the amplifier registered 17.2 amps at full power 1 KHz. The thermometer registered 158 degrees fahrenheit on the top case of the cover where it is attached to the heat sink. It was cookin'.

Chuck
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post #58 of 1918 Old 06-10-2007, 12:34 PM
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Dang, it seems to hold up very well, now I am dying to see what it does with 8, 4, and especially 2ohms bridged.
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post #59 of 1918 Old 06-10-2007, 12:42 PM
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If that's the temp with 4-ohms/channel I'm worried what 4-ohms bridged or 2/1-ohm(s) if you're crazy would do...

So far it looks good...kinda. We'll see!

...
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post #60 of 1918 Old 06-10-2007, 01:21 PM
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Hey, any chance you would eventually test one of the Butttkicker amps?
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