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Measuring Amplifiers - Page 56

post #1651 of 1917
Thread Starter 
Here is the basic S/N, Frequency Response, and 8 ohm power tests.



And here are the 4 ohm power tests.


You will notice that I was only testing at 1% THD levels. That is because without sophisticated filters any THD levels that I measured at .1% were very obviously just not true and were unduly influenced by the lack of test equipment. (When I would set the THD at .1%, power dropped so low it was just not true.)

With all that being said, I did try this amp in several of my systems at different operating points, i.e. sub amp, mid amp, full range amp. There is a lot more to it than the numbers reveal.

Chuck
post #1652 of 1917
Thank you very much for this Chuck. I have been holding off on purchasing one of these amps, and now I just might pull the trigger.

Interesting to see how your measurements compare with the specs in the manual:
Code:
T.H.D. (2 x 4 ohms) - <0.1% @ 470 watts per channel from 20 Hz to 20 kHz
T.H.D. (2 x 8 ohms) - <0.1% @ 250 watts per channel from 20 Hz to 20 kHz
On talkbass.com, BbbyBld, a young MI amplifier engineer at Peavey, provided a method of bridging the IPR 1600. I would be interested to see the eight-ohm bridged numbers for this amp if you could manage another test.

Thanks again!
post #1653 of 1917
Not bad.

Thanks Chuck.
post #1654 of 1917
Thanks for the results, Chuck, looks like solid power.

Quote:
Originally Posted by chasw98 View Post

With all that being said, I did try this amp in several of my systems at different operating points, i.e. sub amp, mid amp, full range amp. There is a lot more to it than the numbers reveal.

Could you elaborate?
post #1655 of 1917
Chuck, thank you for your fair review. I appreciate your attention to detail and know that this one was frustrating for you. Posting both cold and hot load resistor values is a helpful touch. It shows that our measurements aren't too far apart. The measured output voltage applied to 4 ohms yields 513 watts, pretty close to what I measure as the 4 ohm 1kHz power of 530. Your analyzer measures THD+N (noise) and you had lots of ultrasonic carrier noise to contend with. Given those circumstances, kudos.

When are you taking us for a ride in your new car? Do you have lots of insurance?
post #1656 of 1917
Thread Starter 
Quote:
Originally Posted by noah katz View Post

Thanks for the results, Chuck, looks like solid power.

"Quote:
Originally Posted by chasw98
With all that being said, I did try this amp in several of my systems at different operating points, i.e. sub amp, mid amp, full range amp. There is a lot more to it than the numbers reveal."

Could you elaborate?

This is where it gets more into the subjective a s opposed to the measuring of numbers that are straightforward. What follows are my opinions and impressions and should possibly be taken as the ravings of a lunatic fool!

I tried the IPR-1600 as a subwoofer amp in my dedicated 2 channel system that usually has a QSC PLX3402 driving a pair of sealed 15 inch subs which also have a Marchand Bassis being used to tune them. This is only 2 channel, not home theater so no WOTW bass stuff. Nobody could tell any difference whatsoever when the Peavey was being used vs. the QSC except when it ran out of power. Had I used one of the bigger Peavey amps, nobody would have been able to tell the difference at all between the 2 amps. My subs are crossed at 40 Hz and I am playing High Resolution (upwards of 44.1/16 KHz) music through this system. And yes, there are a lot of pieces with stunningly low bass that sound wonderful in hi res 2 channel music.

I used the amplifer for a while in my bedroom system that uses a pair of Dayton 3 way floorstanding speakers with dual 8 inch woofers, 5 1/2" mid, and Seas H1212 tweeters. Over the years I have used many different amps in the bedroom (usually cast offs from the main system) such as Onkyo receivers, Bryston 3B-ST, Hafler DH-220 modified, and currently a Harmon Kardon AV receiver. I heard a much cleaner upper mid range/high range than I have heard with any other of the mentioned units. I find it very hard to admit that the Peavey IPR-1600 sounded really good as a full range amplifier because my own built in prejudices formed over many years of using pro gear and home audio gear still tell me quite loudly that "PEAVEY IS NOT A HIGH FIDELITY AMPLIFIER". But my ears told me that I could hear more detail that was cleaner and more open than the other amplifiers. It has been quite hard to get over built in prejudices vs. what I heard.

OTOH, when I used the IPR-1600 in my system and pulled out my Pass amplifiers and inserted the Peavey, there was a difference between the two. The Pass amplifiers sounded much better in all areas. This was a comparison of a $3,000+ amplifer vs. a $300 amplifier. That being said, there was not a 10X difference between the two. Law of diminishing returns. And my class A Pass amps double as space heaters also

The amplifier sounds better than the numbers reveal, even the factory specs. If I had to criticize this amplifier, it would be external to it. GET RID OF THE BLUE LED's!!!! (marketing's fault) The thing lights up like a roadhouse in the middle of the night on a lonely southern road. Where are the binding posts? (a cost cutting measure). The fan in the amplifer is just too damn loud for the unit to sit in the same room. All of these criticisms are a moot point as soon as you use the amplifier for it intended purpose. Pro Sound Amplification. If you can work around these points, you have a damn good $300 amp that will play good high fidelity music.

Chuck
post #1657 of 1917
Chuck,

Very interesting comments indeed. Thanks for taking the time to test and report on this amp.

James
post #1658 of 1917
i had sent a note to chuck with a couple questions including how much time it takes to perform the kind of measurements that he just posted. a lot more than i thought. apparently, it is not as simple as hook up a load, blast the amp, and measure. the amount of time involved makes me appreciate his work even more.

here is my pm and chuck's reply (posted with his permission):

Quote:


Originally Posted by LTD02
just out of curiousity, how long does it take, start to finish, for this kind of measurement?

It usually takes about 3 days on and off to get any given amplifer to measure correctly. There is usually always a whoopsie that you have to contend with to get the amp running properly on the test bench. Then you want to make sure that it is properly warmed up but not so hot that the measurements are influmeced by heat or cold. Almost always I end up taking a series of measurements that give me a sense of how the unit will respond and then give it the best shot at performing like it should once that is done. I would say that I took around 6 3 to 4 hour sesions to get the measurements on this unit.

Chuck
post #1659 of 1917
Color me impressed... Time to post on that Peavy thread too shut up the troll that was posting there. Thanks Peavy for being a stand up company and sending it to Chuck for testing even knowing that his tests are much different then yours.
post #1660 of 1917
Definitely a kudos to Peavey!!! Well done guys and looking good. Not too shabby for less than 7 lbs.
post #1661 of 1917
Chuck's subjective comments about its full range potential has me thinking about the Peavy DSP version.
post #1662 of 1917
anyone know if there is a rolloff below 20Hz on the peavy amps?
post #1663 of 1917
Quote:
Originally Posted by penngray View Post

anyone know if there is a rolloff below 20Hz on the peavy amps?

For the IPR1600 only, -3dB @ 1.6Hz calculated. I measured .1dB down at 10Hz.
post #1664 of 1917
Thats great! When is the IPR3000 being released? I want to buy one!!
post #1665 of 1917
Quote:
Originally Posted by penngray View Post

Thats great! When is the IPR3000 being released? I want to buy one!!

Keep in mind the IPR3000 rolls off at more like 16Hz (per SNH's earlier posts). Only the IPR1600 extends down that low.
post #1666 of 1917
Quote:
Originally Posted by Stereodude View Post

Keep in mind the IPR3000 is more like 16Hz. Only the IPR1600 extends as low.

really, why would that be inherently true?
post #1667 of 1917
Quote:
Originally Posted by penngray View Post

really, why would that be inherently true?

Got me, but that's what JD said. The IPR1600 is limited strictly by AC coupling, and the others have something else, though I don't recall what it was, and it seems that JD edited it out of the post.

The reasoning given by JD is that the filter is there to protect pro audio gear from damage by high power low frequencies.
post #1668 of 1917
Quote:
Originally Posted by Stereodude View Post

Got me, but that's what JD said. The IPR1600 is limited strictly by AC coupling, and the others have something else, though I don't recall what it was, and it seems that JD edited it out of the post.

The reasoning given by JD is that the filter is there to protect pro audio gear from damage by high power low frequencies.

Thanks and that sucks, it should be a modifiable filter
post #1669 of 1917
Quote:
Originally Posted by penngray View Post

Thanks and that sucks, it should be a modifiable filter

It's probably just a blocking cap at the input; easy enough to change, but will likely void warranty.
post #1670 of 1917
Quote:
Originally Posted by A9X-308 View Post

It's probably just a blocking cap at the input; easy enough to change, but will likely void warranty.

Thx, I will consider it when the amp comes out. I like 7 lbs and lots of power!!
post #1671 of 1917
Quote:
Originally Posted by penngray View Post

I like 7 lbs and lots of power!!

I would assume that for most instances, an HT sub amp doesn't get moved much unlike a PA or MI rig. So why care about weight?
post #1672 of 1917
Quote:
Originally Posted by A9X-308 View Post

I would assume that for most instances, an HT sub amp doesn't get moved much unlike a PA or MI rig. So why care about weight?

because I move things around and test, I also put amps sometimes high up and its getting harder to lift 50lbs suckers some days (must get back to working out)....I have sold off amps ONLY because they weigh too much!
post #1673 of 1917
Chuck, any idea why it increase in volts as you raised the hz? It's within +/-2 volts through out the spectrum where as the behringers had +/-5
post #1674 of 1917
Nice job again Chuck. Thanks.
post #1675 of 1917
Thread Starter 
Quote:
Originally Posted by stgdz View Post

Chuck, any idea why it increase in volts as you raised the hz? It's within +/-2 volts through out the spectrum where as the behringers had +/-5

Yes, actually it is because of the way the amplifier works. There is a lot of high frequency in this amplifier (when I say high frequency, I mean much higher than 100 KHz). Part of my problem in measuring this amplifier is that I was able to use a 30 KHz filter in my HP to cut off some of the high frequency and try to just measure the fundamental, but it also allows the non audible harmonics to come through and be measured as THD+N at the lower frequencies. When measuring 20 KHz with a 30 KHz filter I was able to get "more" perceived fundamental than harmonics out of the amplifier so more voltage. Had I been able to switch the filter as I switched the fundamental, you would have seen a smoother response. I questioned JD and the factory about this and they confirmed what I saw on my scope. They use a very sophisticated active filter for their measurements.

Chuck
post #1676 of 1917
How does that correlate to real full range usage? Are we going to see small votage changes in higher frequencies?
post #1677 of 1917
thanks Chuck, how hot did the heat sinks get during testing? I would gather they stayed pretty cool.
post #1678 of 1917
Thread Starter 
Quote:
Originally Posted by penngray View Post

How does that correlate to real full range usage? Are we going to see small votage changes in higher frequencies?

It doesn't really correlate to 'real full range usage' because it is an effect of my older test gear measuring this particuar piece of equipment. If I had the burst testing Audio Precisoin test gear with the active filter, this would not have shown up as much as it did. What you might find interesting is that the 8 ohm tests showed the 20 KHz measurement as higher than 20 Hz & 1 KHz measurement. But we are only talking about 1 to 2 volts. In the 4 ohm measurements there was a 2.5 volt swing in the other direction.

I could probably have come up with 10 different sets of figures on a single day and maybe showed a trend, but it is hard to say using 'hook up a load, steady state sine wave testing' method as opposed to computer controlled bursting.

To me it is a conundrum. Should the way you test a piece of equipment to get specifications matter? If Peavey chose to manufacture this amplifier and present its specifications using numbers obtained from steady state sine wave testing, would not as good a specification do the amp justice and then the amp would look unfavorable compared to the competition that did not use that method. And now you are back at the beginning wondering why or if there can ever be a common standard for measuring amplifiers? Wait till the next generation of technology is developed and the bursting method in current use does not apply, what next? How will you measure the wattage of a true digital amplifier that only puts out zero's and one's instead of analog waveforms but claims to have 100 watts per channel?

Sorry for the long windedness (sp).

Chuck
post #1679 of 1917
Thread Starter 
Quote:
Originally Posted by stgdz View Post

thanks Chuck, how hot did the heat sinks get during testing? I would gather they stayed pretty cool.

I never felt them get warm at all. As a matter of fact the fan would kick in very quickly when running a sine wave into a load and keep them cool.

Chuck
post #1680 of 1917
CHuck, welcome back to AVS (even if its a short time)

Thank you again for the new tests and for your input.

btw, did you ever get your Active XO built?
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