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Measuring Amplifiers - Page 54

post #1591 of 1917
Quote:
Originally Posted by chasw98 View Post

A Pass 150, an Aragon 8008BB, and an Art SLA1 but it will be a little while yet.

I would be interested in the Aragon test. A year or so ago I replaced my pre-Klipsch Aragon 8008BB/8008ST/8002 amps stack in my Paradigm HT speakers system with all Mackie FR1400s. Plan to put the Aragons back on the Maggies.

I had tried the Mackies on my Thiels and Magnepans, where they didn't sound so hot, where as the Aragons did much better. But for whatever reason, in the HT system, they sounded just as clean, with more dynamics. Now I'm planning to add two more Macks for the HT IB system.
post #1592 of 1917
I'm in for $40.00 if Ricci stores the money OR maybe Sickneedhelp can handle the purchase directly within the company. Do we trust him?
I'm curious about the Peavey IPR 1600 too. It's discounted at Sweetwater for $299.99 and weighs 7lbs???
post #1593 of 1917
Quote:
Originally Posted by LINEARX View Post

I DO believe you are employed by Peavey and may have everything to do with the quality of their amps, and Peavey electronics is headquartered in Meridian Ms. where you live

Quote:
Originally Posted by chasw98 View Post

Well, 'Sickneedhelp', apparently you work for Peavey or you work in or own a dealership that carries Peavey. I don't even know if you design amplifiers, much less respectable ones.

He does... he was up front about it in post #136 here: http://www.avsforum.com/avs-vb/showt...1150665&page=5

I have no problem trusting the guy responsible for all the good Crests from back in the day, as long as he is who he says he is
post #1594 of 1917
It'd probably be best to just have a pitch in to buy the amp without worrying about Sickneedhelp or Peavey being involved. If they want to furnish an amp for testing that's awesome and very commendable of them, but I can see why they would not want to. They have more to lose than to gain by it.

I'm willing to throw in a a few bucks towards the IPR testing cause myself. Thing is, if the amp performs well in the tests I see them getting very popular. At that point one of the people who chipped may want to keep the amp and pay off the other contributers and Chuck minus a reasonable amount. I'll likely be in for a few of the IPR's myself if it does well, but I'm still mostly interested in the 6000w rated model. If it does badly then we just sell it off and split the money and take a small loss.
post #1595 of 1917
Quote:
Originally Posted by LINEARX View Post

I'm in for $40.00 if Ricci stores the money OR maybe Sickneedhelp can handle the purchase directly within the company. Do we trust him?
I'm curious about the Peavey IPR 1600 too. It's discounted at Sweetwater for $299.99 and weighs 7lbs???

I'm engineering, not marketing. Because it's not a normal activity, I can't poof up amplifiers to send out without lots of paperwork and approvals. It's life in a large company. It will be easier for me to also chip in than to get past all the justifications. Anyway, I'm working on it. Please be patient.

As for "Do we trust him?", I won't be holding the money. I would like to have some one on one with Chuck to make sure he has the AP AUX0025 (or eq.) low pass filter necessary to measure a class D amp. I also have concerns about clean sinewave AC. The variac I saw in the equipment pictures is small. I've been burned too many times by power specs measured by others while their AC was flat topped and not producing the peak voltage required to fully charge the caps. Even if the reviewer puts in a qualifier like "we didn't have the proper equipment to measure accurately" the numbers tend to stick but the qualifier doesn't as they get passed around.

I'll take Chuck at his word that he will be fair despite the pre judgement.
post #1596 of 1917
"...to make sure he has the AP AUX0025 (or eq.) low pass filter necessary to measure a class D amp."

Is that to simulate speaker inductance? Don't some speakers, like panel types, have very low inductance?
post #1597 of 1917
Quote:
Originally Posted by noah katz View Post

"...to make sure he has the AP AUX0025 (or eq.) low pass filter necessary to measure a class D amp."

Is that to simulate speaker inductance? Don't some speakers, like panel types, have very low inductance?

The purpose of the filter is to strip out any residual HF carrier. It's only a THD + Noise test concern. The carrier is noise and adds to the measured number. It's not a real world issue since it's 400kHz noise. Since this is a discerning group here, I'd hate to be dinged because the measurement was 0.5% at rated power instead of 0.1 due to residual carrier.
post #1598 of 1917
You're an interesting guy JD. I just finished reading the other thread where some of our members did their damdest to "disqualify" you as an expert and then to discredit your amp. LOL we can be so severe on here. It was an entertaining 'give and take' and educational as well. Overall, you won!
You have a lot of engineering to share and that's beneficial for all of us. You also have a product that seems to fit into a lot of our entertainment schemes. It would be excellent to be able to fill your desires by finding some consumers within this forum and it would be a step forward for a lot of us if we had a newer/better amp with which to power our systems.
You've convinced me that your new 7lb baby is for real, you just gotta do an "in situ" performance by which we can all see for ourselves that the IPR 1600 is the real deal and it's advertised specs are real world . . . . so to speak.
post #1599 of 1917
Quote:
Originally Posted by chasw98 View Post

A Pass 150, an Aragon 8008BB, and an Art SLA1 but it will be a little while yet.

good! as long as you are not touching my X250 or the twins
post #1600 of 1917
Quote:
Originally Posted by Sickneedhelp View Post

The purpose of the filter is to strip out any residual HF carrier. It's only a THD + Noise test concern.

Umm, isn't the filter supposed to be IN the amp? Or do you simply use the speaker inductance as part of the RF filter.
post #1601 of 1917
Quote:
Originally Posted by Th3_uN1Qu3 View Post

Umm, isn't the filter supposed to be IN the amp? Or do you simply use the speaker inductance as part of the RF filter.

There is a low pass filter in the amp.... of course. Otherwise, there wouldn't be any mosquitoes within miles of your house.

The purpose of the extermal filter is to stip out residual carrier before it goes into the distortion analyzer. It connects to the input of the analyzer, not to the speakers. The high frequency content can play havoc on the sensitive input circuitry of the analyzer. Measuring class D requires special equipment. If you go to the AP site, you should see some discussion about how it affects some of their equipment and the models they have that are tolerant of same. Unfortunately simply using selectable low pass filters inside the analyzer doesn't work well enough because of the problems that already occured prior to the filter stages.

Technology moves on and life gets more complex.
post #1602 of 1917
Quote:
Originally Posted by Sickneedhelp View Post

There is a low pass filter in the amp.... of course. Otherwise, there wouldn't be any mosquitoes within miles of your house.

I'll take two without the filter, please. Summer's coming
post #1603 of 1917
Quote:
Originally Posted by Oklahoma Wolf View Post

I'll take two without the filter, please. Summer's coming

Summer?? They told me it was Global Warming.
post #1604 of 1917
Quote:
Originally Posted by Sickneedhelp View Post

There is a low pass filter in the amp.... of course. Otherwise, there wouldn't be any mosquitoes within miles of your house.

Now that would be a good thing actually.
post #1605 of 1917
the slew rate seem slow relative to the other amps in the market...are these highend loser amps?
post #1606 of 1917
Quote:
Originally Posted by LINEARX View Post

........... You've convinced me that your new 7lb baby is for real, you just gotta do an "in situ" performance by which we can all see for ourselves that the IPR 1600 is the real deal and it's advertised specs are real world . . . . so to speak.

Okay ........ hopefully by now everyone has read Eva's commentary at http://www.avsforum.com/avs-vb/showt...150665&page=11

Reading her input on another forum, she definitely knows her stuff. That should make some on here feel a bit better about the wild claims some of us are making in regards to the technology.

Marketing says they will provide an IPR1600 for the Chuck test. As I noted previously, I have concerns about Chuck being able to measure class D accurately. However, it's unreasonable to expect someone who measures amps as a favor to forum members to spring for the $$ to buy input filters, mondo variacs, mondo AC mains wires and a day of residential electrician's time. The folks on here will have to accept that Chuck's results, best case, will be approximate due to no fault on anyone's side.

I don't know if Marketing will choose to ship one directly or to have the regional rep drop one off at Chuck's doorstep.

Tag, you're it
jdb
post #1607 of 1917
Excellent JD. WE couldn't ask for more . . . . . that doesn't mean though, that we won't. Have you 'PM'ed Chasw98 to see when and if he's available to run the tests?
post #1608 of 1917
Excellent.

Regardless of how the test turns out (if Chuck is interested in testing it), this is laudable of Peavey to step up.
post #1609 of 1917
Thank you JD.

As others have said, it is wonderful to see a manufacturer stand behind their product like this. I will soon have a spot in my system for an amplifier like the IPR, so I will definitely watch for the results.
post #1610 of 1917
Quote:
Originally Posted by LINEARX View Post

...... Have you 'PM'ed Chasw98 to see when and if he's available to run the tests?

I did just now.

Thanks to the three of you for the kind words
jdb
post #1611 of 1917
"Regardless of how the test turns out (if Chuck is interested in testing it), this is laudable of Peavey to step up."

+1

my mantra is "efficiency, efficiency"...first in speakers, now in amps. i'm looking forward to the results. thanks peavey.
post #1612 of 1917
Thread Starter 
JD and I have been PM'ing and we will be talking next week to work out the details. Looks like I get to test an IPR 1600. Stay tuned.

Chuck
post #1613 of 1917
Thanks JD, thanks Chuck. History is being written as we watch.
You tell me, which Chinese company manufacturing and/or selling their products in the U.S. would let U.S. Consumers test them before buying??? Would it be NONE?
. . . . Geez I hope Peavey isn't a Chinese conglomerate . . . . yet.
I hope Peavey isn't Chinese for manure. Those are just a couple random thoughts passing on through my brain.
Here's another, what do you flavor BEETS with?
post #1614 of 1917
Quote:
Originally Posted by LINEARX View Post

I hope Peavey isn't Chinese for manure. Those are just a couple random thoughts passing on through my brain. Here's another, what do you flavor BEETS with?

I use chocolate syrup



Quote:
Originally Posted by chasw98 View Post

JD and I have been PM'ing and we will be talking next week to work out the details. Looks like I get to test an IPR 1600. Stay tuned.
Chuck

Chuck, based on your substantial experience fixing amplifiers, it's a given that you also know how to kill one. When you receive the 1600, please make a serious attempt to kill it either before or after you run the tests, your choice. Sustained mains above 140VAC might make for messy blown supply caps. Sustained sine wave at clip above 20kHz unloaded should eventually fry the zoble network as the output filter resonates. I'd consider those limits of the bounds.
post #1615 of 1917
i don't suspect chuck's goal is to torch the amp, just to measure it under similar testing conditions of the other amps in order to provide some basis for comparison. the results will be compared only against other amps in chuck's tests, as all amp testing is bench specific (most of us get that around here). again, i'm looking forward to the results.
post #1616 of 1917
That's it! I gotta try that.
post #1617 of 1917
Quote:
Originally Posted by Ricci View Post

This seems like a decent place for a discussion I'd like to have.

There always seems to be an argument over just how long an amplifier should be able to maintain output, ratings and some other things. Some of us would prefer that an amp could sit there and do a sine wave for an hour without cooking itself. Others feel that 30ms is enough duration. Most are probably somewhere in between. Do you use a real unregulated AC line? Lately it seems that manufacturer's are siding with marketing and the bigger the # you can claim the better, so we are getting burst ratings of 4000w (EP4000), 6000w, 18000w etc...A lot of people suggest that you "test the amp in the real world" and that's what I'd like to discuss.

Exactly what would be a valid real world test procedure of an amplifiers performance that could be used for nearly any amplifier? I'm not talking about evaluating SQ differences in some kind of listening panel, but I guess subjective comments could be a part of it. I'm interested in determining real world output limits both dynamically and long term, overload characteristics, reliability, long term performance with heavy demand, etc. That kind of thing. I'm thinking it would be something involving a bank of high power speakers probably limited to the bass range mostly as the default load? I don't think anyone wants to try max output or overload testing with tweeters and mids involved...
Perhaps a normal high power full range speaker to gauge the subjective performance of the amp with music?

Ideas?

How long should you be able to do RMS output? I would say that this is entirely based on the music itself.

I saw you mention drum transients later on...with uncompressed music, it could easily introduce 30dB of crest...which is to say peaks that require 1000x more power than the RMS level. So if you're listening to 90dB sensitivity speakers at 90dB (1W), then you're going to need an amplifier that can drive the speakers with 1000W for the duration of the kick drum transient...so what, like half a second maybe? Since most speakers will introduce 3-10dB of compression with those transients, you probably won't notice much of a difference between 500W or even 250W feeding the same speaker.

But now change your source material to some kind of synth bass sound that needs to deliver +20dB sustained for a few measures...so like 10 seconds? Now you need an amp capable of delivering 100W for 10 seconds in order to for the amp to not introduce distortion when listening at a nominal 90dB.

One of the advantages to class AB designs is that the rail voltage is often much higher than the RMS voltage the amplifier can deliver continuously. This is because class AB designs are usually limited by thermal performance. For this reason, a 100W class AB amp is probably going to sound more ballsy than a 100W class D amp. The class D amp will (should) be cable of delivering the RMS voltage that corresponds to the rail voltage (within a few percent). So where the 100W AB design might be able to reproduce a short 400W transient, the class D amp is always going to clip at 100W, regardless of RMS or peak transients. All that is really saying is that Class D output stages are not limited by thermal performance.

With a class D output stage, you just need to make sure the RMS power is enough to handle your loudest transient....and then you don't have to worry about how long it can sustain transients. With an AB output stage, you can theoretically undersize it a bit if you know how it handles transients.

To save on costs, I'm sure commercial class D designers are gonna cut back on the power supply feeding the class D output stage, which in turn can be a source of compression at sustained output levels. However, this is not something that is inherent to the class D amplifier topology. The same would be true for class AB or any class of amplifier actually.

So with that in mind, I would propose measuring how long the amplifier can deliver various voltages limited by 1% THD into various resistive loads. The absolute instantaneous maximum would be determined by the unloaded rail voltage (so just measure the rail voltage). Then I would set the output to 1dB lower than the rail voltage and measure how long it can deliver output before reaching 1% THD. Then drop the output 1dB and continue dropping by 1dB increments everytime 1% THD is hit. You can probably stop the test once it takes longer than 1 min to reach 1% THD. And then you'll want to repeat at 10Hz, 100Hz, 1kHz, and 10kHz into resistive loads of 2, 4, 8, and 16 (so sixteen total plots). What you're measuring is the output level limited by 1% THD over time, so what you should see is an exponentially decaying curve starting at the rail voltage until it reaches the steady state capabilities of the amplifier.

With this information, you can look at the amplitude envelope of your source material to determine if your amp can accurately reproduce the source material. If you want to be really crazy, you can even throw in the frequency content of the music against the impedance response of your speakers to determine where the breaking point is.

Sadly, such a test would be difficult to do accurately without automated gear. The new APx525 series should be capable of it though. The other problem is that you have the thermal history from delivering the higher output levels before stepping down the output...so it will look worse than a real case scenario. You might even want to measure the output when limited by 0.1% THD and 10% THD too.

The real problem with trying to find a single meaningful amplifier marketing spec that is that it requires many variables to fully describe all the behavior of an amplifier, and it is incredibly dependent on the source material and speakers being used.

Anyways, just a thought about how I might go about measuring an amplifier and capture some information about the time domain nature of its performance.
post #1618 of 1917
Dayton SA1000 Subwoofer Amplifier Rack Mountable

What ever happened to the follow up on this amp? Is its output and half of rated?

Quote:
Originally Posted by DaytonAudio View Post

As a follow-up, I'd like to say I’m concerned by some here that immediately assume this amplifier is “bad”, especially in light of the fact that this is a tracking amplifier that's designed to deliver high voltage into reactive loads (ie, loudspeakers). They are not optimized for fully resistive load banks. So much of this talk in this thread is not relevant to driving woofers. These hi-tech amps can put a ton of power into the actual woofer and cannot be fully tested using standard non-inductive resistant loads. That being said, we'll post additional information as soon as we complete our internal testing.

Our ultimate goal here at Dayton Audio is to provide audio enthusiasts with products that meet and exceed expectation, and we apply that to our customer service as well. Thanks again.

Rich Taylor
Dayton Audio
post #1619 of 1917
Quote:
Originally Posted by LTD02 View Post

i don't suspect chuck's goal is to torch the amp, just to measure it under similar testing conditions of the other amps in order to provide some basis for comparison. the results will be compared only against other amps in chuck's tests, as all amp testing is bench specific (most of us get that around here). again, i'm looking forward to the results.

I'm asking Chuck to make it a goal. He knows what might be thrown at it in the real world ...... and a bit of the unreal world. My feeling is that unless the manufacturer lets you know their product is intended for the confines of an AV room, reliability should be part of a performance test.
post #1620 of 1917
Quote:
Originally Posted by Sickneedhelp View Post

I'm asking Chuck to make it a goal. He knows what might be thrown at it in the real world ...... and a bit of the unreal world. My feeling is that unless the manufacturer lets you know their product is intended for the confines of an AV room, reliability should be part of a performance test.

That's pretty cool actually - not sure a lot of engineers/manufacturers would be so keen on giving the OK for such a test.

OT: I have an old illuminated "Peavey Authorised Dealer" sign (90 x 125cm) that I'm rebuilding as I bought it with a broken frame and bad flouros. If I get time tomorrow I'm going to pick up some Tassie Oak for the frame and perf board for the back so I can use a heap of white LEDs to illuminate it from behind. I think I'll hang it at the bottom of the stairs in my apartment, and maybe keep one of my T40s (got 3 and a T60) on a stand next to it to complete the theme.

Gratuitous T40 pic.
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