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post #91 of 1917 Old 06-15-2007, 01:03 PM
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Quote:
Originally Posted by Richard Mayer View Post

Chuck,

First of all, thank you for doing these tests.

Have you considered taking some peak/burst output tests? I mean 30 second steady sine wave is not a very common event in real program material. I know you're trying to test whether manufacturer's specs are true or not, but IMO it would be beneficial to try to "replicate" the real program material too. 20 ms burst is pretty commonly used to test the peak output. That way you wouldn't also have any heat problems.

Just a suggestion.

Burst test: Amplifier taking a vacation in Hawaii drinking margaritas
Rms test: Amplifier working on the farm 24/7 as slave labor.

I tested my Crest 10001, 4 ohm bridged, dual 110VAC [30A] -> ~5,500w
continuous. I can do more with a solid 120VAC input. I can run like this for hours
with no issues. Many proamps [or amps in general] can only do rms type of
testing for seconds before something happens. I did a burst test on the Crest
and measured a 18kw transient using the scope playing a drumming solo track.



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post #92 of 1917 Old 06-16-2007, 03:39 PM
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Chuck, thank you for having me over this afternoon and helping me determine if any of my amplifiers don't meet spec. Thanks for taking the time to test six amplifiers that probably are too low-powered to be of interest to people here. My requirements are obviously different. Before coming over I had some idea which amps to keep and which ones to sell. Now it's not so clear. The Adcom that kept on blowing the fuse, I moved that to the main speakers in my living room for now. As we expected, it did fine; in fact, it sounds pretty good, even when loud.

I'm going to test the Hafler with my own rig to see if I get the same results that we got this afternoon. Can you PM me the numbers? BTW, I'm looking forward to seeing the test results of your Cinénova amps.
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post #93 of 1917 Old 06-16-2007, 03:52 PM
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I will second (or third ) the Buttkicker amp request.

Chuck, when you replicate those manufacturer power ratings, do you test how much further it will go?
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post #94 of 1917 Old 06-20-2007, 11:22 AM
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Quote:
Originally Posted by thylantyr View Post

Burst test: Amplifier taking a vacation in Hawaii drinking margaritas
Rms test: Amplifier working on the farm 24/7 as slave labor.

I tested my Crest 10001, 4 ohm bridged, dual 110VAC [30A] -> ~5,500w
continuous. I can do more with a solid 120VAC input. I can run like this for hours
with no issues. Many proamps [or amps in general] can only do rms type of
testing for seconds before something happens. I did a burst test on the Crest
and measured a 18kw transient using the scope playing a drumming solo track.

For this reason I see Richard's idea very interesting/important...true program
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post #95 of 1917 Old 06-20-2007, 12:43 PM
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Quote:
Originally Posted by blaser View Post

For this reason I see Richard's idea very interesting/important...true program

Burst test, IMO is not as important because.... A continuous rms test will give you
a better amplifier vs. amplifier comparison as it exposes the weakness of the
amplifier very easily. If you know the rms values, you can estimate the burst
numbers to be in the ~ 1.5x - 3x higher range.



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post #96 of 1917 Old 06-20-2007, 12:50 PM
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Quote:
Originally Posted by thylantyr View Post

Burst test, IMO is not as important because.... A continuous rms test will give you
a better amplifier vs. amplifier comparison as it exposes the weakness of the
amplifier very easily. If you know the rms values, you can estimate the burst
numbers to be in the ~ 1.5x - 3x higher range.

Wouldn't burst numbers be based on who has more capacitors? (basically speaking)
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post #97 of 1917 Old 06-20-2007, 01:26 PM
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Quote:
Originally Posted by crackyflipside View Post

Wouldn't burst numbers be based on who has more capacitors? (basically speaking)

Capacitors get all the glory on burst tests but there is more to it than
just caps. If you want more info, pm



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post #98 of 1917 Old 06-21-2007, 03:43 PM
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Thylantyr,

Can you pls post your thoughts for everybody to see? PMs will deprive many from learning.
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post #99 of 1917 Old 06-21-2007, 03:51 PM
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Quote:


Capacitors get all the glory on burst tests but there is more to it than
just caps.

*ahem*

A good power supply/transformer combo?

My Dual 18" LLT subs 120dB down to 10hz

 

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post #100 of 1917 Old 06-21-2007, 06:22 PM
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Quote:
Originally Posted by blaser View Post

Thylantyr,

Can you pls post your thoughts for everybody to see? PMs will deprive many from learning.

You can probably write a big story just on one issue. You can probably
write a book if you include more issues. This thread would go way
off topic.

Here's one simple issue.

The conventional power supply design uses a simple transformer for 50/60hz operation to mate with your house voltage.

Not these kind;
http://www.transformersmovie.com/

But these kind.
http://en.wikipedia.org/wiki/Transformer

The output connects to diode(s) to make a rectifier, usually full wave, but full wave
bridge rectifiers are more common. It converts the AC to DC but it's not
a clean DC, it has ripple.

Green = ripple
http://en.wikipedia.org/wiki/Rectifier

The output of the rectifier connects to the power supply capacitors to smooth
out the ripple.

http://en.wikipedia.org/wiki/Capacitor

Pic #2 shows the capacitor installed and ripple reduced.
http://hyperphysics.phy-astr.gsu.edu...ic/rectbr.html

You can see when the capacitor discharges and recharges again on the
next cycle. So, capacitor refresh is determined by that transformer frequency.
If the frequency is low and you want less ripple, then you need to install
more capacitance in the power supply design. High end esoteric home
amps may have 100,000uF of capacitance per voltage rail, maybe higher,
but it's a big chassis to hold all those caps. A cheap home amp may have
5,000uF give or take. There is nothing written in stone on how much you
should use, usually the physical design of the amp will limit your choice,
so even if you wanted to make an uber amp with 100 volt rail voltage and
10 farads of capacitance, it would be a huge.

***

Another type of power supply is a high frequency switching power supply,
SMPS is a common name {switch mode power supply}. A common design may
use AC to DC conversion {minus big transformer} and the raw DC connects to a
few caps for smoothing, then that high voltage DC connects to a smaller dinky
transformer but it switches at a much higher frequency, for audio purposes, SMPS
are in the 50,000 - 200,000 hz range. This is huge compared to 60hz
transformers. To switch the transformer on/off at 50khz - 200khz you need
semiconductors {transistor, etc}.

Imagine the ripple you get, it's uber high in frequency so... you don't need
very high capacitance because the refresh rate is so high that you can accomplish
the same task with just a few thousand microfarads of capacitance.

To answer the question. You can have a big 60hz based power supply inside
a gigantic power amplifier with 200,000uF of capacitance, but on the same
token you can have a clever, more modern power supply design with 2000uF
{100x less} and accomplish the same task because it's a SMPS design.

EP1500 - 60hz power supply design {big transformer}
http://home.pacbell.net/lordpk/proam...r_EP2500-1.jpg

PLX3402 - SMPS {dinky transformer}
http://home.pacbell.net/lordpk/proam..._PLX3402-1.jpg
[yellow square on the right]

The PLX is rated for about 1000w more watts.

If you were to judge the amps just on rail capacitance without knowing
the power supply design, it would be hard to form a conclusion. Also,
adding more capacitance to a SMPS design may not bring that much to
the party - from an audible point of view - , but you can measure the
voltage stabilizations it offers. I've done these experiments with my PLX.
I beefed up the primary caps {big blue ones} and the SMPS caps {small banks},
with some huge caps. I can measure things but it's too hard to distinguish
the improvement if you were to do a listening test.
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post #101 of 1917 Old 06-21-2007, 06:30 PM
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Sweet my 2500 pic is actually getting used by someone

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post #102 of 1917 Old 06-29-2007, 01:29 PM
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What happened to this thread?

Chuck, don't tell me you quit already? We need more amps!
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post #103 of 1917 Old 07-01-2007, 04:56 AM - Thread Starter
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Quote:
Originally Posted by Richard Mayer View Post

Chuck,

First of all, thank you for doing these tests.

Have you considered taking some peak/burst output tests? I mean 30 second steady sine wave is not a very common event in real program material. I know you're trying to test whether manufacturer's specs are true or not, but IMO it would be beneficial to try to "replicate" the real program material too. 20 ms burst is pretty commonly used to test the peak output. That way you wouldn't also have any heat problems.

Just a suggestion.

A little catch up is in order here.

Richard, I have looked into 'burst' testing and amplifier testing in general as it is being done today. The way an amplifier is being tested today really has less to do with what it will actually put out than what is calculated to put out. For instance to do a 20 ms on, 100 ms off burst test, a very accurate, fast (and expensive) peak hold meter is needed to grab the reading. I won't even mention what it takes for the oscillator. A storage scope is needed to capture the waveform (I have one) so that you can see that it actually does not clip. Measuring THD is next to impossible under these situations for a guy at home, or even a guy at a fairly reputable shop. You will only find these capabilities at very high end shops (a dying breed) or the manufacturers facility! So burst testing is very hard to replicate at home, but I am looking into it.

As far as manufacturer's specs, they are very hard to even read what they are publishing and even harder to figure out how they achieved it. The Behringer manuals are a classic for obfuscation in specifications. They list their power ratings and all ratings are sort of referenced to 0.1% or 1% and the next line after power ratings says "DISTORTION <0.01%". Go figure what that means.

I have found that I can easily cool the load bank for a 6 hour session by starting out with filling the tank with ice and then using cold water to fill it to the top and then heat does not become a problem.
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post #104 of 1917 Old 07-01-2007, 05:02 AM - Thread Starter
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Quote:
Originally Posted by thylantyr View Post

I'm not sure what the inductance is on these elements as I only did low frequency
tests. If it has significant inductance, your high frequency test can be erroneous.

It is less than 20 microhenries at any impedance on either channel.
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post #105 of 1917 Old 07-01-2007, 05:06 AM - Thread Starter
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Quote:
Originally Posted by thylantyr View Post

Burst test: Amplifier taking a vacation in Hawaii drinking margaritas
Rms test: Amplifier working on the farm 24/7 as slave labor.

I tested my Crest 10001, 4 ohm bridged, dual 110VAC [30A] -> ~5,500w
continuous. I can do more with a solid 120VAC input. I can run like this for hours
with no issues. Many proamps [or amps in general] can only do rms type of
testing for seconds before something happens. I did a burst test on the Crest
and measured a 18kw transient using the scope playing a drumming solo track.

yuk, yuk..... very good thy! As funny as the comments are, they kind of sum up old school bricksh!thouse amps versus todays lightweights. The old amps were heavier in weight, put out less power, didn't heat up, and ran forever. Todays amps are lightweight, megawatt, monsters that are cheap enough that you can afford to keep a spare or two in the rack in case of failure.
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post #106 of 1917 Old 07-01-2007, 05:10 AM - Thread Starter
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Quote:
Originally Posted by Richard Mayer View Post

I will second (or third ) the Buttkicker amp request.

Chuck, when you replicate those manufacturer power ratings, do you test how much further it will go?

Absolutely, yes, I do. The Behringer amps will barely make rated specs when using sine wave testing and in some cases not get that high. When testing Yuriv's conglomeration of amps, sme (the Haflers) would put out 10 to 20% more power than rated. It all appears to depend on manufacturer and method of rating power. Once again, the need for a standard is needed.

And, yes, I wuld love to put a buttkicker through it paces, but I don't have one or know anyone in South Florida that does.
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post #107 of 1917 Old 07-01-2007, 05:10 AM
 
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Chuck ... I do believe I have a Buttkicker amp, new in the box. If you are interested in testing it out, let me know, and I will ship it to you.
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post #108 of 1917 Old 07-01-2007, 05:16 AM - Thread Starter
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Quote:
Originally Posted by crackyflipside View Post

Wouldn't burst numbers be based on who has more capacitors? (basically speaking)

Chris, that is simplifying the equation quite a bit, but it is correct in general theory. In todays amps, a 'sophisticated' power supply will adjust rail voltage up or down as needed very quickly. Some circuits are very good at this, some are done very cheaply and just won't keep up. Which is why some amps will keep up with very quick, power demanding transients in music or movies and deliver the needed power quickly so that you do not go into clipping and some amps just can't keep up.
You also have to remember that 'green' is the buzz word of the era today and manufacturers like to advertise how much less power is used, or how power is only there when you need it instead of being instantly available. Kind of like a 1969 Chevy Nova with a SS396 under the hood and a little rice car today. The Chevy has power available at any moment in time, but you pay for it. The rice car must wait for the turbo to spin up and give you the power.
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post #109 of 1917 Old 07-01-2007, 05:25 AM - Thread Starter
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Quote:
Originally Posted by Richard Mayer View Post

What happened to this thread?

Chuck, don't tell me you quit already? We need more amps!

I have not quit already. I just graduated a kid from High School and had the family down for that. My next one will probably be sherv's K2 amplifier. He has been busy and so have I, but we will get together in the next week or so, I hope.

I think this will just be ongoing as I accumulate amps to test. The other problem is testing relevant amps that people actually might want to go out and buy. When Yuriv brought his amps over most of them were not what we would use in our systems. A 100 watt per channel SUNN amplifier is not very relevant. He also had 2 Adcom amplifiers that were rated at 60 watts per channel. The easily met their specs and actually did 90 watts per channel at rated distortion, but again, are these relevant to today's usage?

Anyway, I am aleways in search of more amps. Hoping to purchase something in the QSC RMX line shortly, but have to sell some of what I have around right now. And that takes time. So stay tuned, as I get 'em, I'll test 'em.
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post #110 of 1917 Old 07-01-2007, 05:26 AM - Thread Starter
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Quote:
Originally Posted by craigsub View Post

Chuck ... I do believe I have a Buttkicker amp, new in the box. If you are interested in testing it out, let me know, and I will ship it to you.

I will PM you for details. Thanks.

Chuck
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post #111 of 1917 Old 07-01-2007, 11:10 AM
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I'd love to see a Crown XLS-602 tested.. considering I just picked up one last night for my TC3K.
got a great deal on it too.. at guitar center of all places.
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post #112 of 1917 Old 07-01-2007, 12:03 PM
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Thanks, Chuck and Craig.
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post #113 of 1917 Old 07-09-2007, 07:16 AM
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any new measurements?
im interested in the crown k2 results.

GIG
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post #114 of 1917 Old 07-09-2007, 09:21 AM - Thread Starter
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Very shortly a Buttkicker and if I can break into Sherv's house and steal his K2, we will get that on the bench. So look for 2 more amps within the next 2 weeks I would expect.

Chuck
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post #115 of 1917 Old 07-09-2007, 10:05 AM
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Quote:
Originally Posted by chasw98 View Post

Very shortly a Buttkicker and if I can break into Sherv's house and steal his K2, we will get that on the bench. So look for 2 more amps within the next 2 weeks I would expect.

Chuck

Fantastic.
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post #116 of 1917 Old 07-09-2007, 10:07 AM
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Where's the non-variac tests, you know the tests where the consumer just plugs
the amp into the wall and performance levels are realistic not optomistic



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post #117 of 1917 Old 07-09-2007, 10:15 AM
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Quote:


Where's the non-variac tests, you know the tests where the consumer just plugs
the amp into the wall and performance levels are realistic not optomistic

I am also looking for a similar test...

I wanna know if I can squeeze out at least 1400w RMS outta my EP2500.

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post #118 of 1917 Old 07-09-2007, 10:17 AM
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Chuck,
can you measure response down to 5hz or below for these two units? I've been wondering just how much roll off in the very low end theese two units have. Being a K Series owner I've been wondering what the particular difference is between the two. Some pics of the innards of the BKA1000a4 would be enlightening.

Thanks
Dan

Quote:
Originally Posted by chasw98 View Post

Very shortly a Buttkicker and if I can break into Sherv's house and steal his K2, we will get that on the bench. So look for 2 more amps within the next 2 weeks I would expect.

Chuck


Regards,
Dan
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post #119 of 1917 Old 07-09-2007, 10:59 AM
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Iirc...the K series had a 3rd-order rolloff centered around 7-8hz.

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post #120 of 1917 Old 07-11-2007, 09:20 AM
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[quote=chasw98]I am a certified, factory trained Crown Technician.



What is your opinion on the crown I-tech series? I am powering 4x 15" 2000 watt RMS subs, and was looking at a used IT8000 for $2500. Would you recommend my money is better spent on 8 behringer amps? Not only do I want the power to match, but I also want the sound quality to definately be there.

PS...I had buttkickers for my subs, and they didn't sound good to me at all. Now I replaced adcom 5500's with these to get more power, so I may have just been used to how good they sounded. Buttkickers have decent power output, but the punch was not there like the adcoms.

Let me know
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