Measuring Amplifiers - Page 18 - AVS Forum
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post #511 of 1917 Old 01-26-2008, 06:48 AM - Thread Starter
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Here are some pictures of the interior. Note the innovative use of cardboard or 'fish paper' in the wind tunnel.





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post #512 of 1917 Old 01-26-2008, 06:50 AM - Thread Starter
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Initial results of S/N ratio, frequency response, and 8 ohm stereo power.

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post #513 of 1917 Old 01-26-2008, 07:20 AM
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Very impressive! Can't wait to see the bridged @ 4 ohm results.
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post #514 of 1917 Old 01-26-2008, 09:48 AM - Thread Starter
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Here are the 2 and 4 ohm 2 channel results for the QSC PLX3402.

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post #515 of 1917 Old 01-26-2008, 09:50 AM
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Hmm, thats odd, other tests I have seen have shown the PLX class H designs being high frequency monsters, I have seen the 2ohm results getting over 2500wpc at 20Khz, it looks more bottom heavy here.
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post #516 of 1917 Old 01-26-2008, 10:24 AM
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Will the PLX3402 accept 220V input? I currently am using one EP2500 for my four IXL-18's in sealed cabinets. I would like to add more power and have run a dedicated 220V line to my component rack. I want to use an amp or amps that are capable of 220V input.
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post #517 of 1917 Old 01-26-2008, 10:40 AM - Thread Starter
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Here are the results of bridged mono 8 ohm and 4 ohm testing. You will notice that I was only able to take a 1 Khz reading for 4 ohm bridged mono. I blew 5 25 amp fuses just to get that reading.

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post #518 of 1917 Old 01-26-2008, 10:45 AM - Thread Starter
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This amplifier is very interesting. Its Achilles Heel is that the 25 amp main fuse is buried in the rear left corner and you must remove 13 screws to replace it. (Why duidn't QSC use a fuseholder or circuit breaker?). The good news is that it will probably never blow even when abusing the amplifier.

I am sure with more sophisticated micro processor controlled burst testing equipment that this amp would meet the specifications that the manufacturer has published. But when you use steady state sine wave testing on a class H amplifier it will not. Even at 2 ohm and 4 ohm testing, I could watch part of the waveform collapse as the upper part of the power supply ran out of gas so to speak.

Chuck
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post #519 of 1917 Old 01-26-2008, 10:47 AM - Thread Starter
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Quote:
Originally Posted by tsloms View Post

Will the PLX3402 accept 220V input? I currently am using one EP2500 for my four IXL-18's in sealed cabinets. I would like to add more power and have run a dedicated 220V line to my component rack. I want to use an amp or amps that are capable of 220V input.


Yes, most mainstream pro amplifiers will accept 220 volts.
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post #520 of 1917 Old 01-26-2008, 11:48 AM
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Not bad!

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post #521 of 1917 Old 01-26-2008, 04:46 PM
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Comments.

I had my PLX3402 on the test bench for a month torturing it, and even blowing it up, lol.
I even did cap mods......

With no variac, I was only able to get 2kw rms in bridged mode @ 4 ohms with 110VAC
input, 20hz tone for about 10 seconds before the amp went into protect mode. I talked
to Bob Lee about this. He said it will do over 3400w in bridged mode @ 4 ohms
with 120VAC input, not 110VAC. But this was a long time ago. Later I looked
at the datasheet for PLX series and the higher power ratings are not for any frequency
other than 1khz!!!!!

http://www.qscaudio.com/products/amps/plx/plx.htm

20hz - 20khz rating;

It's rated for 1100w/ch @ 4 ohms/ch.

It's rated for 2200w bridged @ 8 ohms.

Only the 1khz test shows more output, 1700w/ch @ 2 ohms,
3400w bridged @ 4 ohms.

It doesn't matter to me. 2kw or 3kw, who cares. I have ten of these amplifiers and
there is no need to be nitpicky ... I just find it odd that an extra 10VAC could
skew the data so much, but if you look at Binks pro amp tests, 117VAC vs. 96VAC,
21 volts can make a big difference, so I guess 10VAC can make a difference. lol


Quote:


Hmm, thats odd, other tests I have seen have shown the PLX class H designs being high frequency monsters, I have seen the 2ohm results getting over 2500wpc at 20Khz, it looks more bottom heavy here.

I linked a test a while back from the prosound forum. I believe someone was
doing burst tests on a few amps. I thought the PLX3402 did 5kw [total] with
a 25mS or 50mS burst. I can see this happening because the PLX has high voltage
rails and a transient like that can record big numbers. But if you do continuous
sine waves, forget it. All amplifiers will record lower numbers than easy burst tests.

Questions
1. Your PLX tested at approx 2kw/ch in stereo mode @ 2 ohms/ch. I'm assuming
this is not a 'both channels driven test' as there is no way this amp will do 4kw
total. hehe .. If you read 2800w @ 1khz, bridged mode @ 4 ohms, but blew many fuses trying to do
these bridged mode tests, then you would be blowing fuses like mad on the stereo test trying to register 4kw rms.

2. What is the AC input voltage? Your tests never show this as it's an important
variable. Low AC input can cause amplifier scores to register low numbers, or
generous 'unrealistic' higher input voltages can make the amp look like
a Wall Street darling. lol



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post #522 of 1917 Old 01-26-2008, 05:46 PM - Thread Starter
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Quote:
Originally Posted by thylantyr View Post


Questions
1. Your PLX tested at approx 2kw/ch in stereo mode @ 2 ohms/ch. I'm assuming
this is not a 'both channels driven test' as there is no way this amp will do 4kw
total. hehe .. If you read 2800w @ 1khz, bridged mode @ 4 ohms, but blew many fuses trying to do
these bridged mode tests, then you would be blowing fuses like mad on the stereo test trying to register 4kw rms.

Yes, I did get measurements at one channel only at a time. AT the end I got brave and rigged a 'larger than the rated fuse' circuit breaker in to see if it would do both channels simultaneously. It will do both channels simultaneously but only very quickly. Not long enought to get 'nitpicky' readings.

Quote:
Originally Posted by thylantyr View Post

2. What is the AC input voltage? Your tests never show this as it's an important
variable. Low AC input can cause amplifier scores to register low numbers, or
generous 'unrealistic' higher input voltages can make the amp look like
a Wall Street darling. lol

Read post 13 in this thread.
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post #523 of 1917 Old 01-26-2008, 07:58 PM
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Thanks for the tests Chuck! I wasn't expecting new tests today but its always a treat. Great results I think. And looking at completed ebay listings, the average price for a used 3402 seems to be ~$690.
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post #524 of 1917 Old 01-26-2008, 08:00 PM
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re: post 13

Quote:


The first part involves verifying whether or not the amplifier meets the published specs of the manufacturer or not.

QSC says the PLX's are tested with both channels driven [stereo mode]
http://www.qscaudio.com/products/amps/plx/plx.htm

Your test was done with one channel driven. You didn't follow your own
testing protocols, naughty naughty

The amplifier testing debate rages on, everyone debates on what is
a proper methodology. The problem is, there is too many variables.

Is the rms test method the best? This is akin to a continous test tone.
Is music a continous test tone? Usually not, perhaps on a rare piece of
music you might find a continous test tone. Maybe a 'special effect' found
on movies. Overal, the rms method is my favorite method because it will
torture the amplifier more than those easier tests that inflate the scores.

What if you do an rms test method plus a burst test to mimick music playback in general?
This is good too, I like this a lot.

Test duration? This is so important, yet overlooked by everyone. How
long was test performed for? Was the scores captured after
a 1 second test? 10 seconds? 1 minute? 1 hour? Manufacturers might follow
certain guidelines, but what is a good time period ? Perhaps a better
test is just to note how long the amplifier performed using a certain
ambient temperature as a reference. In other words, you
hook up the amp at a reasonable ambient temp, run the amp to full power,
then write down how long it operated before going into thermal protect
and/or blowing a fuse, or blowing itself up. hehehe

Test Duration Example;

* I tested my PLX at 2kw total.

* You tested the same amp at 4kw total.

* Lets throw in the the Crest 10001, I got 4kw - 5.5kw bridged depending
on if it was a 2 ohm or 4 ohm load.

A person looking at this data will assume the PLX is the same as the Crest.

But the test method and duration tell a bigger story. My PLX test is
both channels driven. Your PLX test is one channel driven, the Crest
is two channels driven. My PLX went into protect mode after 10 seconds,
your PLX had issues very quickly, but the Crest ran all day without going
into thermal protect.

PLX3402 is my favorite 'general purpose' high end amplifier. Excellent for midranges and
tweeters, works great for subwoofers, but expect less power. But if you were to use
an LMS-5400 caliber woofer [or equivalent, or beefier] and needed only one amplifier,
the PLX, PLX2 isn't good enough.



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post #525 of 1917 Old 01-26-2008, 10:43 PM
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Quote:
Originally Posted by Willd View Post

Thanks for the tests Chuck! I wasn't expecting new tests today but its always a treat. Great results I think. And looking at completed ebay listings, the average price for a used 3402 seems to be ~$690.

Yeah, they come and go a lot, sometimes I can't find any for under $1000 for weeks, other times it seems the site is full of buy it now's for under $750, one time I saw a lot of 10 2402's go for $3100, I wish I would have bit but I didn't have the cash at the time, tuition is killing me.
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post #526 of 1917 Old 01-26-2008, 11:19 PM
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PLX3402 pricing. Before PLX2 was released, I paid an average of $765 each.
About a year later, when PLX2 and new Crown amps came out, it seemed like the
upgrade itch hit certain people and they were selling their older PLX's for about
$100 less, for a certain time period. I saw some sell for ~$550 each. I would say
that $550 - $750 is a good price. When you look at the performance numbers
and compare this to high end home audio amplifiers with much less power that cost
thousands, these used PLX's are a bargain. PLX2402, 3002, 3402 are the class H
models, get those to have class H 'high rail'.



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post #527 of 1917 Old 01-27-2008, 04:57 AM
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Or would that be wasted bandwidth?
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post #528 of 1917 Old 01-27-2008, 08:11 AM
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Quote:
Originally Posted by armystud0911 View Post

Yeah, they come and go a lot, sometimes I can't find any for under $1000 for weeks, other times it seems the site is full of buy it now's for under $750, one time I saw a lot of 10 2402's go for $3100, I wish I would have bit but I didn't have the cash at the time, tuition is killing me.

Yeah, its like that with a lot of products.
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post #529 of 1917 Old 01-27-2008, 08:39 AM
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Quote:
Originally Posted by Willd View Post

Yeah, its like that with a lot of products.

It was the same with the CEs.

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post #530 of 1917 Old 01-27-2008, 08:52 AM - Thread Starter
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Quote:
Originally Posted by thylantyr View Post

re: post 13



QSC says the PLX's are tested with both channels driven [stereo mode]
http://www.qscaudio.com/products/amps/plx/plx.htm

Your test was done with one channel driven. You didn't follow your own
testing protocols, naughty naughty

No, here is what I did. I could not get a stable distortion reading with both channels driven because my Tektronix analyzer is too slow before the fuse blows. SO I measured both channels individually and got a reading. Now that I knew what voltage it would do, I replaced the fuse with a large circuit breaker and ran both channels at the same time up to the specified voltage and watched the scope for clipping. I could only do this for less than ~2 seconds before the amp would shut down.

Which brings me to my current dilemma. Unless I invest in some micro processor based test gear that will resolve with a low enough reading and will do burst testing, I cannot verify manufacturers published claims. I can sit there and watch the second rail kick in and collapse as I am testing using steady state sine waves. But as you go higher in power and lower in ohms, the time window available before protection kicks in is shorter and shorter.

Quote:
Originally Posted by thylantyr View Post

The amplifier testing debate rages on, everyone debates on what is
a proper methodology. The problem is, there is too many variables.

Is the rms test method the best? This is akin to a continous test tone.
Is music a continous test tone? Usually not, perhaps on a rare piece of
music you might find a continous test tone. Maybe a 'special effect' found
on movies. Overal, the rms method is my favorite method because it will
torture the amplifier more than those easier tests that inflate the scores.

What if you do an rms test method plus a burst test to mimick music playback in general?
This is good too, I like this a lot.

You and I agree 100% on that subject, but don't even go near the testing methodology of a 7 channel receiver that claims 100 watts per channel period. Does it do 100 watts at all? And if so, does it do it with all channels driven or maybe 2 or 3? And on and on.

Quote:
Originally Posted by thylantyr View Post

Test duration? This is so important, yet overlooked by everyone. How
long was test performed for? Was the scores captured after
a 1 second test? 10 seconds? 1 minute? 1 hour? Manufacturers might follow
certain guidelines, but what is a good time period ? Perhaps a better
test is just to note how long the amplifier performed using a certain
ambient temperature as a reference. In other words, you
hook up the amp at a reasonable ambient temp, run the amp to full power,
then write down how long it operated before going into thermal protect
and/or blowing a fuse, or blowing itself up. hehehe

You and I are from the day when you put a Phase Linear 700 on the bench and let it cook for 4 hours to make sure it ran properly. Unfortunately they are rarely made that way anymore.

Quote:
Originally Posted by thylantyr View Post


Test Duration Example;

* I tested my PLX at 2kw total.

* You tested the same amp at 4kw total.

* Lets throw in the the Crest 10001, I got 4kw - 5.5kw bridged depending
on if it was a 2 ohm or 4 ohm load.

A person looking at this data will assume the PLX is the same as the Crest.

But the test method and duration tell a bigger story. My PLX test is
both channels driven. Your PLX test is one channel driven, the Crest
is two channels driven. My PLX went into protect mode after 10 seconds,
your PLX had issues very quickly, but the Crest ran all day without going
into thermal protect.

PLX3402 is my favorite 'general purpose' high end amplifier. Excellent for midranges and
tweeters, works great for subwoofers, but expect less power. But if you were to use
an LMS-5400 caliber woofer [or equivalent, or beefier] and needed only one amplifier,
the PLX, PLX2 isn't good enough.

Once again, you have to look at these as tools. If I had to truck 50 Crests around the country, that is a lot of weight and electricity used versus the PLX's. Size, weight, and electric consumption can be a factor in a lot of decisions. And going by your example I have 2 Cinenova amplifiers that will do 4 Kw without using fans! This is similar to the group of blind men touching the elephant and describing to someone who does not know what an elephant is.
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post #531 of 1917 Old 02-01-2008, 08:18 AM
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This thread is fantastic. I would love it if you tested a standard home reciever to see how it measures up in these tests. That testing equipment you have is very sexy, like Dr. Frankenstein's lab. LOL.
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post #532 of 1917 Old 02-01-2008, 11:12 AM
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[quote=thylantyr;12942259]
It doesn't matter to me. 2kw or 3kw, who cares. I have ten of these amplifiers and
there is no need to be nitpicky
I believe someone was doing burst tests on a few amps. I thought the PLX3402 did 5kw [total] with
a 25mS or 50mS burst. I can see this happening because the PLX has high voltage
rails and a transient like that can record big numbers. But if you do continuous
sine waves, forget it. All amplifiers will record lower numbers than easy burst tests.

Thylantyr,
You're an interesting guy but I can't quite grasp where you're headed or what your ultimate system is going to look like.
You have 10 PLX3402s and you seem to have a complaint about them but add don't be nitpicky. LOL
In a following post you say the PLX3402 is not suitable for an LMS-5400. An LMS-5400 is rated for 2500 watts but under real in-box results that amount of power is not required to reach full output in the 10-80Hz region.
Using Ilkka's testing of the LMS-5400 driven by the CE4000 as an example, the LMS-5400 exceeds the 100 db level for most of the 10-80Hz range and seems to be the best sub performance so far. My question is how loud are you wanting to go and what are you willing to acquire to get there? What amp is suitable to drive the LMS-5400 or isn't there one?
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post #533 of 1917 Old 02-01-2008, 03:53 PM
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Quote:
You have 10 PLX3402s and you seem to have a complaint about them but add don't be nitpicky. LOL

I complain about everything I can look at any amplifier
and nitpick, but in reality I really like the PLX for mids
and tweeters. People in home audio love it for subs.
1/2 the people on the pro audio forum don't think it's
as powerful for bass. It depends on what you want.

Quote:
In a following post you say the PLX3402 is not suitable for an LMS-5400. An LMS-5400 is rated for 2500 watts but under real in-box results that amount of power is not required to reach full output in the 10-80Hz region.

Depends on the subwoofer design. An LMS in a certain
design may reach limits with 200w, in another design
it may need a few thousand. That's why people who
build subwoofers need to look at the power requirements
of the subwoofer [driver + enclosure design].

Quote:
Using Ilkka's testing of the LMS-5400 driven by the CE4000 as an example, the LMS-5400 exceeds the 100 db level for most of the 10-80Hz range and seems to the best sub performance so far.

The CE4000 amp craze on AVS was started by me,
at first in PM's, then word leaked out and now everyone
knows about that amplifier, awesome for subs for it's
price range.

CE4000 > PLX series for subs. But for mids/tweeters, I prefer the PLX.



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post #534 of 1917 Old 02-06-2008, 08:36 AM
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I see the Crown website announced it is offering "Anniversary Editions" of the former Macro-Tech Amplifiers in various watt ratings and are limited in production numbers. They have a "Copper" face plate.

Also they now offer a new model in the XLS series, the XLS 5000.
5000 watts bridge-mono @ 4 ohms.
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post #535 of 1917 Old 02-06-2008, 01:23 PM
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QSC PL380 Pics and Ramblings

http://www.diyaudio.com/forums/showt...5&pagenumber=1

http://www.diyaudio.com/forums/attac...amp=1200373208



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post #536 of 1917 Old 02-06-2008, 06:52 PM
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I see you ran into some "doubters" about the QSC PL380. I've read those people on other threads, they sure like to do a lot of abstract "theoretical testing" . But then I haven't run into any engineers who weren't genetically driven any other way.
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post #537 of 1917 Old 02-06-2008, 08:09 PM
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The Crown K1 is on clearance at a store near me for around $690. Is that a good Amp for the money to drive passive subwoofers? How does it compare to the QSC RMX2450?
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post #538 of 1917 Old 02-06-2008, 08:13 PM
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Thats not a good deal for the K1.
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post #539 of 1917 Old 02-06-2008, 08:14 PM
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E.bay has K1 for 'buy it now' $495.

I would expect similar performance to RMX2450.
You might as well just get an EP2500 for $265 - $350
as all three of these amps would be in a similar boat.

If you want to spend $690, look for used amps, CE4000, PLX3402, Crown Xs was
tested well here. This will take you to the next level.



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post #540 of 1917 Old 02-06-2008, 08:56 PM
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thylantyr,

Great info,as always.

Ask yourself mortal , do you have as much displacement as me ? The answer is no unless you have a Windmere fan sub.
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