Measuring Amplifiers - Page 29

You said -> "So I really don't know what to say about this one. Bid Chuck says one thing partsexpress says another."

Obviously, you know what to say, you expressed your
feelings after I posted.


Trust me, people that do repairs might have zero clue on
how amplifiers work or even basic electronics. There really
is no correlation. I see engineers daily at work that are also
clueless about certain issues, point is, people are human

You are assuming he knows the resistor issue because he
can do an amplifier repair. Even funnier, he's repaired said
amplifiers many times, what does this tell you ?


That's why I said resistor(s)


PE is an electronics store. Need I say more?

I really don't know why people run to the vendors when
a product is independently tested. The test removes the
mystery.

Crown Forum.

XTi1000 performance questions
http://www.crownaudio.com/forums/ind...showtopic=2438

The test results posted on the Crown Forum asking for feedback
from the Crown people.

4 days, no response.

I don't even think a 10 foot pole will work.


Given time, the issue is.............

Thanks Chuck you have been helpful beyond words.
If I get down to florida anytime soon I will have to look you up and buy you a beer or 12.


thylantyr....... well whatever you are not helpful nor insightful. Your comments (and I"m paraphrasing) here such as:
1. Any test is a bad test cause now one agrees on what the peramateres are for each test.
2. What do you expect its an electronics store.
3. I see people everyday at work that don't know how to do there job.(because there human)
4. He's got a headset so he must be lying.

You have obviously spent a little to much time @ your test bunch and not enough time socializing.

I think my favorite line of yours is "I complain about everything" thats obvious there buck-o.

You have obviously done a little work in the audio field don't you have anything more to offer this conversation than a critique of my posts?
No really it was a rhetorical statement.

Just pull out the old fan and put in a quite one .......well that seems extremely easy.....thanks a bunch
It also eliminates any issue I would have with that amp....
I'm sure this has been discussed before (little noobish of me to ask) any issue with going from balanced to unbalanced inputs?

Just know that, simplistically speaking, the quieter the fan is, the less air it'll move. With that said, I used 2, 14db 12v fans piggy backed.

You found the "piggie backing" the fans effective?
Any heat issues?



I have a Pair of 120mm Sitting on the shelf that I be leave are rated at 83cuft per minute and 16dba?thoughts?

I have to go there and rattle the cage. Is Crown operated by a clown ? That is THE question, time for them to pull their heads from the sand and face the music.

If they don't respond, another picture for you to post
there.

Yes there is a voltage and power issue going from an AVR with RCA (unbalanced connections) to a amp with XLR (balanced) connections.

No matter what you are not getting full power of the amp with these connection, some people dont care or realize the power loss others use a "line shifter" type device like a Art cleanbox or a Ebtech line shifter.

The other issue sometimes is that connection and the voltage issues cause a ground hum in the loop.

Thylantyr,

I think this is the new public relations officer they now have in place ! I will be on them like stink on ...shhh...


IT

If you can get the amp into clipping are you still not getting full power? I would think you were.

From what Ive read my unbalanced Onkyo receiver can send a maximum unclipped subwoofer signal of 7.4v which is much higher then the required 1.2v-1.4v most pro amps need for full power. Am I wrong here?

I was just cruising the Crown forum to see if they had responded to the thread about the XTi measurements and found this information. It appears someone had requested some information concerning the wattage specs for the XTI 4000 at 20hz-20khz were. Below is what the Crown rep replied with (after some discussions). I do not have time to review all of it but I figured some of you may be interested in reading it. I have also placed the link to the thread below.


Thread:
http://www.crownaudio.com/forums/ind...opic=2088&st=0

From the Crown rep:
What I got back from the engineers is that the XTi series for FTC rating is measured at being down 1db in out put from the EIA spec (both channels driven). So what does that mean well lets look at the math for XTi4000 8-ohm spec.

The XTi4000 is EIA (both channels driven) for 650 watts into 8-ohms.

To do this we will need to calculate for the 20-20k output voltage spec. (Vspec2) and then we can calculate the output power.

1) First lets calculate the output voltage for the EIA (both channels driven) (Vspec1).

Vspec1=SQR(650*8)
Vspec1=72.11 volts

2) Now for the heavy math and reverse calculating the 20-20k output voltage spec (Vspec2) for 1db down.

-1db=20 log(Vspec2/Vspec1)
-1db=20 log(Vspec2/72.11)
-1db/20={20log(Vspec2/72.11)}/20
-0.05=log(Vspec2/72.11)
Antilog -0.05= Vspec2/72.11
.89125= Vspec2/72.11
Vspec2=.89125*72.11
Vspec2=64.27


3)Now use the power formula to calculate the 20-20k output power from the Vspec2 voltage.

W= V2/8
W= Vspec22/8
W= 64.272/8
W= 516.3 watts output for 20-20k


Continuing along the same line you come up with the following chart.

XTi1000
Imp.________EIA Spec._______Calc.20%____________1db down 20-20K spec
8-ohms_______275w___________220w____________________218w
4-ohms_______500w___________400w____________________397w

XTi2000
Imp.________EIA Spec._______Calc.20%____________1db down 20-20K spec
8-ohms_______475w___________380w_____________________377w
4-ohms_______800w___________640w_____________________636w

XTi4000
Imp.________EIA Spec._______Calc.20%____________1db down 20-20K spec
8-ohms_______650w___________520w____________________516w
4-ohms______1200w___________960w____________________953w

From this you can see that, taking into account tolerances between components in different amplifiers, the XTi series sits right at the 20% difference between our EIA (with both channels driven) spec and their 20-20k output power

Mr. DGlass from Crown in these exchanges and explanations is using ONLY math calculations from "some measurements" starting with EIA specs for the XTi 4000 and at one point does "reverse calculating" from an EIA output voltage.
The question difflvl asked, "what's my power at 30-150HZ" never got answered.
Chuck can answer that though, and has . . . . . the XTi series amps apparently fall apart somewhere around 50HZ his tests PROVE it.
How easy it would have been for the Crown rep to just publish an ouput chart like Chuck did. Question answered problem solved.

"Yes there is a voltage and power issue going from an AVR with RCA (unbalanced connections) to a amp with XLR (balanced) connections.

No matter what you are not getting full power of the amp with these connection"

Not necessarily so at all, many, myself included, use pro amps and can make them clip no problem.

Certain receivers ( Pioneer is one ) have low voltage in the pre-amp outs and LFE out. They need a device like the ART or Rolls to boost the voltage.

Yes, we are aware of that, the discrepancy lies with the fact that he said "no matter what, you are not getting full power" when this is quite false, in many if not most cases, you are quite able to get full power.

DGlass half full or half empty ?

How about asking Jock Chung if Crown's XTi is meeting spec?

(3) Power Output Claims for
Amplifiers Utilized in Home
Entertainment Products, 16 CFR 432.
Agency Contact: Jock Chung, (202) 326-
2984, Federal Trade Commission,
Bureau of Consumer Protection,
Division of Enforcement, 600
Pennsylvania Ave., NW, Washington,
DC 20580.

as seen in:
http://www.ftc.gov/os/fedreg/2008/ma...ceofintent.pdf

And the FTC Rule 432

http://ecfr.gpoaccess.gov/cgi/t/text...1.4.47&idno=16

making them clip no problem has nothing to do with voltage drops, I can make my EP2500 clip too and I KNOW Im not getting full power becuase of the voltage drop between my AVR and the PRO amp.

All I said was that we will not get full amp power from our receivers unless they have the correct voltage out. Weather we know the difference (hear it) is irrelevant. Kind of like these tests

Maybe you need to use special "audiophile" quality interconnect cables to eliminate that "voltage drop"!!!

I lIke this specification of the XTI-1000.


"Frequency Response: +0/–1 dB from 20 Hz to 20 kHz at 1 watt into 4 ohms."


How does it measure at 100 watts into 4 ohms?

How does it measure at 250 watts into 4 ohms?

How does it measure at 500 watts into 4 ohms?

okay, I will bite on that...what would those be? Its the connections that have different voltages so it would be cool to see a cable that can adjust those voltages.

XTI is marketed as a DJ product, not even Cinema.

I wouldnt run anything except your sub through the DCX2496. Let your AVR handle the crossover and all the EQing above your set sub freq. (80, 100, 120, etc).

This is getting off topic and you should probably create another thread to discuss all of this.

"making them clip no problem has nothing to do with voltage drops, I can make my EP2500 clip too and I KNOW Im not getting full power becuase of the voltage drop between my AVR and the PRO amp."

If the amp is clipping, you've hit the limit of its PS voltage, and nothing you do to the signal level will change that.

Agreed but that is a moot point too

Ignore the following rant.....

Man!!! People just constantly want to argue the voltage issue between Pro and home audio systems. No matter how much we debate it exists, I already posted that sometimes you will not notice it but its still there.

Why does anyone even post "I can clip my amp so there isnt a problem" ?? What does it mean to the person asking about it, what does it mean to anyone? Should we go out and buy everything that person owns so we can also post "Hey, I dont notice it"?

Sorry for the rant but this is really a meaningless debate because there is simply ONE FACT. AVRs have a different voltage then pro amps do, It can be up to +4 dB vs -10 dB in difference. Individual experiences will vary but that is STILL A FACT.

Noah, you have lots of info and you are very helpful but I dont know what your purpose is here? You want to tell the guy interested in this info that he will have no problems because you dont? What if he does have a problem, what will you say then? Heck there are threads and threads on this, should we just ignore because you say you can clip your amps...I can clip my EP2500 too but I know there is a huge loss in dB to start with. I know because I can hook up a regular home audio amp and get much more power @ half the rating.

As for my personal testing....

I have Velodyn sc-1250 vs QSC 1850 bridged, I have velodyn sc-1250 vs EP2500... to balance the SPL on two subs I have to crank up the pro amps and I have to turn down the sc-1250 amps.....and this is ON 4 different types of receivers, Yahama, Pioneer and Denon and Emotiva.

Simple conclusion, There is a dB discrepancy when connection Pro amps to our AVRs and you dont know it until you actually test it.
So that is my rant...I will leave it at that and let the thread go back to AMP testing.