Phoenix Gold Phorum

I just fixed a M44, and measured 17.5V as a safe non clipped RMS output with my Fluke 76 DMM.

I thought somewhere we had started a database of this, but I was not certain, or could not remember where.

If you do the math, this makes the M44 about 75W x 4 into 4 ohms, which really is not all that unreasonable to expect.

Nice! Thanks for the info Eric.

... A database of this info would be super cool!

Also a database of jpeg or pdf birth sheets would be great as well.

Nice!!!!! Eric

MQ430 & MS275 True RMS Voltage
Geri

one thing i never get is how pg did power print outs, was just a graph with no actual power figures

marko wrote:one thing i never get is how pg did power print outs, was just a graph with no actual power figures

It was not a power test, just distortion against frequency.

Kind of OT for the purpose of the thread, but:

How did you do the testing to see when it clips?... I have a feeling the answer will include an o-scope. Maybe not.

Thanks!

O-scope.

Eric, when testing to the clipping point on the scope do you have any idea how much % THD this would be approx?? Is there even a way to correlate between the two??

I think from memory the birthsheet for my M44 shows approx 75 RMS at just under 1%THD.

I don't have a distortion meter, so I have no clue.

In the case of this amp, it would hit 17.9V prior to clipping. When I backed it down to 17.5V the signal looked beautiful. This is why I consider 17.5V "safe".

Update:

M25 = 13.5V
M100 = 27V
ZX350 = 23.5V

Eric, are you putting a load on the amp, if so what are you using, as I would like to get one.

No, no load. Putting a load on it would likely drag the voltage down. Then the argument starts.

Some people think you need to test the amp loaded for max unclipped output. I am not one of those people. Playing a sine wave on an amp loaded is very hard on it. Some amps will die doing this. Besides, the amp's headroom is its ability to play beyond its normal level when playing music.

What I have done in the past is set an amp with no load, then add speakers, then play music up to that same output level and look at the signal on an 0-scope to see if it clips. In the case of the PG amps I have done this with, they would still play music up near the clipping limitations of their no load setting, so I knew the power supply was not being drug down by the speaker load with the music signal.

it does seem strange to me that you would do all your calculations based on the speakers impedence, but then measure the output with it.










I still have never tuned a system with my meter, I am sure it is a disco fan..........

ttocs wrote:it does seem strange to me that you would do all your calculations based on the speakers impedence, but then measure the output with it.










I still have never tuned a system with my meter, I am sure it is a disco fan..........

Huh?

Did u test the MS2250 u repaired for me too?

Eric D wrote:

ttocs wrote:it does seem strange to me that you would do all your calculations based on the speakers impedence, but then measure the output with it.










I still have never tuned a system with my meter, I am sure it is a disco fan..........

Huh?

yeah???! x2?

Sadly I did not test the MS2250. But I do have data on other MS2250s some where around here.

Nice Eric!

I think the M100 is just a little bit underrated...

The ZX350 is nicely over like I would expect.

Interestingly enough I thought the M44 and M25 would be a bit closer in power output. The M44 has more guts than I gave it credit for.

Thanks for sharing!

ZX500v2 = 30V would be safe.

ZX500v2 = 30V would be safe.

There is a lot of beef in that amp then!

more than i expected for the zx500. thx Eric

Ti600.2 = 33V

I am pretty impressed, this is much more than the ZX500v2.

WOW again.

that is 225 versus 272! That is a huge difference for a "similar" amp.

Ok,
So if I read correctly how an amp works when bridged.
Then the ZX500 bridged will make 900 watts into 4ohms.
And an M100 bridged will make 729 watts into 4ohms.

Is that right ? seems like they were VERY underrated.

Your numbers are right, but it does not mean the amp will actually do that.

With a test tone, you won't get 900W from a ZX500. With music, and some capacitance on the input to the amp, you will get peaks of 900W.