Axiom Home Page Forums General Discussion Technical Questions Emotiva MPS-1 shutting down? Amp gurus help

The 80's have been able to handle over 1,000 watts in lab tests for extended periods of times, as well as other tests where they ran them at 700 watts continuous for weeks at a time. A Denon AVR of 100 watts (more like 80) is far different than an amp rated at a tru 200 watts into 8ohms.

Ok, here are my findings. Please note - I'm not an engineer and don't have expensive equipment. Hopefully these results will at least give a clearer picture. I understand that my SPL meter is not the same as say using an expensive faster/more accurate meter like an audio toolbox.

With some help from Mojo I wanted to verify the accuracy of my meter. So, I took my digital multimeter which measures AC voltage up to 1000V. I verified that I was getting 120 volts from my wall outlets (actually 122). So we would have a voltage of 60hz at the outlet. I then played a 60hz WAV tone (2mb filesize) and took measurements with my meter hooked to the speaker wire terminals from various volume levels to compute power. We know the ohm ratings of the 80's per the graphs from the NRC, so I'm off to the races.

Now I also made note of when I noticed distortion starting to kick in, as the results would then become less meaningful. Following this, I ran a 100hz tone, assuming it would be fairly accurate at this freq also as it was close to 60hz. And finally, I played some music.

Below are my results from my lab. It appears based on my defense above, that the amp is not defective, and functioning as designed. Again, you guys need to remember I'm trying to fill 8,000 cubic feet. Plus, I've acoustically treated my room pretty well with OC703 which is actually helping the potential problem of rooms that have no treatments.

Also, if you look at the music peaks before it shut down, and the 100hz tone(which is easier to drive than higher freq's) the amp actually went beyond its ratings.
I will need to work with Emotiva to discuss my options.


Volume Knob, Voltage, P=Vsquared/5 60hz tone

-25, .64, .08
-20, 1.11, .24
-15, 1.99, .79
-10, 3.40, 2.31
-5, 6.08, 7.39
0, 10.75, 23
+2, 13.48, 36
+4, 16.85, 56.7
+5, 18.8, 70.5
+6, 21.1, 89
+8, 26.2, 137 (buzzing/distortion started)
+10, 33, 218
+12, 36.7, 269
+13, 38.5, 296 (clicking sound, amp shut down)


Volume Knob, Voltage, P=Vsquared/4 100hz tone
-25, .64, .1
-20, 1.11, .3
-15, 1.99, .99
-10, 3.40, 2.89
-5, 6.03, 9.09
0, 10.67, 28.46
+2, 13.36, 44.62
+4, 16.71, 69.8
+5, 18.69, 87.3
+6, 20.9, 109.2
+8, 26.2, 171.6
+10, 33, 272
+12, 36.7, 336 (Buzzing/distortion started)
+13, 40, 400 (clicking sound, amp shut down)

Music Listening - I picked 2 songs from my brother inlaws band "Left is West" which

is a very popular Des Moines based band that I would put up against any of the

bigger city bands. Their CD was recorded last year in Omaha by Barely Bias Label. I

would describe them as pop-rock with similar influences from bands from the 70's to

today, just a whole mishmash. Anyway, I picked 2 songs that had a very fast

rock beat that didn't change or fluctuate much, just very intense and powerful.

I used 4 ohm for figuring power, the results would be slightly lower had I used say

4.5-5 ohms for an average. Both songs had similar results except for the last

reading.

Volume Knob, Voltage, P=Vsquared/4 Music
-20, 2, 1
-15, 3.3, 2.7
-10, 6.1, 9.3
-5, 13.3, 44.2
0, 19.8, 98
+2, 24.5, 150
+3, 28.8, 207
+4, 40-50, 400-625

Fascinating results. Glad to hear the amp might not be the problem, and that you're just running into the laws of physics. As in Jaws, "We're going to need a bigger amp".

Have you tried bi-amping your M80's? I wonder if that would get you an extra db or two before the amp shuts down. Might be enough to satisfy your needs, and I would then bow to your awesomeness of having M80's driven by four EPM-300's.

That I have not, hmmm, it would require me to purchase two more amps to accomplish.

Than just bi-wire!

I was thinking of the same thing,you could use the center amp on one main channel and see what happens?

Your right, I shipped 2 back last friday. So I assume you have to get a splitter cable of some sorts since my Denon only has one preout per channel?

I don't know Peter, I'm just getting tired of messing with this thing. First the light switch static issue when I first purchased it, now this issue. I just want to enjoy my equipment.

Correct (I think) . You'd need a splitter for each channel.

Too bad you're not just a wee bit closer to where I live, I'd bring over the LPA-1 just for fun to see how it performs. I still haven't officially tested my LPA-1 w/ db meter to see if I can 'max-out' my system. But I know that -5 (max is +15, I think) equates to absurd volume levels on my M80+LPA-1 combo with no distortion and no shut-down problems. I mean, worried-about-my-hearing, cat-runs-and-hides, pictures-fall-off-walls loud.

I do hope you find a workable solution. It just seems very odd that your measurements appear to indicate the amp is working as advertised, and the M80's most certainly aren't bad, but you're still having these shutdown problems.

Quote:

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Your right, I shipped 2 back last friday. So I assume you have to get a splitter cable of some sorts since my Denon only has one preout per channel?

I don't know Peter, I'm just getting tired of messing with this thing. First the light switch static issue when I first purchased it, now this issue. I just want to enjoy my equipment.

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