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Author Topic: EXCLUSIVE: OBJ2 vs Magni full spectrum distortion at various power levels.  (Read 3610 times)

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Willakan

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Re: EXCLUSIVE: OBJ2 vs Magni full spectrum distortion at various power levels.
« Reply #10 on: January 08, 2013, 10:27:35 PM »
Good good. Not sure how the timing on my edits worked out (EDIT: badly), but how about the IMD tests? Please :D?

« Last Edit: January 08, 2013, 10:41:11 PM by Willakan »
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Marvey

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Re: EXCLUSIVE: OBJ2 vs Magni full spectrum distortion at various power levels.
« Reply #11 on: January 08, 2013, 10:32:34 PM »
LOL! Patience! I need to examine the amp carefully. Don't want something exploding again!
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Willakan

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Re: EXCLUSIVE: OBJ2 vs Magni full spectrum distortion at various power levels.
« Reply #12 on: January 08, 2013, 10:43:39 PM »
On the subject of possible mistakes with voltage/power levels, I can't see how this could be causing your problem.

1) The O2's input stage would be clipping if the voltage levels were performance-compromisingly wrong, which occurs independent of volume control position (volume control between gain and output stage).
2) Quoting NwAvGuy on the measurements of his amp:

"I've run the O2 at full power into 15 ohms with sine waves for several seconds at a time and haven't noticed any changes in its measured performance let alone had any failures despite the fact the dissipation per channel is (briefly) over 2 watts"

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Marvey

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Re: EXCLUSIVE: OBJ2 vs Magni full spectrum distortion at various power levels.
« Reply #13 on: January 08, 2013, 10:51:36 PM »
I don't think the input stage was clipping, as that would be painfully obvious at the low power tests (I only used volume control to vary voltage/power).

The other thing is that it wasn't seconds. I left the darn thing on for several minutes... I got to sleep on it to see what went wrong.
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2000impreza

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Re: EXCLUSIVE: OBJ2 vs Magni full spectrum distortion at various power levels.
« Reply #14 on: January 08, 2013, 10:53:18 PM »
Frying a JRC 4556 is not unheard of. I fried a JRC 4556 on one of my early O2 builds running a 100Hz sine tone through it. I put heatsinks on the output opamps after replacing them.

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Marvey

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Re: EXCLUSIVE: OBJ2 vs Magni full spectrum distortion at various power levels.
« Reply #15 on: January 08, 2013, 10:55:28 PM »
Interesting. I know the 4556s are a dime-a-dozen and would expect supreme quality control. I'm gonna take a nap.
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Willakan

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Re: EXCLUSIVE: OBJ2 vs Magni full spectrum distortion at various power levels.
« Reply #16 on: January 08, 2013, 11:09:26 PM »
Quote from: purrin on January 08, 2013, 10:51:36 PM
I don't think the input stage was clipping, as that would be painfully obvious at the low power tests (I only used volume control to vary voltage/power).

The other thing is that it wasn't seconds. I left the darn thing on for several minutes... I got to sleep on it to see what went wrong.

Yeah, I would agree that input stage clipping would be obvious...good luck on figuring out the problem.
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Marvey

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Re: EXCLUSIVE: OBJ2 vs Magni full spectrum distortion at various power levels.
« Reply #17 on: January 09, 2013, 03:14:01 AM »
I think I know what it was - the DMM wasn't measuring VRMS correctly. It was never designed to do that for complex signals. Doh!
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Willakan

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Re: EXCLUSIVE: OBJ2 vs Magni full spectrum distortion at various power levels.
« Reply #18 on: January 09, 2013, 08:03:19 AM »
Quote from: purrin on January 09, 2013, 03:14:01 AM
I think I know what it was - the DMM wasn't measuring VRMS correctly. It was never designed to do that for complex signals. Doh!

Hadn't even registered that you were using a DMM... :)p8 What else have you got to measure output levels?
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Solderdude

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Re: EXCLUSIVE: OBJ2 vs Magni full spectrum distortion at various power levels.
« Reply #19 on: January 09, 2013, 08:45:34 PM »
To fully test an amplifier (and even get distortion numbers) you can test amplifiers under actual loads with actual music while listening to either the error signal (distortion) or the music signal.
You will need to build that test device yourself though, which is not that hard.

It's called a differential amplifier and reveals amplitude, phase/timing problems at the same time so throws the total deviation on a pile though.

To test amplifiers that have an output resistance of above 1 Ohm you would need to seek a testpoint inside the amp before the output resistors when testing with actual loads.
Very enlightening.
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