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Amp measurements: Obj2, Magni 2, Vali, Studio

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Marvey:
Did these for fun. I think most people here have had a chance to hear these amps for themselves.

Two tone tests
1kHz and 123Hz @ ~2V
0dbFS = 20 volts (using 10x probe so QA400 doesn't explode)
100 ohm resistor load.

Note that output had to be reduced with Obj2 to prevent clipping because of its retarded architecture.

Vali is not as bad it it looks. 2nd harmonics are -45db (0.5%) down, and IMD bands are -40db (1%) down. Lots of smaller IM bands from the HD distortion too! I won't kid you as I do feel this distortion is audible. This distortion doesn't take away that the Vali subjectively more lively and resolving, albeit slightly warmer and thicker compared to the excellent measuring Obj2.

P.S.

Distortion measurements should always be on a log scale, never linear percentage. We hear logarithmically, not linearly. Distortion graphs in linear scale can be very misleading and make things look better than they really are. Here are some examples:

http://www.changstar.com/index.php/topic,2105.msg59347.html#msg59347
http://stereos.about.com/od/Measurements/ss/Oppo-Digital-PM-1-Headphone-Measurements.htm#step5

Solderdude:
The distortion of the Vali might probably drop a lot when the output voltage is lowered by 10dB.

How does a TOTL EC amp measure comparatively ?

Marvey:
I'll measure the Studio when I get a chance. It's at the lab. We are still checking it over since it was a first build in a new chassis that we just finished the day before the meet.

In the meantime, here is Vali 10db lower @ ~0.6V peak. Both IMD and HD are down another 6db. Same 100ohm load. Not going to bother with Magni 2 or Obj 2 since measurements were already awesome and distortion was far far below what people can hear.

M0 and M2 are the tones. M1 and M5 and their second harmonics. M3 and M4 are the IMD bands.

thune:
Looking at the measurements: I kinda wish the second channel was connected, to look at the distortion of the crosstalk. John Atkinson has said that the distortion of the crosstalk can be pretty ugly, but he hasn't shown it. Seems possible that the distortion of the crosstalk in a channel could be worse than the inherent distortion of the channel itself, in some instances. Anyway, I should investigate this for myself.

ultrabike:
Noise profile and distortion for the Vali seem in good agreement with what I had before. Though I used slightly different voltage settings. When comparing to other measurements note the noisefloor is less than -130 from 20Vrms.

It is also nice to see a zoom in plot aroudn the 1kHz frequency. Previously I was using RMAA which did not allow that AFAIK.

The Magni 2 and O2 measurements seem pretty close. O2 seems to measure a hair better.

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