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Author Topic: AMB Labs Gamma2 DAC Measurements (y2)  (Read 3634 times)

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Hands

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AMB Labs Gamma2 DAC Measurements (y2)
« on: May 01, 2014, 01:16:15 PM »
Test Hardware and Setup

-AMB Labs Gamma2 DAC (y2) - USB input for data and power from desktop. Has nifty digital filter switcher. Anti-clip mode off. See notes below.

-DIY Gaming Desktop - i5 2500K locked at 4.5GHz, Biostar TZ77XE3 motherboard, GTX 780, Antec EarthWatts 650W Green PSU, Auzentech Bravura sound card, 4 140mm fans, goofy UV cathode lights in case, Fractal Design Define R4 case...overall, most likely not optimal for audio, but does well enough as an output in tests and represents a real-life scenario for many. Plugged into APC H10 power conditioner. I did run Fidelizer on it for the tests. Used USB 3.0 ports from the mobo, tested for which ones produce best results and use those. Generally does not cause issues.

-Creative X-FI HD USB (SB1240) - Takes line-out signal from DAC to line-in for recording purposes, powered by USB bus, plugged into Surface Pro. Unit is limited to 48/96KHz input/output.

-1st gen Microsoft Surface Pro - Records from SB1240 via USB. Running Fidelizer tweaks. Battery powered. Screen is touchable and thus 27% more betterer. Produces cleaner and generally better results than running the SB1240 from the desktop as well.

Software

RightMark RMAA 6.3.0, ARTA

Misc. Notes

This particular Gamma2 does not use hardware upsampling, and it can only run at 16/48 max.

Gamma2 output is ~3dB lower than a "standard" DAC, and I didn't bother compensating for that in measurements. Not really a problem if you keep that in mind.

Could not get reliable results from some tests, like the -90dB low-level resolution test. Will have to invest in other gear in these situations.

Creative SB1240 has a slight roll-off in the bass.

I do not guarantee 100% accuracy with these measurements.

Links

AMB Labs Gamma2 DAC - http://www.amb.org/audio/gamma2/
Creative SB1240 - http://us.creative.com/p/sound-blaster/sound-blaster-digital-music-premium-hd
RightMark Audio Analyzer - http://audio.rightmark.org/index_new.shtml
ARTA: http://www.artalabs.hr/
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Hands

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y2 - Filter A - RightMark 16/48 Measurements
« Reply #1 on: May 01, 2014, 01:23:57 PM »
y2 set to 16/48 for all tests, as mentioned in first post. ADC set to 24/48 or 24/96, the latter which gives a view of what happens up to 48KHz. The lack of hardware upsampler affects the treble roll-off. This is for filter A. You'll notice it pushes the limits of what the ADC is capable of in some situations.

Frequency response (from 40 Hz to 15 kHz), dB   +0.02, -1.93Average
Noise level, dB (A)   -97.2Excellent
Dynamic range, dB (A)   97.1Excellent
THD, %   0.0013Excellent
THD + Noise, dB (A)   -89.5Good
IMD + Noise, %   0.0044Excellent
Stereo crosstalk, dB   -95.8Excellent
IMD at 10 kHz, %   0.0057Excellent
General performance   Excellent

RMAA attachments will be in following order:
1. Frequency Response
2. Noise
3. Dynamic Range
4. THD
5. IMD
6. IMD swept
7. Crosstalk
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Hands

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y2 - Filter B - RightMark 16/48 Measurements
« Reply #2 on: May 01, 2014, 01:28:31 PM »
Filter B RMAA measurements.

Frequency response (from 40 Hz to 15 kHz), dB   +0.02, -1.62Average
Noise level, dB (A)   -97.2Excellent
Dynamic range, dB (A)   97.1Excellent
THD, %   0.0011Excellent
THD + Noise, dB (A)   -89.8Good
IMD + Noise, %   0.0042Excellent
Stereo crosstalk, dB   -95.7Excellent
IMD at 10 kHz, %   0.0054Excellent
General performance   Excellent
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y2 - Filter C - RightMark 16/48 Measurements
« Reply #3 on: May 01, 2014, 01:31:37 PM »
Filter C RMAA measurements

Frequency response (from 40 Hz to 15 kHz), dB   +0.02, -0.06Excellent
Noise level, dB (A)   -96.9Excellent
Dynamic range, dB (A)   97.0Excellent
THD, %   0.0013Excellent
THD + Noise, dB (A)   -89.3Good
IMD + Noise, %   0.0047Excellent
Stereo crosstalk, dB   -96.3Excellent
IMD at 10 kHz, %   0.0059Excellent
General performance   Excellent
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AMB y2 Square Wave and Jitter Measurements
« Reply #4 on: May 01, 2014, 01:40:04 PM »
Attached are some square wave and jitter measurements. You'll see that filters A and C are both linear-phase, but A is a very mild form of it. B is a mild minimum-phase filter, similar to what Ayre implements in their DAC. Wolfson has good info on this on the DAC chip's white paper. My preferences are B>A>>C.

1. 1KHz Square wave, -3dB, 16/48 - Filter A
2. " Filter B
3. " Filter C
4. JTest 16 48 - Filter A
5. " Filter B
6. " Filter C
7. " Filter C - Upsampled to 16/48 in JRMC

It could be that the lack of hardware upsampler is what causes the jitter measurements to not look super "clean." I'd like to measure a y2 with the upsampler in place, mostly to see if that affects the digital filter ringing characteristics in the end or not (much like I'll show in a later thread how it affects the PWD MK1).
« Last Edit: May 01, 2014, 01:56:28 PM by hans030390 »
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AMB y2 ARTA Measurements
« Reply #5 on: May 01, 2014, 01:44:52 PM »
13/14KHz and 19KHz sine wave tests, at both 0dB and -3dB. Attached in order A, B, C with the 13/14KHz test first.
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AMB y2 White Noise Measurements
« Reply #6 on: May 01, 2014, 01:46:00 PM »
White noise measurements for the 3 filters, averaged over time.
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firev1

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Re: AMB Labs Gamma2 DAC Measurements (y2)
« Reply #7 on: May 01, 2014, 04:50:30 PM »
Could you do a high res -3dbFS 1khz sine spectrum with ARTA? I'm surprised to see that the "skirting" does not show up in the RMAA measurements.

Also to acquire CCIF IMD measurement numbers on ARTA(ADC side), set mode to "Two Sine" mode and calibrate the generator to match the twin tone test signals you are playing from the other ARTA(DAC side) window, even if there is supposed to be no signal output in that ARTA(ADC) window.

Below is how I would set an "External" signal CCIF IMD test, except probably with diff windows.




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Hands

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Re: AMB Labs Gamma2 DAC Measurements (y2)
« Reply #8 on: May 01, 2014, 06:34:06 PM »
Good tip. I was only really using it for the spectrum, but those numbers would be good to see. I also need a better multimeter for calibration purposes. I can probably whip up a quick 1KHz test tonight.
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mechgamer123

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Re: AMB Labs Gamma2 DAC Measurements (y2)
« Reply #9 on: May 01, 2014, 11:15:49 PM »
Could you explain what the different filters are, and why filter C has much better extension than the other two?
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