CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS
Lobby => Amp and DAC Measurements => Topic started by: atomicbob on May 28, 2015, 02:07:18 AM
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Here are measurements for a DAC / Amp combo that provides enjoyable listening in a very portable format; Leckerton UHA-6S mkII. If you have been following my other measurement posts, you may begin to see some trends.
The data presented were collected as follows:
1. PrismSound dScope III, picoscope 5243B
2. DAC unbalanced output RCA
3. 100 Kohm load used for measurements dScope measurements
4. 50 ohm load used for square wave measurements
5. 44 KHz sample rate, 24 bit depth
6. USB input – Audioquest Forest
7. S/PDIF input - Canare broadcast grade 75 ohm BNC cable
8. TosLink - Mediabridge 0.5 meter
9. Unbalanced cable Radio Shack nothing special 3.5mm TRS to stereo RCA
10. Vaunix Lab Brick USB hub
11. output gain switch set to low position
Tests were run at a gain consistent with my personal listening sound levels which is between 70 to 77 dBC SPL.
Frequency Response
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9856;image)
Frequency Response (y-axis zoom)
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9858;image)
Dynamic Range
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9860;image)
THD+N (updated 20150530)
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=10017;image)
IMD
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9864;image)
Crosstalk
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9866;image)
1kHz @ -70dBFS
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9870;image)
1kHz @ -90dBFS
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9872;image)
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Measurements part B
inferred jitter - USB
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9874;image)
inferred jitter - S/PDIF
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9876;image)
inferred jitter - TosLink
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9878;image)
gain linearity
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9880;image)
imaging
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9882;image)
imaging with 19 KHz tone
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9884;image)
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Measurements part C
20 Hz sqr 0dBFS 600 mVpp 50 ohm load 10 mS/div
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9886;image)
20 Hz sqr 0dBFS 600 mVpp 50 ohm load 500 uS/div
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9888;image)
What happens when the mastering engineer sets the limiter very close to 0 dBFS during the final processing of the music to which you listen?
Here are four THD+N and THD measurement sets depicting the behavior at -0.1, -0.2, -0.5 and -1.0 dBFS maximum signal for the UHA-6SmkII. The closer to 0 dBFS the greater the risk of recovery filter inter-sample overs and the rise in distortion, typically below 200 ~ 500 Hz. Please note the Leckerton is not unique. All DACs exhibit this more or less as can be seen in the THD+N and THD measurements I've made at -0.1 dBFS for other DACs.
THD+N and THD with signal generator set to sweep at -0.1 dBFS
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9906;image)
THD+N and THD with signal generator set to sweep at -0.2 dBFS
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9908;image)
THD+N and THD with signal generator set to sweep at -0.5 dBFS
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9910;image)
THD+N and THD with signal generator set to sweep at -1.0 dBFS
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9912;image)
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measurements part D - amplifier section only:
dScope measurements
UHA-6SmkII amplitude - phase - gain
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9914;image)
UHA-6SmkII signal to noise
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9916;image)
UHA-6SmkII THD+N THD nth harmonic distortion
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9918;image)
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9929;image)
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9931;image)
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9933;image)
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9935;image)
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Imaging with 19khz tone, is the tone an overlay? Its supposed to be two separate test that are just superimposed on one another for easy reference. Its easy enough to see the aliasing though.
For amp testing does the dscope come with a notch filter? Just asking. :3
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Imaging with 19khz tone, is the tone an overlay? Its supposed to be two separate test that are just superimposed on one another for easy reference. Its easy enough to see the aliasing though.
For amp testing does the dscope come with a notch filter? Just asking. :3
I tried something new, I pre-mixed white noise and the 19 KHz tone for a source and then ran the dScope asynchronously to see how the imaging components changed from the white noise alone.
The dScope has a notch filter, which can be swept. It also has more configurable components than I have yet to explore in depth.
For the Leckerton, I combined measurements as the DAC / Amp combination is being measured together. I could have measured the Amp portion separately but I didn't see an easy way to get at just the DAC without opening the unit and putting a probe onto the PCB, which would no longer be representative of a typical user use model.
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The only problem with the pre mixed signal is that most of the aliasing components from the 19khz tone is covered by the ripple in the stopband.
Would like to have a glimpse of the Leckerton's amp only performance, which I reckon might require the notch to measure, maybe.
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Amp measurements would be nice as many of use just that in a brick setup. No surprise about toiling and coax measuring better than USB here. Cool.
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I'm not understanding the THD plots ( 0.1%<=100hz seems excessively large.) Also the Leckerton UHA-6S THD plot (http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9862;image) appears eerily similar to the Mousai MSD192 (http://www.changstar.com/index.php?action=dlattach;topic=2450.0;attach=9727;image) and Yggdrassil (http://www.changstar.com/index.php?action=dlattach;topic=2405.0;attach=9472;image) THD plots. I'm wondering if there is a setup/equipment issue with this test.
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I'm not understanding the THD plots ( 0.1%<=100hz seems excessively large.) Also the Leckerton UHA-6S THD plot (http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9862;image) appears eerily similar to the Mousai MSD192 (http://www.changstar.com/index.php?action=dlattach;topic=2450.0;attach=9727;image) and Yggdrassil (http://www.changstar.com/index.php?action=dlattach;topic=2405.0;attach=9472;image) THD plots. I'm wondering if there is a setup/equipment issue with this test.
Updated 20150530.
In this case it was a USB driver issue creating inter-sample overs due to modifying the data stream with some math operation.
But the dirty little secret of recovery filter inter-sample overs when the source approaches 0 dBFS still is a problem. As soon as we drop below -0.5 and -1.0 dBFS most DACs look a lot better. Look at the Leckerton handling it very well as soon as the signal is -0.2 dBFS or lower. Another reason this little DAC / Amp rocks.
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Using the most common definition* of dBFS, a -0.1dBFS sine wave (by definition) does not have any inter-samples that exceed -0.1dBFS. Stereophile does 0dBFS testing at 1kHz and/or 50Hz for digital products. Almost all products easily do >-80db@50hz. The only one I've seen that sucked bad was the Dragonfly near full scale.
*AES17-1998 3.3-3.4 (page 5) (https://www.ak.tu-berlin.de/fileadmin/a0135/Unterrichtsmaterial/KT-Labor_WS0809/1_ADDA/aes17.pdf)
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Using the most common definition* of dBFS, a -0.1dBFS sine wave (by definition) does not have any inter-samples that exceed -0.1dBFS. Stereophile does 0dBFS testing at 1kHz and/or 50Hz for digital products. Almost all products easily do >-80db@50hz. The only one I've seen that sucked bad was the Dragonfly near full scale.
*AES17-1998 3.3-3.4 (page 5) (https://www.ak.tu-berlin.de/fileadmin/a0135/Unterrichtsmaterial/KT-Labor_WS0809/1_ADDA/aes17.pdf)
This will get you started. It is a real problem mastering engineers face.
http://www.solid-state-logic.com/music/X-ISM/
https://www.gearslutz.com/board/showwiki.php?title=Tips-and-Techniques:Intersample-peaks
http://www.digido.com/forum/mfit/77-intersample-peaks.html
http://www.askaudiomag.com/articles/why-you-need-an-intersample-meter-when-mastering
http://www.musictech.net/2012/09/10mm-no211-inter-sample-peaks/
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I appreciate the detailed response. Yes, I am aware signals are reconstructed and reconstruction of some signals can generate "overs". But a sine wave <=0dBFS is not such a signal. The definition of 0dBFS sine wave is one that kisses the positive max, but never touches the negative max. A full scale sine wave does not "over" in reconstruction.
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I appreciate the detailed response. Yes, I am aware signals are reconstructed and reconstruction of some signals can generate "overs". But a sine wave <=0dBFS is not such a signal. The definition of 0dBFS sine wave is one that kisses the positive max, but never touches the negative max. A full scale sine wave does not "over" in reconstruction.
Did you notice section 8.5.1 in AES17-1998:
8.5.1 Total harmonic distortion and noise versus frequency
The measurement should be conducted with a sine wave at – 1,0 dB FS and repeated with a sine wave at – 20
dB FS. The test signal present in the output should be removed by means of a standard notch filter and the
remaining signal bandwidth limited to the upper band-edge frequency or 20 kHz, whichever is lower. The
level of the filtered signal should be measured and reported as a ratio to the unfiltered signal level. The
measurement should be repeated at each octave frequency from 20 Hz to one-half the upper band-edge
frequency.
There is a good reason the spec was written to use -1.0 dBFS.
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BTW, thanks for measuring and posting the UHA-6S THD results for -0.2, -0.5 and -1.0 dBFS. (http://www.changstar.com/index.php/topic,2462.msg68573.html#msg68573) These plots seem to better reflect the native performance of the device. Great work. That said, I'm still unconvinced that -0.1dBFS should have unclean sine-wave THD from properly operating DACs. I continue to suspect some issue in the chain, setup, or test.
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Ok, here is another look at the UHA-6SmkII THD
Test setup:
1. Cool Edit Pro DAW with -0.1 dBFS and -0.2 dBFS 100 Hz and 1000 Hz sine 44KHz 32 bit wavefiles as signal generator
2. Vaunix Lab Brick powered USB hub
3. UHA-6SmkII USB connected
4. picoscope 5243b - see screen shots for setup parameters
5. USB cable provided by Leckerton
6. Radio Shack nothing special 3.5 mm TRS to stereo RCA
7. RCA to BNC adapters from Markertek / Allied Electronics / Digikey etc.
The tests are performed at 240 mVpp, which is a level consistent with my listening levels of 70 to 77 dB SPL for an HD600 or HD650
The UHA-6SmkII is capable of producing greater than 9 Vpp without clipping so we are well below any analog section limitations
UHA-6SmkII 1000 Hz -0.1 dBFS sine 240 mVpp
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9941;image)
UHA-6SmkII 100 Hz -0.1 dBFS sine 240 mVpp
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9943;image)
UHA-6SmkII 1000 Hz -0.1 dBFS spectrum THD = 0.023%
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9945;image)
UHA-6SmkII 100 Hz -0.1 dBFS spectrum THD = 0.101%
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9947;image)
UHA-6SmkII 100 Hz -0.2 dBFS spectrum THD = 0.025%
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9949;image)
UHA-6SmkII 100 Hz -0.1 dBFS spectrum THD = 0.102% - expanded spectrum x-axis
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9951;image)
UHA-6SmkII 100 Hz -0.2 dBFS spectrum THD = 0.025% - expanded spectrum x-axis
(http://www.changstar.com/index.php?action=dlattach;topic=2462.0;attach=9953;image)
Different system setup, similar results to the dScope.
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I'm led to suspect that the digital signal being fed to the DAC has itself been distorted by a conversion error, a level error, or some other OS/driver processing that has kicked in.
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I'm led to suspect that the digital signal being fed to the DAC has itself been distorted by a conversion error, a level error, or some other OS/driver processing that has kicked in.
Yes, you are correct. It is an inter-sample over as I stated, but it is coming from the windows driver, not the DACs. I thought I had this solved with the appropriate configuration for exclusive mode of the WASAPI, but I have since discovered that the configuration reverts for reasons I don't understand. This leaves the driver behaving as if the KMixer were engaged, running MS idea of sample interpolation rather than sample accurate output. AAAARRRRRGGGGGGHHHHHH!
I am in the process of rectifying those measurements affected. I will be spending the next several days performing the measurements again and posting corrected results.
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I don't know if this is the place to ask, but is there a Changstar opamp preference for the UHA-6S MkII with IEMs?
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^Yes! Anax did the legwork on the ADA4627 and we later bought ADA4627-BRZ uprated versions that we all like. Nick sold enough of them to put them up on his site as an option. I think they are +$15 to put in the unit. For my iems, I also had Nick adjust down -6 from stock. I tried -12, then stock, then -6 for the best range on low gain. At times with very quiet recordings, I need high gain. I do get hiss in high gain with UERM but have it if I need it. Low gain works great 90% of the time.
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I don't know if this is the place to ask, but is there a Changstar opamp preference for the UHA-6S MkII with IEMs?
ADA4627-BRZ (B1). Also, get the gain dropped on it.. ideally, I'd drop it so I can use the high gain with sensitive IEMs.
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Thanks CEE TEE & FlySweep. When I ordered my UHA-6S MkII awhile back, I got the OPA627A installed. At the time, I didn't anticipate IEM listening. Now that I have an IEM, the gain is unmanageable. I assume I could switch out the op-amps, although I've never performed that sort of operation before. Is the same true for adjusting the gain? Alternatively, might one send the amp back in for some modifications?
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^Yes, Nick was very cool about adjusting gain until I settled on -6 for my IEMs and recordings. I shipped it back to him and paid at least shipping back to me.
If you have sensitive IEMs, I recommend starting at -6 and taking it from there. Maybe others have some other experiences?
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^Yes, Nick was very cool about adjusting gain until I settled on -6 for my IEMs and recordings. I shipped it back to him and paid at least shipping back to me.
If you have sensitive IEMs, I recommend starting at -6 and taking it from there. Maybe others have some other experiences?
Excellent, thanks! I'll contact Nick about having my Leck retrofitted with the ADA4627-BRZ (B1) and the gain dropped 6dB. Now I'll have to start looking around for an economical solution for my full-sized headphones.
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Excellent, thanks! I'll contact Nick about having my Leck retrofitted with the ADA4627-BRZ (B1) and the gain dropped 6dB. Now I'll have to start looking around for an economical solution for my full-sized headphones.
FWIW, I preferred the Leck with many full sized phones, too.. HD800, HD650, HE-560, etc. If you're in a pinch, you could do a helluva lot worse..and those phones will remain pretty damn resolving even with this 'modest' amp (it isn't). Hell, I preferred the Leck w/ the HD800 over the Valhalla 2 in some cases (cleaner, faster, more resolving treble.. but V2 tubes do matter).
I sense the Geek Out V2/+ would be a nice option for full sized cans since it's got adjustable gain, class a, etc. etc.
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FWIW, I preferred the Leck with many full sized phones, too.. HD800, HD650, HE-560, etc. If you're in a pinch, you could do a helluva lot worse..and those phones will remain pretty damn resolving even with this 'modest' amp (it isn't). Hell, I preferred the Leck w/ the HD800 over the Valhalla 2 in some cases (cleaner, faster, more resolving treble.. but V2 tubes do matter).
I sense the Geek Out V2/+ would be a nice option for full sized cans since it's got adjustable gain, class a, etc. etc.
This. The Leckerton with 4627-1B makes life very, very hard for midrange desktop amps. Every time I'd get a new amp in - Vali, Magni 2 Uber, Asgard 2, Gustard H10, fuck even Project Ember - the Leckerton made them have to justify taking up room on my desk.
Apparently the V2/V2+'s are shipping ahead of schedule, so we won't have to wait long for a comparison ;)
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FWIW, I preferred the Leck with many full sized phones, too.. HD800, HD650, HE-560, etc. If you're in a pinch, you could do a helluva lot worse..and those phones will remain pretty damn resolving even with this 'modest' amp (it isn't). Hell, I preferred the Leck w/ the HD800 over the Valhalla 2 in some cases (cleaner, faster, more resolving treble.. but V2 tubes do matter).
I sense the Geek Out V2/+ would be a nice option for full sized cans since it's got adjustable gain, class a, etc. etc.
This. The Leckerton with 4627-1B makes life very, very hard for midrange desktop amps. Every time I'd get a new amp in - Vali, Magni 2 Uber, Asgard 2, Gustard H10, fuck even Project Ember - the Leckerton made them have to justify taking up room on my desk.
Apparently the V2/V2+'s are shipping ahead of schedule, so we won't have to wait long for a comparison ;)
That's exactly it: I've been so impressed with the Leck, I've made it my desktop unit. It's more or less pushed the EF-6 to the side, so I plan to sell the latter. My worry is that if I retrofit it for IEMs, it might then be lacking when I try to drive the LCD-2.2 or HE-500. Hence my starting the look for an amp for full-sized cans. Of course, if the Leck should still have enough power after having been retrofitted, then I won't need a new amp. At least until I pick up GO V2/+. The GO450 with the Leck is so serious.
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The GO450 with the Leck is so serious.
This statement got me. :)
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Is the Leck with the 4627-1B significantly more powerful than with the 8610? The listed specs with the 8610 are less powerful than the GO450, but with the 4627-1B on high gain, the Leck drives my LCD 2 to quite a bit higher volume than the GO 450 on its own. This leads me to believe that the Leck is more powerful, but I could be completely mistaken in my understanding that more power equals more volume.