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Author Topic: Yggdrasil Measurements  (Read 8539 times)

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ultrabike

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Re: Yggdrasil Measurements
« Reply #30 on: May 15, 2015, 12:18:01 AM »

LOL! I more than understand Bob. Thanks!
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atomicbob

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Re: Yggdrasil Measurements
« Reply #31 on: May 15, 2015, 02:07:54 AM »

LOL! I more than understand Bob. Thanks!
BTW, I've probably watched A Night in Casablanca more times than anyone else alive. It comes to life heard through a WA7 and T90 from an OPPO 103
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Armaegis

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Re: Yggdrasil Measurements
« Reply #32 on: May 15, 2015, 03:30:54 AM »

What kind of work do you do that gives you access to a dscope? Or do you just have one for home/personal use?
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Do you think there may be an acoustic leak from the jack hole? ~Tyll Hertsens

Not sure if I like stuffing one hole or both holes. Tending toward one hole since both holes seems kinda ghey ~Purrin

atomicbob

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Re: Yggdrasil Measurements
« Reply #33 on: May 15, 2015, 04:14:01 AM »

What kind of work do you do that gives you access to a dscope? Or do you just have one for home/personal use?
That is a very good question. I found my passion in life and have developed it for both professional and personal benefit. It is a long story I should document sometime. Suffiice it to say that I am responsible for voice prompting systems used by Emergency Medical Services devices in 40 languages, in almost every country in the world. Robust systems that are critical to be heard in noisy environments. Psycho-acoustics and the human auditory system are quite important to me. Building my personal acoustic lab has been an obsession, rather than owning a boat, sports car, motorcycle, helicopter, etc. My personal lab is far more sophisticated than my corporate lab, though budget is slowly being made available to bring parity at sometime in the future. I intend to keep at my acoustic research as long as I am able to function.
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Armaegis

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Re: Yggdrasil Measurements
« Reply #34 on: May 15, 2015, 05:54:53 AM »

So, if you ever need to hire an engineer...  :)p8
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Do you think there may be an acoustic leak from the jack hole? ~Tyll Hertsens

Not sure if I like stuffing one hole or both holes. Tending toward one hole since both holes seems kinda ghey ~Purrin

Solderdude

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Re: Yggdrasil Measurements
« Reply #35 on: May 15, 2015, 07:05:24 AM »

I'm surprised by the cross over distortion. I don't see it when measuring the outputs of my M7 (using Rigol DSO)... Will post a SS when I'm not posting from iCrap.

I'm not experienced on the matter, and the FFT measurements show all other signals other than fundamental are near noise floor. But I wouldn't of expected it in a device where fidelity is meant to be the main goal...

The M7 has a sign magnitude DAC (PCM1704) that is actually intended for audio.
Because it is sign magnitude the MSB doesn't 'topple' at the '0' Volt point but it does at the -6dBFS point instead where it is 'masked' by the large signal level.

The chip (AD5791) used in this DAC is not designed for audio in a sense that it needs another physical input signal (non standard audio related format) and post processing of the analog signal (deglitching) compared to chips designed for audio.
Because of its wide operating temperature range and stability it has been approved/designed for military and aerospace.
Not because it is more accurate or 'better'. :o

The somewhat confusing part here is that Schiit uses 2 of these chips per channel and claim 21 bit resolution so it stands to reason mr Moffat made it signed magnitude as well.
As the smallest 'step' of the PCM1704 is 23 bit (accuracy seems decent so who knows how small the steps can be) and the AD5791 is 'merely' 20 bit the accuracy of the first steps of the 1704 are likely to be better as in more accurate as theoretical the smallest possible step is 8x smaller in the PCM1704.

The large amount of spikes that run fairly high in level compared to most other DAC's around are caused by the LSB step size most likely or a very, very small DC offset in the DAC output signal which would only be a problem if used in signed magnitude configuration.
Again, that chip isn't designed for this specifically.
It stands out even more because the noise floor of the analog section is very good as well.
In practise it is too bad that extremely low noise floor is decreased by say 20 to 30dB as when music is played there will be lots more 'poles' all over the freq band creating a higher noise floor.

I wouldn't care about this because I would like to see a recording that actually has a noise floor below -100dB anyway.

However, like with everything else it's not just the DAC chip that matters but the implication.
The digital and analog signal handling, PCB design, power supply and other used parts are of greater importance.

I seriously doubt if any 'garbage' below say 120dB would be audible as you would have to play extremely loud for it to reach audible levels.
At least that's what I think.

Aside from that, Schiit uses magic in their designs where AGD just uses chips.  8)

It seems to me mr. Moffat knows his Schiit and if its good enough for the goose .....
And ... did I tell you I am impressed with the amount of jitter (even though I could not care less about this)



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Use your ears to enjoy music, not as an analyser.

atomicbob

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Re: Yggdrasil Measurements
« Reply #36 on: May 15, 2015, 01:09:45 PM »

I wouldn't care about this because I would like to see a recording that actually has a noise floor below -100dB anyway.
Not going to happen in a live situation due to the room background noise. Might be possible in a studio that has attended to HVAC, Low Frequency isolation, etc. Not many studios manage both along with good room acoustics. Very expensive. Then again, we have the microphone self noise with which to contend. The greater the number of mics in use, the higher the residual noise.

Quote (selected)
I seriously doubt if any 'garbage' below say 120dB would be audible as you would have to play extremely loud for it to reach audible levels.
The sound level necessary would only be listenable during a very very quiet passage of a classical recording or dramatic pause in anything else. The rest of the recording would be distorting the electro-acoustic transducers due to the SPL being produced at such a high gain.

Quote (selected)
And ... did I tell you I am impressed with the amount of jitter (even though I could not care less about this)
Very impressive jitter performance, yes. I used to be of the same opinion that jitter below a certain point didn't matter. But rereading the 1992 and 1998 AES papers on the audibility of jitter one notes that no listener training was performed. The subjects didn't know what they were supposed to detect. When we have all kinds of comments about digital hash, glare, something not quite right etc. one has to wonder if jitter is possibly a contributor along with the recovery filter characteristics.
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Stefan

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Re: Yggdrasil Measurements
« Reply #37 on: May 15, 2015, 05:47:59 PM »

Yes, measurments on AES/EBU input would be nice...given all the attention USB gets, I'm wondering if it by now measures better (e.g. my paranoia).

First post for me, didn't do intro post yet. 
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atomicbob

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Re: Yggdrasil Measurements
« Reply #38 on: May 16, 2015, 04:24:44 PM »

I'm surprised by the cross over distortion. I don't see it when measuring the outputs of my M7 (using Rigol DSO)... Will post a SS when I'm not posting from iPhone.

I'm not experienced on the matter, and the FFT measurements show all other signals other than fundamental are near noise floor. But I wouldn't of expected it in a device where fidelity is meant to be the main goal...
Did you make some measurements with your DSO? Which model?

I'm guessing it was hard to find anything to observe, as even Rigol 2000 series and above have only 500uV/div resolution. The yggdrasil crossover distortion measured on the dScope is at approximately 43 uVpp so it would be very hard to see on most DSOs.
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aive

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Re: Yggdrasil Measurements
« Reply #39 on: May 16, 2015, 04:56:51 PM »

Oh I have the piccies on my iPhone but need to get onto a PC to post them, will update this post with them when I get home.

I've done some more reading to try and understand all this. The PCM1704 chips implement signed magnitude so I wouldn't expect to see any cross over distortion. But my waveform SSs also aren't zoomed in to the scale you mentioned so it may not be evident (if it exists). One thing I still don't understand is reconciliation of the rated distortion figures of the AD chips vs the distortion measurements - is what you've measured within spec of +/- 1 LSB? (Probably because I don't understand the DBFS scale lol.... Next thing to read up on).

I'm not sure how Schiit have implemented the chips per channel but I don't think it signed magnitude - prolly one chip per balanced hot signal.

My DSO is a Rigol DS1054Z (software upgraded).

For context, I took these measurements to understand the full scale output of the DAC so I could fix gain of my amp accordingly (did these a few weeks ago) - I didn't trust AGD website's ratings... So they may not serve our purpose here...


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