USB Audio ADCs
 

I've now started writing up the results of measurements on three different
devices. FWIW The best of these is a Focusrite 2i2. I'll put results on the
web and in a magazine article when done.

However I'd still be interested in other alternative devices. Steinberg
claim that all their 'UR' series *except* the UR22 are USB audio class
compliant. Which is daft from my POV as the UR22 is the only one aimed at
stereo. Anyone use any of their UR range and can comment on them?

Sadly, many makers totally ignore emails, or give a reply which doesn't
answer the questions about class compliance. Guess they don't know ('made
in china' syndrome), or don't care (Windows is the only fruit). :-/

Oh, and measurements show the choice of USB hub+psu can indeed affect
audio performance to a measureable extent.

Jim

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USB Audio ADCs
 

Jim Lesurf (for it is he) wrote:

Oh, and measurements show the choice of USB hub+psu can indeed affect
audio performance to a measureable extent.

Obviously you want a gold-plated power connector on the hub.

--
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USB Audio ADCs
 

On 10/03/2014 15:15, alexd wrote:
Jim Lesurf (for it is he) wrote:

Oh, and measurements show the choice of USB hub+psu can indeed affect
audio performance to a measureable extent.

Obviously you want a gold-plated power connector on the hub.

Or a Russ Andrews usb psu with yerrite beads.
Yerrite? That's the correct response when he tells you how it works,
or what it costs.

--
Eiron.

USB Audio ADCs
 

In article , Eiron
wrote:
On 10/03/2014 15:15, alexd wrote:
Jim Lesurf (for it is he) wrote:

Oh, and measurements show the choice of USB hub+psu can indeed affect
audio performance to a measureable extent.

Obviously you want a gold-plated power connector on the hub.

Or a Russ Andrews usb psu with yerrite beads. Yerrite? That's the
correct response when he tells you how it works, or what it costs.

Actually the main effect that made me notice was that one hub + psu caused
both a low level 485Hz tone *and* modulated a test sinewave to have 485Hz
sidebands. I presume these are AM due to the device's ADC having this
ripple on its 5V (sic) output. A change of hub and psu and I found one
where this effect vanished.

I don't think either hub or psu cost more than a few quid. The effects were
low level. I probably wouldn't have noticed them with 16bit samples. But
they showed there are some gotya's lurking if you are after high
resolution.

No gold was harmed in the making of these tests. :-)

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

USB Audio ADCs
 

On 10/03/2014 16:49, Jim Lesurf wrote:
In article , Eiron
wrote:
On 10/03/2014 15:15, alexd wrote:
Jim Lesurf (for it is he) wrote:

Oh, and measurements show the choice of USB hub+psu can indeed affect
audio performance to a measureable extent.

Obviously you want a gold-plated power connector on the hub.

Or a Russ Andrews usb psu with yerrite beads. Yerrite? That's the
correct response when he tells you how it works, or what it costs.

Actually the main effect that made me notice was that one hub + psu caused
both a low level 485Hz tone *and* modulated a test sinewave to have 485Hz
sidebands. I presume these are AM due to the device's ADC having this
ripple on its 5V (sic) output. A change of hub and psu and I found one
where this effect vanished.

I don't think either hub or psu cost more than a few quid. The effects were
low level. I probably wouldn't have noticed them with 16bit samples. But
they showed there are some gotya's lurking if you are after high
resolution.

No gold was harmed in the making of these tests. :-)

Jim


Just to make your blood boil:

http://www.theguardian.com/technolog...usic-converter

or https://tinyurl.com/q8ju7p9

Incidentally, can you *hear* any difference between all these DACs?


--
Cheers, Rob

USB Audio ADCs
 

In article , RJH
scribeth thus
On 10/03/2014 16:49, Jim Lesurf wrote:
In article , Eiron
wrote:
On 10/03/2014 15:15, alexd wrote:
Jim Lesurf (for it is he) wrote:

Oh, and measurements show the choice of USB hub+psu can indeed affect
audio performance to a measureable extent.

Obviously you want a gold-plated power connector on the hub.

Or a Russ Andrews usb psu with yerrite beads. Yerrite? That's the
correct response when he tells you how it works, or what it costs.

Actually the main effect that made me notice was that one hub + psu caused
both a low level 485Hz tone *and* modulated a test sinewave to have 485Hz
sidebands. I presume these are AM due to the device's ADC having this
ripple on its 5V (sic) output. A change of hub and psu and I found one
where this effect vanished.

I don't think either hub or psu cost more than a few quid. The effects were
low level. I probably wouldn't have noticed them with 16bit samples. But
they showed there are some gotya's lurking if you are after high
resolution.

No gold was harmed in the making of these tests. :-)

Jim


Just to make your blood boil:

http://www.theguardian.com/technolog...sb-dac-review-
digital-music-converter

or https://tinyurl.com/q8ju7p9

Incidentally, can you *hear* any difference between all these DACs?




LOL!...

And I quote....



But I'm totally in agreement with you in your last line. I could hardly
believe the assertions in the article were being published in a
reputable newspaper. Did nobody think of running this past someone with
even half a clue as to the subject matter before running the piece?


--
Tony Sayer

USB Audio ADCs
 

In article , RJH
wrote:
On 10/03/2014 16:49, Jim Lesurf wrote:
In article , Eiron
wrote:
On 10/03/2014 15:15, alexd wrote:


No gold was harmed in the making of these tests. :-)


Just to make your blood boil:

http://www.theguardian.com/technolog...usic-converter

Seems fairly typical for 'subjective' reviews.

or https://tinyurl.com/q8ju7p9

Incidentally, can you *hear* any difference between all these DACs?

Well, in this thread I've been talking about ADCs rather than DACs.
However...

FWIW I don't personally write, or take very seriously, a lot of what
appears as 'subjective comments' in audio reviews. I can't comment as yet
on any relative audible differences between the ADCs I've been testing. So
far, I'd only prefer one to the others because it clearly has better
behaviour in terms of distortion, noise floor, etc. i.e. ye olde basic
injuneering.

Have I sometimes heard differences between various DACs, CD players, etc?
Yes, I think so. Generally slight to negligable when I do. Do I think that
should sway anyone else? No. Not unless I can give a concrete reason.

On that I can say things like:

I preferred the sound of my first CD player (Marantz using the first
Philips chipset) when I added an analogue low pass filter to its output.
(Toko 19kHz low pass filters meant for good FM tuners.) I think that may
have suppressed some garbage around 20kHz and up. May also have altered
the impulse behaviour.

I preferred a Meridian 263 DAC to other DACs and players for many years. No
idea why, but I guess it simply did a better reconstruct and filter job
than others of the period. There are various ways for DACs to seem fine in
some ways but have flaws that cause audible problems.[1] However I didn't
sort out why I preferred it, but it just sounded more pleasing on source
material I liked. [2]

I now prefer the Cambridge Audio DACs, particularly the one in the 851C
player/DAC. Sounds good, and unlike my old 263 and 563 will play higher
rate source material via USB. Also (praise!) has a digital balance control
as well as volume one. Why can't everyone do that!?

So in practice I'd probably still be happy with the decades-old Meridian
263 and 563 if it hadn't been for USB audio, and 'high rez' files, etc.

But I have no idea what I may imagine or what has a real physical basis,
and no idea if anyone else using different ears, room, kit, and sources,
would agree with me. So I avoid giving flowery poetic descriptions of 'why'
one item is 'better' than another. Leave that to people who feel they can
do so, but tend to skip over what they write. :-)

Jim

[1] I've looked at various examples over the years. e.g. the behaviour of
DACs when presented with sample series that require intersample peaks above
0dBFS. Which, alas, happens a lot with modern pop CDs. Yet almost no-one
ever bothers to test for this.

[2] Sometimes the reasons may pass by the standard tests people make. e.g.
I noticed in the ADC measurements that one ADC's noise floor rises quite a
lot when you apply an input signal. So simply measuring the noise level
with no signal doesn't tell you what happens when a signal is applied. I
don't *know* why this happens, only that I can measure it. I can *guess*
various reasons for it happening. But whatever they are, it makes me feel
it is a mark against the ADC. That said, I can of course also say that ye
olde analogue mag taps used to exhibit modulation noise, probably at a
higher level, and we all survived that OK. :-)

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

USB Audio ADCs
 

In article , Jim Lesurf
wrote:
That said, I can of course also say that ye olde analogue mag taps used
to exhibit modulation noise,

Oops! Replace "taps" with "tapes".

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

USB Audio ADCs
 

On Tue, 11 Mar 2014 10:52:45 +0000 (GMT), Jim Lesurf
wrote:

In article , Jim Lesurf
wrote:
That said, I can of course also say that ye olde analogue mag taps used
to exhibit modulation noise,

Oops! Replace "taps" with "tapes".


No need, I'd guessed you meant 'tapes' (as I suspect did everyone
else).

Talking about 'what we survived' regarding tape. I remember reading a
remark 30 or 40 years ago that even with studio recordings, the IM
distortion products could reach as high as 30% on peaks. It really is
amazing what we can tolerate for some types of distortion.
--
Regards, J B Good

USB Audio ADCs
 

In article ,
Johny B Good wrote:
Talking about 'what we survived' regarding tape. I remember reading a
remark 30 or 40 years ago that even with studio recordings, the IM
distortion products could reach as high as 30% on peaks. It really is
amazing what we can tolerate for some types of distortion.

Best thing to show up tape at its worst is a belltree. No matter what
level you record it at, it never sounds the same as the send. ;-)

--
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Dave Plowman London SW
To e-mail, change noise into sound.