Hi guys, I got my company to donate you a new hifi

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Sam Ellenby

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Nov 19, 2011, 6:02:12 AM11/19/11
to London Hackspace
Hi,

I'm not a member of Hackspace yet, but a couple of weeks ago, I and a
bunch of my friends came to look around on a tuesday. I have to say, I
was very impressed. I think the Hackspace is great. I will become a
member soon.

Anyway, I was browsing through the stuff you guys have on your wish
list and found that you wanted a hifi. I remember when I walked around
that the sound system was some computer speakers which could be
improved on. I work for the Audiopartnership. We make Cambridge Audio
sound equipment. I am one of their electronic engineers. I asked the
owner of my company, whether he'd be willing to donate some stuff to
the Hackspace and he agreed.

So, probably on Tuesday next week, I will be bringing a Sonata NP30
network radio http://www.cambridgeaudio.com/summary.php?PID=604 and a
651A (it is a pre-production prototype). I will try and scrounge up
some speakers, but they are likely to be a bit crappy. And some
cables.

All I ask in return is that you try and enjoy the equipment and look
after it reasonably well. I look forward to saying hello again. And
will help set up the equipment. Is there anywhere good to put it?

Oh, also, we have a bunch of old test equipment which we were going to
get rid of. Like an old 50mhz Tektronix oscilloscope and a 5V power
supply. Would you be interested in having it as well? The scope is a
bit buggered, but still works. Will bring along if you are interested.

Sam

Tim Hutt

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Nov 19, 2011, 6:49:04 AM11/19/11
to london-h...@googlegroups.com
On 19 November 2011 11:02, Sam Ellenby <sam.e...@gmail.com> wrote:
> Hi,
>
> I'm not a member of Hackspace yet, but a couple of weeks ago, I and a
> bunch of my friends came to look around on a tuesday. I have to say, I
> was very impressed. I think the Hackspace is great. I will become a
> member soon.
>
> Anyway, I was browsing through the stuff you guys have on your wish
> list and found that you wanted a hifi. I remember when I walked around
> that the sound system was some computer speakers which could be
> improved on. I work for the Audiopartnership. We make Cambridge Audio
> sound equipment. I am one of their electronic engineers. I asked the
> owner of my company, whether he'd be willing to donate some stuff to
> the Hackspace and he agreed.

That looks awesome; thanks! By the way, since you're an actual audio
engineer this seems like a good opportunity to ask something I've
sometimes wondered: In the marketing blurb it says "music stored on
computers and other hard drives inherently suffers from jitter and the
NP30 implements a host of advances such as bit-perfect signal path and
jitter suppression to vastly improve the quality of digital music
playback."

This sounds like complete bollocks to me... I meant there's no
"inherent jitter" in digital music, but perhaps there is when it is
played back. I just always suspected that:

a) If there *is* any jitter, it is completely inaudible.
b) Surely DAC's run off a crystal clock... so I don't see how you
could have any "jitter" from an amplifier.
c) If this is talking about digital-digital audio (e.g. computer->amp
via optic fibre), then I guess *maybe* their clocks could get out of
sync or run at slightly different rates or something? Is that what
it's talking about?

Cheers,

Tim

Sam Ellenby

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Nov 19, 2011, 7:43:13 AM11/19/11
to london-h...@googlegroups.com
That looks awesome; thanks! By the way, since you're an actual audio
engineer this seems like a good opportunity to ask something I've
sometimes wondered: In the marketing blurb it says "music stored on
computers and other hard drives inherently suffers from jitter and the
NP30 implements a host of advances such as bit-perfect signal path and
jitter suppression to vastly improve the quality of digital music
playback."

This sounds like complete bollocks to me... I meant there's no
"inherent jitter" in digital music, but perhaps there is when it is
played back. I just always suspected that:

a) If there *is* any jitter, it is completely inaudible.

Jitter isn't something you would necessarily hear, but is an artifact that detracts from the accurate reproduction of music. We put a lot of effort into minimising it, with the aim of making music sound like the original recording. 
 
b) Surely DAC's run off a crystal clock... so I don't see how you
could have any "jitter" from an amplifier.

You are right, an analogue class A/B (for example) amplifier would have no jitter. But differences in propagation delay in the crystal oscillator buffer and phase noise from the crystal all result in added measurable jitter. 
c) If this is talking about digital-digital audio (e.g. computer->amp
via optic fibre), then I guess *maybe* their clocks could get out of
sync or run at slightly different rates or something? Is that what
it's talking about?

In the case of the network player, yes, in part, the clocks we use reclock each sample to provide the minimum of phase noise. We also use DSP's to dynamically resample all of the data resulting in no measurable jitter. We measure this jitter using a test called the Dunn test, where you play a 10k sine wave recorded at 1/4 the sample rate and using an fft, measure the distance of the sidebands from the original frequency of the recording. This is then quantified into a measurement of jitter in the analogue audio. 

Jitter can also refer to timing errors in the digital audio stream over toslink/coaxial spdif. 

Martin Klang

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Nov 19, 2011, 8:19:08 AM11/19/11
to london-h...@googlegroups.com

On 19 Nov 2011, at 11:02, Sam Ellenby wrote:

> So, probably on Tuesday next week, I will be bringing a Sonata NP30
> network radio http://www.cambridgeaudio.com/summary.php?PID=604 and a
> 651A (it is a pre-production prototype). I will try and scrounge up
> some speakers, but they are likely to be a bit crappy. And some
> cables.

Wow, awesome - thank you!

> All I ask in return is that you try and enjoy the equipment and look
> after it reasonably well. I look forward to saying hello again. And
> will help set up the equipment. Is there anywhere good to put it?

There should be plenty of people at hand on a Tuesday to help with this.
Perhaps we can even get it up and running on the day.

cheers,

/m

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