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Subject: Re: how much noise is from the Archos?
From: Mat Holton (mathew.holton_at_surface-inspection.com)
Date: 2004-08-10

Thanks for the response Andreas :-)

This is good news then really, that the majority of the noise was probably
from the jukebox itself.

My brother will record using will be done with a digital 8-track (Roland can't remember exact details)
and then we are trying to find some way of transfering that data digitally. Either remove the hard disk or otherwise.
But i think one of the main uses of thePC will be for creating beats and loops, then adding other sounds using the 8 track.

Thanks for all you help anyway!

cheers,

mat

-----Original Message-----From: Andreas Stemmer <groovingandi_at_gmx.de>To: Rockbox development <rockbox_at_cool.haxx.se>Sent: 10/08/2004 10:01Subject: Re: how much noise is from the Archos?Mat Holton wrote:

> So last night we tested it for background noise by recording 'silence' onto my Archos.
> I increased the gain to maximum and had the PC set to full volume.
> When played back on the Archos (at full volume) we heard extreme hiss.

You recorded the silent output of the pc with your archos and tried to
hear the noise the pc produces this way? It won't work, for several
reasons:

1. Your jukebox is a highly integrated device with the harddisk and the
digital components in close neighbourhood to the analog parts. I guess
it will produce more noise when recording than the worst computer sound
card I've ever heard. The jukebox doesn't sound bad in my ears, but you

can't compare it to studio equipment.

2. The jukebox has a 15kHz lowpass filter on the analog-in which dampens

high frequency parts of the noise.

3. This test won't work with any device with an analog signal path

because there's always a small amount of noise. Studio equipment has

less noise than hifi or home entertainment equipment, but there's noise.

If you turn up the gain to maximum, you'll have no idea how much noise

you really hear if you can't compare it to the normal signal strength.

Not the noise itself is interesting, but the signal to noise ratio (SNR)

> I have two questions:

>

> 1. How much noise is caused by the Archos?

Too much for this application.

> 2. The built in sound card has a digital out (optical and a phone type socket) - how simple is this to connect to the Archos digital in for the ultimate test of hiss production?

If it's a coaxial digital out, it's not difficult to connect them (see

the FAQ for more info), but again: what do you hope to record? Total

silence will remain silence in a digital environment. Perhaps you get

some artefacts by the mp3 encoding, but you won't have any clue about

the noise characteristics of your sound card.

> Any help would be much appreciated!

It depends on the type of usage your brother is planning to have. I

guess it's a simple two channel sound card with stereo in/out. How is

the music going to come into and get out of the computer?

If he's actually going to record things, the input stage of the sound

card is the critical component you should test. Of course, a decent high

quality external mic preamp and good mics are the best way to reduce

noise, the noise of the line in of the sound card is the smaller problem

(but perhaps the frequency response).

The output of the sound card won't be interesting except for monitoring

the signals and mixing. Usually, the produced music will leave the

computer on a burned audio cd.

> Oh, and if anyone knows what would be the best (price/power/quality) choice for a good sound card for music production then that would be cool too!

I use a Terratex EWX 24/96 and I am quite happy with it. Very cheap,

asio drivers (important for fast response times under windows), also

supported by linux (alsa), great sound, digital and analog i/o, but only

2 channels.

But, especially in the music production scene, you normally ask 5 people

and have 5 different opinions afterwards...

Hope it helps a bit...

Andreas

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Surface Inspection Ltd
www.surface-inspection.com
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