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Subject: RE: my facts on mics
From: Justin Fisher (JustinF_at_valvesoftware.com)
Date: 2002-10-21


I think I've noted this before, but I don't imagine everyone saw - I
rerouted the line-in wires in my recorder through the battery compartment,
thus shielding them from the archos circuitry and HDD (the wires are
unshielded and travel the length of the case, right up against the
circuitry). This resulted in the removal of the interference from the archos
operation and disk spins. Hopefully later model recorders have shielded
wires now, but if you can hear interference in your recordings that
corresponds with HDD spins, shielding or rerouting the line-in wires seems
to be an easy and fairly effective fix.

-----Original Message-----
From: Henri DAVID [mailto:hdavid_at_mail.com]
Sent: Monday, October 21, 2002 2:04 AM
To: rockbox_at_cool.haxx.se
Subject: RE: my facts on mics

hello,

I tried the Sony ECM 907 with the archos. you need a preamp. I made one
using one of those http://www.velleman.be/ kits + two 9v batt.
http://www.velleman.be/Product.asp?lan=1&id=8982
I put it in a plastic box with one on/off switch in in and out plugs.

The quality is ok as long as you leave the amplifier level to 0 on the
archos. (this integrated amp is way to loudy if you increase the gain !)
you can check the quality of what I get there :
http://www.cs.helsinki.fi/u/tkt_davi/photos/2002-04/13-labas/labas01-LQ.mp3
http://www.cs.helsinki.fi/u/tkt_davi/photos/2002-04/13-labas/labas02-LQ.mp3
http://www.cs.helsinki.fi/u/tkt_davi/photos/2002-04/13-labas/
(I reencoded them in lower quality, for internet purpose, but can still get
an idea about the quality)
don't pay attention to the saturation, that was my fault I set the level to
and didn't reduced it ! (BTW Archos Firmware VU meter are quite precise as
they showed me the clips !)

Hope it helps

henri

> -----Original Message-----
> From: owner-rockbox_at_cool.haxx.se [mailto:owner-rockbox_at_cool.haxx.se]On
> Behalf Of Uwe Freese
> Sent: Saturday, October 19, 2002 14:24
> To: jimg
> Subject: my facts on mics (was: Microphone)
>
>
> Hello jimg,
>
> jimg wrote on Saturday, October 19, 2002, 12:58:07 AM:
>
> j> You're mixing apples and oranges here. The battery for the microphone
> j> provides -phantom power- to drive the condensor; It does not
> "amplify"
> j> the signal coming out of the microphone. This mic is a pro-level mic,
>
> I think this is also wrong. Three possibilities:
>
> - dynamic mic, this mic doesn't need power
> - electret condenser: this capsule has a FET inside and needs power
> (>1,5V). Mony mics of this type exist, and they usually have a battery
> inside. This power is not for amplification!
> - condenser: this type needs the phantom power (48 V). This also is not
> for amplification.
>
> Amplification:
>
> - dynamic mic has a greater output volume
> - both dynamic and condenser mics need an amplifier to connect them to
> the AJB line in, but maybe different types
>
> "Mic boxes":
>
> - many of them only provide the battery power. No amplifier inside. But
> sold for much money. :(
> - What I want (for ajb) is a box that
> - gives the power for an electret condensor capsule / mic
> - amplifies
> - needs only a battery (9V)
> - I soldered this type with a simple operational amplifier
> and this costs < 5 ?
> - one can built better boxes with better amplifier ICs inside (see the
> german magazine c't 20/02, page 228, ~ 100 ?)
> - minidisco.com: I think they are very expensive and I don't think that
> these battery boxes are worth the money
>
> Mic types:
>
> See http://arts.ucsc.edu/EMS/Music/tech_background/TE-20/teces_20.html
>
> I think the best for recording a concert would be a one-point stereo mic
> with mid-side technique. And the Sony ECM 907 is the cheapest I've seen
> (~ 100 ?).
>
> Bye, Uwe.
>
>



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