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Subject: Re: Problem - line in clipping when recording, signal way to hig
From: Jerry Van Baren (gerald.vanbaren_at_smiths-aerospace.com)
Date: 2003-05-15


Disclaimer: I have not done this myself, YMMV.

You should be able to make a "resistive pad" to reduce the line level
externally using four resistors in-line with the line input. I would
suggest buying a stereo interconnect cable (or sacrifice the one you
already are using), a small project box, a terminal strip (solder or screw
type, depending on your capabilities), and four resistors (two per
channel). Everything is available off the shelf at Radio Shack or equivalent.

For a 11:1 pad (-21dB) use 1K and 100 ohm (or 10K and 1K) resistors
For a 110:1 pad (-41dB) use 10K and 100 ohm resistors

Line Out RockBox line in
              1K or 10K
<-o-O------------/\/\-----+------------O-o->
   | | 1K or 10K | | |
   +--------------/\/\--+-----------------+
     | | | |
     | 100 ohm > < 100 ohm |
     | < > |
     | | | |
     +------------------+--+------------+

The ends are 1/8" stereo connectors (buy a cord and cut it in half). The
"tip" of the plug is one channel ("<-" above), the first "ring" is the
second channel ("o" above), and the big ring is ground ("O" above). This
forms a 11-to-1 or 110-to-1 voltage divider. Note that your source must be
on the left side and your Rockbox on the right side (label your box!).

You may want to try 10K/1K for higher impedance but it should not be needed
(line out drives into a 600 ohm load and we are above 1K with the 1K/100
configuration). The RockBox input impedance should be very high. If my
assumptions on impedance are wrong, you will get more attenuation than the
specified -21dB but, other than that, it should work fine. Theoretically,
1K/100 ohms will give less noise (our golden ear friend might be able to
tell the difference, but I'm pretty sure I wouldn't).

gvb

At 06:49 PM 5/15/2003 -0400, meirion_at_e-knowledge.net wrote:
>Hi there,
>
>I recently found the Rockbox site and must say you guys have done some
>fantastic work here.
>
>Puts Archos' software effort to shame!
>
>
>I have a problem when recording from a lot of line-in analogue sources. I'm
>recording from mixers in clubs, using TAPE-OUT or REC-OUT, and a phono to
>3.5mm jack.
>
>A lot of the time I can't turn the gain on the Rockbox down far enough to
>record properly, the input is way to high and clips a lot or all of the
>time, resulting in a useless recording.
>
>I can turn the gain down to -3db, is that as low as it will go?
>
>Is there any way I can get it lower, or is this a hardware restriction? Does
>anyone know if the Archos software goes lower, as this is the sole reason I
>bought a JBR, and if I can't make these recordings I'm stuffed :(
>
>Unfortunately I can't really make any adjustments on the mixer(s) because
>when the DJ is using them they will just turn the volume back up!
>
>
>Thanks for anyone's help,
>
>Meza

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