AV News 193 - August 2013
No Overloads for Me!
Howard Bagshaw ARPS
When I was using an Edirol R09 portable recorder, I could connect my external
mono microphone and set the recorder to record a mono track. Now that I have
moved to a Sony PCM M-10 recorder, which only records in stereo, I needed
a different strategy when I connect an external microphone.
I could record the same signal on both tracks, but it seemed an opportunity
to record the same signal, but at different levels. Some recorders can do this,
but not my Sony. But why do this? Well, I've often found that when recording
ambient and unpredictable sound, whatever I set the level to, there is always
a louder bit that overloads the recorder and 'clips' the signal. So I decided that
what I needed was effectively a volume control in one channel to reduce the
volume to that channel, while the other channel received the unattenuated
signal.
I contacted Howard Gregory to see if he could suggest suitable resistance
values to provide the correct impedance for the microphone and recorder and
produce about 15db of attenuation. To my delight he had the solution and
suggested values which were known to work with Nagra recorders.
So I purchased from Maplins an XLR female plug to go into the Sennheiser
K6/ME64 microphone, a 3.5mm stereo plug to go into the recorder, a bit of
microphone cable and a couple of small but good quality resistors.
These were 1.8K and
470 ohms and were
wired as shown in the
circuit diagram.
Fortunately there is
quite a bit of space
inside the XLR plug so
I was able to house
them inside the plug.
I now have a simple
connecting lead which does
what I want - a full signal to
the left channel and a 15db
attenuated signal to the right
channel, so when that steam
whistle or shouting child
catches me out, I still have a
safety track with a usable
recording.
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