wrote:
> In a message dated 1/13/03 3:17:05 PM Pacific Standard Time,
> writes:
>
>
>
>>The reason why I attenuate the signal from the MP2 to the Portadisc is
>>so I can use the Portadisc set on mic input instead of line input. More
>>options like high pass filtering on the low frequencies, limiting and so=
>>on are available in the mic settings than are available in the line
>>settings on a Portadisc.
>>
>
>
> Dear Walt,
>
> OK! I am confused. With my Portadisc and using either the Telinga or the=
> Sennheiser 66-67, I can only get input by setting the Source to MIC. If I=
set
> it on LINE, I get no input.
I get the same as you if I connect the mics direct to the portadisc.
The MP2 is a separate microphone preamp, it increases the signal from
any mic roughly from mic level to line level. At it's full gain setting
a maximum of 66dB increase in the signal is possible from it. I can,
therefore, connect the output of the MP2 Preamp to the Portadisc and set
it on LINE and that will work. Except for two things, the signal level
will be a slight bit high, slightly overdriving the Portadisc's line
input so I'm having to set the gain level on the portadisc and MP2 lower
than I'd like. And when the portadisc is set to line input, most of the
input options are turned off, unavailable. That last bit is the main reason=
.
If I were to connect the MP2 directly to the portadisc and set the
Portadisc to MIC input with no attenuation it would severely overdrive
the portadisc. So, I choose a middle road. I use a -15dB attenuation
cable to connect the output of the MP2 to the portadisc. Sound devices
has this available for use with other recorders that are overdriven by
it's output. I made my own cable after finding out what was in theirs.
Now I find that even with the -15dB decrease in the MP2's output it's
still overdriving the mic input setting on the portadisc some, again for
my tastes in gain settings. So, I set the portadisc to use a additional
-15dB attenuation. By doing it this way the match between the portadisc
and the MP2 is optimized, and I still have all the input options active
in the portadisc. And both the MP2 and the Portadisc can be set to a
intermediate sweet spot on their respective gain controls.
Think of it this way, the portadisc has a series of input sensitivity
settings. MIC is the most sensitive, LINE is the least sensitive. There
are two intermediate sensitivity settings available, which are accessed
from the MIC setting by setting either -15dB or -30dB attenuation. I
choose to use one of these intermediate settings to get a optimum match
to the MP2 mic pre. I'm sure others would approach it differently.
You will note that by attenuating the MP2 by a total of -30dB I'm making
it's contribution a maximum of 36dB. I don't need it's full capability.
In fact at the usual mid range setting I use I'm getting more like a
additional 15 dB over just using the Portadisc at the same gain settings
on it. As I've noted in the past, this is only useful as the MKH mics
are so low noise. Since the portadisc is so sensitive, using the MP2
purely for extra gain may not be justified. I could just crank up the
portadisc's gain to near the top to do the same thing at the expense of
a slight bit of change in sound quality. My primary reason for having
the MP2 is to provide decoding of the M/S setups in the field for my
headphones. I've yet to determine if I'll use it all that much for other
things. But I certainly will try it everywhere to find out.
Does that explain it?
Walt
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