Klas Strandberg wrote:
>
> Scott and all:
>
> "Impedance mismatch"..?
>
> No designs today have low input impedance. The input impedance of a recorder
> is always 2-10 kiloohms. I know SQN had a transformer input on some
> pre-amps, but that was long ago.
>
> This is the one and only principle for impedance matching: The input
> impedance must be much higher than the output impedance.
> All recorders / mic amplifiers today have an input impedance around 2 - 10
> kOhms.
Unfortunately the HHb specs are given in a different form. For the mic
input with the level control at full it's specified that -52dBu from the
mic will give you a 0dB level. Paul Isaacs reported the input impedance
of the mic inputs of the Portadisc at 1.2 kOhms however. Go back to his
post of November 28 last year to see what he said about using a matching
transformer.
> The problem for all you guys using ME-series, is mainly because the mic is
> made to handle pop-music. For the birder, the output is too low. A
> transformer will boost the voltage.
The other part of the equation is remembering that there is no extra
gain from a shotgun mic. They record the same as a ordinary mic, just
pick up from only a narrow angle. They are not a long range mic.
> Using such a transformer will not lower the noise, unless the mic amplifier
> is noisier than the microphone. No recorders today have such noisy mic amps.
The Portadisc has a pretty quiet preamp. Especially for the realm of
battery operated portable gear. But crank the levels up to the max and
the headphone up to max and you can hear some noise. A lot of it does
not record as it's in the headphone amp.
> Using a ME-mic into the HHB, I'm sure it is the mic noise you hear.
Those used to recording with cassette are often surprised by the noise
they pick up. The much higher dynamic range records all the quiet stuff
that the cassette could not. Of course that can easily be mic noise.
They farther increase the mic's noise by cranking the record level up to
push the peaks up to the 0 dB level. This has the additional result of
clipping. Even minor clipping will mess the sound up. In addition, if
there is any noise produced by the mic pre, setting the level high
increases that too. So, for quite a few reasons take advantage of the
higher dynamic range of digital and be happy with the peak sound at -20
dB or so.
You do, of course, have to make sure your transfer to computer is not
losing the dynamic range. Even digital transfers often have level controls.
And once in the computer, don't go for maxing out the levels. For the
same reasons you don't want to be over amplifying the signal. The modern
music trend is to compress the dynamic range in a few dB at the top to
make it sound louder. But we don't have to do that and it won't sound as
good to do so.
BTW, my typical setting on the Portadisc for the Telinga is about half
way. Even for the MKH 816's it rarely wants more than 3/4.
Walt
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