[Terry Pinnell]

(Dave Platt) wrote:

I have a very old but apparently high quality mic, a Sony 'F-99B', just
rediscovered in my shed: 'One point stereo dynamic microphone IMP.LOW'

It proved useless when I tried it on my PC, in the usual mic socket,
presumably because of its low impedance. (My multimeter shows its left and
right connections as about 170 ohms.)

Can anyone suggest an inexpensive UK supplied mic transformer I can buy
please?

You might want to review the discussion at

http://www.audiobanter.com/showthread.php?t=118737

which captures a USENET thread from rec.audio.pro back in '09.

Based on what I read here,

- The F-99B is already supposed to have a "high-impedance" output
(i.e. it may already have a transformer in it). You may be
reading the DC resistance of the transformer coils, rather than
the audio-frequency impedance of the system.

- You're likely to need a separate amplifier stage to boost the
signal enough to operate into a PC's "mic" input. PC inputs
are usually designed to be used with active (buffered and amplified)
condenser microphones, which have a relatively high voltage output
(tens to hundreds of millivolts) and a fairly strong ability to
drive current. If the mic and its built-in transformer (assuming
it has one, as the discussion implies) won't drive the mic input
successfully now, adding an additional transformer stage may not
help... you'd gain voltage, at the cost of an even higher impedance,
and the input impedance of the "mic" receiver stage may load down
the source impedance too much.

- It may not be worth the effort... several discussions of the
F-99B suggest that it's not a terribly good microphone.

Thanks a lot Dave, very helpful.

In view of your comments I'll probably not now try to use the F-99B, But
that leaves me looking for some other simple solution, and I wonder if I
can get some advice here please?

For the narrative in my family DVDs I've been using cheapish PC
microphones. These include the long stalk type that are supposed to sit on
the desk but which I hold closer to my mouth, and the headphone type slung
around my neck. (I don't use the earphones, which I find uncomfortable.)
Ever now and then I hand over another £5-£10 for yet another. The last,
bought at the weekend, is a 'tie-pin' type. Clipped to my shirt below the
open collar it seems quieter and not so bright as I'd expected, so that's
probably another one that will gather dust.

In fact quality isn't very good with any of these. It's either muddy and
too quiet or loud enough but spoiled by distortion at the start of some
words. So I just want to move up a bit in quality. My googling so far has
left me confused, as there seem to be so many types, and a *huge* range in
cost.

My ideal would simply be a better quality PC mic, for plugging straight
into the mic socket as at present. Do such devices exist, or is there some
inherent limitation in the technology? I'd be happy to pay £20-£40 or so
to get significant improvement.

What about these 'USB microphones'? If I bought one of those at the budget
end if their range (£30-£70?) would I be able to use it without any
special software or setup? Could I continue to work in my applications
without change? For example, the drop down box in all the audio programs
I've used, and my video editor, looks like this:
http://dl.dropbox.com/u/4019461/RecordingSources.jpg
(I use the Realtek option, as this PC came with that built into its ASUS
motherboard.) With the addition of a USB mic, would that become an
additional entry in the list, or what?

Any practical advice (pitched to my very low level of technical savvy in
this area) would be much appreciated please.

--
Terry, East Grinstead, UK