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Re: Minidisc Mic Input

Subject: Re: Minidisc Mic Input
From: "Adam Liberman" <>
Date: Fri, 20 Aug 2004 18:23:37 -0000
We use the Panasonic FC 27uF/25v cap in the Minidisc mic cables that 
we sell. It is Digikey P11214 and it fits nicely inside the XLR 

The FC series replaced the HFS series, and is regarded as a good 
audio cap - low dissipation factor and long life. The measured roll-
off with a 200 ohm source impedance into a Sharp MD-DR7-A MiniDisc 
recorder is only 0.3dB at 20Hz. You won't find any poly cap that 
will fit inside the XLR connector and not have excessive roll-off.

As far as the resistor, the value would depend on the input 
impedance of your MiniDisc. But any value will add noise, and some 
MiniDisc mic pre's are already not as quite as they should be, so I 
wouldn't use the resistor. Putting the same signal on both channels 
may be redundant, but redundancy can be a good thing as far as 
reliability is concerned, and it will also mean that both ears in 
your headphones will have an equal signal level which is more 
natural for monitoring.

Adam Liberman
Liberman Sound

--- In  "Dave J" <> 
> That may be a good idea to have an attenuated channel
> just in case I ever have a clipping problem. I thought
> 100uF was rather huge but that is what they show in the
> AKG booklet. Maybe because it is a low-z mic? Probably 
> of no concern unless I record bullfrogs. I will look in 
> Digikey for poly caps.
> --- "Rich Peet" <> wrote:
> > 100 uf would be to big, 2uf in a quality cap would be 
> > better. I use tantalum but poly would be best. I recall
> > the cap as really not needed if you short the channels. 
> > You may wish to try a metal film resister on one channel
> > so that you have high and low gain channel to choose 
> > from.  I would guess that 5,000 to 10,000 ohms would be
> > about right but that is a educated guess right now.
> > 
> > Rich
> > 
> > --- "Dave J" <> wrote:
> > > Am I correct that for mono microphones I can simply 
> > > short the L & R minidisc mic channels together? I'm
> > > not inclined to do true mono recording so I'll just
> > > waste disc space with bogus stereo. I realize there
> > > is 2.5VDC on both of them so once I short them I'll 
> > > use a 100uF coupling capacitor to get the signal in.
> > > 
> > > Thanks,
> > > 
> > > Dave


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