Dan Dugan wrote:
> Walt, I'm not surprised you're having problems with the MKH 110 into the MP-2.
>
> The MKH 110 is a special mike, designed for measurement purposes. In
> the old days measurement mikes were only used with measuring
> instruments that had special preamps wired for the particular mike.
> The MKH 110 is DC-coupled at the output (presents 5V on pin 1 of the
> DIN connector, which is the audio output (unbalanced)) and therefore
> the preamp must be AC-coupled at the input. The 110 is not phantom
> powered, and not T-powered either; it expects 8V +/- 1V on pin 3 of
> the DIN connector with pin 2 grounded. This is not compatible with
> the standard phantom-powered input on the MP-2, I'm surprised you get
> any sound at all!
I was aware of all this except the 5 volts. But I'd suspected that too.
I have Sennheiser's wiring diagram for it, such as that is. I did make
up a 8 volt power supply running off a 9.6volt NIMH battery, which is
how I have it running. Sennheiser is not clear on on the 5V on pin 1,
showing it direct connect to the pre, or through a cap. They also show a
alternate of a second battery of 3 volts with a variable resistor to
adjust the pin 1 input. They call that audio compensation. I asked
Sennheiser direct on connecting the mic and the diagram is all I got out
of them. No one there seemed to know much about them. I did all that
before even getting the mics. I don't think any of the mics back then
were phantom or T powered, I also have the stuff for the other models of
the period. Two other powering options depending on model.
I'm not using the phantom power on the MP-2. But did find a considerable
current drain into the MP-2 from the mic with direct connect. The
Portadisc must have AC coupling inside it as it does not have that
problem. I'm now at the point trying to sort out a value for the cap as
Sennheiser did not specify. And that's all they show, just a cap symbol.
They did spec the cap on the 8volt line at 500mf. Also speced a 8 volt
zenar in there, but I've not been able to locate those, so just have the
voltage adjusted with trimpots.
I'll be happy for any suggestions on that part if you have worked with
the mic.
> BTW, are yours MKH 110, or MKH 110-1?
MKH 110, though the boxes are labeled MKH 110 with another box next to
it -1. Their sensitivity seems right for a straight 110 too. I've seen a
photo of a 110-1, and that was stamped into the mic housing. Mine are
stamped 110.
Walt
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