Additional: 200 Ohms BALANCED means 100 Ohms per lead!
Klas.
John, Syd and all:
John and Syd! 90% of all recordists I know of, could have asked your
questions! Even very clever and experienced recordists!
But the same totally "ignorant" people may know everything about Md
compression errors and they might be real masters, using their PC or Mac or
whatever. Not to speak on their skill with their camcorder!
So: They are not technically stupid. But:
Since I started Telinga in 1982, I have heard so much of technical
jumble-bumble from "expert" people that it is almost like "political
correctness": You don't have to be right, the important is that you're nice.
This creates confusion.
This is "the truth" but simplified a bit:
1/ "Low impedance is 200 Ohms and less.
2/ 600 ohms can be called "medium impedance".
How long cables you can have does not only depend on the output impedance,
but also on the cable design and quality:
Every cable is also a capacitor between the signal output lead and
ground/shield. This capacitance is mostly descibed as pf/meter, or feet. (pf
= picofarad)
It also depends on the design of the output stage: If the output transistor
delivers 50 Ohms output, you can add a 150 ohm resistor in series, to get
200 ohms. (Telinga) Such a resistor will protect the output transistor from
capacitive loads, caused by a long cable.
Too much capacitive load will cause loss of high frequencies, even distortion.
So: If you record low frequencies and there is no audible distortion (with
the cable you use) - go ahead with as long cable as you can, and need. If
you use a telinga and get losses / distortion with a 100 meter cable, I
suggest that you use that cable for your wet laundry, and buy another one
for recording work.
Radio disturbances is a VERY difficult problem, however. Such problems
follow no "quality" aspect. A very good cable with a low impedance mic,
connected to a fully professional balanced input, might cause a lot of RF
(Radio Frequency) disturbance, while the cheapest design might work
perfectly. Or vice versa.
Syd! The advice you got, - that it is better to put the power suppy near the
recorder and a long cable to the mic - I'm not sure that is a good advice.
It depends on the design of the power supply. Perhaps someone else know.
Lang? - who has long experience of MKH mic's and power supplies?
Finally: Walt - you recommended somewhere NOT to digitally maximize every
recording. I definitelly agree! A series of edited wildlife sounds must
"harmonize" with oneanother, not be as loud and even as possible! When I
hear a "normalized" Nightingale next to a recording of a "normalized" bumble
bee, (or frog??) the listening becomes very unpleasant.
Klas.
At 21:03 2002-06-01 +1000, you wrote:
>
>Hello Klas, Doug, Walt, et al.,
>
>JOHN (John V. Moore Nature Recordings) wrote:
>>
>>I hesitate to post this on the list server because
>> some of the questions I have will be very basic to many, but the DELETE
>> button is, thankfully, easy for all to use!.
>>
>
>The same goes for me. Only more so! I'm so technically ignorant that I
>don't even understand what impedance is. On May 29, Klas wrote:
>
>>
>> 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.
>>
>
>When I started recording bird song (06:00 hrs Oz EST, June 21, 1968) I had
>the good fortune to have been well advised on the recorder: I had a Uher.
>(Recently overhauled, and apparently working well. How's that for a 30
>year-old piece of technology!)
>
>I was also advised that to get a good recording of a lyrebird one needs to
>place a mic on a long lead, where the bird is going to sing, and for this,
>one must use a LOW IMPEDANCE microphone. The Uher mic I got with the
>recorder worked OK with 50 metres of cable, and so too did a couple of
>Sennheisers I got later. I assumed they must be low impedance.
>
>Of the shotgun Sennheiser (MKH-815), a friend said that what the Sennheiser
>people don't tell you, is that you can put the power supply at the recorder
>end of the long cable. I have soldered up a few connectors, but I thought
>of the cost of the mic. and the depth of my ignorance of electronic matters,
>and didn't try!
>
>A couple of years ago I got a Tascam DAT recorder and have successfully used
>a small Sennheiser ME 20 on the long cable with it. But I now have the
>great good fortune to have a Telinga mic which is just so much better. I
>feel sure that with the reflector it will be a definite improvement over a
>shotgun mic for recording lyrebirds at a distance - if the poor
>drought-stricken lyrebirds sing this year.
>
>But can I use the Telinga mic. on a long cable? Is it of low impedance - if
>indeed that is critical?
>
>If so, is it a matter of getting a suitable cable and connectors and still
>using the Tascam's phantom power? Or is it possible to get an external
>power source for the Telinga? The latter, I would prefer: lyrebirds
>sometimes sing for an hour or more, and battery life becomes critical. One
>doesn't wish to have to change a battery in the middle of a performance:
>Murphy's Law applying, that would be exactly when something unusual
>happened.
>
>I would use the Services of Music Lab, a local electronics firm, to make the
>cable, and external power supply, if that is possible. Tascam/TEAC are
>pretty big in the music industry, and I'm sure Music Lab would be familiar
>with the Tascam recorder. But not the Telinga microphone. And in the music
>industry they probably don't get much call for recording 50 metres away from
>the microphone(s) and kilometres away from any power supply - 240 V mains AC
>or even motor vehicle 12 volt DC.
>
>It usually takes me a few days study of an individual lyrebird to get him
>singing at my mic. And if I've gone to that much trouble, it would be great
>to be able to take advantage of the outstanding Telinga quality.
>
>Any advice would be most gratefully received.
>
>TIA
>
>Syd Curtis (Brisbane, Australia)
>
>
>
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>
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