Microphone Impedance vs 5D MK II Input Impedance

[mearle_gates]

<p>OK. I ordered an Audio Technica AT-897 Microphone today to use with my Canon 5D MK II. The microphone has an output impedance of 300 ohms (with the AA battery). The question is: What is the 5D's audio input impedance? What is the amount of mismatch, in other words? Do I NEED the Pearstone LMT100 low to high impedance transformer cable, or will a regular XLR to minijack cable be all I really need?</p>

[MichaelChang]

<p>Although you don't strictly need the Pearstone LMT100 for its impedance matching function, it's a cheap and convenient way to connect your AT-897 which is a (mono) balanced microphone to the stereo unbalanced (microphone) inputs of the 5D-MkII.</p>

[steve m smith]

<p>If the impedance of the microphone is lower than the input impedance then you shouldn't have any matching problems. I would be very surprised if the 5D had a low input impedance. It is probably around 10K.</p>

<p>However, you may want to use the matching device mentioned above (or any other similar device) to keep the benefit of balanced line which eliminates electrical noise pickup from the cable.</p>

[mearle_gates]

<p>I already have the regular XLR to mini-jack cable ordered. My theory is that with it being only 18" long, how much noise is it liable to pick up anyway - if indeed noise is the real issue. And the Pearstone has about the same length of unshielded cable downstream of the transformer, right?</p>

[MichaelChang]

<p>It's more of an issue of going from a balanced microphone to an unbalanced stereo inputs on your camera. </p>

<p>The microphone has 3 connections: signal high (pin-2 XLR), signal low (pin-3 XLR), and common or ground (pin-1 XLR). This makes up the balanced signal where the high and low signals are anti-phase.</p>

<p>The mini jack at the other end goes to stereo inputs on your camera: Tip is one channel, ring is the other channel, and sleeve is ground.</p>

<p>Do you know how the cable (you ordered) is wired? I suspect it's a straight one-to-one wiring, meaning the tip/ring/sleeve on the mini plug will reflect high/low/common on the XLR. If so, this will be incorrect as the stereo channels on your camera (recording a mono signal) will be out of phase, and you will additionally lose 6dB of signal if you use only one of the two recorded channels.</p>

<p>Therefore the "Pearstone LMT100 low to high impedance transformer cable" appears to be the correct item to use.</p>

 

[mearle_gates]

<p>Michael - Why would you suspect the cable I ordered is wired incorrectly? Here is the link to the one I bought.<br>

http://www.adorama.com/HOSXVM249.html?utm_source=ET&utm_medium=TransactionalEmail&utm_campaign=2point0Product1<br>

I personally would suspect the company knows about what you are doing when they make these things.</p>

[MichaelChang]

<p>Mearle, the cable you bought is described as "<strong>For certain Stereo Microphones</strong> that use a single XLR as output for both Left and Right signals."</p>

<p>The Audio Technica AT-897 you purchased is a Mono microphone.</p>

[mearle_gates]

<p>I see that now. I should have ordered the Hosa XVM100 Series adapter which is for mono microphones.<br>

I have yet to find Pearstone specs that tell whether it is for a stereo, or for a mono microphone.</p>

[MichaelChang]

<p>As far as I can tell (from on-line reading and B&H customer review), the Pearstone LMT100 is for mono microphones.</p>

[mearle_gates]

<p>You would think the company would clearly put an important bit of information like that in their product description. God knows, there must be a lot of folks using it with stereo microphones, and not knowing the difference. I'd like to see definitive information on that point before I rely on customer reviews where the topic is not even brought up. Does anyone have a link to some explicit data on the Pearstone LMT 100 wiring?</p>

[mearle_gates]

<p>I wrote Pearstone, and this is their response:<br>

"Hello Mearle, <br /><br />Thank you for contacting the Pearstone Customer Service Desk. <br /><br />The LMT100 from Pearstone is one of our most popular products. <br />Without knowing the specific microphone from Audio Technica. <br />This is where we stand. In general, the standard XLR 3-pin is a mono-connection. <br />On the mini side of the connection, the mini will provide a dual-mono reproduction<br />in the camera or recording device. <br />This method is very common among professionals. <br /><br />Hope to be of Service, <br /><br />Joey Quintero<br />Customer service Pearstone Corporation"</p>

[MichaelChang]

<p>That looks like a confirmation of what you need, Mearl.</p>

[craig_shearman1]

<p>If you need to connect microphones to a camera -- video camera, DSLR with video, etc. -- go to <a href="http://www.markertek.com">www.markertek.com</a> They are a professional broadcast supply house serving the television/video production industry. They make every cable you can think of, and if nobody has thought of it before they will custom make it for you. Their prices are very reasonable and their web site and printed catalog are very precise as to how the cables are wired.</p>