Can someone explain to me what exactly a low to high impedance cable actually does? Specifically, what does this cable do: https://www.bhphotovideo.com/c/product/885062-REG/kopul_lmt_100_lo_to_hi_impedance.html that just some normal 3.5mm to XLR cable doesn't do?
Low to High Impedance XLR to 3.5mm Cable
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Richard Crowley
Veteran
That adapter cable has an impedance-changing transformer inside the (enlarged) body of the XLR connector.
The purpose is to take the relatively low impedance of the microphone (perhaps a few hundred ohms) and converts it to a thousand or two ohms.
Now virtually all mic inputs on consumer gear (i.e. 3.5mm jacks) is designed for pretty low impedance anyway, so most people don't bother this kind if thing. However, it does actually provide some benefit of increasing the signal level passively which most will improve the performance of such low-end mic preamp inputs.
The purpose is to take the relatively low impedance of the microphone (perhaps a few hundred ohms) and converts it to a thousand or two ohms.
Now virtually all mic inputs on consumer gear (i.e. 3.5mm jacks) is designed for pretty low impedance anyway, so most people don't bother this kind if thing. However, it does actually provide some benefit of increasing the signal level passively which most will improve the performance of such low-end mic preamp inputs.
Noiz2
Sound Ninja
It is also going to convert your balanced XLR to an unbalanced signal and block the plugin power. With out the transformer there are a number of weird things that could happen depending on how the cable is constructed.
If it is a straight through cable you would get 180 degree inverted signals on the left and right channels. That may seem like "stereo" but it's actually a problem waiting to happen because those signals when mixed will completely cancel out. So for instance if you film gets played on something that is mono like many phone speakers are the dialog would disappear. The other wiring that would be common would be to short one of the "hot legs" to ground. That should work but as Richard said you loose about 1/2 of your signal strength. The transformer itself is going to eat a bit so the actual boost is probably more like 150% rather than 200% but still a bit of free gain.
If it is a straight through cable you would get 180 degree inverted signals on the left and right channels. That may seem like "stereo" but it's actually a problem waiting to happen because those signals when mixed will completely cancel out. So for instance if you film gets played on something that is mono like many phone speakers are the dialog would disappear. The other wiring that would be common would be to short one of the "hot legs" to ground. That should work but as Richard said you loose about 1/2 of your signal strength. The transformer itself is going to eat a bit so the actual boost is probably more like 150% rather than 200% but still a bit of free gain.