Topic: Powering AT853's

[Gene Poole]

I dug up my old AT853's the other day to blow some cobwebs out of them.  These are the original Audio Technica models with the AT8531 power supplies. 

I'd like to ditch the PS's if possible since all I use them for is adapters from mini-XLR to XLR most of the time (with 48V phantom from my preamp).  I had assumed that the AT8531 was some sort of boost converter providing phantom power to these when fed from the single AA battery, and passing through phantom when supplied from the preamp, but before I decided to just solder up some mini-XLR to XLR cables, I figured I'd check out the voltages and was surprised by a few things.  First, there is no boost with only the AA battery, they supply exactly 1.5V to the mic amplifiers.  Second, they don't pass phantom power through unchanged, but reduce it to about 4.5V. Third, the supply on hot and cold pins is not the same. Hot has 4.5 volts and cold, about 2.3V (1.5 and 0.6 respectively when only the AA is used).

Searching on this topic yields several threads, but mostly arguing back and forth with no consensus on how much and what kind of voltage these things should be supplied.  So what's the deal with these?  I assume the amps can handle at least 9V since this is how they are configured when Church, Sound Pro, etc. mod these for PIP and 1/8 unbalanced output.  Does anybody know for sure?  Does anyone have an actual schematic of the mic body internals?

[mixedplate]

Did you come to any conclusions on AT8531?  I found some oddball small 9v batteries, sort of like a short AA size, made an adapter plug and stuffed one into an AT8531.  After a quick test with AT853a, no problem so far.  Cannot tell how much, or if, the output is better than with plain old 1.5v AA, I need to figure out a better way to test.  Anyway, 9v seems to work in the AT8531.