Topic: AT853 Direct into Microtrack TRS

[eman]

I understand there is already a wealth of information regarding the Microtracker both I and II, maybe too much. Yes, I've searched and combed through the results.
The AT website says that you can phantom power the 853's with 9-52V. It also says that the phantom impedance is 200ohms, which would yield a current of 150mA at 30V (MT 1 supposedly) or about 75x the "typical current draw" published. I have read that the MT phantom will fry these. This makes no sense given the rated voltage but maybe not so with the impedance.

I already have a 9100 box so that's not the issue, I just want to run with one box if possible.

Anybody know if I can do this? If so, what would be the wiring from the TRS to the mini xlr on the AT 853's? I am thinking those mics are unbalanced with ground on the outside, phantom on one pin, and signal from each of the mics on the other 2 pins. I have a MT1.

If the MT will indeed fry the mics, is there some way to limit the current to run them without an additional box?

[setboy]

to run AT853 with phantom power you need an adapter to take down the power so you don't kill your mics. If the MT really out puts phantom power it will indeed kill your mics

[eman]

Anybody have any additional information? Why are these mics rated to 52V phantom power if that will kill them?

[setboy]

Anybody have any additional information? Why are these mics rated to 52V phantom power if that will kill them?

They are only rated to that with the adapters on them.............

[eman]

What are these adapters you are talking about? Do they limit current or something? Why does the spec sheet fail to mention these adapters?

[setboy]

http://www.soundprofessionals.com/cgi-bin/gold/item/AT8538
This is one kind...there are others as well

if you search phantom adapter around here you will come up for some answers
 

[eman]

OK, I see that AT published the spec in regards to the mic/phantom adapter combo, not for the mic on its own.

What I'm wondering now is can I buy one of these phantom adapters which presumably bump the voltage down to 9V and wire it in such that both mics are powered by the same output? Or does each mic need its own separate circuit? A single phantom power unit is considerably smaller than my CA9100 (and wouldn't eat 9V batteries like the 9100) but if I need two of them I might as well stick with what I have.

[setboy]

don't know he answer to that...................

[barrettphisher]

OK, I see that AT published the spec in regards to the mic/phantom adapter combo, not for the mic on its own.

What I'm wondering now is can I buy one of these phantom adapters which presumably bump the voltage down to 9V and wire it in such that both mics are powered by the same output? Or does each mic need its own separate circuit? A single phantom power unit is considerably smaller than my CA9100 (and wouldn't eat 9V batteries like the 9100) but if I need two of them I might as well stick with what I have.

Honestly, the 9100 would be much smaller than the adaptors and trs cables.  Just have Darktrain or one of the other cable makers make you a 1/8th to TRS and you are good to go.  I went with the M10 to further reduce my  footprint.
Barrett

[eman]

Well, I'm still stuck trying to get an SD card formatted, so the whole thing might be a worthless effort anyway. I can read it from my computer from the MT/usb, and I loaded the newer firmware 1.4.5 but still says the card needs formatting every time it boots. Do I just keep trying different cards until it works? Could get expensive. If I get past that point I might try the simple circuits shown in another thread- caps, resistors, and diodes.

[dallman]

I have not had any trouble with 7 or 8 different brands of CF card formatted on the MT. I hope you mean CF and not SD, as SD would not work in the MT. If it is an CF to SD converter, that will not work either. Also, you should format the card in the MT, not on your computer. That should make the difference. Good luck!

[eman]

Doh! Blew $12 on the converter. Starting to think this is a waste of time and blowing too much cash in trying to not blow any cash. Who wants a CF-SD converter?

[eman]

OK, got my new CF card 8Gig which is really 7. Looking back on those old MT2496 threads people were shelling out hundreds for CF cards so I guess I don't feel so bad about paying $23 for 8 gigs. Kinda cheap, actually.

I have an order in for the components in this circuit from
http://www.epanorama.net/circuits/microphone_powering.html#basics

which is a good resource for phantom power and electrets. I plan to package it in one small box that will plug directly into the top of the MT with no cable.
 
Balanced electret microphone circuit

This circuit gives out balanced signals and has around 2 kohms output impedance which enables it to be
used successfully with mic cables of several meters or tens of meters.

                                  10u
    +---------o-------------||------o-----------------  HOT    (2)
    |            |                            |
    |            |-                           |
    |         CAPSULE                 22k
    |             |+                         |
    |              |            10u         |
    |             o-------------||------|------o----------  COLD   (3)
   2k2          |                          |        |
    |            2k2                      |      22k
    |              |                      |        |
    |             o--330R---o----o------o------+
    |           +|            +|       |+
    |           10u        12V  10u
    |            -|          -|       |-
  --o---------o---------o----o------------------------  GROUND (1)

The component "12V" is a 12 Volt zener diode

The 10u capacitors in the HOT and COLD signal leads should be high-quality plastic film types. The values
of these may be reduced to 2u2 if the preamp input impedance is 10k or greater. If you for some reason use
electrolytics for the capacitors which couple the audio signal then those these mutst have >50V working
voltage and you must bypass them
with 100n plastic film caps. The 10u capacitor in parallel with the zener should be a tantalum type, and
can have a 10n plastic film cap in parallel if you wish.

The cable to the capsule should be twin+shield. The shield should be connected to ground near the zener
diode, and left unconnected at the capsule. The pinout given is the standard for XLR3 mic connectors.

Source: PZM Modifications web page by Christopher Hicks.

[eman]

The AT853's are wired with the (-) sides tied together in a 3 pin mini xlr for the CA9100 so I guess to use this circuit I'll have to get a 5 pin mini xlr connector for the MT2496 and rewire the input split cable for the CA9100 with a 5 pin as well. I'll have to redo the wiring on the perfectly functional CA setup to do this so if anyone feels that this is a stupid thing to try please let me know sooner than later. It was $22 for the components, board, and a spool of wire.

In the picture, I have the components for one channel mounted on the board. I will only use half of that board, or one square and the stuff on it will be mirrored. The CA9100 is underneath to show scale and how much pocket space will be saved. I plan to make a small box myself out of scrap plastic if I can't find the perfect one to mount this in. I can cut down the trs ground to maybe make it a little smaller.