Topic: Phantom power vs. battery box for AT943's

[som]

I have read a few threads on here that rave about the improved performance when going from a battery box to phantom power on the AT943's and other SP-modded AT stealth mics.

In looking at the SP site, it says that most MD and DAT recorders that provide plug-in power will provide 3 or 4 v to the mics. The battery box will provide 9+ v, which inches up towards 10v, which is the "optimum voltage". I can see how that is an improvement.

Now, I know that these mics can't take straight 48v phantom power, and that some sort of voltage adaptor is required between the mics and the phantom power source. What does the adaptor regulate the voltage down to? If 10v is the "optimum voltage" and the battery box delivers 9+v, what is the huge improvement with adapted phantom power? What am I missing?

Thanks in advance for any info.

[Sean Gallemore]

it's not so much the voltage, as it is the resistance over which the phantom power is applied......or atleast I'd like to think

[som]

Thanks for the reply, but could you elaborate? I'm not sure what that means....

[Sean Gallemore]

the phantom adaptors drop the voltage down to 5V, so the "more volts is better" theory goes out the window, so it has to be something else

[leegeddy]

the phantom adaptors drop the voltage down to 5V, so the "more volts is better" theory goes out the window, so it has to be something else

i'm sure jon @ jklabs could provide some technical answers as well.

with a battery box operation, the supply voltage and the audio signal are carried along on the same lead (hot). with the phantom power modules, the supply voltage and the audio signal are separated: audio (pin 2), supply voltage (pin 3).  would this difference be the answer? i don't know. it's beyond my scope of understanding.

jon, where are ya?

marc

edited for stupid grammar mistakes!

[jk labs]

'

the phantom adaptors drop the voltage down to 5V, so the "more volts is better" theory goes out the window, so it has to be something else

i'm sure jon @ jklabs could provide some technical answers as well.

with a battery box operation, the supply voltage and the audio signal are carried along on the same lead (hot). with the phantom power modules, the supply voltage and the audio signal are separated: audio (pin 2), supply voltage (pin 3).  would this difference be the answer? i don't know. it's beyond my scope of understanding.

jon, where are ya?

marc

edited for stupid grammar mistakes!

I'm here. Just ain't able to overlook anything with "AT943" in the subject line.

The original poster is right. And so are the respondents! More or less 

The reported differences in performance are real enough: "P48 powering" is better than "9V-battbox" is better than plug-in-power. (The use of quotation marks will be clear in a second). 


Why the differences?

Voltage is part of the reason why plug-in-power doesn't measure up (low voltage together with high gain resistors force the AT943 beyond its linear region. The mic pre in typical consumer units don't exactly help on the situation either).


But that's about it as far as the voltage goes: 10 Volts is the official limit as was stated. So the proper voltage is within reach for a system built around a 9 Volts battery.     

If you look at electric current the tables are turned: the P48 scheme is limited to about 10 mA. The 9 Volts battery delivers 100 mA without a sweat. But 10 mA is plenty :-) 

So what is left?

Schwilly suggests resistors. Leegeddy the wiring.

In a grand scheme that's just it - the actual circuit topologies used causes the differences.
 
So the often seen statement that "P48 powering" is better than using a "battery box" just reflects the fact that current P48 powering schemes (PM-4, 8533 etc) are built so as to interface more properly with the AT943 than the current crop of battery boxes.  


As for jk labs.... (possible improvements w/ a hint of commercial flavor):
Having now analysed Kevin's AT943/PM-4 combo in detail, the very challenge of both modding/tweaking the transformer-coupled PM-4 and making an even better stand-alone 9V battery box solution for the AT943 is just, well ... irresistible ..  

Jon

(mildly edited for readability :-))

[som]

Don't resist, then!   

+T all around....

[Zaphod]

Thank you for that info Jon, +T.

I look forward to any updates you have for your P48 solution to the PM4/AT943 (as well as AT853?) combo.

[som]

making an even better stand-alone 9V battery box solution for the AT943

I hope you will follow through on this and keep us posted! I would be *very* interested in this, as I'm sure many others on the board would be.

[jk labs]

Thank you for that info Jon, +T.

I look forward to any updates you have for your P48 solution to the PM4/AT943 (as well as AT853?) combo.

Well, I could post a picture or two (by end of the week I imagine).

The solution I'm working on will work for all ATs mics of similar electronic build ( & terminated in a miniXLR). In fact it would probably work equally fine with a few bigger electret mics like Sennheiser K6, AKG BlueLine, C1000 guts, but I need to revisit their respective schematics to know for sure.

And of course Leggeddy's modded Nak 300s.....

[Zaphod]

Very nice.

[Sean Gallemore]

what about DPA 406Xs?  They both run off the same battery box

[som]

The solution I'm working on will work for all ATs mics of similar electronic build ( & terminated in a miniXLR).

I hope you will also look into the possibility of an improved battery box like you hinted up above, something that will work with a 1/8" mini-stereo plug. It would be nice to get a boost in quality but still have the stealthiness of a battery box / 1/8" plug.

[jk labs]

what about DPA 406Xs?  They both run off the same battery box

That's an interesting question. It's almost accidental that the AT mics (831 851 943 etc) and the DPA 406x can be run off the same plain vanilla 9 Volts batterybox.

Why is that? Well, the two mics are very different internally. So much so that by the time you are finished making a really sweet solution for the AT mics, the DPA 406x can't even be connected.

I think the optimum powering soluion for the DPA mics is very near a plain 9 V batt box but built wth good parts.

[Sean Gallemore]

what about DPA 406Xs?  They both run off the same battery box

That's an interesting question. It's almost accidental that the AT mics (831 851 943 etc) and the DPA 406x can be run off the same plain vanilla 9 Volts batterybox.

Why is that? Well, the two mics are very different internally. So much so that by the time you are finished makig a really sweet solution for the AT mics, the DPA 406x  can't even be connected.

I think the optimum powering soluion for the DPA mics is very near a plain 9 V batt box but built wth good parts.

why can't they be connected?