Thoughts on external FX1 microphone at DVinfo.net

Bjorn Moren · June 7th, 2005, 01:53 PM

Perhaps you are already bored with FX1 mic discussions, but here's one more.... ;-)

The Audio Technica AT 897 seems to be what I need for some of the types of shots I do. And it seems many of you guys think it's worth it's price, so I'll try it out.

I want to carry as little extra equipment as possible, so I was thinking of skipping the pre-amp (=no Beachtek or similar). The FX1 has a low impedance unbalanced mic input. Since the input is low impedance no impedance transformer is needed for the mic, so it ought to work pretty fine just using a standard XLR to 3,5 mm jack, as long as the cord is short to minimize noise and such. The mic can be powered with a battery, no prob. Anyone tried that and compared it with using a pre-amp?

Next step would be to fix phantom power to the mic, since the specs show that the dynamic range will improve for the mic. The FX1 provides 2.5 V DC out of its mic input, so we just need a DC-DC converter to step up the 2,5 V to 24 V to use as phantom power. I was thinking about building it really small, all from surface mounted parts, (for instance around a SO8 mounted MAX630), perhaps small enough to fit inside a XLR jack. And then mount a pair of these XLRs more or less permanently on the FX1.

Any comments? Will DC ripple from the DC-DC converter ruin the sound? It's just parts for maybe $30, so it's a pretty cheap try.

I've looked on the web for this kind of adapter but not found one. I think it would be ideal for FX1 or camcorders with similar problems.

EDIT: The output impedance of the 2,5 V mic jack is 6.8 kohms, so it will probably not be enough current for the phantom power. But it could be worth a try.

Radek Svoboda · June 7th, 2005, 03:49 PM

You need 48 V if you record drums at very close distance or something, I think. For camera mounted mic or fishpole mount, etc., internal battery is fine. Just use transformer, nothing else.

Radek

Bjorn Moren · June 8th, 2005, 12:18 AM

Thanks for the reply Radek.

Why would I need a transformer for the mic? It seems to be no impedance mismatch. The mic has 200-300 ohms, and the FX1 spec says "low impedance", which probably is about the same.

http://www.audio-technica.com/cms/wi...4dc/index.html

Have you tried this setting, just using a XLR - 3,5 mm jack with built in transformer with success?

Robin Davies-Rollinson · June 8th, 2005, 12:46 AM

Bjorn,
My AT897 goes straight into my FX1 - and the sound is superb - no problems.
I have the choice of going via the Beacktek box as well, but it's not really necessary...

Robin

Bjorn Moren · June 8th, 2005, 11:24 AM

Thanks for the info Robin. I will try it out.

June 7th, 2005, 01:53 PM	#1
Bjorn Moren Regular Crew Join Date: Apr 2005 Location: Stockholm, Sweden Posts: 65	Thoughts on external FX1 microphone Perhaps you are already bored with FX1 mic discussions, but here's one more.... ;-) The Audio Technica AT 897 seems to be what I need for some of the types of shots I do. And it seems many of you guys think it's worth it's price, so I'll try it out. I want to carry as little extra equipment as possible, so I was thinking of skipping the pre-amp (=no Beachtek or similar). The FX1 has a low impedance unbalanced mic input. Since the input is low impedance no impedance transformer is needed for the mic, so it ought to work pretty fine just using a standard XLR to 3,5 mm jack, as long as the cord is short to minimize noise and such. The mic can be powered with a battery, no prob. Anyone tried that and compared it with using a pre-amp? Next step would be to fix phantom power to the mic, since the specs show that the dynamic range will improve for the mic. The FX1 provides 2.5 V DC out of its mic input, so we just need a DC-DC converter to step up the 2,5 V to 24 V to use as phantom power. I was thinking about building it really small, all from surface mounted parts, (for instance around a SO8 mounted MAX630), perhaps small enough to fit inside a XLR jack. And then mount a pair of these XLRs more or less permanently on the FX1. Any comments? Will DC ripple from the DC-DC converter ruin the sound? It's just parts for maybe $30, so it's a pretty cheap try. I've looked on the web for this kind of adapter but not found one. I think it would be ideal for FX1 or camcorders with similar problems. EDIT: The output impedance of the 2,5 V mic jack is 6.8 kohms, so it will probably not be enough current for the phantom power. But it could be worth a try.

June 7th, 2005, 03:49 PM	#2
Radek Svoboda Major Player Join Date: Mar 2005 Location: Prague, Czech Republic Posts: 500	You need 48 V if you record drums at very close distance or something, I think. For camera mounted mic or fishpole mount, etc., internal battery is fine. Just use transformer, nothing else. Radek

June 8th, 2005, 12:18 AM	#3
Bjorn Moren Regular Crew Join Date: Apr 2005 Location: Stockholm, Sweden Posts: 65	Thanks for the reply Radek. Why would I need a transformer for the mic? It seems to be no impedance mismatch. The mic has 200-300 ohms, and the FX1 spec says "low impedance", which probably is about the same. http://www.audio-technica.com/cms/wi...4dc/index.html Have you tried this setting, just using a XLR - 3,5 mm jack with built in transformer with success?

June 8th, 2005, 12:46 AM	#4
Robin Davies-Rollinson Trustee Join Date: Dec 2002 Location: Gwaelod-y-garth, Cardiff, CYMRU/WALES Posts: 1,215	Bjorn, My AT897 goes straight into my FX1 - and the sound is superb - no problems. I have the choice of going via the Beacktek box as well, but it's not really necessary... Robin

June 8th, 2005, 11:24 AM	#5
Bjorn Moren Regular Crew Join Date: Apr 2005 Location: Stockholm, Sweden Posts: 65	Thanks for the info Robin. I will try it out.