astatic jt-30

n-Track Studio Discussion Forum
1

vintange high-impedence mic

2

hey guys - just aquired this. an astatic jt-30 mic. looks to be in good condition, want to hook it up and see how it sounds. basically looks like this:

http://www.vintage-microphones.de/Astatic_JT_30__big.jpg

it uses this old style screw-on single pin cable. what i think i need to pick up is something like this:

http://cgi.ebay.com/ws…ores_IT

my concern is that it is a “high impedence” mic - this stuff is the part where i only have a partial understanding and don’t want to do anything funky to my gear. what do i need to know to connect this to my board? my mixer has a few channels that are switchable to HI-Z (for direct guitar input). is that all i need?

thanks. i would love to hear any feedback on this mic and potential applications - i read that it was typically a harmonica mic?

3

Ya if you have a HiZ input it should match the impedance of the mic. Even if you didn’t have this it wouldn’t damage your equipment, you would end up with a signal roll off.

If the mic doesn’t seem to be performing well through the HiZ inputs you could try routing the mic through a DI box.

4

The primary problem with a high-impedance microphone is that it limits the length of cable you can use. For some mics they recommend a 10 foot maximum. The precise length depends on the actual impedance and the cable capacitance. As StuH said, this will affect the high-frequency response, causing a roll-off if too much capacitance is present. High-impedance microphones tend to have higher output but may be more susceptable to induced noise (RF, hum and buzz).

In any case it won’t hurt anything to plug it in. Thes mics are popular for “Chicago” style blues when plugged into a guitar amp which is driven into distortion. The high output helps saturate the input and helps give the characteristic sound. While you can run it into the DAW directly you will need an amp emulator if you want to get the “Chicago” sound.

Jim

5

Quote (jimbob @ May 14 2006,00:41)
While you can run it into the DAW directly you will need an amp emulator if you want to get the “Chicago” sound.

Jim

Nomad Factory Rock Amp Legends if you can afford it is the best amp mod VST on the planet.

Jimbob you shoulda been a teacher.

www.nomadfactory.com
6

I wouldn’t worry too much about hf rolloff. The frequency response on these mics only goes up to 10KHz anyway.

Don

7

I have the exact same mic. Got it for 10 bucks at the local pawn shop. Hard wired it to a 1/4 inch plug, use it for harmonica - it doesn’t sound as good as the Shure one, but still cool. You have a direct box? Use that for impedence matching.

edit: yes, the guitar input setting on the mixer will work perfectly.

8

thanks guys. ended up making my own cord to test the mic - using the amphenol connector on one end and a 1/4" on the other - but no dice. turns out the crystal in the element was shattered inside (which is a common problem with these mics - one fall and bye bye). so now i’m left with a cool looking bullet shell and alot of options for modding the innards with something cheaper :wink:

while i was in there, read the manufacturating stamp - march, 1956 - almost exactly 50 yrs old.

9

Too bad, sorry to hear that. :(