Topic: Cheap and compact... AT853 as your only mics....

[setboy]

Sanjay, poorlyconditioned keep us updated on this. i was going to phantom mod mine but if this sounds just as good (or close) i may do this


Raphael

[Zaphod]

+t, and again in 12.

Lots of effort there, particularly liked the "mad prof" style blackboard circuit diagram.

Heh that's funny because he is a professor! +T Richard that looks like a solid stealth setup!

[mattb]

Yeah, very cool! +T

[thunderbroom]

Could you modify this to have a 9V for each mic? I  I've searched around the forum for this a while ago, but I remember reading that you couldn't/shouldn't run 18V to both mics through a mini.  I would think that if you had two mini XLRs it would increase performance.  If not, why?

[setboy]

Could you modify this to have a 9V for each mic? I  I've searched around the forum for this a while ago, but I remember reading that you couldn't/shouldn't run 18V to both mics through a mini.  I would think that if you had two mini XLRs it would increase performance.  If not, why?

i think if you run 18v into them you are going to kill them

you can only run so much into them


Raphael

[Sanjay]

You can only run up to 10v into these mics before they fry, i'm wiring it with 1 9v to send 9v to each mic.  There is no reason to have to 9v's when one will go for quite awhile.

[thunderbroom]

So a 9v battery will send 9v of power to each mic?  I was thinking that the voltage would split between the two.

[Brendan]

i'll fluff the at853's as well.  personally i think they are the best set of under 800/pair mics out there.

richard... you need to put up some pics of that 3 wire battery box. 

i would love to ditch both the ps-2 and the spsb-7 for a well crafted 3 wire battery box.  ideally in an otterbox (although i would consider something else smaller) with mini xlr inputs and stepped gain would be nice (say 10-15-20 db)

I've got a prototype built already, built one this afternoon, I had the gain stages built previously, and I was working on a 48v phantom circuit for the adapters to integrate into one box, but if there is no quality difference between 3 wire and phantom I will simply do a 3 wire part.  Right now I have it built into a metal box about the size of a pack of cigarettes.  However I plan to make it smaller.

You're using an opamp for gain, right?  If so, what chip are you using?  I built a simple circuit using an OPA2134 chip.

OK, I just took some photos:


My full AT853 rig, including a headphone mount (bought from Soundprofessionals.com, modified by me to wear around neck), a home-made battery box (3-wire), a home-made preamp, a minidisc, and a set of Shure E3 in-ear monitors.


Battery box and preamp box.


Battery box circuit.  (Preamp not shown, but standard design.)


Wearing the mics.


Removed windscreens, elements are approx. 90deg apart.

   Richard

hey i was wondering how you modded those headphones to place the mics how you did? Any details? thanks alot

[poorlyconditioned]

hey i was wondering how you modded those headphones to place the mics how you did? Any details? thanks alot

I did not do the original headphone mount.  They are from SoundProfesionals.com, something like shown here:
  http://www.soundprofessionals.com/cgi-bin/gold/item/ISI-HMAB-1
(Those have a battery box too, mine just had the AT853 mics.)  These are just Sony "MD-101" headphones ($10 retail) with the speakers removed, a hole cut in the side and the mics glued (hot melt glue) in the space the speakers would occupy.  The cushions act as windscreens and cover the mic.  The only trick is you have to let the mic protrude a bit so the "vents" on the capsule are outside the plastic ear cap.  (This also allows you to change capsules.)  A final note: inside were AT933 bodies + adapters, then AT853 caps.  I'm not sure if the 933 body + adapter is smaller than the 853 body.  I think they are both about the same size.

So, you're supposed to wear those over your ears, and the mics will point forward.  But that looks wacky.  So I took a heat gun and bent/molded the headband so the mics point forward when you put them around your neck.  This is much more natural looking (who listens headphones at a concert anyway?) and also allows more natural movement (you can move your head as long as you keep your body facing the stage).

A funny point to this story.  I originally bought the headphone mount because they were on clearance and much cheaper than a plain AT853 pair.  But once I started wearing them I was hooked.

  Richard

[pfife]

I loved the stealth-mics in headphones as well...

[poorlyconditioned]

I loved the stealth-mics in headphones as well...

OK by popular demand here is the schematic for my variable gain preamp.  It is a simple modification of the one at:
  http://www.geocities.com/ferocious_1999/md/micpreamp2.html

Schematic:


It is based on a single 8pin DIP chip, like NE5532, OPA2134, LM833N, etc.  The voltage gain is from 2..11.  That is 3 to 10.5dB voltage gain, or 6 to 21dB power gain.  You can easily add more gain, but I don't really need it with the AT853 mics (and recording from a PA).

I'm interested to hear what others have to say about this amp.  I haven't used it much.  I usually just run line in on my MD or mic in on a UA5 or Presonus Firepod (eight inputs!).  The circuit was just a hacking exercise.

  Richard


  Richard

[lordbelial]

Thanks dude! You rock.

[lordbelial]

I guess I'm goona go this way.

Since my mics (CMC-4) terminate in mini plug end, I'll need to wire the two outputs to a single mini plug female, am I right?

[lordbelial]

hi!

Just to say that I recorded three heavy metal bands yesterday with the CMC4 in Hat, placed in X-Y config and the recording came out really amazing!

I'll post photos of my hat and my rig later.

Thanks everybody for the effort.

[Sanjay]

The 3 wire version battery box based off of poorlyconditioned circuit diagram is complete.  It isn't too pretty on the inside but its nice on the outside.  Mics connect with minixlr's and have a 1/8" output. 

Pictures coming later tonight or tom.

Box #1 is going overseas to Humbug.
Box #2 stays with me.

I have materials to build a few more and I could be enticed to make some.