Topic: Greenmachine Mics (omni) [w/ samples]

[bugg100]

WAIT JUST ONE MINUTE! Off the Christmas card list.... Better think carefully here.

Some people are beyond reason, though.  By the way,   Canada Post sent me some email, Thanks Chris.

Joe

[boyacrobat]

Chris, when someone steps over the line into that space of public discredit, squash him/her.
your god given right to do so.
spare no one.

g

[afri-cola-man]

and please no pictures of wires with duct tape..LOL...eager minds want to know and SEE!

If you go to the Greenmachine website (link is in my original post) you can find a zillion pix of the batt-pack without tape. I wanted to show you how the 'mini-rig' looked like, when I take it out in the field. 

[Roger Gustavsson]

They are omni and when you do my 4.7k mod to them look out they sound great.. Thats a good capsule still available at digikey... I cut the trace between the ground and the negative pad then solder a 4.7k 1/8th watt resistor I then connect the output to the + terminal and the ground to the case side of the resistor you have a reduction in distortion from 1.5% @ 114db to just under 0.3% @ 114db @ 1k.


The key to my mod is making sure the resistors you use are exactly 4.7k.. if they are not your distortion figures will suffer.. I also make sure both capsules are matched at 1k. for output and distortion then I measure the resistors and match them.. After all that's done you have a well matched set of mics with high spl handling  good frequency response.. I then coat the back of the capsule in epoxy because any air leak in the back of the capsule will cause low end distortion to increase. After that I heat shrink the capsule wires to the back of the capsule, then I use a copper foil tape to sheild them then I put the mics in a brass tube and fill that with epoxy and heat shrink over that. You then end up with a very nice looking mic that will handle all kinds of abuse.. Just heat shrinking the capsule alone does not decrease the noise floor you must have good shielding at the back of the capsule imo...If you really want to sheild the capsule well I also use a fine brass mesh screen over the front of the capsule this further eliminates inducted RF and EMI from getting into the capsule...

Chris
PS... I am not trying to sell anything here this is simply just how I make a omni panasonic mic...

Is this what you are doing? http://sound.westhost.com/p93-f8.gif Seems that the output impedance gets very high.

Roger Gustavsson

[Church-Audio]

They are omni and when you do my 4.7k mod to them look out they sound great.. Thats a good capsule still available at digikey... I cut the trace between the ground and the negative pad then solder a 4.7k 1/8th watt resistor I then connect the output to the + terminal and the ground to the case side of the resistor you have a reduction in distortion from 1.5% @ 114db to just under 0.3% @ 114db @ 1k.


The key to my mod is making sure the resistors you use are exactly 4.7k.. if they are not your distortion figures will suffer.. I also make sure both capsules are matched at 1k. for output and distortion then I measure the resistors and match them.. After all that's done you have a well matched set of mics with high spl handling  good frequency response.. I then coat the back of the capsule in epoxy because any air leak in the back of the capsule will cause low end distortion to increase. After that I heat shrink the capsule wires to the back of the capsule, then I use a copper foil tape to sheild them then I put the mics in a brass tube and fill that with epoxy and heat shrink over that. You then end up with a very nice looking mic that will handle all kinds of abuse.. Just heat shrinking the capsule alone does not decrease the noise floor you must have good shielding at the back of the capsule imo...If you really want to sheild the capsule well I also use a fine brass mesh screen over the front of the capsule this further eliminates inducted RF and EMI from getting into the capsule...

Chris
PS... I am not trying to sell anything here this is simply just how I make a omni panasonic mic...

Is this what you are doing? http://sound.westhost.com/p93-f8.gif Seems that the output impedance gets very high.

Roger Gustavsson

No thats not it....

[Roving Sign]

I posted that one too Roger - not it - explained in another thread...

And for the record - I wasnt trying to participate in discrediting Chris - but I have been reading about DIY mics since the USENET days and the 4.7 mod rang a few bells - I thought back to the Linkwitz mod as well...

Not it...

[Church-Audio]

I posted that one too Roger - not it - explained in another thread...

And for the record - I wasnt trying to participate in discrediting Chris - but I have been reading about DIY mics since the USENET days and the 4.7 mod rang a few bells - I thought back to the Linkwitz mod as well...

Not it...

YES YOU ARE! 


Just kidding How did the EV lavs work out??

[Roving Sign]

Here's the link to Chris comparing his mod to Linkwitz...the devil is in the details...

http://taperssection.com/index.php/topic,85208.msg1145083.html#msg1145083

The EVs lavs worked OK - but I used a shitty DAT deck for the show that had drop outs here and there - so I need to try again - plus it was piano music...I need some loud rock and roll to test those babies out!

[Roving Sign]

Here's a funny story - I once made a set of mics to stealth with - tried them out at the HORDE tour in 94-95?

I must have used some info similar to the Linkwitz mod - but didn't pay attention as carefully as should...

I had the capsules and some 9V batteries - went to Radio Shack and bought two of these...



Yeah - they worked - but super bassy...

[Church-Audio]

Here's a funny story - I once made a set of mics to stealth with - tried them out at the HORDE tour in 94-95?

I must have used some info similar to the Linkwitz mod - but didn't pay attention as carefully as should...

I had the capsules and some 9V batteries - went to Radio Shack and bought two of these...



Yeah - they worked - but super bassy...

That's a lot of storage 250 volts I think that 4.7uf is good for cardioid mics but for Omni mics 1uf or 2.2uf is a better choice for a coupling cap. And besides these caps are huge

[Roving Sign]

Here's a funny story - I once made a set of mics to stealth with - tried them out at the HORDE tour in 94-95?

I must have used some info similar to the Linkwitz mod - but didn't pay attention as carefully as should...

I had the capsules and some 9V batteries - went to Radio Shack and bought two of these...



Yeah - they worked - but super bassy...

well - not those exactly - whatever Radio Shack would have - I thought I had just exchanged the words "resistor" and "capacitor" - but maybe I did follow the directions - Whats a coupling cap do?

[Church-Audio]

Here's a funny story - I once made a set of mics to stealth with - tried them out at the HORDE tour in 94-95?

I must have used some info similar to the Linkwitz mod - but didn't pay attention as carefully as should...

I had the capsules and some 9V batteries - went to Radio Shack and bought two of these...



Yeah - they worked - but super bassy...

well - not those exactly - whatever Radio Shack would have - I thought I had just exchanged the words "resistor" and "capacitor" - but maybe I did follow the directions - Whats a coupling cap do?

Its the cap that blocks the dc voltage the capsule operates on and allows just the signal out of the capsule to connect to the next stage with out passing DC So the value of the coupling cap is important. if its too low of a value it will reduce bass if its too hi it will allow to much to pass...
it sounds like what you created was a low pass filter on the output of your mic lopping off all the top end

Chris

[Roving Sign]

it sounds like what you created was a low pass filter on the output of your mic lopping off all the top end

Well that sure is what it sounded like!!! No amount of Eq could tame the bass!

[Church-Audio]

Seems that the output impedance gets very high.

Roger Gustavsson

In fact on the Linkwitz site, he has posted a following opamp-based circuit that buffers and balances the capsule output.   That is less of a concern with relatively high input impedance portable recorders.  I believe there is also merit in operating the capsule in common drain rather than source, but it is less convenient with low-voltage 2-wire configurations.

Regards

Jon

But again what I do is not the linkwitz mod..

Chris

[Church-Audio]

I have not seen your schematic, but I think this may be correct based upon your description.  If so, I believe has the same impedance as the linkwitz capsule.

That schematic is correct.

Chris