Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #260 on: August 03, 2018, 12:10:50 PM »
Can someone please explain me exactly where to intall the mesh included in the package?
I presume it's for the capsule, but i cannot figure out how to open the capsule and install the mesh ....or i'm in the wrong direction ?

Mesh covers the air-slots of the bodytube, right underneath where you screw on the capsule. They're not installed in case you want to paint the tube first.

The capsule is fully ready. Once your mic is finished, just screw them on and you're good to go.


jordan s

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #261 on: August 06, 2018, 01:17:07 AM »
Where can I find a replacement mesh? I am missing one.

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #262 on: August 06, 2018, 11:25:15 AM »
Where can I find a replacement mesh? I am missing one.

Hey Jordan, I can send you a replacement sheet – you can cut a few new ones out. Shipping would be a few bucks.

Otherwise you can find them in specialised hardware stores: anything around 50 mesh should be similar (stainless steel).
« Last Edit: August 06, 2018, 12:19:50 PM by Banzai »

lkipod

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #263 on: August 06, 2018, 02:55:48 PM »
Hey Ikipod,

The screws were included in the spring/mesh bag. If you have a couple of units, it will be in one of the bags.

Size is M2.

Great!!
Thanks a million!
Moshe

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #264 on: August 07, 2018, 04:54:41 AM »
Thank you, jordan s
I see.
Still, it seems difficult to try any of these methods.
I need to experiment.
Thank you anyways.
I posted 3 different methods borrowed from the U87 project above.

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #265 on: August 07, 2018, 03:25:55 PM »
Hey everyone

I've just built my first one and no luck yet... It's "windy", like with lots of constant artifacts and VERY LOW gain... Something is very wrong...
Double checked all the solder joints and looks fine...

BUT, first I figured out that I placed the C4 inverted (duhhhhh), tested it with 48V on, etc... and of course it won't work properly...

Then I corrected it and nothing changed...

Any ideas?! Maybe I screwed the FET?

Thanks!!!


Any ideas?! Heeeeeelp!

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #266 on: August 07, 2018, 05:27:30 PM »
Just built the second one and it's exactly the same!!! DAMN!!!

Is there something really dumb that I'm missing?!

To measure the voltages, I plug the XLR without the capsule screwed and then measure the test points as in the schematic?

Thanks

jordan s

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #267 on: August 08, 2018, 02:08:43 AM »
If you're like me, you bought bad fets from China/ebay.

Just built the second one and it's exactly the same!!! DAMN!!!

Is there something really dumb that I'm missing?!

To measure the voltages, I plug the XLR without the capsule screwed and then measure the test points as in the schematic?

Thanks

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #268 on: August 08, 2018, 02:43:12 AM »
Feeling REALLY dumb... I missed connecting the white/red and white/brown xformer wires together... :/

damn...

Now the mics are working perfectly... VERY nice sound!

I'm in for another pair! haha

THANKS!
« Last Edit: August 08, 2018, 04:34:00 AM by guismarquesrj »

GraemeWoller

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #269 on: August 08, 2018, 09:38:45 PM »
Sorry folks, I've been way off-grid doing trying to clear a backlog of recording/mixing work.

For those who have had a go with something other than the 2N3819 and it's not playing the game, I'd say it's worth double checking the pins on the FET.

I got caught with that a while back using a J211. Good FET, but totally user error! It was super quiet when powered up and I buggered around for ages trying to work out what the hell was going on. Turns out the pins are different on that FET and I hadn't picked up on it when I looked at the data sheet. It could be the same with some of the other things (maybe Chinese rip-offs) that people are using so it's worth a check, I reckon.

G


gyraf

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #270 on: August 09, 2018, 09:24:27 AM »
..the last two batches of 2N3819 I bought turned out fake, just some rebranded generic NPN transistor..

They were branded, with laser marking:
(Fairchild-Logo-F)
BJ12
2N3819
..note to self: don't let Harman run your company..

Winetree

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #271 on: August 09, 2018, 01:20:48 PM »
I just ordered some 2n3819s from china.
I bought 30 of them to check the HFE and use the highest ones.
Is that enough testing?
If they are fake, will they work?

jordan s

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #272 on: August 09, 2018, 05:24:43 PM »
I would highly recommend NOT buying the Chinese FET's as gyraf has pointed out, they are rebranded BJT's and will not work. The ones I got from Small Bear were very cheap and good quality. Why deal with fakes?

GraemeWoller

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #273 on: August 09, 2018, 11:10:33 PM »
To be fair, even though the prices are good for the Chinese ones it's not much use if it doesn't work in the circuit. You're better off getting them from a better source,  or try some equivalents. Just double check those pins... Like I said above, it's a simple mistake, but it got me.    ::)

gyraf

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #274 on: August 10, 2018, 03:05:24 AM »
I just ordered some 2n3819s from china.
I bought 30 of them to check the HFE and use the highest ones.
Is that enough testing?
If they are fake, will they work?

No Hfe on JFETS, has infinite current gain

I simply test with a transistor tester like https://www.banggood.com/DIY-Meter-Tester-Kit-For-Capacitance-ESR-Inductance-Resistor-NPN-PNP-p-929603.html - it clearly identifies your transistor type and idss etc for jfets

Jakob E.
..note to self: don't let Harman run your company..

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #275 on: August 10, 2018, 01:00:40 PM »
Simple questions about BIASing the mics when feeding 1Khz at the gate:

Is it meant to be measured with the capsule disconnected and feeding 48V trough the XLR?! Or simply with everything disconnected?!

Can I feed the 1khz trought the spring connector? Doesn't it make sense?!

Thanks

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #276 on: August 10, 2018, 04:34:22 PM »
Just finished and calibrated my pair. Amazing sounding mics! Thank you for putting this together.   :)

RuudNL

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #277 on: August 11, 2018, 07:22:05 AM »
Are there already thoughts about a next batch?
There is a solution for every problem!

http://www.vansteenisaudio.nl

dissonantstring

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #278 on: August 12, 2018, 02:09:39 AM »
I was thinking the same thing!  Second round would be very much appreciated Banzai!  :)

Re: Neumann KM84 DIY Body & PCB kit – CLOSED
« Reply #279 on: August 12, 2018, 05:31:55 AM »
Still didn't get how to proceed to calibrate! Can any good soul help me?!  :)

Worried to do something wrong and screw the FET  :-[