iturnknobs

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #20 on: November 15, 2018, 01:23:19 PM »
...and here is where I am attempting to check signal at fet drain which also is the junction of C2, C4 and R4. I do not seem to be reading anything with my scope. I have double checked scope operation by referencing the injected signal. I have tried this with phantom power applied and not. 48v does not seem necessary for this calibration. I have built 2 of these mics and each is the same. I thinik I am either making a silly mistake or my FETs are no good. Seems odd that 2 would be bad, but I did buy "real" 2N3819s off eBay from someone in the UK. Any ideas?


TillM

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #21 on: November 15, 2018, 01:26:28 PM »
Ruud give an advice at the white market, you can’t bias it like a U87, I remember that he told, that’s capacitor is needed for.
Maybe he can tell us something about the biasing again.

wowi

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #22 on: November 18, 2018, 03:59:07 AM »
I am not shure, but i think you have to feed the signal into the coupling cap c1.
So you can go to the capsule terminal.

To the CM-5722: Can i cut the Whi/Brn  Whi/Red and the Whi/Blk Whi cable or do i have to connect them ?

TillM

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #23 on: November 18, 2018, 04:23:43 AM »
Connect them

mrcase

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #24 on: December 05, 2018, 05:34:54 AM »
will there be another batch of these. I remembered there was talk about that. ;)
I would love 2 of these!

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #25 on: December 06, 2018, 05:41:05 PM »
will there be another batch of these. I remembered there was talk about that. ;)
I would love 2 of these!

Next week  ;)

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #26 on: December 07, 2018, 07:58:38 PM »
Yay!
Seth

The definition of insanity: "Hey, this thing could be really cool - if I had the money to fix it up, which I don't, but if I did it could be really cool - if I had the time, which I don't, but

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #27 on: December 09, 2018, 09:32:12 PM »
I'm wanting two!!!  Can't wait to order. 

RuudNL

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #28 on: December 17, 2018, 03:11:35 PM »
There is a solution for every problem!

http://www.vansteenisaudio.nl

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #29 on: December 25, 2018, 04:20:14 AM »


Potato Cakes

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #30 on: December 28, 2018, 05:12:23 AM »
Hello, everyone,

Just in case the White Market thread disappears with information like calibration, I thought I would post it here for safe keeping. Many thanks to RuuDNL for originally providing this procedure:

"Connect a signal generator through a capacitor (~1000 pF) to the gate of the FET. 1Khz or so is fine.
Replace the source resistor temporarily with a 10 K.ohm trimpot.
Increase the level of the signal generator until you get distortion (oscilloscope or distortion analyzer).
Adjust the trimpot for lowest distortion and symmetrical clipping.
Measure the value of the trimpot and replace the trimpot with a fixed resistor with the value you measured.
That's it
!"

And a further explanation:

"Just connect the capacitor to the 'pin' that connects to the capsule.
The audio generator signal feeds to the (not connected) side of this capacitor.  (And the ground wire of course.)
The capacitor is to separate the polarisation voltage. You don't want +46 V or so on you signal generator!
If you don't have an oscilloscope or a distortion analyzer, you can also do this by ear.
Turn the trimpot slowly until minimal distortion (on a sinewave) is heard.
Then increase the level of the signal level, and adjust the trimpot again.
Of course you need to connect the XLR to an amplifier!
"

Thanks!

Paul

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #31 on: December 28, 2018, 09:53:45 AM »
THANKS for posting that procedure!!!

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #32 on: January 11, 2019, 10:56:19 AM »
Hey guys, I’m wanting to pull the trigger on a couple of these, but I don’t own or have access to an oscilloscope, so I’m a bit concerned at how I would calibrate. Anyone have a guide on a work-around?

Potato Cakes

Re: Banzai's KM84 DIY Body & PCB kit build thread
« Reply #33 on: January 11, 2019, 11:50:10 AM »
Hey guys, I’m wanting to pull the trigger on a couple of these, but I don’t own or have access to an oscilloscope, so I’m a bit concerned at how I would calibrate. Anyone have a guide on a work-around?

Read the above post again. All the way through this time....


Thanks!

Paul


 

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