can i make this KM84 work with what i have?

http://www.gyraf.dk/schematics/Neumann_KM83-84-85.GIF



i have left over parts and would like to experiment a little. im not very electronics savy, but i know my way around an iron.

not really interested in making the "best sounding mic but just one that works, and possibly learn a thing or two.

i have
(16) 1/4 watt 2.2k resistors
(2) 4.70uf 35V tantalum cap.
(2) 22uf 6.3V  tantalum cap.
(4) 10pf 200V  tantalum cap.
(4) 51pf 200V  tantalum cap.
(2) 1uf 35V  tantalum cap.
(2) 220pf 100V WIMA cap.
(3) 2N3819 Fairvhild JFET


I had planned on
-dropping the 16ohm resistors

-swapping the 3,9k and 4,7k with (2) 2.2k in series
-swapping 4pf with the 10pf
-swapping the 15pf with the 51pf
-swapping the 470pf with (2) 220pf in series

-using the 1uf in the C2 postion
-using the 4.7uf in the 4,7uf
-using the 2N3819

Capsule would be a left over 990 from a swap i did, and transformer would be one out of an arucyle a460 kit.(its either a 2:1 or 10:1 never have gotten it confirmed.)

could this work at all? thanks guys. just trying to mess around today.

berkleystudios said:

I had planned on
-dropping the 16ohm resistors

-swapping the 3,9k and 4,7k with (2) 2.2k in series
-swapping 4pf with the 10pf
-swapping the 15pf with the 51pf
-swapping the 470pf with (2) 220pf in series

-using the 1uf in the C2 postion
-using the 4.7uf in the 4,7uf
-using the 2N3819

Capsule would be a left over 990 from a swap i did, and transformer would be one out of an arucyle a460 kit.(its either a 2:1 or 10:1 never have gotten it confirmed.)

could this work at all? thanks guys. just trying to mess around today.

Click to expand...

16ohm is actually1G (1000M), the 4.7k is a 47K and the resistor (3.9k) at the fet source will need to be selected for each individual fet to set it's gain and the supply voltage at the drain.

You can leave out the 4pf and 15pf if you don't have a non-polarised cap for there and put it in later.

The two 220pf caps in parallel for 440pf.

A 10:1 transformer is fine but not a 2:1.

you'll need some more parts that you can see in the full km84 schematic but if you don't have them you can setup the 2n3819 with a 47k resistor and a 22v supply. You'll then need a trimmer or other way of varying resistance between 2k and 20k or so to select the source resistor value. You'll see 10v on the schematic at the drain which is what you'll want to aim for when adjusting source R.

how would i get a 22 volt supply?

how would i get a 22 volt supply?

Click to expand...

Phantom supply!

The schematic linked is only a simplified version - the full phantom version is here....

http://www.xaudia.com/xaudia/Schematics/Pages/Neumann_files/Media/NeumannKm8345sch/NeumannKm8345sch.jpg