Rode NT2 (the old one) upgrades / mods?

[ln76d]

"A long time ago in a galaxy far, far away...."

...i bought almost dead NT2 (without A) for cheap.

Probably some diode or transistor is burned.
Accidentally i broke one choke
Capsule looks fine.
I want to repair it...

(Fuck you anal.ogguru - dig deeper you pointless creep)

I'm planning to change almost everything.
Why? For fun 
Boards are soldered very weak so i want throw out everything, clean pcb and bring it to live. All caps change for wima etc. (my version have only three wima caps rest are some cheap).
If anyone know some good mod for this mike i'll be appreciate for any ideas.

http://www.users.on.net/~effect/RodeNT2tl.pdf

For now, differences what i found between my nt2 and a schematic is:

- 220uF/ 270uF electrolytics
- C2547 / 2SC2240

Which better?

All resistors values same.
There's a different markings on my pcb, for example C20 from schematic is C7 on a board.

It's there any good equivalent for N-J305A FET?
I cannot found anywhere in good price this one.

C17 and C18 (15nF) are smd, probably ceramic, change them for foil caps?

C25 and C26 are ceramic, change them for silver mica or foil caps?

 

[HellfireStudios]

Check out http://recordinghacks.com/microphones/Rode/NT2

Jim Williams from Audio Upgrades designed that circuit. The sound of the mic should be fine stock. If it is broken, I would suggest either a U-67 or U-87 circuit to complement that capsule and headbasket shape nicely. You easiest option would probably be to repair the mic, see if you like it stock. If you don't like the stock sound, come back here with what you don't like about the sound, and someone will probably be able to suggest changes to suit your design goals. FYI, the subjective nature of audio dictates no capacitors can be categorized as "better." They do sound different, but those differences are up to taste, and only account for around 5-15% of the tonality (depending on who you ask) of the mic.

-James-

 

[patosandia]

don´t change the j305! it´good enough. change both wima 470pf green caps for 3300pf or 5600pf wima fkp or mkp, that will make it a little less harsh, you can also upgrade both wima 0.1uf caps, i put there ero mkt 0.47uf bypassed with wima mkp 0.01uf. good luck!

 

[ln76d]

Check out http://recordinghacks.com/microphones/Rode/NT2

Jim Williams from Audio Upgrades designed that circuit. The sound of the mic should be fine stock. If it is broken, I would suggest either a U-67 or U-87 circuit to complement that capsule and headbasket shape nicely. You easiest option would probably be to repair the mic, see if you like it stock. If you don't like the stock sound, come back here with what you don't like about the sound, and someone will probably be able to suggest changes to suit your design goals. FYI, the subjective nature of audio dictates no capacitors can be categorized as "better." They do sound different, but those differences are up to taste, and only account for around 5-15% of the tonality (depending on who you ask) of the mic.

-James-

Thank You James!
I've read this review before.
I cannot tell You how sounds my NT2 sounds because i've never hear it.
Few Years ago, when i worked in few music stores, i've tested few nt2.
Truly i can't tell did i liked them, because i've never recorded with them only simple tests in a store. What i remember, that's they sounds different relative to each other.
I remember that some of them had very sharp highs and high middle.
That's what i don't like. I prefer warmth and round mid.
I don't want to apply U-67 or U-87 circuit. For this, I still have time
In case different types of caps i know, that there's no "better" and i didn't write in that meaning.
I recaped many different types of gear and i know that they sounds different.
Since my knowledge of capacitors is unfortunately limited, i wanted to know whether the type will be good in place of ceramic, because as You know, not every capacitor works well in the different parts of circuit due to its various properties.
"Better" concerns value of electrolytic and transistor type which are different than on my version.
50uF is not a small value difference...
I don't know what's the rev of this schematic, my PCB is probably "4".

 

[ln76d]

don´t change the j305! it´good enough. change both wima 470pf green caps for 3300pf or 5600pf wima fkp or mkp, that will make it a little less harsh, you can also upgrade both wima 0.1uf caps, i put there ero mkt 0.47uf bypassed with wima mkp 0.01uf. good luck!

Thank You for advice!
My question for j305 it's only because i have problem to buy a new one.
I can buy 3,3nF and 5,6nF which value will be better? Probably with higher values it will be little bit darker as i guess.
Unfortunately before i've read your post, i've put new one 0,1uF WIMA MKP2 so i'll stay with them. I've put new 10nF Wima MKS02.

Reading that review posted before, it makes me laugh, because i have "different" microphone
No Roederstein, only two 470pF (blue, not green) and one 1nF green Wima, no Hitachi transistors.
1nF/630v from arctronics, rest's some unmarked probably cheap caps. Electrolitycs - Hitano.
I threw out almost everything from pre board. Only stayed 1Gohm resistor. Unfortunatelly potentiometer died on a operating table.

Here's my cleaned PCB version . There was weird glue on solder mask so i removed it.

 

[patosandia]

i like 5.6nf, for c4 and c5
and 0.47uf for c2 and c3

 

[ln76d]

i like 5.6nf, for c4 and c5
and 0.47uf for c2 and c3

So i'll try 5.6nf and an extra 330nF on the bottom, parallel to 100nF. 430nF should works similar to 470nF. MKT, MKP or maybe  styroflex?

 

[TijuanaKez]

My NT2 has had a wierd buzz / hum in it. I lent it to a friend and mysteriously when I got it back, one of the caps had snapped a leg. I replaced it with a good quality poly prop. It's working now but has a permanent hum/buzz in the signal. I noticed a trimmer on the board, what is this for? Do I need to re-bias or something?

Thanks.

 

[HellfireStudios]

When you replaced the cap did you touch the cap leads and/or PCB traces? If so, you may need to clean the solder side of the board and the leads of the capacitor with the purest isopropyl alcohol you can find. Dirt, dust, and oil can cause all kinds of noise problems. I hope that helps.

-James

 

[ln76d]

I found very interesting instructions for mod from Jim Williams:

"Yes, there are a couple of problems in the NT2's I designed. First, the inductors off the output leads need to have a series resistor installed, I use 56.2 ohms. That stablizes the mics driving long lines and rejects rf.

Then the capsule polarization voltage is set too high. It needs to come down to +60 volts. To do that, I install a series resisor (1.5K) from the + V line feeding the oscillator pcb. Then a zener diode is fitted to clamp that voltage down until +60 volts is reached. Anything from 6.2 to 8.5V zeners will get there, select imperically.

Other mods include removing the input coupling caps and wiring the capsule switch directly to the jfet gate. That requires polarizing the capsule back plate instead of the diaphram. Then the output wires are reversed from pin's 2+3 on the XLR to retain phase.

Other fixes include raising the capsule post a bit to eliminate the dome reflections that creates a bump at 200 hz. There is also a lot of oscillator leakage into the outputs, you can see that on a scope. A piece of copper foil across the rear of the oscillator pcb stops that.

The circuit was designed flat to 50k hz. If you use the original or a k-67/87 capsule, those have a large hf lift that needs to be attenuated. Replace the 470 pf green Wima FKP-2 caps with 5600 pf to smooth those out, including the original capsules."

 

[ln76d]

Since english is not my language, sometimes i have problem to understand meaning. Could someone can help me to understand few things.
For all circuit points, please look on schematic from first post.

"First, the inductors off the output leads need to have a series resistor installed, I use 56.2 ohms."

Do i think correct, that Jim put two 56.2R resistors in series, one between L1 and xlr pin and second between L2 and next xlr pin?

"Then the capsule polarization voltage is set too high. It needs to come down to +60 volts. To do that, I install a series resisor (1.5K) from the + V line feeding the oscillator pcb. Then a zener diode is fitted to clamp that voltage down until +60 volts is reached. Anything from 6.2 to 8.5V zeners will get there, select imperically."

Do i need to put 1.5k resistor instead "white wire" (from schematic) on +V point?
And here's the worst part:
"Then a zener diode is fitted to clamp" - where, what clamp? Where i need to put zener diode? Or He mean a zener D3 from schematic?

"Other mods include removing the input coupling caps and wiring the capsule switch directly to the jfet gate."

Do He  mean  C21 and C15 capacitors from schematic?

For any help i'll be thankfull!

 

[TijuanaKez]

When you replaced the cap did you touch the cap leads and/or PCB traces? If so, you may need to clean the solder side of the board and the leads of the capacitor with the purest isopropyl alcohol you can find. Dirt, dust, and oil can cause all kinds of noise problems. I hope that helps.

-James

I may have touched the leads but there is a healthy amount of solder there, I'm positive the connection is solid.

Does anyone know what the trimmer is there for?

 

[Sredna]

Read James's comment again! 

 

[dhammer]

I went the other way modding this mic & swapped capsules.  I put a Microphone Parts RK7 in there and wound up with a very smooth sound.  The RK7 is an M7/K47 style & doesn't have the high-end bite of the 67/87 style capsule that comes stock.  I haven't heard anything out of it that makes me want to do any component swaps but I'm using with short cable runs.

FWIW I am very happy with the sound I'm getting from the $250 I have in the mic and use it alongside my U89 and U87.

 

[ln76d]

Since those are Jim Williams mods, who  designed this circuit. I belive that will works fine. I have faulty electronics on  NT2 and it's later version on cheap parts, so it's good option for experiments. I don't want to put more cash on this mike, so i'll stay with original capsule. Maybe for next, completely diy mikes. I have few teflon CK12, so probably i'll used them for another projects.
Can somebody help me with those Jims instructions?

 

[TijuanaKez]

Read James's comment again! 

Well I tried it in a couple of other preamps and the noise is gone so it's probably a problem with the phantom on my drip four seven.
Thanks for the help. You could have told my what the trimmer was for though

 

[HellfireStudios]

Read James's comment again! 

Well I tried it in a couple of other preamps and the noise is gone so it's probably a problem with the phantom on my drip four seven.
Thanks for the help. You could have told my what the trimmer was for though

As I don't own the NT2, so I can't say for sure, but it would seem plausible that the trimmer is for FET biasing.

-James-

 

[ln76d]

Read James's comment again! 

Well I tried it in a couple of other preamps and the noise is gone so it's probably a problem with the phantom on my drip four seven.
Thanks for the help. You could have told my what the trimmer was for though

As I don't own the NT2, so I can't say for sure, but it would seem plausible that the trimmer is for FET biasing.

-James-

It is for biasing j-fet.

TijuanaKez - If you were not so lazy, you could look at the schematic in my first post, or at technical documents section

I believe it needs to be set on constant value independent of any changes.

On schematic it's described as "set to 358K on J-fet Side".

 

[TijuanaKez]

Read James's comment again! 

Well I tried it in a couple of other preamps and the noise is gone so it's probably a problem with the phantom on my drip four seven.
Thanks for the help. You could have told my what the trimmer was for though

As I don't own the NT2, so I can't say for sure, but it would seem plausible that the trimmer is for FET biasing.

-James-

It is for biasing j-fet.

TijuanaKez - If you were not so lazy, you could look at the schematic in my first post, or at technical documents section

I believe it needs to be set on constant value independent of any changes.

On schematic it's described as "set to 358K on J-fet Side".

Yes I saw it on the schematic but still did not understand it's function. I'm still learning and a little piece of information here and there helps a lot.
Thanks for the explanation. Mine reads 158K on both sides which seems like a rather large deviation from 358K, I'll try setting it to 358k on the j-fet side and see what happens.

P.S mine seems to have been stuffed slightly different to the origional pcb markings. A resistor is added to D3 and C9 and c10 spots are empty.

 

[ln76d]

Read James's comment again! 

Well I tried it in a couple of other preamps and the noise is gone so it's probably a problem with the phantom on my drip four seven.
Thanks for the help. You could have told my what the trimmer was for though

As I don't own the NT2, so I can't say for sure, but it would seem plausible that the trimmer is for FET biasing.

-James-

It is for biasing j-fet.

TijuanaKez - If you were not so lazy, you could look at the schematic in my first post, or at technical documents section

I believe it needs to be set on constant value independent of any changes.

On schematic it's described as "set to 358K on J-fet Side".

Yes I saw it on the schematic but still did not understand it's function. I'm still learning and a little piece of information here and there helps a lot.
Thanks for the explanation. Mine reads 158K on both sides which seems like a rather large deviation from 358K, I'll try setting it to 358k on the j-fet side and see what happens.

P.S mine seems to have been stuffed slightly different to the origional pcb markings. A resistor is added to D3 and C9 and c10 spots are empty.

Do a photo of your pcb and post here. It's weird that on both side You have 158K.
If You have 1M pot as on schematic, You can't have those values, because it's to low.
If You measure resistance on soldered to pcb element, it can show lower than in reality. If You didn't do any regulation on that pot, leave it for now, probably it's not the point.