Rode NTK question re Gus mods

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metako

Member
Joined
Jul 3, 2012
Messages
11
First post here and first time modding a mic, though plenty of soldering experience.

I'd like to swap some caps in my Rode NTK to smooth out the top end a bit and plan to follow Gus' suggestions below:

http://web.archive.org/web/20100811083829/http://www.diyfactory.com/projects/gus/ntkmods.htm

I'd like to use Elna Silmic II caps (mainly for their smoothness and bass) for the 47uf/160V but the max they offer is 100V. Looking at the circuit on the link, would it be OK to use 2x(22uf/100V) caps to make 44uf/200V, or would it be better to use 22uf/100V + 33uf/100V to make 55uf/200V ? I'd prefer to use 2x 22uf as it would be easier to fit but would this have much effect on the mic?
 
That was written in 2004
I would leave the stock parts.

Why do you want to "mod" the microphone?
 
To try to smooth out the top end which in certain circumstances can sound a bit hard. I was planning to just change C1, C2 and C9 as per your previous suggestions, and look for an Amperex 6922 PQ USA white label tube at a reasonable price. Have you changed your mind about the value of modding the NTK (and NT1000-I have one of those too)? Is C9 the output cap?

I've just re-read another post of yours from Dec19 2008 where you name the pinnouts and it looks like C1 and C2 are the output caps-and they are Hitano electros!!! Surely replacing these with better quality electros like the Silmics and even bypassing with some 0.01uf Wimas if they fit would make a worthwhile improvement.
 
Changing the caps is not going to change the top end. 
I bought a K2 and changed caps and I did not notice a difference.
 
Can I ask what the replacement caps you used were? Did you find any improvement with a tube change? What about with the NT1000-did new caps help there? Thanks.
 
I recently built a nice and simple grounded cathode tube circuit for nt1000 (with quality caps in the signal path and all) and I think it made the mic sound worst. I think the capsule sounds very bland and the grit introduced by the stock electronics actually made the mic sound more interesting. Go figure  :eek:
 
Maybe the new circuit was too open for the capsule and highlighted it's flaws. Did you try changing the caps in the NT1000 before you put in the new circuit? Which caps did you use in the tube circuit? I wonder if it's possible to replace the capsule with something better without having to change the circuit.

Here's a blog by someone who seemed to find a big improvement in changing to a NOS tube (click on the link just under the first paragraph for a bit more on his findings):

http://dalesimmons.com/2012/06/rode-ntk-tube-replacement-telefunken-e88cc-mullard-6922-gold-pin/#comment-48
 
I have a number of different 6dj8 tube(numbers and brands) that I tried in my K2.  Except for noise and microphonics I don't know what people are hearing with the tube change.

I have an NT1000 I changed caps in I heard no difference.

 
I think what Gus is getting at is that the RODE mics are well designed, and most likely not going to improve much, if at all, with modification. In fact, you can make it sound much worse. If you do still decide to mod a RODE, keep all the old parts.
Have you tried EQ to soften the highs? Maybe a multi-band compressor or de-esser would result in a more naturally smooth top.
 
HellfireStudios said:
I think what Gus is getting at is that the RODE mics are well designed, and most likely not going to improve much, if at all, with modification. In fact, you can make it sound much worse. If you do still decide to mod a RODE, keep all the old parts.
I second that.  Their prices are NOT the result of cheap Chinese labour but cos they probably have the most modern mike manufacturing facilities and the best QC in the world.  Everything is CNC machined by Sydney virgins out of solid Unobtainium.  Their R&D is pretty good too  8)

IMHO, some of their mikes are the equal or better than their vintage (or modern) German or Harman equivalents.
 
Interesting opinions. Perhaps you are all correct. I might hold off on swapping the caps until I swap the tube and listen to the results. (I have just bought an Amperex 6922 PQ USA which is supposed to be even better than the Telefunken). Will take a couple of weeks to receive the tube.

I do work around the issue with an EQ when needed but would prefer to change it at it's source for the sake of a few dollars in parts and an hours work. Maybe Rode have tested the mic with all available caps and tubes and found the best mix but in the link above even they seem to admit a Telefunken would sound better. The Silmics are supposed to be the smoothest and most detailed electro caps around. That's why I asked what brand of cap those of you who have tried cap swaps used-perhaps you swapped like for like.

As an interesting aside, I emailed Rode here in Australia and they told me the circuit in the NTK and the K2 are identical, and the only reason for any difference in sound is due to different reflections in the K2 capsule due to it being a dual sided structure, and that they should sound identical in an ideal environment.

Gus if you are still reading: C1 and C2 are the output caps but what is the C9 cap?
 
metako said:
Interesting opinions. Perhaps you are all correct. I might hold off on swapping the caps until I swap the tube and listen to the results.
This isn't opinion.  Its fact.  OK the Sydney virgins are just myth  ;)

For the IMHO bit, the only way to confirm this is to do a real comparison with vintage German hardware.  When you do this, make sure your C12 or U47 has been certified musical by true Golden Pinnae cos the genuine stuff is a bit variable (!?!!  :eek:)

I do work around the issue with an EQ when needed
Which mikes do you try to emulate and what EQ settings do you use for which Rode mike?  I've had some success making Chinese copies sound like U87.
 
I'm not really in a position to compare the Rodes to hi end mics - I just have a small home studio. The EQ I use is just the software EQ that comes with Ableton Live. Will let you know if I can hear any significant improvement when I install the new Amperex tube.
 
The link in my first post doesn't seem to produce Gus's circuit so hopefully this one will:

http://web.archive.org/web/20060819045655/http://www.diyfactory.com/projects/gus/ntkmods.htm
 
Note what is circuit is printed on the NTK pcb.
I like the negative power supply.

Again note the date of 2004.  I now would not change any caps on the board. This is one of the good/bad parts about the web, once something is posted it does not go away.  Also the extra lead length of the leaded vs smd caps might cause an instability issue.  I did that part changing as learning exercise.  I even cut a trace and installed a jumper and tried 12ay7 type tubes.

Also go to the Rode web site and look at the frequency response of the microphones.




 
http://web.archive.org/web/20060819045655/http://www.diyfactory.com/projects/gus/ntkmods.htm

This is a refreshing take on mike circuits unlike the widespread naive cloning of old Germans.  This will have subtle valve type sound with very good noise & distortion performance too.  Rather like JLH's Class A amp, it will satisfy both the measurement freaks as well as the Golden Pinnae brigade.

My opinion of Rode just went up another notch.

The sound is AKG C12 rather than U47 (though the capsule is U47 type).  Stephen Paul has a series of articles detailing the differences in sound.  Some people find the C12 HF harsh while others love it.

http://mixguides.com/microphones/vintage_products/audio_vintage_microphones_part/

This is due to the capsule and difficult to change electronically unless you replace everything.
 
Point taken Gus. I'll hold off any cap swapping till I hear the mic with the NOS tube-it might be all I'm looking for sound wise. And thanks for the link to 'Mix' Ricardo. Some good articles and reviews on that site.
 
Congratulation!

Very unusual that people don't start the common cap swapping procedure.

Tito

P.S.:
I have not seen any reliable A/B comparison to that kind of amusement.
even the capacity of the caps was rarely measured. 10% tolerance are common.

As well the sideeffects of a non ideal capacitor can't  get to the surface in most circuits:
http://www.cliftonlaboratories.com/capacitor_voltage_change.htm


 
A very good link there Tinn, although it seems to support the idea of replacing electros with film caps due to inherent instability of electros doesn't it?
 
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