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Thread: RODE NTK Tube Replacement

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    RODE NTK Tube Replacement

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    I sent an email to RODE asking about which tubes I could use in my NTK. Nothing's wrong with the current tube, but I read recently about possible improvements in the sound quaility by trying dofferent tubes, so I asked the manufacturer about it. Below is the reponse I received. I thought some of you might be interested in what RODE had to say about it.

    From Darren Rose at RODE

    The NTK circuit was based on the 6922 tube specifications and thatís the one we recommend for field replacement when not purchased from Rode Microphones. Obviously you know that some valves sound better than others, like the (NOS) Telefunkens. When you make thousands of microphones, like we do, NOS are not an option as we could never obtain enough stock.

    As I am sure you will understand it is the designersí job to make sure that every microphone leaves the factory with the same sound quality (tone). We source tubes from all over the world and like all the components that Rode buys donít rely on markings. We have found two identically labeled valves to be totally different in specifications.

    We test every tube before it leaves the factory ensuring that they meet their specifications. A good tube is one that has good specifications, but because they are essentially an electro-mechanical device it still must be tested in house by Rode staff. I donít have a view when it comes to the manufactures as long as they meet specifications: (Whether they be Siemens, Amperex, Sovtek or Svetlana)

    The 6922 tube is basically electrically equivalent to the 6N11, 6DJ8, ECC88 and the 6N1P (Obviously the 6N1P uses 635mA max heater current which is twice as much than the other tubes.)

    Now the NTK power supply was designed to supply 350mA to the tubes heater elements. The NTK power supply can supply up to 650mA heater currents which means the 6N1P will work in the NTK although I would want to have a listen. The power supply will maintain its 6.3Volt output even at 650mA heater load current.

    The 6922, 6N11, 6DJ8, ECC88 and the 6N1P are all plug in replacements to each other. The manufacture datasheets for all these part suggest that you will not have any problem with plate voltages or other specification when used in the NTK. How they all perform and how well they operate is another question all together.

    Just incase you were wondering about plate voltages in the tube, here is some brief technical information.

    The nominal grid voltage (pin 2 on the tube) is: -77V

    The anode (pin 1 on the tube) is connected to ground via a 43K ohm resistor. The anode voltage can swing between 0 Volts to -50 Volts.

    The cathode (pin 3 on the tube) and the internal shield (pin 9 on the tube) can swing in voltage from 0 Volts to -125 Volts.

    You can try any of these tubes quote in this email. Remember, even thou two tubes have the same markings they may sound very different, I guess this is the fun with NOS. It really is a case of personal flavor so try them and make up your own mind.
    Last edited by Simmons; 10-26-2004 at 01:52.

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    By the way......can anyone give me an idea of the difference in sounds quality between the Telefunken 6DJ8 and the Telefunken 6922? They are both new old stock (NOS). I realize that this is very much a subjective thing, but I need a ballpark idea of what these tubes are about.

    I'm hoping someone with first hand know of NOS Telefunken tubes will be able to answer this question.

    Thanks,
    Simmons

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    just been covered and somewhat extensively... sound samples and all
    https://homerecording.com/bbs/showth...ht=NTK+upgrade
    Last edited by Big Kenny; 10-26-2004 at 07:05. Reason: oops forgot the post
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    OK…so it only took me 8 years to try this. I had other things going on

    If you’re curious how to do the tube swap it’s pretty easy…

    Rode NTK Tube Replacement – Telefunken E88CC / Mullard 6922 Gold Pin

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    Now that was a long wait!

    Am on my 3rd alias since this thread started -

    The tube in my NTK was replaced with a Telefunken like the one you show within your link after an hour of owning it.
    You did forget to say that there should be a few days burn in time where the microphone should be left on. Then it settles in quite nicely.
    ♫♪♫ I have a fever and the cure is cowbell ♫♪♫ .......... *LIVE FREE OR DIE* .......... ♫ I'm all ears ♫

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    Any mic you buy will be perfectly suited to your needs, until you use it long enough to learn that it's not.

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    Good point....I did burn mine in for 2 days. I honestly wasn't expecting the difference to be so pronounced. The Mullard was awesome too, but there was something about the Telefunken that added a sheen/vibe to the overall response that I liked better. I noticed the proximity effect is now a bit more pronounced with the Telefunken. The Mullard went into the A-Designs REDDI where it will live forever. Really great combo there...

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