I have a Rode NTK mic, which I think is too harsh and not thick enough (rushed purchase).
People get sucked into the tube thing, thinking they're buying something warm and round sounding. I have heard the NTK sound very good on the right voice, but it is a very strident sounding mic. "Harsh" is not a bad adjective.
You can try swapping the tubes. The tube type is a 6922. The most common replacements you'll find are the Sovtek it shipped with and a JAN Philips. I tried a Philips--it seemed to have less noise, but less gain, too. Don't expect any miracles if you try it.
been a NTK user for about 4 years, I think it's quite a forgiving mic.
I agree that it depends on the voice although having recorded quite a few vocalists with the NTK it's never made anyone sound terrible just sometimes they've sounded better with something else.
worked with a female singer and had NTK and U87 to choose from... U87 made her sound nasty and thin, the NTK was full and warm. vocal went on to be a minor radio hit in uk and shows that the NTK can produce extremely pro sounding results.
having said that, adding a new tube that improve it still further sounds great to me.
I think the NTK is a good mic and has its uses, but as has been mentioned, too harsh at the upper end for my taste. I just sold mine on Ebay since it wasn't getting any use any more, I was keeping it "just in case" it turned out to be the magic bullet I needed for a specific source. Finally decided to part ways...
I just had the stock tube in mine, but I am pretty sure the harshness that I hear is in the capsule, but that is just my opinion.
Here a message I've got from GYang, who seems to know a lot from tubes.
Thanks again Yang!
Insomnio
In my case NTK was slightly harsh sounding and overly bright. Anyhow, this mic is very good on some male vocals, so to improve situation on lower end and make it more pleasant on higher end tube can tune the mic..
I tried and found as exceptionally well Telefunken ECC 88 cc, Mullard 6922 ('59) and Cryovalve Amperex.
Reasonable price range 150-250 $ for the best NOS examples.
I tried plenty of Chinese, Russian tubes, but no success.
Cheaper tubes are either newer or fakes or used (short life expectation).
What's improvement?
More space, wider scene, nicer bass and less harsh in the mix later. You cannot change the character of mic, but it will be definitely refined.
Is it worth the price? Depend on how much you use it.
How to found? Very often patience is needed, as good tube rarely stays long time in stock.