Too much noise from Microphone tube!

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

silverknit

New member
Joined
Apr 9, 2012
Messages
3
Hello everyone,
I am trying to upgrade the stock tube from a Rode K2, as advised by some people, and I already tested 2 tubes without success.
  I found and bought a Mullard ECC88 and a Philips Jan Nos which are supposedly a good replacement for the chinese stock one. After a burn out period my hear can tell they sound better than the old one but both have a loud hiss (like white noise) when gain is turned up. They are pretty unusable because of that, and I've worked a few days with them and it still won't disappear.
  I'm gonna get back to the stock tube which is silent after all, untill I find the cause of that noise or find a better/ silent tube.

  I guess these tubes are microphonics and weren't tested  (or where tested but failed to pass it and aren't suitable for audio use, at least for preamping) That is probably why I got them for pretty cheap. This is my guess.

So what do you think about it? Did you know of such tubes? Even noisy JAN?
What other tube could you advise me to buy, and on what website / at what price ( I know the hype makes them overpriced)??
I don't want to get fooled again, i want to be sure it will not be noisy again, I want to be sure the reseller is honest .


Thanks for you help!
 
You can never be sure they won't be noisy. The best you can do is to find a seller that offers a guarantee and a good refund policy if you are not satisfied. This will push up the price considerably, but it is the only way to be sure of getting your money back if the tubes don't measure up - and even then they will have to be true to their word.

You can of course be lucky, even on eb*y, but you will have to be very patient and take your time to find the good ones among the not-so-good - and remember that most have been sifted through and rejected for low-noise applications already, so this may be a somewhat thankless task.

There are a few sellers that offer pre-selected tubes for microphone use at a premium price - AllegroSound comes easily to mind - but you will pay well for the convenience of not having to select them yourself - there is no free lunch in this regard. Time is money, it is up to you which of them you wish to trade.

Best of luck to you.

 
I ended up buying a bunch of cheap tubes on Ebay, tried one after another until I found a nice quiet one. Nobody on Ebay will test tubes for performance in an audio circuit, add certainly not in tube mics. They all spent way too much on their holy grail Hickok testers to realize that there are better ways to test a tube.
 
Ok thanks ! I got it...
  I understand i just have 2 options : 
  I spend a lot on a trusted tested low noise tube ( and I cross fingers I'm not crooked)
  Or i find cheap ones and try them until I get the holy grail... (I don't believe in the last option, because I think most of the cheap nos are the ones that didn't pass the test...)

Well well , I wonder if it's worth it now..
 
If you search the web you might find my hand drawn schematic of the K2.  The tube to my ears does not matter that much except for noise with that circuit.

I have a K2 I tried different 6dj8 types no big difference.  I even installed a 6072a after I changed some wiring.

With tubes you often need to try more than 2 you can try many more than 2 and still not be happy.

How can tubes sound better if they have more hiss?  Did you record before and after?
 
what kind of tube is it?

pentodes are always noisy, ef86, etc,

you can drop the screen voltage if it is a pentode, if it is a dual triode, 

you can try dropping the plate voltage,

it is expensive to get a good ef86 circuit going, you need about 10 tubes to get one good one,


and then it gets noisy after a few years, but they sound great,



 
I recently went through this with my G7. I used a Siemens PF86 from ebay first because I read on here they are easier to find and handle noise better. Not my experience. It produced a lot of noise and crackles. I found a Mullard EF86 on Ebay for a reasonable price and that made all the difference. Luck of the draw I suppose. Maybe I'm fortunate that it only took me two tries.
 
What was the stock tube? A Chinese 12AX7? A lot of these are surprisingly good these days. Why were you dissatisfied with it?

I have a boatload of Mullard, Mazda, GE, etc. NOS tubes that are noisy. :( Noise is something that is difficult to characterize, and no almost no one rates tubes they're selling on that basis. Noise (both hiss and microphonics) is something I fight all the time building & servicing high gain guitar amps, sigh.

--mark
 
Back
Top