Self Noise ? Tube Noise?

S

Smokepole

New member
I think that's the right term.

I have a Shure Ksm27. I've since borrowed a Marshall tube mic from a friend. I think it's an MXLV77.

I like the sound of the second one much better. I know it's subjective but I find it to be rounder and have more brightness as I'm recording my acoustic guitar at the moment. They are similarly priced.

The problem is that I hear a sort of sputtering hiss with the tube mic while nothing is playing. I don't believe it's room noise because When using the KSM27 at the same distance, (about 4 feet), it's quiet?

Do inexpensive tube mics tend to do this or do you think there is another reason. Any help or input would greatly be appreciated.

I did my last vocal recording with the V77 and it sounded great! But then again there was background music playing before the vocals kicked in so you didn't notice any noise.

This new tune starts with an acoustic intro so the noise is noticeable.


Thanks

Joe
 
If you are getting a "sputtering hiss" noise from the tube mic, several things come to mind: all of which are problems with the mic, and all of which should be relatively easy for a good mic tech to fix.

The first thing that comes to mind is that the tube socket is dirty and the crud on the pins is causing intermittent noise problems. Easy thing to try: pull the tube and reseat it a couple of times, and ideally clean the pins with Cramolin or Caig DeOxIt, and use their contact preservative on the pins when you seat the tube again (this works wonders for noisy tube guitar amps as well, BTW: but in either case mind the voltages there, and work with care).

The second thing is that the tube might be gassy: gassy tubes get hissy (but usually not sputtery). To find out, swap it out for another one.

The last thing that comes to mind is that the PCB inside the mic, and the tube socket, might be dirty or contaminated with flux: this is a *very* common problem with the Russian mics, and you hear of it occasionally with the Chinese mics as well. if that's the case. a thorough cleaning of the PCB with defluxer can help a lot. If it's a dirty board, you'll generally notice the noise problem getting worse as the humidity rises: the greater the moisture content of the flux, the more leakage current flows, and the greater the likelihood of noise. Condenser mics are extremely high-impedance devices, and it doesn't take much leakage to bump your noise floor up a lot.

If the noise floor isn't way down there, and completely neutral, the mic needs attention. No good mic should make a "sputtering hiss" for its floor: tell your buddy to consider getting it serviced...
 
What preamp are you using? I have had tube mics that were too hot for the preamp and this happened. If your preamp gets too hot it could cause this too. Heat dissipation could be an issue.

Or.....


Your mic might be bad. Hopefully not.
 
Hi guys. Just came up from the dungeon.

Recording Engineer, it's the cheaper one the 27, but the difference is day and night?

skippy,
I think I read a review that mentions the tube is soldered in to the little power box/tube box that comes with the mic. It mentioned it as con in the design.

I'm going from there to a DMP3 > RNC > Deck.


If the noise floor isn't way down there, and completely neutral, the mic needs attention. No good mic should make a "sputtering hiss" for its floor: tell your buddy to consider getting it serviced...

I can actually see the meter moving ever so slightly on the deck. I guess I'll have to break the news to him.

I'll pass on this info and hopefully we can get it repaired. I really like the sound of it considering it's a fairly inexpensive model.

Joe
 
I don't know about sputtering, but many inexpensive tube mics ARE way noisier than their solid state counterparts. if you could get ahold of another of the same model and compare their self-noise, you may have a better idea if there is something wrong with your mic or if the amount of noise is normal for that model.
 
I meant to type 27... The KSM27 has an S/N of 81dB (it's not indicated, but I'm suspecting A-Weighted since the self-noise figure is) while the V77 has 77dB-A.

As for self-noise, the KSM27 is 14dB-A and the V77 is 16dB-A... Nothing you're gonna drastically hear there either.
 
It's definitely under the weather then. I had both mics hooked up together to experiment a little with acoustic guitar recording. One close, one a few feet away and then switched them. That mic was constantly audible even when it was close and the gain was set lower. Off to the mic doctor.

Damn, this song was definitely another million-dollar hit!

Thanks gents!

Joe
 
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