[Igor (t4a)]

Yes, I am still struggling with certain issues. In the meantime I am
quite pleased with the sound (performer remains a permanent problem
though). Here is an example, recorded at a distance of 10 inches (Sure
Beta 58-Behringer Ultravoice set to 60 dB gain, no soundprocessing -
M-Audio 2494 PCI analog in).

http://home.arcor.de/t2c/hoh_noise.mp3 1.7 MB

What I really dislike is the noise though. Unfortunately, I do not
know who or what is to blame. I prepared a short soundfile. All data
are indicated above. The original 24 Bit wave file has been boosted by
6 dB and then reduced to 16 Bit. Finally it was saved as mp3.

http://home.arcor.de/t2c/hoh_noise_2.mp3 402 KB

What you hear is a short announcement, after it "silence" in the
recording room, then disconnecting the microphone from the pre-amp
(open circuit) and finally short circuiting the preamp.

Can anyone give me a few pointers on what to focus for a noise (hiss)
reduction?

- recording room
- microphone
- pre-amp
- me
- ...?


Regards,
Igor

[Igor (t4a)]

Sorry, I forgot about the notoriety of the indicated server. Here is a
(hopefully) more trustful site for download.

http://download.yousendit.com/0A245FDD4222E356

http://download.yousendit.com/C406C8710B924136

Regards,
Igor

[Anahata]

Igor (t4a) wrote:

Can anyone give me a few pointers on what to focus for a noise (hiss)
reduction?

- recording room

Unless you can hear something hissing when you sit quietly in the room,
it's not likely to be that.

- microphone
- pre-amp

Clearly the open ciruit preamp inut is very noisy, the shorted input is
quiet and the mic is somewhere in between. The next step is to figure
out the source impedance of the mic, put a resistor of the same value
across the preamp input and listen to the noise of that.

If it's similar to the mic, the mic's not adding much noise.
If it's quieter than the mic, then the mic is the noisier component.

There's a bit of hum there too. Tracing the source of that is a separate
excercise, and the room is more likely to be a source in that case.

Anahata

[Anahata]

Anahata wrote:

If it's similar to the mic, the mic's not adding much noise.
If it's quieter than the mic, then the mic is the noisier component.

Duh. The mic's a dynamic, so it's not really generating noise. A diffent
dynamic mic might have higher output, though, which would improve the
S/N ratio.

If noise is a big concern (it doesn't sound intrusive to me), wouldn't
you be better off with a condenser?

Anahata

[Igor (t4a)]

On May 15, 10:50 am, Anahata wrote:
Anahata wrote:

If it's similar to the mic, the mic's not adding much noise.
If it's quieter than the mic, then the mic is the noisier component.

Duh. The mic's a dynamic, so it's not really generating noise. A diffent
dynamic mic might have higher output, though, which would improve the
S/N ratio.

If noise is a big concern (it doesn't sound intrusive to me), wouldn't
you be better off with a condenser?

Anahata


Maybe. After I've learned that there is much more to microphone
recording than just the microphone I try to take my recordings least
one decisive step further before changing/upgrading my equipment.

I briefly tested two condenser mikes (AT2020, Behringer B5) and found
them even noisier than the dynamic mike (Beta 58).

Of course, if it is room noise I should treat the room accordingly.
But I don't think it's the room (the source for the hum is not
identified though). Personally, I tend to blame the pre-amp. But I
don't want to jump to conclusions.

You are right, I should check the pre-amp with a correct termination.

Thank you.

Regards,
Igor

[Scott Dorsey]

Anahata wrote:
Anahata wrote:

If it's similar to the mic, the mic's not adding much noise.
If it's quieter than the mic, then the mic is the noisier component.

Duh. The mic's a dynamic, so it's not really generating noise. A diffent
dynamic mic might have higher output, though, which would improve the
S/N ratio.

No, dynamic mikes generate noise too, except at absolute zero. Everything
with resistance generates noise.

If it weren't for thermal noise caused by resistance, ribbon mikes would
be dead silent. But they aren't.

If noise is a big concern (it doesn't sound intrusive to me), wouldn't
you be better off with a condenser?

Depends.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Adrian Tuddenham]

Scott Dorsey wrote:

Anahata wrote:
Anahata wrote:

If it's similar to the mic, the mic's not adding much noise.
If it's quieter than the mic, then the mic is the noisier component.

Duh. The mic's a dynamic, so it's not really generating noise. A diffent
dynamic mic might have higher output, though, which would improve the
S/N ratio.

No, dynamic mikes generate noise too, except at absolute zero. Everything
with resistance generates noise.

If it weren't for thermal noise caused by resistance, ribbon mikes would
be dead silent. But they aren't.

There is Brownian noise from the movement of the air molecules. If the
sensitivity of the mic is high enough, this should be at about the same
level as Johnson noise.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[Arny Krueger]

"Igor (t4a)" wrote in message
oups.com


I briefly tested two condenser mikes (AT2020, Behringer
B5) and found them even noisier than the dynamic mike
(Beta 58).

In all liklihood, the condenser mics also have greater acoustic sensitivity.

The particular mics mentioned are very unlikely to have similar acoustic
sensivities.

Of course, if it is room noise I should treat the room
accordingly.

Room treatments don't do a lot for noise - most noise is due to room noise
which in turn is due to HVAC, etc.

But I don't think it's the room (the source
for the hum is not identified though). Personally, I tend
to blame the pre-amp. But I don't want to jump to
conclusions.

You are right, I should check the pre-amp with a correct
termination.

If you're using condenser mics, one quick way to isolate acoustic noise
sources but not leave the mic preamp unterminated is to simply turn off the
phantom power.

[anahata]

Arny Krueger wrote:

If you're using condenser mics, one quick way to isolate acoustic noise
sources but not leave the mic preamp unterminated is to simply turn off the
phantom power.

I doubt it. When the power goes, the actively-maintained low output
impedance goes too.

--
Anahata
-+- http://www.treewind.co.uk
Home: 01638 720444 Mob: 07976 263827

[Igor (t4a)]

Arny Krueger" wrote:
"Igor (t4a)" wrote:


I briefly tested two condenser mikes (AT2020, Behringer
B5) and found them even noisier than the dynamic mike
(Beta 58).

In all liklihood, the condenser mics also have greater acoustic
sensitivity.

The particular mics mentioned are very unlikely to have similar acoustic
sensivities.

.... as the Beta 58?

Of course, if it is room noise I should treat the room
accordingly.

Room treatments don't do a lot for noise - most noise is due to room noise
which in turn is due to HVAC, etc.

Actually, the room appears quiet especially with regard to hiss. There
are two potential culprits for the hum. One is the recording computer
(two rooms away) and the control room for the heating which is also
seperated by two walls from the recording room. Both possible sources
create a noticible hum in their vicinity. If that is the reason for
the hum in the recording I don't know. I still ponder the possibility
that the hum is of electromagnatic origin rather than acoustic origin.

But I don't think it's the room (the source
for the hum is not identified though). Personally, I tend
to blame the pre-amp. But I don't want to jump to
conclusions.

You are right, I should check the pre-amp with a correct
termination.

If you're using condenser mics, one quick way to isolate acoustic noise
sources but not leave the mic preamp unterminated is to simply turn off
the phantom power.

I don't have a condenser mic yet.

Oh, there is one thing that (to my knowledge) was not yet discussed.
The microphone impedance is given with

"Rated impedance is 150 ohms (290 ohms actual) for connection to
microphone inputs rated low Z Phasing."

while pre-amp specification says

"Impedance MIC 2.6 k balanced"

Could that be a problem?

I've uploaded a new recording.

http://download.yousendit.com/C5ACFB5D5C680769

This soundfile contains the following sequence (all data are as in the
previous recordings in this thread).

open circuit - 2.7 kOhms - open circuit - 270 Ohms - open circuit -
150 Ohms - open circuit - short circuit

Thanks for all the answers.

Regards,
Igor

[Paul Stamler]

"Igor (t4a)" wrote in message
oups.com...

Oh, there is one thing that (to my knowledge) was not yet discussed.
The microphone impedance is given with

"Rated impedance is 150 ohms (290 ohms actual) for connection to
microphone inputs rated low Z Phasing."

while pre-amp specification says

"Impedance MIC 2.6 k balanced"

Could that be a problem?

Nope, this is pretty normal for modern microphones and preamps. Mics these
days are designed to operate into impedances of 1k or higher. A few older
mics (SM57, SM58) were designed for lower impedances, say 500-600 ohms, but
more recent mics aren't. We did a quickie listening test of a Beta-57 with
loads switched from 2k to 500 ohms; almost no audible difference.

Peace,
Paul

[Anahata]

Igor (t4a) wrote:

Oh, there is one thing that (to my knowledge) was not yet discussed.
The microphone impedance is given with

"Rated impedance is 150 ohms (290 ohms actual) for connection to
microphone inputs rated low Z Phasing."

while pre-amp specification says

"Impedance MIC 2.6 k balanced"

Could that be a problem?

No, those figures are both quite typical and it's usual for the mic to
see a load somewhat bigger than its own impedance.

Anahata