low volume and hum using mic

[kozikowski]

The goal is not Warner Brothers Record and Tapes. I produced an ACX compliant sound clip with that inexpensive and common but workable equipment. The UCA-202 has Burr-Brown chips inside and works very well. I have and use two. Koz

[kozikowski]

Do you agree with Chris that the Dual Pre is the source of my noise?

If it's hiss, yes. Unless you have a serious gas leak in your house, that kind of noise is almost certainly coming from the microphone preamplifier inside the digitizer. Those are stunningly hard to build correctly and cheaply. Microphones produce molecular-level signals and it's very difficult to amplify them with no damage.

Koz

[chris319]

The clip Koz asked for is #96, sixth post on this page:

http://forum.audacityteam.org/search.ph ... h%E2%80%A6

Dude, I followed the link you posted and counted 6 posts down. There was no audio file, just a post from Saturday at 12:33 pm PST and there was no link to an audio clip. If you want us to hear this problem, post a link to the damn file or post the file itself instead of making us chase all over hell and gone for it.

I still haven't heard this problem, but assuming it's hiss, it's likely not from the USB port. USB noise is more likely to be clock pulses or data than Gaussian white noise. White noise on the USB line wouldn't produce hiss as it would in the analog domain, because the USB port wouldn't be able to decode it as such.

I'm taking it on faith that the O.P. is using a properly balanced mic cable, and that he doesn't have a VOM to check it with. If his mic cable is shorting one side of the mic to ground, he's losing 6 dB of signal right there. What is really needed for diagnosing this problem is a male XLR connector with a 150-ohm resistor between pins 2 and 3.

This is where you suggest something better.

I already recommended the MXL 24-bit USB mic. If you want me to recommend a USB interface so he can use the SM58: I haven't used this but it looks interesting. If I were looking for a USB interface I'd probably buy one. It has 24 bits and a published S/N ratio of > 100 dB. The levels from the SM58 may still be a trifle low but with 24 bits and a low noise floor that likely won't be a problem and you can normalize it

http://us.focusrite.com/usb-audio-inter ... ifications

It is not uncommon for designers of mic preamps to underestimate the amount of gain needed for a dynamic or ribbon mic. 60 dB of gain should be available IMO.

[kozikowski]

I have to catch up. Didn't we say you could filter your work to gain compliance? It's not going to be drop-dead easy, but it could be done. Oddly this is where higher recording standards (24bit, etc) would be handy. It's easier to effectively use filters and effects.

So yes, the lower end equipment least likely to have advanced recording standards is the same equipment most likely to benefit.

Isn't this fun?

Please note that my first test clip would almost meet ACX compliance had I not had that [email protected]#$&) hum in the background. I really need to figure out where that's coming from. I have one microphone that's almost unusable because of that.

Koz

[kozikowski]

If his mic cable is shorting one side of the mic to ground, he's losing 6 dB of signal right there.

On an SM58, the other side has a 6dB gain. It floats. You do lose the balanced noise rejection, though.

What is really needed for diagnosing this problem is a male XLR connector with a 150-ohm resistor between pins 2 and 3.

A quiet one.

It is not uncommon for designers of mic preamps to underestimate the amount of gain needed for a dynamic or ribbon mic. 60 dB of gain should be available IMO.

Very few of them have ever been on a difficult sound shoot. Also, the goal is a quiet recording. Overload is fatal.

I already recommended the MXL 24-bit USB mic.

How far back? Are you going to make us chase all over hell and gone for it.

I haven't used this but it looks interesting.

Doesn't count. That way lies nasty surprises. Hands on.

Koz

[steve]

I already recommended the MXL 24-bit USB mic

Is that because it is 24 bit, or for some other reason?

I don't really understand the point of a USB mic using 24 bit (other than marketing hype). The SNR of the mic is probably in the region of -70 dB (MXL don't appear to publish that measurement), so 24 bit seems like overkill - do you really need the noise floor in 12 bit fidelity?

[kozikowski]

That could be a problem.

Note: To optimize the performance of the Studio 24 USB with Windows,
we recommend downloading and using the free Asio4All driver from www.
ASIO4ALL.com]

Koz

[kozikowski]

I'm a little fuzzy here, but If you need ASIO software to get the microphone to do all its tricks, that may be a problem. Audacity doesn't natively work with ASIO software.
Koz

[chris319]

I don't really understand the point of a USB mic using 24 bit (other than marketing hype).

There is less quantization error at 24 bits than at 16 bits, noise floor notwithstanding. This is true for any analog signal that is digitally sampled, not just audio.

I'm a little fuzzy here, but If you need ASIO software to get the microphone to do all its tricks, that may be a problem. Audacity doesn't natively work with ASIO software.

Unlike MME and DirectSound, ASIO is bit perfect (as is WASAPI). This is true for any device under Windows, be it a USB or FireWire interface or a PCI sound card, not just the MXL mic. That's my guess as to why MXL wrote that. I believe Apple's Core Audio is bit perfect as well.

24-bit hardware is plentiful nowadays so why not take advantage of it?

[chris319]

If his mic cable is shorting one side of the mic to ground, he's losing 6 dB of signal right there.

On an SM58, the other side has a 6dB gain. It floats.

Check your facts (see fig. 24). There is a 6 dB loss: http://www.rane.com/note110.html