CAD M179 Noise

[Wokit]

Hi,

I just bought two CAD m179s, but they have an intolerable amount of noise, plus a scratching sound that comes and goes every once in a while. I sent them back to CAD who tested them, and sent them back saying they couldn't hear any problem.

My setup is as follows:

Logic Pro on a Macbook with a 2.4 GHz Intel Core 2 Duo, 4 GB RAM
Apogee Duet
Monster and Musician's Friend-brand mic cables
Monitoring on Sennheiser headphones

I've hooked up other mics to the exact same setup and they sound fine; clean and quiet. The mic cables aren't crossing any power cords; the air conditioning is turned off when I record, and I've tried the mics in another room than the computer, separated by two walls... and I still get the noise. The phantom power is turned on properly, also.

I've attached a clip of the noise; first is the random scratching sound, second is a close-miked acoustic guitar, with the noise present.

Any ideas for what the problem could be? Don't be afraid to make me feel stupid about my setup by simple suggestions; I want to get this fixed.
-Wokit

[tINY]

I'm guessing that the Duet's phantom power isn't up to the task. The M179 is a heavy feeder.



-tINY

[scrubs]

That crackling sound can sometimes be moisture on the capsule, especially if you're in a humid place. Try putting in in a zip-top bag overnight with a few desiccant packets and see.

[Wokit]

Ok, I'll try the ziplocked bag idea.

tINY: I've never heard of a microphone being a heavier feeder than another; I assumed if it said it takes 48V then it's the same as any other that takes 48V. Do you know what causes this about this mic?

[Wokit]

tINY, you were right! I plugged the CAD into my little Behringer mixer and plugged that into the Duet, and the noise problem is gone.

Do you know of any way to boost the power from the Duet without using another interface like this? I don't like adding too many gain stages.

Thanks,
Wokit

[warhead]

Grab a dedicated 2 channel phantom power supply, plug the mics into it, then feed the output into your mic preamps on the Duet.

Done.

War

[dkelley]

Originally Posted by Wokit

Ok, I'll try the ziplocked bag idea.

tINY: I've never heard of a microphone being a heavier feeder than another; I assumed if it said it takes 48V then it's the same as any other that takes 48V. Do you know what causes this about this mic?

it happens all the time, haven't heard of it? the issue isn't the mic, it's that some mics let you get away with less current (and sometimes less voltage) from phantom power than the true spec is supposed to have. and because there are actually many mics that let you get away with that, there is a surprising number of devices supplying below spec phantom power because they can get away with it.

a mic like the m179 will show if a device has issues with it's phantom power.

it's nothing wrong with the mic, it's the mic showing a problem with the preamp's phantom supply.

and by the way, the m179 is one of the quietist mics in my collection.

edit: I see you worked it out and Tiny was right.... gotta love getting things fixed eh?

cheers,
Don

[tINY]

The spec on the M179 is 8mA of phantom power. If I remember the circuit diagram right, they are using precision op-amps in there, which require a bit more power.

Anyway, if you have a standard P48 with a pair of 6.8k resistors feeding 48v to the mic, you get a 27v drop across them at 8mA. Since Apogee didn't do an adequate job of making a 12-25v to 48v boost converter, you hear the noise of the converter on the input when supplying higher currents.

The specs on distributed power for firewire are a little murky, so it may be the Apple too. But Apogee should fix this.



-tINY

[audiostout]

Good post tINY. I learn something new everyday on here!

[Empr]

Hi, I just came across this thread while doing some searching. Since it's fairly recent, I was hoping to ask some additional questions. I am planning on getting a duet, and thinking about getting the M-179 microphone as well. I've heard good things about both products. Do you think this noise thing is a flaw of the duet (and that there are better interfaces that could handle the M-179 in the same price range) or is the noise something to be expected from this type of audio interface? Thanks.

[Jeff Jasper]

The Duet itself isn't noisy, but it's relatively weak phantom power supply causes the M179 to be noisy. The M179 uses about twice the current of most other transformerless condensor mics.

Just turn the phantom power off on the Duet, and use a decent dedicated phantom supply (such as a Stewart) between the mic and the Duet. Problem solved.

The two-channel Stewart is about $125, which may seem pricy, but I've had one in 24-hour duty for years with no problem, ever.

[Empr]

Thanks for the reply. Is this something that would be reoccuring when using condenser mics with the Apogee Duet, or is the M-179 fairly unique in this respect?

[Jeff Jasper]

Frankly, I don't know. But I don't think I've ever seen a mic with a bigger current draw than an M179, so the Duet may work just fine with, say, a TLM-103.

That said, I wouldn't view that as any kind of reason to avoid the M179; samples I've heard sound very good, and I've considered buying one myself given the performance/price ratio.

Fletcher knows everything, and sells the Duet, so maybe he can chime in with his expertise on how it performs with other mics.

[Empr]

I'm wondering more if it may be a reason to avoid the Duet, rather than the M179. Do you know if other interfaces at a similar price range would have the same troubles?

[Fletcher]

P=EIR

Power [P] = Voltage [E] X Current [I] X Resistance [R].

So... you have 48v, at what current draw?, figure resistance is 1 [which is nothing for all intents and purposes].

One sign of a good phantom power mic's amplifier is a high current draw so while most mics will draw under 10ma, several will draw more which isn't a problem until you start to reach the end of the pre-amp's current supply capabilities.

In this case you ran toward the end of the Duet's phantom power capabilities... either get an outboard phantom power supply or use a different mic as you're not going to get the requisite current to properly run the mic.

Make sense?

[Empr]

Thanks Fletcher, I haven't yet bough a duet or a m179 but was thinking of buying them. Do you think other under $500 audio interfaces would also run into this problem with the M179?

[tINY]

Apogee obviously cut a few corners to fit the price and industrial design they wanted (small box with no external power source). There are a lot of decent condenser mics out there for under $500 that draw a lot less current than the M179.

People who like the sleek little mac books and snazzy little recording box from Apogee should just find another mic that works with the Duet. Or, you could look at a clunkier interface that has an option of using a wall wart to supliment the power.



-tINY

[TurboJets]

tINY nailed it, I just saw this post. I'd like to add, I learned a long time ago that the M37 & M177 (which share the same 177 pc board) exhibit the same behavior. Great mics, but if they're under-powered, watch out. They'll fold under high SPL, make noise, have spongy lows... everything the others have mentioned. Interesting thread.

[Empr]

Thanks for the replies tINY and TurboJets. I think I'll probably still go with the Apogee. It seems to have good reviews, and it sounds like this mic problem won't be a big deal, or insurmountable if I encounter it.

[daffy]

Hi all!

First post on the forum - I registered specifically to reply to this.

I have already returned one CAD mic and was about to return a second one when I stumbled across this and I think you've just solved my problem too. I'm currently using a Tascam US-122L with a stereo pair of CAD M179's and when they work the sound is great, but I had/have the same noise issues.

Why I thought I had a problem with the mic is that I get it on one but not both mics - I swapped leads, inputs, patterns and one mic was consistently really noisy.

I sent it back and got a replacement, but now the other mic has developed noise. I was recording using an MS configuration last night and the side mic was full of white noise.

I even checked with Tascam and they said the phantom should be fine, but it may even be the USB supply from my laptop. I'm going to try another phantom power source before sending this one back. I hope this solves my problem too - they are lovely mics and ridiculous value for money!

[j-uk]

Originally Posted by daffy

Hi all!

First post on the forum - I registered specifically to reply to this.

I have already returned one CAD mic and was about to return a second one when I stumbled across this and I think you've just solved my problem too. I'm currently using a Tascam US-122L with a stereo pair of CAD M179's and when they work the sound is great, but I had/have the same noise issues.

Why I thought I had a problem with the mic is that I get it on one but not both mics - I swapped leads, inputs, patterns and one mic was consistently really noisy.

I sent it back and got a replacement, but now the other mic has developed noise. I was recording using an MS configuration last night and the side mic was full of white noise.

I even checked with Tascam and they said the phantom should be fine, but it may even be the USB supply from my laptop. I'm going to try another phantom power source before sending this one back. I hope this solves my problem too - they are lovely mics and ridiculous value for money!

I've got 3 CAD 179s that I use mostly as tom mikes. They're different ages so they sound a bit different to each other but I"ve never had a problem with noise.
I reckon using phantom power from a USB source is the root problem here. Get dedicated power and you're issues will disappear.

[gehauser]

Interesting info on the heavy current draw of the m179. I had the same crackling noise recently when I used my m179 with an ART Tube MP PS pre, but the problem disappeared when I replaced the ART with my Grace m101.

Later...

I just read in the ART Tube MP PS manual that its phantom power supply "is current limited to protect your sensitive microphones", so I guess that explains its problem powering the m179. Won't try that again.

[kshepitzki]

Great thread.
I have a Saffire Pro 24. I searched the specs but didn't find the phantom current draw of the Saffire.
Does anyone know if the 24 will hold the current draw of the M179?
Thanks

[Igor2012]

Originally Posted by j-uk

I've got 3 CAD 179s that I use mostly as tom mikes. They're different ages so they sound a bit different to each other but I"ve never had a problem with noise.

Are they all different because the sound changes as they age, or because of inconsistencies in manufacture?

I was thinking of getting a pair to experiment with stereo miking techniques, but wonder if unit-to-unit consistency is good enough for stereo use.