Ribbon Microphone Noise

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I’ve read in a couple places that passive ribbon mics don’t have noise, i.e. the kind a condenser does, so assumed they are sort of like dynamics, with no “self noise” per se. Then I found the sE Electronics Voodoo VR1 and VR2 mics where they give the passive VR1 a noise spec of 19dB and the active VR2 a noise spec of 18dB.

I did ask via the manufacturer’s support email to explain it and they said it was because the VR1 needed more gain. So, they are basically saying they can make a preamp (the one that tack on to the VR1 to turn it into a VR2) with -1dB of noise?

Can anyone explain passive ribbon mic noise to me?
 
As far as I understand, it's basically thermal noise or Johnson noise. It can be controlled somewhat through impedance matching of the ribbon motor to the transformer. The input impedance of the preamp plays a role as well, such that having buckets of gain and a very high input impedance should help. I'm guessing that having a head amplifier for an active ribbon design would help the potential self noise figures by sorting the impedance issues within the mic as well as giving a 15 dB or so gain boost so you don't need to lean so hard on the preamp.

5 Reasons To Upgrade to an Active Ribbon Microphone | AEA Ribbon Mics & Preamps
 
snow lizard said:
As far as I understand, it's basically thermal noise or Johnson noise. It can be controlled somewhat through impedance matching of the ribbon motor to the transformer. The input impedance of the preamp plays a role as well, such that having buckets of gain and a very high input impedance should help. I'm guessing that having a head amplifier for an active ribbon design would help the potential self noise figures by sorting the impedance issues within the mic as well as giving a 15 dB or so gain boost so you don't need to lean so hard on the preamp.

5 Reasons To Upgrade to an Active Ribbon Microphone | AEA Ribbon Mics & Preamps
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Thanks for that explanation and link. I've looked at the AEA mics but the much lower cost of the [pretty well reviewed] VRx models had me curious, as I have a mic preamp I could stick in front of the interface just for a single passive ribbon, and save a few bucks.

gecko zzed said:
I note the Rode ribbon has self noise of 15dBA.

ROEDE Microphones - NTR
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It looks like the NTR is an active ribbon, which I'd been assuming had noise because of the preamp circuitry, but now realize that was an "assumed" problem.

I've managed to lighten up my mic "locker" by 5 mics (net 4 after a tube acquisition) and have toyed with getting a ribbon just to see what it does - not that I have any use for it in the [drum] overhead/speaker-cab/wind instrument realm but maybe find a place for it on acoustic guitar or ensemble sometimes, if those things start to feel safe. My Zoom F8n has about 75dB of clean gain, so I was thinking an inexpensive passive is something that could easily handle, plus I've got a spare preamp in my music room that's main purpose is holding up whatever is stacked on top of it :). But, I clearly need to take a deep breath and learn a lot more. Thanks.
 
Alissa said:
Passive ribbon mics have a low output compared to condenser mics and require a preamp with more gain than a typical preamp to allow you to record quiet sources without running into noise problems. A high-gain and high-impedance preamp let a passive ribbon mic operate at its peak performance level.
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I looked at possibly getting a preamp specifically designed for ribbon mics, but between that and the cost of the mic, it tempered my enthusiasm quite a bit. Still looking at a couple active mics, but going to probably let that whole idea drift down the list of things I'm looking at for now.
 
Noise only comes from resistances (or their equivalent in active devices) so the noise output of a passive ribbon mic is just going to be the transformer's winding resistance. I shall look soon for some numbers for that but don't hold your collective breaths!

Paradoxically an active ribbon can have a better signal to noise ration than the same mic and the best pre amp in the world. This is because it is possible to built very low noise amplifiers when the source resistance is very low, either that of the ribbon directly or using a low ratio and therefore very low resistance transformer. The same principle is employed to make very low noise pre amps for moving coil phono cartidges.

With the exception of the Coles 4038 and some others the actual sensitivity of modern ribbons is actually comparable to modern dynamics. The need for more quiet gain comes about because ribbons are used at several time the distance from the source than 57/58/7b...

Note too, all mics generate noise due to random air motion and few here have room THAT quiet.

Dave.
 
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