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Old March 17th, 2013, 10:33 PM   #1
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Sound Devices 302 for Ribbon Mic Preamp?

I'm about to get some ribbon microphones and am considering options for mic preamps, which I think I'll need in view of my intended primary use for choral recordings (not a hot input). I'm aware of many mic preamps, including Cloud Lifter and Fethead designed specifically for ribbon mics. Not looking for suggestions.

I just realized that I have an SD302 that I don't use much anymore but might work well here. 75db gain and 2.5k ohm load at the input seems great for a ribbon mic. The 302 is probably overkill just for a mic preamp, but since I have it, I might not need to purchase more gear.

Anyone use the SD302 for a ribbon mic preamp? If so, comment on its performance? In case it matters, my contemplated chain is mic --> SD302 --> Tascam HS-P82 recorder.

Cheers.

Last edited by Steven Reid; March 18th, 2013 at 08:00 PM. Reason: corrected 2.5 to 2.5k ohm
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Old March 17th, 2013, 11:43 PM   #2
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Re: Sound Devices 302 for Ribbon Mic Preamp?

I've never used one, but I don't know of any technical reason it wouldn't work just fine. The SD-302 is a great 'field mixer'. I'd look into obtaining a 14 VDC battery power source, though, just to be safe. I wouldn't want to run out of power in the middle of the performance. Of course, if you're using "mains", batteries are a moot point.
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Old March 18th, 2013, 03:47 AM   #3
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Re: Sound Devices 302 for Ribbon Mic Preamp?

It should be fine as I frequently use an SQN type mixer for ribbon mic's but mainly for broadcast commentary work.

Not sure if they are the right mic for a choral recording though as they are very low level and by the time you add enough gain the noise may be too much and you would be better off with a more sensitive mic such as a condenser.

All the Beatles drum sounds were recorded by Geoff Emerick using ribbon overhead mic's but as a drum kit puts out a fair whack noise is not a factor.
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Old March 18th, 2013, 11:29 AM   #4
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Re: Sound Devices 302 for Ribbon Mic Preamp?

As Gary said, the only issue would be the microphones 'sensitivity' and pushing the 'noise floor'.

J.
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Old March 18th, 2013, 01:14 PM   #5
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Re: Sound Devices 302 for Ribbon Mic Preamp?

To be honest I'm a little dubious too. I have a lovely ribbon here - but it gets very little use because of the low output. Most better quality preamps don't automatically work too well with the ribbon, because when the preamp gain is towards the top, the sound suffers. The preamps in my portable kit (a Lexicon Omega) are not quite good enough for the ribbon on quieter sources, but the Soundcraft in the studio is ok. My new Behringer X32 does not have enough input gain to use the ribbon at a distance, which is a shame. With a decent preamp, the benefits work for me - but it's not my mic of choice!
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Old March 18th, 2013, 01:31 PM   #6
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Re: Sound Devices 302 for Ribbon Mic Preamp?

I seem to recall that most ribbon mics are also very low impedance so may not be suited to most modern mixers, I think some are as low as 50 ohms!
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Old March 18th, 2013, 02:33 PM   #7
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Re: Sound Devices 302 for Ribbon Mic Preamp?

I used a number of RCA broadcast ribbon mics "back in the day" ... 11's, 44's, 77's, and my favorite announce mic the BK-5. The actual internal ribbons were extremely low impedance, but all of these mics had internal transformers to step up the impedance (and voltage) to what were then standard broadcast values, typically 50, 150, 250 ohms. And mics of that vintage expected to have their impedance matched, unlike a lot of today's mics that want to be bridged by a much higher impedance.

Sorry I can't advise about your [presumably newer] specific mics. But I do wonder about the spec you quoted for the SD302: "2.5 ohm load at the input." That would be essentially a short circuit to any microphone... I doubt that that figure is correct.

--

edit: Of course some of the current ribbon mics are "active ribbon" with their own internal preamp (requiring phantom power), to bring the output up to a level that's more in line with other present-day mics.

Last edited by Greg Miller; March 18th, 2013 at 03:28 PM.
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Old March 18th, 2013, 02:55 PM   #8
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Re: Sound Devices 302 for Ribbon Mic Preamp?

The OP probably meant K (x1000) ohms.
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Old March 18th, 2013, 05:18 PM   #9
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Re: Sound Devices 302 for Ribbon Mic Preamp?

Sorry for the belated response -- I am in transit. First, yes, I meant to write 2500 ohms.

Second, I, too, harbored sensitivity concerns until I listened to some orchestral and choral recordings from a DIY ribbon mic. Gads. It was beautiful.

I often record children's choirs with two SDC cardioids in ORTF and two omni outriggers. What I can't fix in post is the terrible sibilance from immature voices (12-13 years old) combined with the bright condensor sound. I reasoned that a ribbon would fatten lows and mids while tame highs, all to the effect of mellowing the sound.

The CloudLifter provides 3000 ohm impedance and the FetHead around 18000. Whopping difference, but both work well with ribbons. The SD 302's specs fall toward the former but offers so much more gain. And I would expect the SD's preamps to be pretty quiet.

My mics will be passive with Lundahl transformers. I'll post some samples when I get my project complete.

Thanks for the replies. Much appreciate the thoughtfulness.
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Old March 18th, 2013, 11:27 PM   #10
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Re: Sound Devices 302 for Ribbon Mic Preamp?

If you look back at a lot of the better studio and symphonic recordings from the '50s and '60s (if not later), I think you'll find that a lot of them were made with ribbons (before condensors came into vogue).

A bunch of shrieking kids (apologies to the kids) are not all that quiet. Hopefully sensitivity won't be an issue for you.

Condensor mic diaphragms are low mass and tightly stretched, giving them a resonance that's above the audio passband. I think that's why they're sometimes so overly bright sounding. (When they had audio output transformers, the frequency response was related to proper impedance termination, too; newer mics with transformerless outputs wouldn't have that problem.)

Ribbons, by contrast, are loose and floppy; I think their resonance is below the audio passband. They won't get out of control if the source material has a lot of HF content. On the other hand, they are extremely sensitive to wind and LF room rumble.

Also, ribbons have a figure-eight pattern, so they will pick up a lot more reverberation from the back side. You'll have to get used to that when you decide on your mic array.

I think you're making a good choice, and I look forward to hearing about the results.
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Old March 18th, 2013, 11:44 PM   #11
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Re: Sound Devices 302 for Ribbon Mic Preamp?

Quote:
Originally Posted by Greg Miller View Post
If you look back at a lot of the better studio and symphonic recordings from the '50s and '60s (if not later), I think you'll find that a lot of them were made with ribbons (before condensors came into vogue).

A bunch of shrieking kids (apologies to the kids) are not all that quiet. Hopefully sensitivity won't be an issue for you.

Condensor mic diaphragms are low mass and tightly stretched, giving them a resonance that's above the audio passband. I think that's why they're sometimes so overly bright sounding. (When they had audio output transformers, the frequency response was related to proper impedance termination, too; newer mics with transformerless outputs wouldn't have that problem.)

Ribbons, by contrast, are loose and floppy; I think their resonance is below the audio passband. They won't get out of control if the source material has a lot of HF content. On the other hand, they are extremely sensitive to wind and LF room rumble.

Also, ribbons have a figure-eight pattern, so they will pick up a lot more reverberation from the back side. You'll have to get used to that when you decide on your mic array.

I think you're making a good choice, and I look forward to hearing about the results.
Thanks, Greg. Much appreciate the feedback.

These kids are quite talented, sing in tune, but their young voices possess a harsh, crunchy HF edge that is really hard (for me) to tame, even with EQ. I'd prefer to mic closer with the ribbons, but the director likely would not countenance that for live performance.

I'm well aware of picking up much more room presence with the ribbons's figure 8 pattern: my initial foray into their use will be to implement the tried-and-true Blumlein array. I've read about, and actually seen photographs of, ribbon mics being positioned high and aimed so that the rear lobes point gently toward the ceiling, thereby minimizing typical audience noise.

On my last shoot utilizing the four microphones I mentioned above, I first recorded room noise, which included ventilation and noise from vending machines (!); it was a school cafeteria. The venue was far from ideal, I know, but my foresight and later application of Izotope RX broadband noise reduction resulted in nearly 100% elimination of the noise.

Cheers.
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Old March 19th, 2013, 09:56 PM   #12
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Re: Sound Devices 302 for Ribbon Mic Preamp?

Steven,

If you have the mics anywhere near the ceiling, be sure you keep them away from any HVAC diffusers. Once you get those ribbons flapping, you're in a heap of trouble.

Back when I was 16 (a puzzling long time ago -- I even had hair), I worked at a local AM broadcast station that had a "daytime" license; i.e. they had to sign off at local sunset (the time changed every month). While playing around with the ribbon mics, I discovered a unique way to shut down the transmitter at the appointed time. I'd pot up one of the mics (an RCA 44), step back, and slowly swing a broom (just the normal home floor sweeping variety) past the mic, at a distance of perhaps 6 inches between the bristles and the microphone. This caused the mic to generate a huge LF pulse. The VU meter on the board would pin, the audio compressor would pin, the LF pulse would travel down several miles worth of copper pair (leased from TELCO), and hit the audio input on the transmitter. The plate overload relay on the transmitter would trip from the huge current spike, and the transmitter would shut down. Much more fun that pressing the "Plate Off" button on the transmitter remote control. ;-)

The point being, if there is a good breeze near your ribbons, they *will* generate a huge amount of LF information which will plague you no end. So keep those mics out of any air currents.
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Old March 19th, 2013, 10:02 PM   #13
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Re: Sound Devices 302 for Ribbon Mic Preamp?

Well, that does sound like something a 16 year old would do! Gave me a chuckle.

I've educated myself on the care and feeding of ribbons, and I certainly don't mind the extra helping of caution. During my last shoot (not with ribbons) I had exactly the problem you warned of. For a moment I couldn't figure out why I was hearing a rumbling through my cans until I looked up to see a long vent right above my mic array. A chair, 4" gaffer tape, and a few minutes eliminated the problem.
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