Opinions requested: ribbon mic and pres

Discussion in 'Recording/Live Sound' started by Greggy, Feb 23, 2008.

  1. Greggy

    Greggy Member

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    Ok, I finally bit and bought a Fathead II. My current mic pre setup is simple, I have built 3 channels of Seventh Circle Audio pres, 2 channels of the T15 and 1 channel of the API inspired pre. I intend to build 1 channel of the Neve inspired pre soon. In your experience, do ribbon mics like the Fathead mate better with API on Neve circuits for electric guitar tracking? How about MS recording of acoustic guitars (the Fathead is Figure of 8)? The T15s are very good for acoustics, I know that from recent experience. So perhaps that's the ticket for acoustic instruments (the T15s are clean and largely uncolored yet smooth on the high end and on dynamics, really nice). I know, just try for myself and let my ears dictate, but one thing I have learned is that the best guide comprises a combination of following my ears and listening to the "informed" opinions of others.

    Any thoughts on impedance matching. According to published specs, the Fathead has output impedance <=200 ohms. The load impedance from the pres is 1,200 ohms. Any thoughts on this? I don't see a problem here, just asking. Thanks.
     
  2. elambo

    elambo Member

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    I've played around with impedance matching and never found a drastic difference among the options I tried.

    By the way, those 7th Circle pres aren't just Neve "inspired" -- former Neve engineers have said that they are one of the few clones that "got it right."

    You'll find that both the API and Neve pres work fine with your mic at their current impedance. It will only be a matter of taste. And if you haven't already, you'll quickly pick up on the sonic signature of each and know when to use one vs the other.
     
  3. louderock

    louderock Member

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    Input impedance of the pre should be about 5 times that of the output impedance of the mic. i.e.-- mic output is 300 ohms, mic pre impedance should be 1500 ohms.
     
  4. drfrankencopter

    drfrankencopter Member

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    On Neve 10series preamps, it's the output impedance that makes more of a difference IMO. These preamps were designed to interface to 600 ohm loads, and most modern deveices have input impedances in excess of 10kOhms. This mis-match generates a bit of a high frequency rise that ends up giving a 'bump' that starts around 18kHz up to 24khz. Strapping 600 ohms across the output brings this resonant peak down.

    FWIW, most mics have an output impedance of around 200 ohms, so the fathead should be fine into pretty much any preamp. Older ribbons, like my RCA77D can have much lower output impedances, like 50ohm (depending on how the transformer has been set up)...and might work better into a lower input impedance.

    Like elambo said though, it doesn't really make a big difference.

    Cheers

    Kris
     
  5. Greggy

    Greggy Member

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    Thanks for the helpful info. Now I'm curious what the input impedance is for my Lexicon A/D converter. I typically run the XLR outs from the pre into the XLR inputs of the Lexicon, then coax digital out and into the digital input of a Roland VS 2400 DAW.

    EDIT: Lexicon XLR inputs have 50K impedance.
     
  6. decay-o-caster

    decay-o-caster Member

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    So I have an ART Digital MPA 2-channel pre that has input impedance knobs that go from 150 - 3000 ohms, and by twiddling them I can hear a big difference in the mics I run in. You guys are saying input impedance doesn't make much difference? Confused...
     
  7. Greggy

    Greggy Member

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    Perhaps over the range of 150 to 3,000 ohms you would hear a big difference. That's a 20 fold range.
     

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