Ribbon mic into TRS input?

Saxomohawh

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Hi,
The XLR (mic) inputs are low impedance (2.4 kohm), and the TRS (line) inputs are high impedance (22 kohm). Normally, a mic shall be connected via XLR and not TRS. But what about a ribbon mic that according to spec. requires a preamp with input impedance >9 kohm? Would it be ok (better) to connect that via TRS? Is there really any other difference between the XLR/TRS inputs apart from impedance? Both passes through the internal preamp.
 
The XLR input allows more gain. Have never used one, but from what I've read, ribbon mics have a lower output than normal so I guess XLR is your best shot... although if the gain still isn't enough, you'll need a more suitable preamp. The only other thing I remember is they can be destroyed by phantom power so make sure that's off, or use a mic which is known to be tolerant.
 
What you write is correct. The best would be to have a separate preamp. But since the input impedance is too low on the XLR, and the TRS is higher (better in this case) would it be wrong to use that in this case? The only negative would be that the gain might not be enough?
 
There's nothing 'wrong' with using either (imo), but if we're surmising the XLR gain may be too low, the TRS definitely will be. If you've got the mic though, try it and see. As far as I know, it won't cause any damage, and if it works ok, you've saved a lot of money. Hopefully someone else will chime in with some hard facts.
Update: a quick search came up with this. Seems the worst that can happen is the performance is degraded... so it's back to try it and see how it sounds to you.
 
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@Mark Richards' investigation of the circuitry revealed that the trim knob is simply an attenuator, and there is no impedance matching network in the preamp section. Plug it into the XLR and see what it sounds like. If you don't like it plug it into the 6.6mm jack and see what that sounds like. What matters is how it sounds.
 
Which ribbon is it? Cause there are modern ones that electronically behave like any capacitor mic and use phantom power. I know since I have one of those, the Sontronics Sigma.
 
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The question was more in general, I don´t have a ribbon mic yet. But the one I have in mind, and for which the impedance data (>9 kohm) comes from, is AEA R84.
Another (but related) thing: If "the trim knob is simply an attenuator", which seems very reasonable, then that is in conflict with what is written in the sticky post that the "one o clock" position of the gain knob should be the unity gain position (neither attenuation nor amplification). Or not?
 
Hi @Saxomohawh the term "attenuator" is not a literal description of the function of the knob. It is a potentiometer in the audio circuit. The circuit handles both attenuation and amplification throughout the range.
 
Ok, but where does this statement about "one o clock position" come from? It is not in the Tascam data. Does it come from studying the schematics?
 
The one o'clock position comes from measuring signals in and out of the machine. Note it only applies to the TRS input, which as mentioned above, is less sensitive than the XLR inputs.
 
Do any of you guys have access to the schematics of these inputs?
 
I have a pair of Fathead ribbons, and they are on the low side in terms of output, as might be expected. I use a Cloudlifter in the path right after the mic, to add impedance and gain to the mics, and it works very well. Level is up, and high frequency response is better because of better "loading" of the mics.

I still run them through a free-standing pre-amp into my 2488 (TSR in,with the the built-in pres turned down to line) but if you want to go "straight in", the Cloudlifter should help get you there.

If you go straight in with the Cloudlifter, you will have to use XLR in on the recorder, as the Cloudlifter is driven by Phantom Power from the machine, to provide the gain.
 
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