Ribbon Mic and Phantom Power

[zoo_day]

Hello,
I have two questions.

1 I have a mixer that supplies phantom power to all channels (Soundcraft E8). I engage the phantom power for my condensor mics. Here's my question. If I use a separate mic pre for a ribbon mic (sans phantom power), that is then sent to the E8 line level, does the phantom power of the E8 reach the ribbon mic?

2 I have a Nagra IS. It has a switch for dynamic and condensor mics (it does not have phantom power). Is it safe to plug a ribbon mic when the Nagra is switched for dynamic mic. i realize this may be obvious, but don't want to ruin a working mic.

Thanks!

 

[cusebassman]

Hello,
I have two questions.

1 I have a mixer that supplies phantom power to all channels (Soundcraft E8). I engage the phantom power for my condensor mics. Here's my question. If I use a separate mic pre for a ribbon mic (sans phantom power), that is then sent to the E8 line level, does the phantom power of the E8 reach the ribbon mic?

If you run the 1/4" TRS line output of a preamp out to the 1/4" TRS input on a channel of a mixing desk, you shouldn't be receiving phantom power - it should only be getting supplied through the XLR jacks.

2 I have a Nagra IS. It has a switch for dynamic and condensor mics (it does not have phantom power). Is it safe to plug a ribbon mic when the Nagra is switched for dynamic mic. i realize this may be obvious, but don't want to ruin a working mic.

Thanks!

Not sure what a Nagra IS is. However, a ribbon mic is technically a variant of a dynamic microphone, so you should be fine as long as you are sure there is no phantom power running through.

 

[Mr. Antrobus]

Not sure what a Nagra IS is. However, a ribbon mic is technically a variant of a dynamic microphone, so you should be fine as long as you are sure there is no phantom power running through.

Watch the movie "Diva" to see a vintage nagra in use. For some time Scott Dorsey on rec.audio.pro used a line from that movie: "C'est un Nagra. C'est suisse, et tres, tres precis" as his signature quote. Basically Nagra manufactures high end audio equipment and their decks have often been used for film location recording.

 

[cusebassman]

Watch the movie "Diva" to see a vintage nagra in use. For some time Scott Dorsey on rec.audio.pro used a line from that movie: "C'est un Nagra. C'est suisse, et tres, tres precis" as his signature quote. Basically Nagra manufactures high end audio equipment and their decks have often been used for film location recording.

Ah, thanks for the info!

 

[zoo_day]

thanks for both of your responses.
as far as the first question, what if the mic pre--in this case a Universal audio solo 610--has xlr line output .There's a switch on the machine for the output to be line or mic. If i use the line output going xlr to the mixer will the phantom power transfer. Should I use an xlr out of the preamp to a trs input on the mixer to be safe?

Thanks again.

 

[Freudian Slip]

An output will not have phantom power in it. Only on a mic input.



F.S.

 

[zoo_day]

Good Information.
thanks much!

 

[cusebassman]

If your preamp has only XLR outputs, that are line-level, and your mixing console has both XLR and TRS inputs, you should indeed get a cable that goes from Preamp XLR -> 1/4" TRS input on mixing console. I don't know if any outboard gear has this sort of protection, but I wouldn't want to see you run the line-level XLR output from your pre to the XLR in on the board, shoot phantom power out to the output of the pre, and blow it up. Plus, the XLR input on the mixing desk won't be getting the right signal level (it is presumably expecting a mic, and you would be sending it a line-level signal).

 

[Freudian Slip]

If your preamp has only XLR outputs, that are line-level, and your mixing console has both XLR and TRS inputs, you should indeed get a cable that goes from Preamp XLR -> 1/4" TRS input on mixing console. I don't know if any outboard gear has this sort of protection, but I wouldn't want to see you run the line-level XLR output from your pre to the XLR in on the board, shoot phantom power out to the output of the pre, and blow it up. Plus, the XLR input on the mixing desk won't be getting the right signal level (it is presumably expecting a mic, and you would be sending it a line-level signal).

Well if the pre sent phantom power out of the output it would either be a major design flaw or it's broken. Has anyone ever heard of one that does? There would be on reason for it. I do agree with running into the line in though since your sending a already preamped signal.

F.S.

 

[cusebassman]

Well if the pre sent phantom power out of the output it would either be a major design flaw or it's broken. Has anyone ever heard of one that does? There would be on reason for it. I do agree with running into the line in though since your sending a already preamped signal.

F.S.

Perhaps I worded wrong. I meant to say that if you were to then enable the phantom power on the mixing console, you would be sending phantom power out the mic-input jack of the console, to the XLR output of the preamp. This is referring to console phantom, not the phantom on the outboard pre.

hehe yea, I'd be a little concerned as well if my outboard preamp were sending phantom power out one of its outputs

 

[Freudian Slip]

Perhaps I worded wrong. I meant to say that if you were to then enable the phantom power on the mixing console, you would be sending phantom power out the mic-input jack of the console, to the XLR output of the preamp. This is referring to console phantom, not the phantom on the outboard pre.

Ahhhhh, Yes that would suck!

F.S.

 

[soundchaser59]

Or you can get a DI box that has a transformer isolated output on it, run your preamp output thru the DI box to the mixer input, and skip the 1/4 inch plugs completely..... phantom power cannot jump thru a transformer.... and you would still be all XLR....

 

[zoo_day]

That would involve new gear and i'd like to avoid that. Maybe if I explain my situation more clearly, folks will have a few ideas:
I'm recording multiple instruments to a mono tape machine--(much like they did before multi-track recorders.)
I have condensor mics and two ribbon mics. They all need to go through the same mixer at some point to get sent to the tape machine, which has only one input. The mixer has 8 inputs.
Let's say I plug 6 condensor mics into the mixer and enable phantom power. Then I plug my two ribbon mics into separate mic pre's which are each sending line level to the two remaining inputs of the mixer. Do all agree that this is safe for the ribbon mics?
Thank you.

 

[Mr. Antrobus]

Does your board have insert points? Would you want to bypass the mic pres--since you would be running a mic pre into a mic pre? could you use a cable like this?

 

[Mr. Antrobus]

Or you can get a DI box that has a transformer isolated output on it, run your preamp output thru the DI box to the mixer input, and skip the 1/4 inch plugs completely..... phantom power cannot jump thru a transformer.... and you would still be all XLR....

The 610 solo has an output transformer--would that protect it from phantom power issues?

 

[ittam]

I can´t remember Nagra IS´s case, but mono models of Nagra IV have phantom power or not debending of the preamp cards installed. Mine had 48v & 12v phantom and 12v T(onader) power. Stereo Nagra IV had them all by default. Switching Cond. to Dyn. at least raises the gain which would be good for your ribbon. Nagra preamps are good, you can use it as your external preamp.

Matti

 

[xstatic]

As for the phantom power problem, there should be no issue with phantom power refeencing back into the Nagra. Most all outputs have buffers and/or transformers that would block phantom power from referencing back in through an output. Without this there would be constant problems with doubling the phantom power.

In addition o this, most all current ribbon mics would not be damaged by the presence of phantom power. Some even require it now. With most crrent ribbon designs, the most damage phantom power would do is when plugging or unplugging a cable while the phantom power is active. This can create an arc between pins and reference phantom power on pins it should not be on.

With the original posters signal chain example from a few posts earlier, there should be no problem with setting things up as described. If the nagra has xlr outputs, I would reccomend getting a female xlr to male TRS cable like suggested above, but for completely seperate reasons. Phantom power would not worry me, but gain mismatch would. Most "affordable" mixers have both an xlr input for mic level signals, and a trs input for line level signals on each channel. In most of these more "affordable" designs they are setup so that the mic preamp is not very capable of dealing with a line level signal is there is a good chance that your line level signal when applied to the xlr input will constantly overload at the mixers input. Personally, I would not use the insert point either. The insert point will bypass the line amp and depending on how the insert point is routed can also affect whether or not you can use the EQ and/or affect proper functionality of pre and post fade aux sends. By using the line input you are assured to be able to have some degree of varying gain or trim, your EQ should you want it, full aux functionality, and your insert pont will be available should you want it for something else. Basically, by using the line input you are using the setup as it was designed and intended to be used.

 

[ittam]

With Soundcraft E8 the phantom current shouldn´t get to the line inputs
which you would use with an ext. preamp.
Typically Nagras output to bananas and propriety din connector; I would use the banana connection.

Matti