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microphone step up transformer Condenser Microphones
Old 17th April 2018
  #1
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Thread Starter
microphone step up transformer

hey,
lately i enjoy recording at home instead of sitting in the dark studio. i bought myself an apogee one interface an neumann tlm102. pretty happy with the sound. sometimes id like a bit of a more colored sound and id like to get it right from the start. i would also not mind adding some noiseless gain to the preamp.

can i use a step up transformer between the mic and my interface? or will it screw up my impedances? the mic has a 50 Ohm output and the interfaces preamp offer 2-3k. im thinking of using something like an old v72 input trafo to add vibe and gain. but im really not sure about impedance. thanks!
Old 17th April 2018
  #2
Gear Maniac
 

Since you want to mess up the sound anyway, I wouldn't worry about impedances. The bigger problem will be how are you going to phantom power the mic once you put a transformer in the path?

Geoff
Old 19th April 2018
  #3
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Thread Starter
hey,
thanks for your reply. stupid me did not think of that. but it seems that there are some transformers that can pass phantom power via their ceinter tap. would this work: SOWTER TYPE 9045 TRANSFORMER
i assume that since the mic has very low output impedance (50 Ohms) i can bump it up to 200 Ohms without a problem? if so what ratio of a transformer would i need?

sorry im a transformer noob
Old 19th April 2018
  #4
Gear Maniac
 

Quote:
Originally Posted by salomonander View Post
hey,

sorry im a transformer noob
OK, a couple things to keep in mind.

The impedance ratio is the square of the turns ratio. So if you want to go from 50 ohms to 200 (1:4), you want a turns ratio of 1:2. You could do that with just a simple 1:1 transformer with split windings (put the primary windings in parallel).

Generally we try to avoid having DC current flow through the transformer, although it might do some "interesting" things to the sound. You would have to be the judge. The Sowter mentions feeding phantom voltage to the primary centre-tap. If you connected the primary centre-tap to the secondary CT, and the input was feeding phantom, that should power a microphone, although I've never tried it. The Sowter is also roughly 1:10, which will give you a lot of gain and maybe put some stress on the mic (once again, you would have to decide whether that is a bad thing or not).

Generally, phantom is fed to the hot and cold lines (pins 2 and 3 of the input XLR)with a pair of matched resistors, which powers the microphone without causing any current to flow in the transformer (if there even is one).

Geoff
Old 23rd April 2018
  #5
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kosi's Avatar
I would suggest something different. The TLM / Apogee combi is superfine modern technology. Made to sound as clean as possible, think lowest distortion. Instead of experimenting with very expensive transformers, I would recommend, that you buy a different mic, first e.g. a Shure SM57. Then have a look at a different preamp, also old Shure mixers come to mind, or an API312 or even an old tube preamp. They are cheap to build yourself (and it's fun) You have to learn, where the "NICE" coloration/distortion comes from. Then go in the line in of your apogee.
Simply putting an input transformer in front of a micpre is not the way to go, the micpre is not built for that, it expects a mic level signal.
just a tip, I also tried your way many years ago.
Old 23rd April 2018
  #6
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This is a condenser mic which means it has a preamp inside. All you're going to do by trying to force a signal through a transformer is mess with the preamps output and with the phantom power involved youre screwing around with something that shouldn't be screwed with.

If this was a dynamic or ribbon mic I'd say go ahead and experiment all you want. Those mics use transformers inside already and you wont harm anything in the process. Placing a transformer of the wrong impedance after a condenser mic is pointless.

If you want to really experiment then using a fill LRC circuit IE an EQ is far better then simply adding inductance especially if you are clueless as to what frequencies will be effected. At least with an EQ you have control over what frequencies are influenced. Just adding a transformer is like a blind man shooting in the dark. You have no idea what you are targeting. A Neumann should have top quality to begin with. No idea why you'd want to jack with something that's ideal other then you're bored with your own musical creativity and if that's the case messing with the gear isn't going to do jack. If the mics a poor match and you're having to constantly mess with the sound you get then go mic shopping till you find the ideal match.
Old 24th April 2018
  #7
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I don't know if this passes phantom, but if not, there are plenty of phantom bricks available:
Cloud Microphones
Old 24th April 2018
  #8
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Brent Hahn's Avatar
 

Quote:
Originally Posted by kosi View Post
You have to learn, where the "NICE" coloration/distortion comes from. Then go in the line in of your apogee.
Apogee One doesn't have a line input.
Old 24th April 2018
  #9
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kosi's Avatar
Quote:
Originally Posted by Brent Hahn View Post
Apogee One doesn't have a line input.
okay, but it has instrument input
Old 24th April 2018
  #10
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Thread Starter
hey guys,
thanks for the input. im aware of all the things you mention. i know what transformers do to sound. and its kind of what im missing in this mobile setup. using another mic or preamp is not an option. i want this to be 100% mobile and battery powered - as small as possible. it all needs to fit into the front pocket of my guitar case. i run an recording studio - this is for the go.

dont get me wrong, the tlm102 into the apogee doesnt sound bad at all. its just a very modern sound. i prefer a slightly rounder picture which in my experience is often achieved by simply inserting a transformer. im not looking for a drastic sound change at all. just want to get rid of some of that micro detail.

sowter could wind me one that passes phantom via the ct and has a 1:2 ration. this would bump the mic up to 200 ohms output -which should be more than fine i guess. it would also give me additional 6db of noisless gain. i might give it a shot.
Old 25th April 2018
  #11
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zvukofor's Avatar
And also it will give you 6dB less headroom for your preamp, BTW.

As for going mobile: how do you plan to get phantom power to mic with a trafo?
Old 26th April 2018
  #12
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If the transformer coil is strong enough to have an effect on the sound its likely to also have a negative effect on the phantom power. The rule of thumb is you never pass phantom power through a transformer because you'll blow the supply or the transformer will simply act like a fuse and blow.


Whether the mics buffer board that uses that phantom power would even be positively impacted would be questionable. Its not going to be any louder, that's for sure. The signal is already being preamplified by the board.
If you want to jack with transformers use a dynamic mic and get the phantom power and preamplified mic signal out of the equation. If you want to filter the sound then skip the coil and use a full LRC, ie an EQ

Last edited by wrgkmc; 26th April 2018 at 08:35 PM..
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