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Old 6th March 2004, 07:22 PM   #1
ubertar is offline ubertar  United States
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Default transformer: can this work

A lot of dynamic mics use step-up transformers to boost the signal. A dynamic mic element is almost the same thing as a guitar pickup except that the coil is attached to a diaphragm so it can move. Also there are fewer windings in the coil.

Would it work to boost the gain on an instrument with a weak pickup to use a transformer in the same way? I've been trying it, and so far it doesn't seem to make any difference, but I don't understand why not. Am I wiring it up wrong?

I don't expect it to be as dramatic as a preamp, but I think there should be some audible difference. Can someone explain this?

I'm using a transformer that came out of an impedance matching adapter for microphones (low to high Z or vice-versa depending which way you go).

Thanks,
Paul
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Old 7th March 2004, 07:20 AM   #2
FredM is offline FredM  Europe
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Hi - Yes, it is easily explained - A transformer cannot amplify, it can only effectively alter impedence.. The POWER you get from the secondary of a transformer will be the power you put into the Primary Minus the losses produced by the transformer.
Assume a perfect transformer - put 1V @ 1mA in, and for a 1:10 winding ratio, you can get 10V @ 0.1mA out -
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Old 7th March 2004, 10:56 AM   #3
sreten is offline sreten  United Kingdom
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Simple impedance mismatching methinks.

A guitar pick up is circa 1K to 2K dc resistance
whilst a microphone is circa 100R dc resistance.

But you'll find with the average controls in a guitar
a very high impedance load is required, in the order
of 100's of kohms.

So the matching transformer doesn't match anything.

sreten.
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Old 7th March 2004, 11:09 AM   #4
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Another point, transformers are specified for respose with a given set of impedances. So that if it was designed to transform 2.2k to 200 Ohms, it might do a bad job transforming 110 to 10 Ohms at least in terms of frequency response. I think the 2.2k to 200 is what is in a lot of condensor mikes. Oktava and Nakamichi are two that come to mind.
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Old 7th March 2004, 01:46 PM   #5
ubertar is offline ubertar  United States
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Default thanks, guys

Fred, that makes sense. I suspected it was something like that. I always thought that transformers needed to be powered up-- it didn't make sense to get something for nothing. I think I'll just coil some new pickups for the damn thing , use some NIB magnets this time for more power.
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