Hello all ... just a thought ...? Considering some transformers offer "free gain", can we imagine a single transformer, or a serie of transformers acting as a passive microphone preamplifier ? Let's say a dynamic mic on a loud source !
Passive mic preamp ?
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ruffrecords
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In practice you need some power gain. WIth passive parts alone, power put cannot be greater than power in. Add a power supply and you can achieve power gain.
On the other hand, back in the 60s I had a Brenell tape recorder with two line level inputs (about 100mV sensitivity?). I fed each input from a ribbon mic and a Grampian 600:50K input transformer and successfully recorded my mates blues band. I still have the tape.
Cheers
Ian
On the other hand, back in the 60s I had a Brenell tape recorder with two line level inputs (about 100mV sensitivity?). I fed each input from a ribbon mic and a Grampian 600:50K input transformer and successfully recorded my mates blues band. I still have the tape.
Cheers
Ian
Transformers don't provide free gain while they can step up voltages as per their turns ratio. As the voltage gets stepped up the drive capability falls. A step up transformer followed by an active buffer is a pretty common topology.
Another mic transformer application is where a step down transformer drops the output of 600 ohm microphones to work well into low Z mic inputs (expecting 150-200 source impedance).
JR
Another mic transformer application is where a step down transformer drops the output of 600 ohm microphones to work well into low Z mic inputs (expecting 150-200 source impedance).
JR
All right 
Thank you !
Thank you !
