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Old 27th January 2010, 08:01 PM   #1
tmblack is offline tmblack  United Kingdom
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Default Solid State Replacement of Ribbon Transformer?

Nelson,

Can we design a FET or bipolar preamp for a ribbon microphone with low noise, wide bandwidth and superior sound to a transformer?

why do ribbon microphones manufacturers use transformers but MC cartridge owners generally use a MC preamp?

Thanks in advance

Tom
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Old 27th January 2010, 11:58 PM   #2
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I don't have experience with ribbon microphones, but I
can assume that one issue is the noise of the environment,
and broadcast applications of ribbons probably want to
avoid that.

To better answer the question we would need some data
on the output characteristics of the microphone.

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Old 28th January 2010, 01:28 AM   #3
tmblack is offline tmblack  United Kingdom
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I have more experience with ribbon speakers than ribbon mics myself, but I will try to design a circuit for it.
Take the specs for an Apex 210 ribbon mic.
That mic has an output impedance of 220 ohms, and let the transformer have a 1:27 ratio. That makes the ribbon impedance 0.3 ohms.
The rated output is -55dBV, 17.8mV at the transformer, or 66uV at the ribbon.
Would feeding it directly into an OP-AMP configured as a I-V converter work?

Tom
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Old 30th January 2010, 08:45 PM   #4
tmblack is offline tmblack  United Kingdom
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I think I keep the transformer and then I'll need a mic-preamp circuit with a gain around 60dB.
How does a three 2N4401 transistor common emitter single ended circuit sound?

Tom
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Old 31st January 2010, 12:08 AM   #5
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I would be inclined to try 2SK170's in a Common Gate circuit.

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Old 31st January 2010, 04:49 PM   #6
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Noise can be an issue, as in device noise and circuit hum+noise - the transformer is a way to get the desired signal above the noise floor. Otoh, there are some commercial ribbon mics, iirc, that use FET or similar front ends... at least this is what the neurons seem to be retrieving at the moment.

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