T-17 carbon mic

[Tubetec]

I thought this topic was worthy of its own post .
arising out of discussions on this topic ,

https://groupdiy.com/threads/carbon-microphone-by-placid-audio.80081/page-4

 

[Tubetec]

https://electriciantraining.tpub.co...phones-Single-Button-Carbon-Microphone-50.htm
The dual button arrangement below looks good , in the case of phantom power tapped resistors across the primary winding can supply the secondary center tap .

The thing I forgot about was the size of the transformer , PRR mentions it in his post on the subject ,
Not everybody will feel the need to scream into a lo-fi mic so you may well get away with a miniature component in the handset . If you wanted full on line level output at high spl you could use a more substantial line level transformer in a phantom powered box down the line .

Its seems pointless spending much money on an output transformer in this application , bandwidth is limited from around 400hz to a few khz . Maybe a miniature mains transformer of the appropriate ratio might be good enough .

And the source of the image below ,
https://www.rfcafe.com/references/r...ned-for-beginners-august-1938-radio-craft.htm

 

[TheJames]

Thanks for this thread. I've been thinking about what to do to get a T-17 up and running. Using phantom would be the most convenient.

 

[revmonkey]

I just ordered a T-17 from Payphone.com. I will report back how it works. Using a carbon compatible electret in the circuit sounded lofi, but not quite what I was looking for. I put the circuit up in the carbon mic discussion. I am adding a U pad attenuator so it's useful for louder sources.

 

[Ricardus]

I just ordered a T-17 from Payphone.com. I will report back how it works. Using a carbon compatible electret in the circuit sounded lofi, but not quite what I was looking for. I put the circuit up in the carbon mic discussion. I am adding a U pad attenuator so it's useful for louder sources.

Post that complete schemo after you've added the attenuator.

 

[revmonkey]

My T-17 transmitter hasn't arrived yet, but I've been working on a PCB for the transformer circuit with an attenuator and a housing based on an old Turner microphone. I just finished my first test print of the grill. The plan is to lay two layers of mesh behind the grill. There are a few changes I'm going to make to the grill design, but I'm pretty happy with the model so far.
I just got the printer and am so excited to get to just make stuff.

 

[PermO]

Cool !... now you should cast it

 

[revmonkey]

I bought some silicon moulding, so I can do a wax cast once it's done.