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T Power for microphone


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Sorry, I don't seem to be able to delete this thread which is now irrelavent. I posted: 

"For many years I have had a Sennheiser 415T micorphone, I do not know whether it works. Some time ago I asked about a power supply for it but connect access the thread. 

Does anyone have a circuit diagram for a cheap  "T" type power supply for it either from battery or to convert from 48V. I have this diagram for one by Rick Chinn but for ease and lack of expense would prefer one without an audio transformer as it is primarily to test the mic."

The circuit diagram I was looking at had a 1:1 150R Audio transformer where the 2 X 100uf caps are. The circuit diagram I linked to does not so I am happy to use it. 

Edited by Bazz339
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I've also had a 415T for many years, & still not built a PSU for it !!  I have several circuits, but Rick Chinn's one is the simplest. Beware that Nagra tape-recorders reversed pins 2 & 3 (they also used MALE XLRs as inputs!!). If your mic has a red dot it will have been used with a Nagra & have pins 2 & 3 reversed.

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On 2/23/2022 at 5:23 PM, kgallen said:

Interesting circuit - but I must be blind - there is no audio transformer in that circuit: 3 caps, 4 resistors and a zener diode. Cheap as chips (potato ones, the silicon ones are costly at the moment!).

You are not wrong, 2 similar circcuits floating around by the same chap. One with a transformer, one without. I thought I had seen the one without a transformer but when I searched for it again could only find the one with hence my query, subsequent to posting I realised the circuit I had linked to did not have a transformer, I could not find a way to delete my post. The components arrived today, about £2 plus postage from Bitsbox

Could someone confirm the PIN out for a Sennheiser MKH 415T with 3 pin XLR please? I think the + 12V should be on Pin 2 (Via 180R resistor) (With 0Ve to Pin 3 via 180R resistor to pin 1 and ground). 

Edited by Bazz339
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  • 3 months later...

As footnote to this thread, having built the cicrcuit , I used the microphone for a job. It was working fine and then failed after an hour or so. 

Today I tested it expecting it to be the phantom to T power adaptor that had failed. A brief test with a multimeter seems to suggest that may be OK I.e +12V on Pin  2, OV on pin 3. I have not tried passing audio through the circuit but it looks like the mic may have failed. It was the first time it had been used in probably 25+ years. I will investigate further out of interest. I doubt I will investigate getting the mic fixed if it is faulty (Sennheiser 415T probably 40 years old). 

Attached is the circuit used redrawn to fit veroboard. The piece I had did not have  continuous copper strip, there were 7 holes then a break in the track and another 7 holes.
I used 5 rows. If you are going to use it please make your own evaluation as to its suitability. As stated my mic appears to have failed after an hour or two's use but it was an old mic and I have not fully investigated yet. 

All credit for the original circuit to Rick Chinn 


T Power Adaptor.pdf

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