Phoenix Area Tech Question

dr bonkers

dr bonkers

Fractal Fanatic
Vendor
Does anyone know of a tech that can convert a AA powered 1/8 inch trs jack mic to +48v phantom power and xlr jack?

I have a vintage mic that drains the battery really fast.
 
dr bonkers said:
Does anyone know of a tech that can convert a AA powered 1/8 inch trs jack mic to +48v phantom power and xlr jack?

I have a vintage mic that drains the battery really fast.
Click to expand...

Hmmmm.... might need both a converter box and a mod to the mic. What mic is it?
 
My soldering skills and electrical engineering knowledge are not up to snuff for this conversion.

Somehow would need to step down 48 v to 1.5 v in a compact way without reengineering the whole circuit.
 
paranoid said:
Not the best looking way, but a wall adapter soldered to the battery tabes and plug into an extension cord. Should be simple, just redneck.
Click to expand...
Actually, if the supply is clean enough, that's not a half-bad idea. Will need to look up the mic and see what I can find out about it. If it has DC-blocking caps on its output, then phantom power might not work....
 
Joe Bfstplk said:
Actually, if the supply is clean enough, that's not a half-bad idea. Will need to look up the mic and see what I can find out about it. If it has DC-blocking caps on its output, then phantom power might not work....
Click to expand...
Looked at some pics on a forum, and on Reverb. The 1/8" plug is only TS, so the hacky way of powering it may be all we have, and is highly dependent on the ability to get the wires for the battery inside the mic.

If you're willing to mod the mic to use a cord with an extra wire, and a TRS plug, we could remote the battery pretty easily on that extra wire, using the sleeve as ground, and run it on a D cell, or several D cells in parallel, so there are no hum worries. Otherwise, a resistor and a couple diodes could make a voltage divider so you could use a "One Spot" 9V 1700mA adapter to power it....

The cord on a "One Spot" is pretty long, so it may work without being too much hassle with the robot mic....
 
paranoid said:
Not the best looking way, but a wall adapter soldered to the battery tabes and plug into an extension cord. Should be simple, just redneck.
Click to expand...
That's very a interesting solution.

Then I can wire two legs of the xlr to the plus and minus of where the mini plug cable is normally wired.

Correct?
 
dr bonkers said:
That's very a interesting solution.

Then I can wire two legs of the xlr to the plus and minus of where the mini plug cable is normally wired.

Correct?
Click to expand...

Not quite. The 1/8" mini plug and cord are an unbalanced line. The external PS ground and audio ground would be shared. The hot would be hooked to one side and the ground to ground, but the DC power rides on both lines in a phantom power setup, so you're stuck. The DC goes between both hot lines and the shielding, and there's internal circuitry on the mic to use the DC and provide balanced audio on the hot lines, with no connection to the shield ground.

An adapter box and a new cable for the mic would let you push DC in on ring and sleeve, and the signal would need to connect to the tip and sleeve. You could get the battery hooked in via a stereo-to-mono 1/8" adapter pretty easily, actually, but you need that extra wire on the cord.

The pics I saw on the forum looked like the thing would be pretty easy to mod for this, and still work with an internal battery if so desired.
 
https://www.amazon.com/Hosa-CMS-110-Stereo-Interconnect-Cable/dp/B000068O36/ref=sr_1_9?crid=3EDL45R7JITA3&dib=eyJ2IjoiMSJ9.fW2wGX2Oi99DiVdd4cVNIMuuyazCFInl8w5h1qKXnH02m2OtWXqE64OFfiy57QsiW0DsGcbNdIuU7sA9sc4RzmQi-v38XxDTxA_SrN41qMQykFF3Cu84iB7XnCwmoyVJxRnKVCESNqL3ew1QxcoGBuW7FevkW95F2m-Z_bHfD2dbEoGwu31zh-_hWC66B_Ry1ZAu0o0sYO89LWDdi9jsCvAORRhOmwc7E6915lgJxgg.Vag2CDTVeI1F3QZeFaLQvguogD7IqKnAmUDDFuJmRgE&dib_tag=se&keywords=1/8+trs+audio+cable+10ft&qid=1722647847&sprefix=1/8"+trs+audio+cable+10ft,aps,202&sr=8-9

Cut the 1/4" plug off and use this ^^^ for the mic's lead. Hook the ring channel wire to the battery terminal inside the thing.

https://www.amazon.com/Plated-Copper-Shell-Heavy-Duty-Female-Adapter/dp/B0785VKZW4/ref=sr_1_5?crid=3HFV7B3YL1MGA&dib=eyJ2IjoiMSJ9.aAblB6geZZ-lBehcfRweCOsh_C1T8LF6OuF9LhNgUkWimIdxgmqQYDeXBefKNuYjX7WF1RWKd3zzayD18t-IiqFjXOtLDsO-ypAllgAM3yvZqEP5Q3XaZqferY_hEWiNVHdAyl_IpezOTthXVOmmYGfDVf5KbkXUwMCrkYzyr1jaNb8-z4LT9ci1zdyQAweXe3bjQCsPl2gukFa-srVq7HrAfof521oOZDJXiAWwaDLgtI3TFRj9OVDm9TXm1_nid97lSM_ttq-tPC1SIllybTHN7uXvvYcoEFGXLpHXnig.6w65DthIABmEaoG5lWNVebi2isvU5XNUPrWurSigZLw&dib_tag=se&keywords=1/8+female+to+Dual+1/8+inch+male+Stereo+Y+Splitter+Cable&qid=1722648833&s=electronics&sprefix=1/8+female+to+dual+1/8+inch+male+stereo+y+splitter+cable,electronics,182&sr=1-5&th=1

Use this ^^^ to let you split the audio and power onto separate 1/8" lines.

https://www.amazon.com/Truetone-NW1...=1722649142&sprefix=one+spot+9,aps,200&sr=8-5
Then all we need is a box to adapt a "One Spot" 9V power supply ^^^^ to 1.5V on a 1/8" female jack....
 
...and the last pieces:
https://www.amazon.com/dp/B07YJJRGZ...p_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWxfdGhlbWF0aWM

This adapts the 9V barrel plug to a 1/8"....

https://www.amazon.com/Gold-Plated-Connector-Splitter-RFAdapter-Headphone/dp/B096XNHTH3/ref=sr_1_4?crid=3HFV7B3YL1MGA&dib=eyJ2IjoiMSJ9.aAblB6geZZ-lBehcfRweCOsh_C1T8LF6OuF9LhNgUkWimIdxgmqQYDeXBefKNuYjX7WF1RWKd3zzayD18t-IiqFjXOtLDsO-ypAllgAM3yvZqEP5Q3XaZqferY_hEWiNVHdAyl_IpezOTthXVOmmYGfDVf5KbkXUwMCrkYzyr1jaNb8-z4LT9ci1zdyQAweXe3bjQCsPl2gukFa-srVq7HrAfof521oOZDJXiAWwaDLgtI3TFRj9OVDm9TXm1_nid97lSM_ttq-tPC1SIllybTHN7uXvvYcoEFGXLpHXnig.6w65DthIABmEaoG5lWNVebi2isvU5XNUPrWurSigZLw&dib_tag=se&keywords=1/8+female+to+Dual+1/8+inch+male+Stereo+Y+Splitter+Cable&qid=1722649561&s=electronics&sprefix=1/8+female+to+dual+1/8+inch+male+stereo+y+splitter+cable,electronics,182&sr=1-4&th=1

This can be used to make the voltage drop - so you can use the 9V supply and end up with 1.4V (two diode drops) for the mic. :)

You can do this with a minimally invasive cable swap on the mic, a couple diodes, and a resistor, and the above list of goodies....

I could help with the little bit of soldering that is needed inside the mic and on the one stereo->dual-mono splitter adapter....
 
You can pull phantom from the xlr with 2 - 6.8k resistors from each balanced line into a v+ buss for the 48v source.

Phantom voltage decreases respective to current draw though.
 
WKSmith said:
You can pull phantom from the xlr with 2 - 6.8k resistors from each balanced line into a v+ buss for the 48v source.

Phantom voltage decreases respective to current draw though.
Click to expand...

Will that work with the mic's preamp? Never looked at condensor mic circuitry before....

My thought was to try to make it failsafe, not subject the circuitry to overvoltage, and able to be used in its original manner (with internal AA battery) when needed.

Mic has an unbalanced output from an FET circuit, according to what I read on a forum about a guy repairing one. With a TRS cable updating the mic, the battery or power supply could be connected outside the mic. The pile of stuff above will make it possible to use a bog standard 9V power supply, with the diodes and resistor to drop and regulate the voltage to ~1.4VDC.
 
Only if it is using +48v sent down the xlr from the mixer to power the condenser mic.
..Which I thought was the original request for the respected Dr Bonkers.

I like to use LEDs and vary the LEDs current limiting resistor to drop +48v phantom power to the desired circuit supply voltage with respect to the circuit's current draw. Its a novel approach but it works like a champ.

But only If we are talking about phantom power from a mixer instead of a separate supply.

You are right on target if we are talking about a dedicated 9v supply ..but it will likely also need reverse biased diodes or preferably reverse biased electro caps (with a discharge path) to get the DC back off of the signal leads and pass the AC. 🙂
 
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This is sounding more and more like this is beyond my skills.

This is why I was looking for someone in my area that solve this riddle for me. Willing to pay.

I don't want to wreck the microphone due to my rusty skills.
 
WKSmith said:
Only if it is using +48v sent down the xlr from the mixer to power the condenser mic.
..Which I thought was the original request for the respected Dr Bonkers.

I like to use LEDs and vary the LEDs current limiting resistor to drop +48v phantom power to the desired circuit supply voltage with respect to the current draw. Its a novel approach but it works like a champ.

But only If we are talking about phantom power from a mixer instead of a separate supply.

You are right on target if we are talking about a dedicated 9v supply ..but it will likely also need reverse biased diodes or preferably reverse biased electro caps (with a discharge path) to get the DC back off of the signal leads and pass the AC. 🙂
Click to expand...

Currently, it has a 1/8" TS plug and coax cord, if the pics I saw on the forum were correct.

My plan would replace that with a cord set up with 1/8" TRS, and send DC in via the ring and shield, keeping the mic as close to original operation as possible by connecting the ring to the appropriate internal AA battery terminal. A stereo splitter would let the output be connected as it was before and give an injection point for the DC. A couple diodes and a resistor would make a decent regulated voltage drop, and could be wired up on the male TRS plug of the other stereo splitter with little difficulty, so you plug the 9V in one side and get 1.4-ish Volts on the other. I opted for a high-ish current capability for the supply, based on @dr bonkers stating it was killing AA batteries.
 
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