Another phantom power ??

cygnus

cygnus

New member
Hello,

I know a lot of people ask about whether or not sending phantom power to certain mics will cause damage, and I think I've read through all of the posts.
They all seem to just mention ribbon and dynamic mics though.

My question is regarding dedicated condenser mic power supplies. Unfortunately all of the microphone inputs to my mixer have phantom power switching for all inputs, so I can't selectively choose which inputs to disable phantom power. Can I send phantom power to (in this case a DJ-8) tube mic power supply without causing harm?

I use the tube mics for the stereo overheads on a drum kit. So far all of the others mics were dynamic, but I would like to be able to try another condenser mic on the snare instead of the sm57 I've been using. So now I need to enable the phantom power.

Thanks!!
 
I wouldn't without at least checking with the mic/PS manufacturer.

People have done it (usually by accident) and many have not had issues. You wouldn't damage the mic itself, but hard to say what if anything would happen to the PS.

So...ask the manufacturer and be sure. :)
 
Like Miroslav said, "So...ask the manufacturer and be sure."

Also note that many mic (signal) splitter boxes will pass one line with and one line without phantom power, so a mic splitter may be a tool you might consider adding to your arsenal.

Paj
8^)
 
Thank you for the replies. Very helpful.

After some research, I figured I'll get an external phantom power supply for the lone condenser mic and leave the phantom power from the board disabled.
I found one for $25. Small price to pay considering the alternative of having to replace two tube mics.
 
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I hade the Phantom power on all the channels of my mixer turned on for 20 years. During that time, I did have a tube mic that I would use frequently. It was fine. But, just to be sure, email the manufacturer.

The ribbon mic thing really only pertains to certain ribbon mics that are both old and expensive. The only dynamics that could be harmed would be those old and expensive ribbon mics. All ribbon mics are dynamics, but not all dynamics are ribbons mics.
 
cygnus said:
Thank you for the replies. Very helpful.

After some research, I figured I'll get an external phantom power supply for the lone condenser mic and leave the phantom power from the board disabled.
I found one for $25. Small price to pay considering the alternative of having to replace two tube mics.
Click to expand...

Stop the cheque! Some of those cheap spook supplies are rubbish. Be back in a tick

Right, the "bTsky single supply is fine. Volts and mA ok and is quiet.

The "Chord" 173.077uk dual OP dual voltage supply is crap. Quiet yes but does not put out even close to spec mA.

I was actually going to suggest the first one but "now you know" why not build a few capacitor phantom power isolator boxes?



Dave.
 
Hello Arizona........

Anyway, I did have reservations about the $25 cheapee, so I ordered a better (and a little more expensive) one from a company that has a reputation of quality.

The schematic. Is that a typical power supply with the 7 pin connector. The 48v would be coming from the 3 pin xlr connectors not the 7 pin connector. I looked everywhere (on the net anyway) for specs on a DJ-8 power supply. I couldn't find anything.

I did find 2 different versions of 48v inline power blocks. Lowest price was >$50 each. The quality seemed a bit dodgy.
 
Thanks for the schematics Mark, rare to see them. The microphone map caused me pause! I did not think a bog S 12at7 would stand a 150meg grid leak, might have to go through a few modern ones to get low enough grid current!

That 9puff anode feedback cap looks sus' to me as well? Feeding that very high impedance grid the tiniest leak would screw the DC conditions. I would have used 2 18pf in series. And why a stage with gain then a stepdown traff? A cathode follower would have been fine with a lower ratio, possibly 1:1 output transformer.

Last of all, if you have to use a double triode why not strap both sections in parallel and get lower noise?

But what do I know! Any valve mic experts about?

Dave.
 
ecc83 said:
Thanks for the schematics Mark, rare to see them. The microphone map caused me pause! I did not think a bog S 12at7 would stand a 150meg grid leak, might have to go through a few modern ones to get low enough grid current!

That 9puff anode feedback cap looks sus' to me as well? Feeding that very high impedance grid the tiniest leak would screw the DC conditions. I would have used 2 18pf in series. And why a stage with gain then a stepdown traff? A cathode follower would have been fine with a lower ratio, possibly 1:1 output transformer.

Last of all, if you have to use a double triode why not strap both sections in parallel and get lower noise?

But what do I know! Any valve mic experts about?

Dave.
Click to expand...

That's just awesome. I had to read that at least 12 times to understand 1/4 of what you are talking about.........:facepalm:
 
cygnus said:
Hello,

I know a lot of people ask about whether or not sending phantom power to certain mics will cause damage, and I think I've read through all of the posts.
They all seem to just mention ribbon and dynamic mics though.

My question is regarding dedicated condenser mic power supplies. Unfortunately all of the microphone inputs to my mixer have phantom power switching for all inputs, so I can't selectively choose which inputs to disable phantom power. Can I send phantom power to (in this case a DJ-8) tube mic power supply without causing harm?

I use the tube mics for the stereo overheads on a drum kit. So far all of the others mics were dynamic, but I would like to be able to try another condenser mic on the snare instead of the sm57 I've been using. So now I need to enable the phantom power.

Thanks!!
Click to expand...

Many valve (vacuum tube in the American language) microphone power supplies will have blocking capacitors on the input so that the phantom power will not get through to cause any damage.

But best to check with the mic. manufacturer first.
 
arcaxis said:
I wonder if MXL would be a manufacturer that would be easy to contact? :)
Click to expand...

Indeed! It is a sad fact that mow that "communication" has never been so easy cheap and available many companies have never made it so hard to contact! There orta be a law!

In any case it is my contention that audio electronics is now so "mature" and well understood that systems should be compatible or at least made by the "no harm" principle. Nothing that is touted as "professional studio" equipment should be in the least bothered by phantom power, signal over level or the normal variations of local mains power. It should also meet decent standards for the ingress and egress of Radio Frequencies. Fork! We have had transistors for over 60 years and valves for much longer. 'Bout time peeps knew how to use them!

Dave.
 
arcaxis said:
I've never forgotten my first........ https://en.wikipedia.org/wiki/CK722 :)
Click to expand...

Heh! I don't think I have ever bought a transistor in my life and only rarely and recently an op amp!

I am toying with the idea of buying some very low Rb transistors to make a pair of ultra low noise mic amps for wildlife recording but eye/hand co-ordination is now pretty poor and I might just plump for a pair of FEtHeads! "Spirit is willing but.......!

Oooo! I DID buy some 6V6s a couple of years ago. Never used them.

Dave.
 
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