Condenser microphone with tube preamp impedance mismatch

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Studiogearlover

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Hey guys, i am not a techy especially when it comes to impedance. I have a tube preamp with transformer, rated and wired for 50 Ohms input ( assuming for 50 Ohms rated microphones) and I am feeding this with a condenser mic rated 150 Ohms electrical impedance, with normal loading impedance of 1000 Ohms.

When I try and record drums, i have signal pops and drop outs. Could this be because of the impedance mismatch ? ..or a faulty mic cable which I am about to check but would really like to know if this is OK to use this particular mic into a 50 Ohm rated tube pre as it sounds pretty awesome, less the drop out...

Please let me know your thoughts on this... many many thanks for your input! :)
 

abbey road d enfer

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Hey guys, i am not a techy especially when it comes to impedance. I have a tube preamp with transformer, rated and wired for 50 Ohms input ( assuming for 50 Ohms rated microphones) and I am feeding this with a condenser mic rated 150 Ohms electrical impedance, with normal loading impedance of 1000 Ohms.

When I try and record drums, i have signal pops and drop outs. Could this be because of the impedance mismatch ? ..or a faulty mic cable which I am about to check but would really like to know if this is OK to use this particular mic into a 50 Ohm rated tube pre as it sounds pretty awesome, less the drop out...
Drums produce high SPL, which may saturate the head amplifier, even more if it is loaded too low. A 150 ohm mic should be loaded with at least 1.5kohm. Do you have another "normal" preamp typically aimed at 200r mics? The mic may oerload even with the correct load. And maybe it's not the mic that farts, it could be the preamp. What is the preamp gain range, and what is your condenser mic?
It may not be an impedance problem but rather a gain setting problem.
 

Studiogearlover

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Hey, thanks for you reply! The microphone is a boundary mic installed into the ceiling above the drums. Its a Crown PZM Omni Condenser, with specs:

Electrical Impedance: 150Ohms
Norml Loading Imp: 1kOhms
SPL: 150dB
Sensitivity: 76dB
Power Level Sp: -53dBM
Distortion: 3% at 150 SPL

The mic pre is a Magnecord PT6V preamp of a tape recorder, the mic input is 50 Ohms, db Gain...i have no idea tbh, i can not see any info anywhere about this. Its a record/playback by a 12ax7 and 12au7, plenty of gain.

I would be happy if its not the mic cable..as I dont really want to take out the cabling from the wall of that PZM :)

Thanks once again your input and suggestions... i have already learned something!
 

abbey road d enfer

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The mic pre is a Magnecord PT6V preamp of a tape recorder, the mic input is 50 Ohms, db Gain...i have no idea tbh, i can not see any info anywhere about this. Its a record/playback by a 12ax7 and 12au7, plenty of gain.
You need to test the mic with another preamp, to make sure it works OK. If it does, your problem is probably that there is too much gain in the Magnecord. You would need to add a pad.
 

Studiogearlover

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Thanks... ok.. tested it with another preamp with input rated at 200ohms. Well, it is either the microphone itself or a faulty/broken soldering or wire it seems. I am starting with a fresh cabling, then maybe I will ask a tech to change the TX taps up to 200 ohms instead of 50... Thanks once again your input on this and wish you all my best and a happier NY!
 

Studiogearlover

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I though will give you a quick update on this as it turned out that the reason for the fault mentioned above came from a completely different issue, but the cable. The mic itself... has a TX inside soldered onto a pcb. Accidently realized that one of the tiny pins of the TX came loose most likely due to old/bad soldering ( the mic is from the 80s). ..its a shame that removed already all the cabling from the wall, re soldered a new cable etc.... but hey... now it is working. .... :)

And thank you again for your advise on a pad...i would need this for sure. All my best and happy new year Abbey! :)
 
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