SM7B pre-amps keep breaking

L

Lcjevans

New member
I recently bought an SM7B and have tried a total of three pre-amps for the same (2xfetamp, 1xfethead) however after a short while the signal completely dies and it's impossible to get a decent level out of microphone.

I've been trying to search for an answer for a while but can't find anything
 
Could be a faulty XLR cable between the interface and the inline booster. Since those things run off of phantom power, there might be a loose connection or a short somewhere in that cable. I'd try different cables as a first troubleshooting measure.
 
Tadpui said:
Could be a faulty XLR cable between the interface and the inline booster. Since those things run off of phantom power, there might be a loose connection or a short somewhere in that cable. I'd try different cables as a first troubleshooting measure.
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7s don't use phantom. Dyanmic. And also a lot o guys are using cloudlifters and the like with them now, I don't see where he said anything about using one.
 
Could there be a problem with your interface? Does another mic work consistently with those same pres? If so, then the problem is obviously the mic.

Does an 7 have a cap(s) in it? Sounds like a cap problem to me.
 
OK, looked it up, no capacitor. And if you meant gain booster instead of preamp, I apologize. Which is it?
 
What are you connecting to that has phantom power for the FetHead and the Thomann FetAmp, interface, a mixer, or something else and does it provide a full 48 volts or is it possibly less (some mixers may only be 15 - 24 volts).
Checking or trying a different XLR cable is a good suggestion.
 
notCardio said:
OK, my bad. I thought there was an actual fethead preamp.

So do those boosters run on phantom power? If so, I agree about the cable from the booster to the phantom supply. Or the pahntom supply itself. Doubtful it has anything to do with the mic.
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Yes...the Fethead runs on 28 to 48 V power.
 
If you've tried three separate devices and they've failed - I suspect your powering system is what is dying. Have you established the units have failed, or did they stop working, so you tried another that stopped and then the same again? Two is coincidence, three very, very unlikely - could your powering device be faulty and the voltage just drops till it stops working. You then take ten minutes to power another one up and that gives it a chance to recover, then fail again?

I assume you have a really low gain preamp, or need to use the mic too far away. I've never needed a gain booster for mine - and it's now on permanent load to a friend (as I hate it) and he uses his without a cloudlifter or similar.
 
I was wondering the same thing, Rob. I'm assuming the OP is running into an interface of some type. If it is powered via USB only, some computers do not have sufficient capacity to run devices with a high current draw. The additional draw from the FETHead may be taxing the system.

It might be good if the OP can fill in some details regarding the rest of the recording chain.
 
FetHead current draw is about the same as a typical condenser mic, about 3 ma, so if the interface or other device can power a condenser that works in the range of 24-48v, it should power a FetHead OK. If the OP has a small mixer that only does 15-18 v for phantom he may have problems.
 
I'd guess it's the [phantom] power supply, if not cable fault or cockpit error.

I looked at these, and the CL-1, and it seems none of them have an LED that shows they are getting a proper, phantom power supplied. I'm guessing that would introduce noise, because I've looked at every one of these things I could find (Klark, Shure, Royer, Soyuz, sE), and not a single one has it.

p.s. [edit] You (or at least, @ecc83) could make one yourself, but this is the cheapest tester I found (eBay link):
https://www.ebay.com/itm/293955915782?hash=item4471235006:g:U2cAAOSwMD1gANcB
 
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I have a Mk 1 NI KA 6 and they have just about only one failing, very puny phantom power (fixed on the Mkll) I can run two AKG P150s or a Sontonics STC-2 but NOT a Fethead. It is possible that the OP's interface has marginal spook capacity and runs out of steam somehow.
The cable feeding the FH is however the most likely culprit, if the screen (pin one) is intermittent one end it will still work just on the '57 but won't pass Ppower...it is JUST possible that the mic has a pin one problem but very unlikely with a BSH Shure!

And yes! FFS get a METER! Then I shall tell you how to use it.

Dave.
 
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