Complete mic/gear failure - PLEASE HELP

[jgimbel]

Something has gone wrong in my home studio. I set up to record some drum OH tests yesterday. I threw up 2 MXL 603Ss that have always worked fine with no issues whatsoever. I plug them in, turn on phantom power, and start to set levels. The mics are plugged into an Art MPA Gold. One mic is getting sound, the other isn't. I thought it might be the mic cable, so I tried a few others with no luck. I tried switching the mics to the opposite channels of the MPA, no luck, that one mic still wasn't getting sound. Tried a different channel of the Firestudio Project they were going into just in case, no luck. I assumed the mic was dead, packed up, went on with my day elsewhere.

I just set up to record some fooling around on guitar. I put up an MXL4000 in fig 8 going into the same MPA Gold, into the Firestudio Project. Put on phantom power, no signal. I tried other mic cables, no luck. Tried the other MPA channel, nothing. Same trials as before. I thought it was really weird, but it's not unusual with me for things to happen in a group like mics to fail within a period of a couple days. Just to be sure, I plugged in an SM57. SIGNAL! I tried wiggling the connections to see if anything was loose, no. Tried the previous cables and they all worked fine.

So I figure okay, something is wrong with the MPA. I switch to a VTB-1 with the SM57 to be sure, and it works fine. I go back to the MXL4000, still no signal. Okay, definitely dead mic. So I felt like using a condensor, so I put up the "working" 603 from yesterday. No signal. So three dead mics? Sounds unlikely. Did all the tests, no signal. I decided to take the preamp out of the equation - maybe there's some deal with them. So straight mic to FSP, none of the mics get a signal (except the SM57 still does). Then I started trying other mics - MXL990, 991, Oktava MK319 - no signal with any of those. Just the SM57. I figure "okay, something's fucked up about the phantom power..in all three units??". I plugged in a Nady Starpower (another dynamic)...no signal. I retested everything with all the cables and mics. Everything that got "no signal" got the SLIGHTEST signal when literally all gain was turned up to max. Anything lower and nothing.

So okay, something's wrong with the phantom power in these units. I've got a standalone phantom power box. Tried it, no signal. Okay, there's something wrong with the FSP?

I switch everything to my Portastudio. Do all the same tests with all the mic cables, all the mics, same thing - no signal for anything but the SM57 (I didn't try the Starpower again). Sometimes when I moved a condenser, it gave a really loud buzz. Not a buzz plus signal, just the buzz.

I'm at a complete loss. A couple days ago I was recording, and now I literally can't do anything. I've got some recording jobs lined up and I'd really love to not have to cancel them.

The only thing that's changed between the last time I recorded and now is that I changed the setup of the room, but only a little. I turned my drum kit in the room, and moved the amps down the wall a bit. Everything is still plugged into the same outlets that they were when everything was fine, so it shouldn't be anything with the electricity. Everything else like computer, monitors, and all lights are working fine.

Has anyone run into anything like this that's similar? I've tested everything I can and I'm kind of freaking out, if you can't tell.

[Snarl 12/8]

I just skimmed your post, but I didn't see any mention of trying different cables. I'm worried that you've got one shorted out cable that's blown out the phantom on your different preamps as you swapped it around. When you've got a systemic seeming problem like this you need to get really systematic about tracking it down. Reduce everything to the least variables and work through the variables one by one until you isolate the source.

[jgimbel]

I mentioned a number of times that with each different thing I tried, I tried a number of different cables. If the way I did it isn't systematic, I don't know what is - doing everything I can to isolate the problem and checking each piece accordingly. No avail.

EDIT: I used different cables each time, I didn't use one series of cables in the same order - if it was the issue of one cable blowing the phantom power, it would be working on at least one of the pieces since I didn't use the same cables on each.

[chris harris]

If the way I did it isn't systematic, I don't know what is ........

I used different cables each time, I didn't use one series of cables in the same order

uhhh......

do you have a cable tester? or, a multi-meter?

[The Scum]

I agree - you've mentioned that you were remaking old cables. Is it possible that there's a flawed cable honking things up?

If you have a volt meter, you can measure phantom power from the pres, too. You should see 48V between pins 1 and 2, and also pins 1 and 3. You should see 0V between 2 and 3. Phantom power is actually pretty robust...a shorted cable won't kill it, but using that cable might keep a mic from working. Also, if a cable were wired so that the 48V were backwards across the mic, that could damage a mic.

If the pre passes the test, plug a cable in, and verify that the phantom voltages are the same, and in the same places at the end of the cable.

Do you have a friend you could take the mics to, to test on a completely different rig?

[jgimbel]

One of my first thoughts was that I had messed up when fixing all these cables I've been talked about. Because of that I made sure I wasn't using those cables (though I did try some of them as well). I don't have a volt meter but I guess I'm going to have to get one. You say I should see 48V between pins 1 and 2 and 1 and 3, would I measure that from the other end of a cord plugged into the FSP? I've never measured something like that before.

If that is the problem and I just messed up the phantom power in each of these units, would it be across the whole thing? Like on the Firestudio, if I messed it up on the channels I tried it on, would it not work on any of the channels, or should it still work on ones I haven't messed up?

[jgimbel]

UPDATE: I just decided to give it another go, this time with a variety of cables again and all mics, but only straight into the FSP this time, no preamps. This is essentially exactly how I did it at the end of last testing. Everything worked. The only thing out of the ordinary is that on one of the channels of the FSP, there is a small "psht" kind of sound that happens when unplugging the mics, after the phantom power has been turned off (and yes it's after the power has completely stopped, I know it takes a bit before it's off, just like a tube amp). On the other channels it doesn't do this. I have no idea if this has anything to do with what happened though, as I used a number of channels last time and this time, not just that one channel.

I haven't tested the preamps again yet. I won't be able to until tomorrow. I'm glad that it's working straight in now, but I still would love to figure out what exactly the problem is so if it's something I did wrong I won't do it again. I don't know if just having the FSP off for a while changed something, but it doesn't seem so, as it wasn't just the FSP that was the issue. Tomorrow I'll test everything again in the same setup with the preamps - hopefully it doesn't shut everything down again.

I'm still definitely looking for any insight if someone has an idea of what the problem is/was. Thanks for the comments so far, you guys are beyond helpful.

[The Scum]

I don't have a volt meter but I guess I'm going to have to get one.

It's not exactly a wonderful tool, but $10 at Harbor Freight can get you one.

would I measure that from the other end of a cord plugged into the FSP?

The same things.

If that is the problem and I just messed up the phantom power in each of these units, would it be across the whole thing? Like on the Firestudio, if I messed it up on the channels I tried it on, would it not work on any of the channels, or should it still work on ones I haven't messed up?

Could be either...

...though I doubt you've killed the phantom supply. Phantom was designed to survive shorts without breaking a sweat.

I'm still definitely looking for any insight if someone has an idea of what the problem is/was. Thanks for the comments so far, you guys are beyond helpful.

One thing to mention is that many power supplies have a "self protect" mode they'll go into if they get uphappy. Sometimes it takes being shut off and just sitting quietly to get them to clear this mode...the power supply needs to fully discharge. No guarantees that this is what you're seeing, but worth a shot.

Is there any chance that you had the phantom on the Firestudio turned on while you were using the external preamps?

[jgimbel]

One thing to mention is that many power supplies have a "self protect" mode they'll go into if they get uphappy. Sometimes it takes being shut off and just sitting quietly to get them to clear this mode...the power supply needs to fully discharge. No guarantees that this is what you're seeing, but worth a shot.

You know I wondered that, but I wasn't sure if there really was such a thing. It definitely seems like a possibility.

Is there any chance that you had the phantom on the Firestudio turned on while you were using the external preamps?

I definitely didn't have the phantom on on the FSP with the external preamps today, but I'm trying to think if I did yesterday, I can't remember. I know that I definitely had it on on the FSP, because I always find it annoying to get levels on it because the phantom power button is a bright blue light that's very close between two channels, and when you're trying to make sure the levels are the same for two channels the blue light is much brighter than the meters. I know that I was having that trouble yesterday when I had the pair up, and that I was getting the signal on one side but not the other. The thing I don't remember is if I was using the MPA, too, which I could have been, in which case I would have have the phantom on on both. However, if having it on on the MPA and Firestudio was the issue, I assume it should have been the same issue for both channels. The FSP has 1 phantom power button per two channels, so if it was on for one it was on for the other. But who knows, maybe it messed one up but not the other. Definitely could have been the problem. I guess if there was that much power going to the mic, it would make sense to have an issue getting a signal in both the preamp and the FSP. We'll see tomorrow.

[dsw]

I wonder if one or more of your mic cables have issues with pin 3 and not pin 2?
Here's where my knowledge falls down so correct me if I'm wrong here folks, but wouldn't a mic cable that's unable to provide phantom power to a condenser mic still be able to supply sound through pin 2with a dynamic mic? leading you to think the cable is alright when really its not?

Just a theory.

[jgimbel]

dsw, I thought you might be right. Here's the update. This morning I went in to test the preamps, since I had gotten the FSP to work fine with the condensers last night. Just to be sure and scientific about, I started by repeating that last test that did work and plugged some condensers in and gave it a go. Surely it'd work right since it was fine last night right? Nope! I was floored. I started playing with the cord a bit to see if I could find anything that made a different when wiggled. I'd get a "ffff" kind of sound when I moved things around, but not at one point I could find. Thankfully it didn't seem to be either the mic's connector, but it didn't seem to be the XLR connector at either end. So it really still wasn't clear, but I assumed it was a problem with the cord itself. I tried another, and it worked. I went through the 12 cords I keep in my mic locker that I use most often. And what do you know, 5 of the 12 gave this same problematic result! I got to work on the cords to see what the deal was. Some of them were in fact ones I had worked on, but the issue wasn't the soldering on those, it was actually a break somewhere in the cord. I chopped the ends off those to use for other cords. The others I hadn't worked on, but were soldering issues. Two of those had absolutely ridiculous solder jobs, I can't believe the factory could let them out. So I fixed those, and got some XLR connectors out of the deal. I didn't find any mixed up pins or anything though. After I did all this I tested the preamps with the cords that I knew worked, and sure enough, everything worked fine.

I guess it just seemed so strange and scary yesterday since I was changing cord after cord and it wasn't working, which normally leads to the conclusion that the problem isn't the cord. I never would have thought that almost half of the cords I have would be broken. It's pretty stupid I admit, but at the same time I've been using all of these cords up to very recently and everything has worked fine, so I don't think I'm COMPLETELY delusional for not thinking the cords were the issue.

I recorded today Maybe sometimes a scare like that can be good for you. Sure gets me out of the mindset of "okay I really need this one piece of gear before I can work on this". Thank you for everyone's help and comments, I really appreciate it. I don't know what I'd do without this board.

[Snarl 12/8]

Cabling almost completely baffles me. I've almost never seen any improvement from trying to upgrade cabling just for upgrading's sake, but there've been many mysterious problems that have been caused by "bad" cables that I couldn't get to test "bad" under any circumstances. I've become quite superstitious about cables. If one works for something I won't mess with it until I have to.

[thunderboy]

Also, if a cable were wired so that the 48V were backwards across the mic, that could damage a mic.

No.

jt

[The Scum]

Oh, I'm sure we could contrive a circuit that doesn't like having -48V applied where it's expecting +48V.

Maybe something using tantalum caps...which don't have much respect for reverse biasing.

[dsw]

Glad you figured it out! I hate it when my gear doesn't work right.