microphone into DI snafu (??)

[jaguarundi]

I was having one of those gig nights where nothing seemed to be working right and one of those things involved running a vocal mic, sm 58, through a DI. What I was trying to do involved running it through a guitar pedal (delay) and then into the DI which went into the board. However, even just running it straight (no pedal) into the DI (XLR on one end, quarter inch on the other cable) I could not get ANY sound. tried different cables, there was no microphone switch, tweaked everything I could think of on the board, NOTHING seemed to make it work. I'd done this before with a microphone and DI and it has worked fine, but this night it seemed no combination of things would do anything. anyone have any idea why this could have been?
thanks!
Adam

[rhythm ranch]

First guess: it wasn't a passive DI.

[ott0bot]

First guess: it wasn't a passive DI.

Yep. If it was an active DI you'd need to send it 48v or have batteries or an ac adapter for the DI to work. You could get a simple xlr to 1/4" in line transformer for like 15-20 bucks....they are smaller and don't need phantom power so you can easily run it into your guitar pedal.

[jaguarundi]

First guess: it wasn't a passive DI.

Yep. If it was an active DI you'd need to send it 48v or have batteries or an ac adapter for the DI to work. You could get a simple xlr to 1/4" in line transformer for like 15-20 bucks....they are smaller and don't need phantom power so you can easily run it into your guitar pedal.

is that the same as a chord with 1/4inch on one end and XLR on the other? if so that's what I was using. as for the active vs. passive, I'm not sure, will find out in a day or two but I know there is a device that provides phantom power for the whole board I believe and all mics that's always on there.

so maybe the batteries in the DI were dead? I don't know, will report back when I'm back over there. . .

[ott0bot]

as for the active vs. passive, I'm not sure, will find out in a day or two but I know there is a device that provides phantom power for the whole board I believe and all mics that's always on there.

well that would be sending the 48v into your guitar pedal....which you don't want. And you guitar pedal will not trasmit that to the DI.

You need a passive DI, a properly powered active DI, or an inline transfomer.

[chris harris]

is that the same as a chord with 1/4inch on one end and XLR on the other? if so that's what I was using.

No it changes the impedience of the mic signal (typically +4) to a line level signal (typically -10). I'd use an XLR-XLR cable if possible. It'll get you a cleaner and properly grounded signal into the DI.

as for the active vs. passive, I'm not sure, will find out in a day or two but I know there is a device that provides phantom power for the whole board I believe and all mics that's always on there.

well that would be sending the 48v into your guitar pedal....which you don't want. And you guitar pedal will not trasmit that to the DI.

You need a passive DI, a properly powered active DI, or an inline transfomer.

I feel like you're misunderstanding what the OP is trying to do.

I'm assuming that the desired signal path is: Mic -> xlr to 1/4" cable -> guitar pedal -> instrument cable -> DI 1/4" input -> xlr cable from DI output to preamp.

[jaguarundi]

I feel like you're misunderstanding what the OP is trying to do.

I'm assuming that the desired signal path is: Mic -> xlr to 1/4" cable -> guitar pedal -> instrument cable -> DI 1/4" input -> xlr cable from DI output to preamp.

yeah, that's exactly right. what might have been confusing when I was first explaining was when I got no sound doing what you just laid out above, i tried just going:
mic -> xlr to 1/4" cable -> DI 1/4" input -> xlr cable from DI output to preamp

[ashcat_lt]

I feel like we'd ought to clarify a little bit so as to avoid the sowing of misinformation.

These numbers +4 and -10 have nothing at all to do with impedance. They are nominal operating levels. Basically, they denote where 0dbVU is for a given unit. They are measured on two different scales and are meaningless as relative values without conversion. They also both describe "line-level" signals. One is considered the professional standard, while the other is more often used for consumer gear.

Typical mic levels are significantly lower than either of these measures, the reason we have mic preamps. Instrument level would be that of a typical passive electric guitar, and what you're pedal likely expects to be working with. It is usually a bit higher than mic levels, but still less than any line level.

Yes, the inputs of gear designed to work with different operating levels do often have different impedance as well, but that's a separate issue.


For the OP, there's no reason your setup shouldn't work. It may not be optimal from a gain-staging perspective (mostly a noise issue). It's also possible that impedance mis-matches could impact your frequency response. It would probably be perfectly acceptable for applications that are not particularly critical or overly sensitive. You said it's worked before.

As others have said, it's likely that an active DI was not powered, and therefore not passing signal. Did you test the mic straight into the board's mic pre?

[jaguarundi]

As others have said, it's likely that an active DI was not powered, and therefore not passing signal. Did you test the mic straight into the board's mic pre?

yeah, mics going strait into the board worked fine, including that mic.

[Dan Kennedy]

I wonder if the problem was an XLR to 1/4" cable that was balanced, into a DI jack that wasn't?

That would float the ring connection, so the mic's output wouldn't go anywhere.

Only the tip and sleeve would connect, but that leaves the low side of the mic out unconnected. You might hear just a trace of very thin, very low signal.

[ott0bot]

Sorry wasn't trying to misinform. It was just explained to me poorly...and better to know better now that to deep on thinking another way. thanks for the info.

But basically am I right in thinking use an xlr to in-line transformer instead of the xlr-1/4" cable on the way into the guitar pedal. Then on the the way out you could go directly into the line input of the board avoiding the DI. Unless the board is too far away and you need to run it into an xlr stage snake....then you need the DI.

From my experience, and obviously limited knowledge of the whole impedence issue, I've found using a DI or the in-line transformer on the way into the guitar pedal to give you a much better sound with far less noise. I thought this was becase the impedence was being changed from a mic to line level signal. Not sure where the +4, -10 thing got thrown in there, becasue thats totally consumer/pro level differences. I guess I wasy typing faster than my brain thinks.

[ashcat_lt]

Yeah, I didn't figure you were deliberately trying to steer anybody wrong. I was hoping I might help you understand a little better. I purposely didn't go too far into it, you can google or check wiki or whatever if you want more in depth.

I'll say again, though, that impedance and level are seperate issues which are sometimes related. The "impedance matching" transformer probably also acts as a voltage step up, which might get the mic's output closer to the instrument level "expected" by the pedal, which will help with noise issues since you won't have to amplify the pedal's noise floor quite so much to get a usable line level. I still don't think the pedal's output will be quite up to what we like to call line level, so it's going to need some gain at the mixer anyway.

The DI actually probably steps the voltage back down closer to mic level, since it's being fed into a mic pre. It also presents (technically, reflects) a higher Z to the output of the pedal, but the pedal most certainly has plenty of current available, and could probably drive the mic pre just fine by itself. More important with the DI is that it balances the signal, which makes it much less susceptible to noise on its (usually fairly long) run to the board.

So, as I said before, the transformer you suggest will probably help noise a little (because the voltage step-up), and might help frequency response (because of Z matching). Lack of a transformer won't stop signal from flowing, though. He should be getting something, even if it's not the cleanest possible signal.

The best solution to this problem is to run the mic down the XLR snake and put a delay unit which is meant for balanced line-level signals in an effects loop at the board. If you must have the unit on stage, you could run the balanced Send and Return on the snake.