How to correctly hook into a DI Box?

Ben Turner · From: Myrtle Beach, SC, USA (deceased)

I've been running the DI next to last, last in the chain being the amp (Webb 614-E, no bal/unbal line out) So basically I'm running the Guitar > Hilton VP > SKB PS-45 Pedal Board > Passive DI Box > Webb 614E Input - Anyhow, some places we play it sounds wonderful without any problems and other places I get a loud hiss or screeching from the PA even when the VP is in the off position, and also sometimes the signal is really weak and the sound guys have to almost max out the gain at the board to get a "decent" signal. Anyhow, am I running it in the wrong position in the loop and if so where should it be? I thought about trying it before the pedal board right after the VP. Any help is appreciated. Thanks Very Happy

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Benjamin Turner

Victor Gillett · From: Boise, Idaho, USA

Are you running parallel out of the DI to the board and the amp? Or using the DI to alter the impedance of your signal into the amp? If it's going to the board, sometimes a ground lift will solve the problem.

Also, if the DI is passive, make sure there isn't a pad on the output.

Phantom power (+48v) across every channel on a mixing desk can also cause problems with some DI's.

Maybe the fact that the FOH guy has to max the channel out is causing the noise? Could be their issue...or a funky channel.

I would assume that if the problem was anywhere before the DI, it'd be coming out of your amp as well as the mains/monitors...supposing that it is in parallel with two outputs from the DI.

-VWG Smile

Ben Turner · From: Myrtle Beach, SC, USA (deceased)

To answer a few of those questions, ground lift stays in the on position, with it off the sound through the PA is nothing but static. It is passive but no pad. To my knowledge there is no phantom being used on anything on stage, the engineer has to (nearly) max out the gain on my channel because the amp/DI isn't sending a strong enough signal. As I said above I'm running from my AMP's input directly into the DI box and from the DI box directly into my pedal board, from the pedal board to my volume pedal and so fourth. I reckon what I'm asking is run the DI box pre or post effects? The amp has no line output and the sound guy/guys have tried mic'ing me before without much luck, I get a clearer stronger signal through the DI but just can't figure out where the static is coming from.
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Benjamin Turner

Lynn Oliver · From: Redmond, Washington USA * R.I.P.

My guess is that your good and bad results depend on what the DI box is feeding.

A typical passive DI has a 1/4" input jack, a second 1/4" jack wired in parallel to use as a passthrough, and an XLR output jack. The input is high impedance and is connected to a transformer that converts it to low impedance at the XLR.

The low impedance output should be connected to a microphone input on the mixer. The signal level is too low to connect to a line input, and if you try you'll have to max out the gain--and that could cause the problems you describe.

Normally the DI should be hooked up just before your amp: take the cable that normally goes to your amp and plug it into one 1/4" jack; take a second cable and connect the other 1/4" jack, and run it to your amp. Connect a mic cable from the XLR out to the mixer.

If you want your effects to go to the amp but not to the PA, then you will need to insert the DI earlier in the chain, just before the effects that you don't want in the PA.

So, the first thing I'd do is make sure you are plugged into a mic input on the mixer and that it has not been configured for line level signals.

Ben Turner · From: Myrtle Beach, SC, USA (deceased)

Lynn, I am hooked up exactly as you describe. just before the amp with an XLR running to the snake. So basically that clarifies that I've done everything right on my end and seeing as how it sounds wonderful through my amp there is a problem on the engineer's side.
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Benjamin Turner

Lynn Oliver · From: Redmond, Washington USA * R.I.P.

Sure seems that way.

Dave Grafe · From: Hudson River Valley NY

Sounds like a real puzzler, Ben, but it's not too hard to be smarter than the gear and thus prevail.

If you want the PA to get the same sound from the DI that your amp is getting (and why wouldn't you?) then you will want to hook up the DI post-effects like this:

Guitar > VP > Effects Pedals > DI 1/4" IN / DI 1/4" OUT > Amp Input, connecting the DI XLR OUT to the Mixer Input via XLR mic cable.

From your first post I understand that this is what you are already doing. If not then stop everything and hook it up this way before proceeding.

The squealing you describe sounds like one of several things. It is possible that the input gain on the mixer channel is cranked wide open and the mixer is unstable enough for this to cause internal feedback because either (1) you are running your VP nearly off most of the time (which I doubt), (2) there is a bad guitar cable (or two) in the line somewhere (easily likely), (3) there is a bad microphone cable between the DI and the mixer (also common) or (4) that the DI itself is defective in some way (not unheard of).

When you say the ground lift switch is "ON" do you mean the DI is grounded or lifted? The fact that you get "nothing but static" when the ground lift switch is in one position or the other again stringly suggests a gunny-sack DI or XLR mic cable or both. You have not given it a name or model so it is hard to deduce much more than this, but the only change you should ever hear when switching the ground lift is a modest buzz underneath your guitar signal in the "don't do it that way" position.

Try playing a known good acoustic guitar, bass or keyboard through the DI. If that works fine start going through your cords one at a time, being sure to wiggle each end of every cord before going on to the next one. If it sucks no matter what cables you use try a different DI.

Lastly, your second post mentions "running from my AMP's input directly into the DI box" which might indicate that you are plugging the guitar's signal chain into the amp and then using the second input jack on the amp to feed the DI. Since nearly all amps have an impedance matching resistor between the two "parallel" input jacks there would definitly be a major loss of signal in this case. Go back to the hookup listed at the top of this message.

Keep us posted and between us all we will help you lick this bugger!

Rich Hlaves · From: Wildomar, California, USA

Ben,

I do a lot of live sound mixing and it sounds like you may have a bad DI unit. The matching transformer has gone south. You have the unit in the correct place in the signal chain. It should be talking to the board quite well. After all the effects and with the volume pedal gassed up you shoud get a good signal at the board. Have you tried another direct box?

I use Radial Pro DIs for all my stage needs, mostly bass and keys, and have never had the issue you describe.

I also can't figure out why they can't mic you with good success. Shove a Shure SM57 in front of your cab(s) and you should be good to go.

Dave Grafe · From: Hudson River Valley NY

Yeah, what Rich said in so many fewer words than I did, but be sure and try a different, known good, mic cord Very Happy

Ben Turner · From: Myrtle Beach, SC, USA (deceased)

Dave, I'll clarify a few of those things you mentioned here. We have tried multiple DI boxes, the one I most commonly use is just an old Rapco I believe. I also tried a LEEM that didn't have a ground lift and stopped using it all together because of an awful hum. The ground stays lifted on the Rapco. We have also at the most recent gig last weekend tried different mic cables. no change. As far as the way it's hooked into the amp is just as Lynn described, I don't use both inputs just input #1 straight to the DI and so on.

I am using an SKB PS-45 and my pedals are patched directly into the pedal board. The pedal board is also marked "from guitar" and "to amp" which is where I have the DI patched in, on the "to amp" side. I don't know if this has any affect on things but that is the way it's supposed to be hooked up to my knowledge and reading the book the board came with.
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Benjamin Turner

Ben Turner · From: Myrtle Beach, SC, USA (deceased)

Larry Bell · From: Englewood, Florida

I really prefer for my full signal -- fx, amp, speaker and all -- to go to the PA. An SM-57 works just fine, but I've also plugged the DI between the amp and speaker. The Radial JDI has a Jensen transformer --AND-- VERY IMPORTANTLY -- a -15dB pad -- to attenuate the speaker level signal. It works well. BUT it requires one that pads down the signal.

Ben, I'm trying to figure out why your Webb can't just be mic'ed. As Dave suggests, the trim and gain on the board should be set correctly. Do you hear that rumble from the amp itself? Sounds like he's got the low end EQ cranked or something like that if you don't hear it where the mic is picking it up. It's gotta be coming from somewhere.
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Larry Bell - email: larry@larrybell.org - gigs - Home Page
My CD's: 'I've Got Friends in COLD Places' - 'Pedal Steel Guitar'
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Dave Grafe · From: Hudson River Valley NY

20 year old sound gear in the hands of someone who knows what they are doing will outperform most modern gear that you can buy at Guitar Center today so that's not the issue, unless it was crap gear 20 years ago (or it has been treated like crap since).

So you have established that it is not the DI or the cables, so it's starting to sound like operator error and I don't mean you.

One of the issues with using a DI for the PSG is that we generally do not run our post-VP signal as hot as what a keyboard or bass guitar might produce, which is why a 200 watt steel amp fully cranked is not usually going to sound as loud as a 200 watt bass or 60 watt guitar amp; inexperienced sound ops usually don't get what is going on and gripe every time they can't get it to behave like the other instruments - our actual signal level is in fact relatively low and that can easily confuse the clueless.

Personally I would recommend close-mic'ing with an SM57 or Sennheiser e609. Besides getting a better signal you will be capturing the sound that you hear from your amp, which could be quite different than the sound going into it. Any "low end rumble" is going to come from either a mic poorly placed (simply hanging a vocal mic or SM57 off the top of the cabinet will mostly pick up the noise on stage mixed in with a little bit of what your speaker is producing), a cheap mic and stand combination that transmits mechanical noise from the floor, a ridiculously loud bass amp or subwoofer very nearby, a clueless sound op who has the bass cranked up on the mixer channel or final mix output, or some combination of the above. Put a good directional mic on the amp, placed as close to as possible to AND POINTED AT the speaker, make certain that the mixer EQ starts out flat for that channel and if you have a problem roll off a little of the lows ONLY on that channel. Make sure your boy (or girl) genius is applying NO EQ BOOSTING of any kind, using the mixer EQ to reduce the sounds that are interfering with the tone and not trying to boost what you can't hear because of them. Of course in the real world you will have to pick your battles....

As I have noted elsewhere, I carry a cute 40-year-old Senn 409 mounted on a little collapsable table-top tripod (the kind sold for camcorders, etc.) that sits on the floor in front of my amp, puts the mic in the perfect place to sound totally bitchin' always. The Senn MD409 and e609 both have the advantage of being side-address mics and as such CAN be successfully hung off the top of the amp, provided you take a moment to ensure that the correct side of the mic is facing the speaker....

Larry has another idea that might work for you but if you choose to go this route BE ABSOLUTELY CERTAIN that you are using a DI or pad that is intended for handling the high power of the amp's output, especially if your tech is a dull crayon, and that there is no way that under heaven that anything could possibly short or reduce the impedance that the amp is facing - an incident like that could ruin your whole amp. A 15dB pad sounds like way to little to me, more like 35 to 50 dB maybe....

OK, next caller....

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