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Eric
May 28th, 2010, 08:12 AM
Hi all. Question for the electronics people here...

My question revolves around going DI into the sound board and the resulting levels.

I've tried going guitar -> pedal -> DI box -> FOH a couple of times at church, and the result is usually wicked-low input levels. From my understanding, all the DI box does is drop the impedance to line level (or other levels if you have the attenuation pad) and give you a balanced output. However, you still need to get the right signal level, correct?

Is this low-signal issue really a matter of voltage? If so, how do you correct it? Wouldn't you need some sort of transformer to get it to the right voltage? Would a headphone amp in between the pedal and DI box help to bring it up to the right level? That's my current idea, but I'd like to know what I'm doing wrong.

Spudman
May 28th, 2010, 09:06 AM
Is the DI you have active or passive? If it's active you need to supply phantom power to it to get proper levels out of it. If passive then your channel input gain on the mixer will determine how much signal you get into the board.

Eric
May 28th, 2010, 09:45 AM
Is the DI you have active or passive? If it's active you need to supply phantom power to it to get proper levels out of it. If passive then your channel input gain on the mixer will determine how much signal you get into the board.
It's passive, but the gain needs to be pretty high to get a decent level out of it.

Spudman
May 28th, 2010, 04:32 PM
Try another device into the DI and see what level of signal you get then. It might be that your guitar/pedal combo doesn't have enough output - or -the DI is bad.

Eric
May 28th, 2010, 04:38 PM
Try another device into the DI and see what level of signal you get then. It might be that your guitar/pedal combo doesn't have enough output - or -the DI is bad.
After some reading on impedance, I think I'm going to read up on the mixer and see if there's a hi Z phone input for that channel, since my theory is that going line level (lo Z) to XLR in (probably lo Z) might be sucking some of the voltage.

BUT...I might try some of the troubleshooting mentioned above too. Thanks for the input.

thearabianmage
May 28th, 2010, 05:01 PM
Marshall stack = problem solved ;) :D

markb
May 28th, 2010, 05:17 PM
You're feeding a passive DI box designed for line levels =~1V with an instrument signal much lower. Some kind of preamp would be useful, maybe your GT2 would get the levels up. Either of your multi effects would handle it but you'd need to use the headphone output on the ME50 or crank the output level on the Digitech if you use those. Plugging into a high impedance input just gets you into problems of signal loss unless you're using short cables.

Eric
May 28th, 2010, 07:30 PM
You're feeding a passive DI box designed for line levels =~1V with an instrument signal much lower. Some kind of preamp would be useful, maybe your GT2 would get the levels up. Either of your multi effects would handle it but you'd need to use the headphone output on the ME50 or crank the output level on the Digitech if you use those. Plugging into a high impedance input just gets you into problems of signal loss unless you're using short cables.
Hmm. My current idea is to use the Behringer headphone amp as a booster before the DI box to give it a little more juice, maybe even taking one of the other headphone channels as a personal monitor, provided I can still hear the band mix from the monitors. I have been using the GT2 before the DI box as my 'amp in a box', but everything on that had to be absolutely cranked to get the signal within normal operating ranges in the mixer.

I think you are addressing my real question here, which is how voltages and signal strength are related. My understanding of line level was that it had mostly to do with a low impedance signal, but I did a brief search after I read this and it seems like there is a 1V reference voltage for line level, so I see your point. I take it a preamp serves to mostly increase the voltage then?

One last point/question: I thought a DI box was more or less a transformer, which I thought was really just a voltage changer. Why must voltage be addressed separately before the DI box?

Thanks for all of the info.

Eric
May 28th, 2010, 07:32 PM
You're feeding a passive DI box designed for line levels =~1V with an instrument signal much lower. Some kind of preamp would be useful, maybe your GT2 would get the levels up. Either of your multi effects would handle it but you'd need to use the headphone output on the ME50 or crank the output level on the Digitech if you use those. Plugging into a high impedance input just gets you into problems of signal loss unless you're using short cables.
FWIW, the sound guy says he gets a very low signal from the TM60 as well (I've been using that lately, going XLR out -> FOH), which I thought was very odd. I think that's a separate question really, but figured I would mention it.

BigJD
May 29th, 2010, 12:44 PM
Kinda wondering if there is a pad on the mixer channel that you are feeding?
Usually you wouldn't have that kind of problem.
Do you know what the mixer is?
Most common levels to the board are -4db or +10db.
If your gain stucture on the board is correct on the channel strip your feeding you should be able to get a good clean signal and let the PA work at putting out you carefully sculptured tone.
Like I said before most mixers should be able to handle whatever signal is given to them. The channel strip is all the preamp you should need after a DI.
Make sure your DI doesn't have a switch on it too.Some do for level matching.

Eric
May 29th, 2010, 01:14 PM
Kinda wondering if there is a pad on the mixer channel that you are feeding?
Usually you wouldn't have that kind of problem.
Do you know what the mixer is?
Most common levels to the board are -4db or +10db.
If your gain stucture on the board is correct on the channel strip your feeding you should be able to get a good clean signal and let the PA work at putting out you carefully sculptured tone.
Like I said before most mixers should be able to handle whatever signal is given to them. The channel strip is all the preamp you should need after a DI.
Make sure your DI doesn't have a switch on it too.Some do for level matching.
I think it's a Mackie SR32-4 mixer.

It's an ART DI with some attenuation pads on it when I use the pedal -> DI box -> mixer, but I don't use a DI box when I use the amp. I just do XLR out on amp -> digital snake, which goes right to the mixer.

BigJD
May 29th, 2010, 01:38 PM
I think it's a Mackie SR32-4 mixer.

It's an ART DI with some attenuation pads on it when I use the pedal -> DI box -> mixer, but I don't use a DI box when I use the amp. I just do XLR out on amp -> digital snake, which goes right to the mixer.
I would tell you not to use the XLR's on the amp,put a SM57 in front of it.
I like miked amps.
As far as the DI is concerned,you should be able to match it to what the mixer wants to see pretty easily.
Like I said before it sounds more to me like a problem the your channel strip on the board.Theres a pad or something engaged that is cutting your signal off.
Whats the model on that ART DI? I'll google it and your board and get a quick education on them.

Eric
May 29th, 2010, 02:19 PM
Whats the model on that ART DI? I'll google it and your board and get a quick education on them.
I think it's this one:

ART ARTcessories Zdirect Professional Passive Direct Box (http://pro-audio.musiciansfriend.com/product/ART-ARTcessories-Zdirect-Professional-Passive-Direct-Box?sku=180635)

markb
May 29th, 2010, 04:41 PM
I would tell you not to use the XLR's on the amp,put a SM57 in front of it.
I like miked amps.
...

I like miked amps too but I suspect you've never used the DI on a Tech21 amp. You can put a '57 in front of the speaker if you like but it'll sound about the same and it's just one more thing to trip over on a crowded stage. The internal DI box is speaker and mic emulated. The only problem I've ever had is that the connector isn't exactly top notch and some XLRs are a bad fit.

A pad somewhere is a very sensible suggestion.

BigJD
May 29th, 2010, 07:35 PM
I like miked amps too but I suspect you've never used the DI on a Tech21 amp. You can put a '57 in front of the speaker if you like but it'll sound about the same and it's just one more thing to trip over on a crowded stage. The internal DI box is speaker and mic emulated. The only problem I've ever had is that the connector isn't exactly top notch and some XLRs are a bad fit.

A pad somewhere is a very sensible suggestion.
You are completely correct.I have not used a tech21 amp or DI.
My bass player uses one of their floor units and it seems pretty well made.

BigJD
May 29th, 2010, 08:01 PM
I think it's this one:

ART ARTcessories Zdirect Professional Passive Direct Box (http://pro-audio.musiciansfriend.com/product/ART-ARTcessories-Zdirect-Professional-Passive-Direct-Box?sku=180635)


Geez they sure don't give up much info on that unit.
But if I was to believe anything about it it seems that it is very much an entry level unit.
If it were me I would probably see if there was anybody about that had a better quality unit to try.
As talked about before I believe its a problem on the mixer end.

Eric
May 29th, 2010, 08:14 PM
As talked about before I believe its a problem on the mixer end.
Well that does help me a good bit as far as troubleshooting is concerned, so I appreciate the input. If I manage to make any headway, I'll update with the results.

Thanks everyone for the help!

Eric
May 30th, 2010, 10:28 PM
Conclusions from today:

1) After we were done playing, I hooked up the pedal-only rig with my friend (the drummer, who I usually discuss this stuff with) with the Behringer HA-400 headphone amp. Everything seemed to be in range, though I never did bother trying it without the headphone amp. Anyway, apparently problem solved.

2) There doesn't really seem to be a pad on the mixer itself. We use two digital snakes to get the inputs up to the board, and it's all bridged connections impedance-wise (we checked). The snake outputs in the sound booth are going to the phone plugs in the mixer, so that takes care of that.

3) There is both a pad and preamp gain (and phantom power) options on the digital snake, accessible from the optional remote. For the guitar channel in question, the pad was not engaged, but there was also no additional gain on that channel. If needed, I think we could use that gain from the snake (which does the preamplification for all channels) to boost the signal.

So yeah, the headphone amp/booster did the trick. I'll keep that in mind for the future. Even something like a Bad Monkey, which seems to have a ridiculous amount of available preamp volume in it, might be a decent workaround if I had the drive on it close to zero.

I think I'll try my ampless setup as option 1 next time and bring my amp just in case. Thanks for all of your help!

guitardan777
June 22nd, 2010, 11:18 AM
A few suggestions:

To see if your pedal rig is putting out enough signal, just plug it in w/ a short guitar cable directly to the mixer (no snake, no cables over 25 ft.)
If the signal level is fine then the problem lies in the 'Line Loss' from trying to run it throught the snake / or cables longer than 25'.
If the signal level is still too low, then you'll need a device like a line driver or clean booster to get the signal up.

Impeadance matching is most important when running a long line or though a snake. Your pedals are a HiZ out. So if you want to run it through a snake w/ or w/out a DI, LoZ is the way to run to the board. You can get Hi to Lo Z adapters for both ends. Or just one to convert the pedal(s) output to LoZ and use the XLR LoZ in at the board.

Eric
June 22nd, 2010, 11:25 AM
A few suggestions:

To see if your pedal rig is putting out enough signal, just plug it in w/ a short guitar cable directly to the mixer (no snake, no cables over 25 ft.)
If the signal level is fine then the problem lies in the 'Line Loss' from trying to run it throught the snake / or cables longer than 25'.
If the signal level is still too low, then you'll need a device like a line driver or clean booster to get the signal up.

Impeadance matching is most important when running a long line or though a snake. Your pedals are a HiZ out. So if you want to run it through a snake w/ or w/out a DI, LoZ is the way to run to the board. You can get Hi to Lo Z adapters for both ends. Or just one to convert the pedal(s) output to LoZ and use the XLR LoZ in at the board.
I'll check out the mixer direct-input thing. Good idea.

For the impedance part, I was going through a DI box before the snake, which should drop it down to balanced LoZ, then the snake input was HiZ. I checked to make sure all other connections were similarly bridged connections (LoZ -> HiZ), and I'm pretty sure they were, so the voltage (i.e. signal) should have been preserved.

In the end, I gave up and will keep dragging my monitor in the immediate future. We're just not set up with proper monitoring capability to do ampless just yet. It would be fighting a major uphill battle at present. Still, a good chance to learn. Thanks for the ideas.

guitardan777
June 22nd, 2010, 03:09 PM
Does the DI have an XLR out or is it a 1/4" balanced?
If its 1/4" balanced it will have a TRS type of jack. (Tip Ring Sleve) which looks like a stereo plug or jack. If that's the case, then you can just use a converter cable or plug to mate it up w/ the XLR input on the snake.

HiZ & LoZ are really the spec of a devices input or output.
So you could run a LoZ output through a snakes 1/4" jack, but at the other end (mixer) that would have to go though gender bender to connect back to an XLR LoZ input. They do make a TRS to XLR adapter / cable that may be the easiest way to connect it up right.

See: http://accessories.musiciansfriend.com/product/Horizon-XLRTRS-Cable?sku=336971

Or: http://accessories.musiciansfriend.com/product/American-Recorder-Technologies-XLR-Male-to-14-Male-Stereo-Adapter?sku=339519

It's all about the impeadance matching or you'll definatly knock your signal down to un-usable levels.

Eric
June 22nd, 2010, 03:17 PM
Does the DI have an XLR out or is it a 1/4" balanced?
If its 1/4" balanced it will have a TRS type of jack. (Tip Ring Sleve) which looks like a stereo plug or jack. If that's the case, then you can just use a converter cable or plug to mate it up w/ the XLR input on the snake.

HiZ & LoZ are really the spec of a devices input or output.
So you could run a LoZ output through a snakes HiZ or 1/4" jack, but at the other end (mixer) that would have to go though gender bender to connect back to an XLR LoZ input.

It's all about the impeadance matching or you'll definatly knock your signal down to un-usable levels.
The DI is 1/4" input, XLR low-impedance, balanced output. I go from that into a high-impedance XLR input on the snake. The other end of the snake (in the sound booth) has a low-impedance output, and is plugged in via 1/4" connector to a high-impedance input on the mixer.

From what I've read, this is not actually "impedance matching", but rather a "bridged connection". Impedance matching involves having the same impedance values for both source and load, which results in maximum power/current transfer, but minimal (virtually zero if my estimates are correct) voltage transfer. In the age of line level and reamplification, pretty much everything is bridged.

I could be wrong on that second paragraph, but what I've read and my current understanding leads me to that conclusion.

guitardan777
June 22nd, 2010, 03:26 PM
The DI is 1/4" input, XLR low-impedance, balanced output. I go from that into a high-impedance XLR input on the snake. The other end of the snake (in the sound booth) has a low-impedance output, and is plugged in via 1/4" connector to a high-impedance input on the mixer.


The DI's XLR output is LoZ, the snake has 'No Z' just connections and wire.
The output end of the snake in the sound booth should just go to an XLR mic input and your done !!
But you are converting it to a 1/4" and plugging it into the HiZ in on the board. This is where your mis-match is. If you need to plug it into a HiZ in, then you need a 'matching transformer' to convert it to HiZ.

Something like this: http://accessories.musiciansfriend.com/product/Audix-T50K-Inline-Impedance-Matching-Transformer?sku=330710

Eric
June 23rd, 2010, 05:33 AM
The DI's XLR output is LoZ, the snake has 'No Z' just connections and wire.
The output end of the snake in the sound booth should just go to an XLR mic input and your done !!
But you are converting it to a 1/4" and plugging it into the HiZ in on the board. This is where your mis-match is. If you need to plug it into a HiZ in, then you need a 'matching transformer' to convert it to HiZ.

Something like this: http://accessories.musiciansfriend.com/product/Audix-T50K-Inline-Impedance-Matching-Transformer?sku=330710
We have this:

http://www.roland.com/products/en/S-0816/index.html

I thought I read in the manual for it that it had HiZ inputs and LoZ outputs, but maybe I'm wrong.

guitardan777
June 23rd, 2010, 07:48 AM
Okay maybe I missed it early on, didn't realize you are using a 'Digital Snake'

Skimming through the manual, I see that there is a gain adjustment available for each channel. Have you palyed around w/ that to try to optimize your signal?

This is copied out of the manual, and it tells me that you still treat the inputs and outputs with respect to the device's (Instrument & Mixer) impeadance.

To connect unbalanced sources:

• use a direct box—such as the BOSS DI-1—or balancing adaptor in-line
—or—
• a cable adaptor with the following wiring: fig.6-27.eps

To connect high-impedance sources—such as the output of an electric guitar or bass with passive pickups—use a direct box or impedance-matching tansformer in-line.

When connecting unbalanced sources that require long cable runs (over 6 meters), a direct box or balancing adaptor placed in-line near the source is recommended for the best audio quality and noise rejection.

You are using a DI with an XLR LoZ output. So your stage setup should be fine. Check the gain on the snake channel and make sure you are matching the LoZ output of the snake to the input of the mixer. (hi or Lo)

Eric
June 23rd, 2010, 07:59 AM
Okay maybe I missed it early on, didn't realize you are using a 'Digital Snake'

Skimming through the manual, I see that there is a gain adjustment available for each channel. Have you palyed around w/ that to try to optimize your signal?

This is copied out of the manual, and it tells me that you still treat the inputs and outputs with respect to the device's (Instrument & Mixer) impeadance.

To connect unbalanced sources:

• use a direct box—such as the BOSS DI-1—or balancing adaptor in-line
—or—
• a cable adaptor with the following wiring: fig.6-27.eps

To connect high-impedance sources—such as the output of an electric guitar or bass with passive pickups—use a direct box or impedance-matching tansformer in-line.

When connecting unbalanced sources that require long cable runs (over 6 meters), a direct box or balancing adaptor placed in-line near the source is recommended for the best audio quality and noise rejection.

You are using a DI with an XLR LoZ output. So your stage setup should be fine. Check the gain on the snake channel and make sure you are matching the LoZ output of the snake to the input of the mixer. (hi or Lo)
Upping the gain on the snake was going to be my next attempt. Because we swap out guitar players from week to week, it means that someone else might be using that same input, so I wanted to see if I could resolve it completely on my end, but point taken.

As I mentioned a couple of posts back, I'm putting this whole concept on the back burner a little bit until the church gets either a) enough wedges to allow for no amp or b) some in-ear monitors. It's just too hard to try to do it by myself with no regular sound person, unfortunately.

Still, thanks very much for the help.