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Double Bass DI question: mic level versus line level

Chris Fitzgerald

Chris Fitzgerald

Student of Life
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Oct 19, 2000
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Louisville, KY
www.chrisfitzgeraldmusic.com
#1
I've been playing a nice steady gig the past couple of months where they have a decent FOH system in the club. One issue the bass players are having is that the DI signals from the bass amps (PJB Super Flightcase and AI Focus) seem to be too hot - even with the controls on the board all the way down, they are spiking the meters. One guy at the club said that the reason was that the XLR DI is sending a line level signal, but it's being plugged into a mic input on the board with the other end of the XLR cable, which makes sense (It's a Mackie board, I think). I'd like to remedy the issue. Should I be looking at an XLR buffer of some sort, or try to use the line out of my amp instead? If there was a simple XLR buffer for this, it would probably be easier and cleaner from a wiring standpoint.

In case it matters, [Invalid or Expired Link Removed] a link to the manual of the PJB amp. It's a little too technical for me to grasp whether what the guy in the club said is likely to be the answer or not. Any/all help appreciated. :)
 
#2
Several companies make a pad that goes on the xlr line...in -10, -20, -30 db cut. Fairly inexpensive and easy to carry for these situations. I regularly used one with my SWR SM-400 and have found it useful for the Clarus, too.

Here's an example:

Invalid Link Removed
 
#3
I'll assume the board's input trim is set fully CCW and the rig is still clipping it? Does backing off the PJ's input level (far left) and/or EQ settings have any effect on signal strength? It should as the DI rolls in post-EQ (per schematic) and pre-master volume.

Riis
 
#5
Zooberwerx said:
I'll assume the board's input trim is set fully CCW and the rig is still clipping it? Does backing off the PJ's input level (far left) and/or EQ settings have any effect on signal strength? It should as the DI rolls in post-EQ (per schematic) and pre-master volume.

Riis
Click to expand...

Turning the input volume down does lessen the signal, but it also affects the onstage sound quality, so I'm trying to deal with the issue on the DI end. One of the nice things about the PJB combos is the ability to control the "directness" or "solidity" of the tone by where the input volume control is set. In a noisy club like this one (the clientele are loud the first 2 sets), it's best to set the input volume to where the clip light comes on occasionally and then back it slightly off. On a more ambient gig, I could get away with a more subtle input setting.
 
#8
Brent Nussey said:
Hi Chris.

What you want to do is bypass the mic preamp. On a Mackie board, this is easiest done by picking up an XLR to 1/4" TRS cable, and plugging into the line input. The channel strip, trim pot etc, will still work the same, just at an appropriate level.

Quick search turns up this one:

http://www.5150musicsupply.com/5150_XLR_Female_to_1_4_TRS_Microphone_Cable_p/4xlrftrs.htm
Click to expand...

+1 on the adapter
Also If your fx send is available you can take it to a DI and send it to any mixer, you should'nt plug your Bass directly to the DI, the input impedance is usually not enough
 
#9
The manual states that the balanced output (out 1 on the back) is not adjustable by the volume control. The signal probably is quite high on that output and, thus, not easy to control on the board.

The manual is not clear about whether outputs 3 and 4 can be controlled by the volume adjustment. If they are controlled by the master volume then they can be adjusted downward to avoid clipping at the mixing board. However, if they are controlled by the master volume you might lose sound onstage by adjusting downward.

An alternative is to take a line out from FX Send (out 3 on the front) which probably is a lower level preamp signal. You can adjust the preamp level to avoid clipping at the board and then adjust master volume to maintain the proper sound level onstage. I use the FX out (preamp out) on a walter woods amp for this purpose because the balanced output on the woods amp is controlled by master volume and is, consequently, a hot signal for a PA system.
 
#12
fingers said:
Guys. You are thinking too hard.
Click to expand...

Really? So you think that buying a $5 adaptor so that you can plug your line level device into the correct input is more complicated than taking that line level output and plugging it into a cheap direct box (but still 35 bucks, right?) to pad down the signal to mic level, so that you can then plug it into a mic preamp and reamplify the signal? In addition to being unnecessarily complicated, it will certainly be noisier.

This kind of adaptor is a simple fact of life when you're using the less expensive brand mixers. Nothing esoteric.

Marc, forgive me, I don't mean to be grumpy, but to be told I'm overthinking it.... I usually find a little thinking is a good thing.
 
#15
fingers said:
Just seems a little Rube Goldberg. A direct box will be more useful in the long run IMHO.
Click to expand...

Brent's right. The simplest solution, in this case, as is often the case, is the correct solution.

The house sound man is knowingly running a line level signal into a mic preamp on HIS console. That's a no-no. He should know that and not hold the musicians-du-jour responsible for solving HIS problem. He needs to plug into a line level input on his console. Most "semi-pro" consoles (small Mackies) have that option (XLR mic pre AND 1/4" line inputs) on board. If his snake coming to the console has all XLR connectors (which it likely does) and he needs to plug into a 1/4" input on his console rather than the XLR mic preamp, then HE needs an adaptor; The adaptor Brent's talking about.
 
#16
Chris Fitzgerald said:
Turning the input volume down does lessen the signal, but it also affects the onstage sound quality, so I'm trying to deal with the issue on the DI end. One of the nice things about the PJB combos is the ability to control the "directness" or "solidity" of the tone by where the input volume control is set. In a noisy club like this one (the clientele are loud the first 2 sets), it's best to set the input volume to where the clip light comes on occasionally and then back it slightly off. On a more ambient gig, I could get away with a more subtle input setting.
Click to expand...

Makes sense. I'll have to go with tornadobass's suggestion: XLR pads.

Riis
 
#18
Dang, you guys are good! I'll try the XLR-1/4 thing first, since what the guy at the club said sounds related to converting line-level output to a connector that will connect with the line in on the board. If that doesn't do it, then I'll think about pads and/or direct boxes. Thanks, guys... more when the shopping is done.
 
#19
Will the adapter cause a hum problem, since the adapter is a balanced Tip-ring-sleeve to XLR and the typical line out from an amp is unbalanced tip-sleeve only? A different scenario here is the Euphonic Audio Micro's line out that is balanced and works fine with the adapter.
 
#20
Brent Nussey said:
Hi Chris.

What you want to do is bypass the mic preamp. On a Mackie board, this is easiest done by picking up an XLR to 1/4" TRS cable, and plugging into the line input. The channel strip, trim pot etc, will still work the same, just at an appropriate level.

Quick search turns up this one:

http://www.5150musicsupply.com/5150_XLR_Female_to_1_4_TRS_Microphone_Cable_p/4xlrftrs.htm
Click to expand...

+1 on this. Using the adapter into the line input keeps the signal unaltered. If you use a direct box you are lowering the signal and then the console pre pulls the level back up. = More noise and less pure signal.

Option #2: If there is a snake, it usually has at least 4-1/4" inputs (female) with the same number of male connectors on the console side. Just use a guitar cable to go from the amp out to the 1/4" in on the snake box. If the line in is balanced, the sleeve on the 1/4" will automatically short the low side to ground.
 

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