Exceeding voltage limit on mixer input when using DI

[Pbassman]

I am wanting to send a post-EQ signal to the mixer via DI.

The mixer is a Presonus 16-channel unpowered mixer. It has a maximum input voltage of 4v according to its owner.

My current combo is a Roland D-Bass 210 which sends a signal pre-EQ. I had to use my Behringer 1200X as a sub the other week, which sends the signal post-EQ, with no problems. The owner checked the input with a voltmeter and found, 'in certain circumstances', the voltage could reach 20v.

I am looking to change my kit and rather fancy a Mark Bass MB58R Little Mark amp which has a selection of Pre- or Post-EQ, as well as a Line Out control which can dial back (or up) the voltage through the DI. The Little Mark has 20Vpp (maximum peak of 10v).

I want to be sure that the voltage sent to the mixer can be dialled back to ensure that the 4v input limit is not exceeded when using the Post-EQ setting.

Any advice, experience is appreciated.

Thanks

[BassmanPaul]

Turn down the bass itself to avoid clipping. Nothing needs to be cranked full on for a recording. You could also just go Direct into a mixer channel.

 

[Downunderwonder]

Start with it at minimum every time until you learn where it needs to be. Then start with it at the minimum every time because if it ever accidentally got bumped up to 20v in transit it's going to do damage. 

[Jack]

That amp seems to have 6 outputs on the back, which were you using? 

 

For the future, with your markbass, just use the normal di output and it should be fine with nearly all mixers. If it ever is too loud then use the pad on the mixer. 

Edited February 4 by Jack

[Pbassman]

Thanks all.

The in-built Mark Bass DI unit seems to have a very good reputation - a proper DI box, so with a little test session we should be able to gauge the required level.

This will be used for the live performances, and the Behringer has happily been used in our rehearsals, via DI, so I reckon the settings I use are nowhere near peak output.

It's not my Presonus so I want to be sure.

[Pbassman]

Update: bought the Little Mark head and tested it through a voltmeter - Presonus Studio 16 mic inputs have 3v max and happiest with mic level voltage (miniscule voltage). However, the test showed the MB peak volume quoted of 10v is with everything cranked up and the Line Out control really did lower the output to well below the mixer tolerances (to avoid distortion). However, we are going belt and braces by using the DI Line Out XLR output into the Presonus Line In input, via TS jack, which has a higher tolerance.

The main issue was, even though the f-o-h sound was ok, the output to the in-ears was distorting. This solution worked well in rehearsal with my practice Behringer combo (which sends post-EQ with high peaks) - no issues at all.

(Just the fan seems noisy).

[Dan Dare]

 

On 03/02/2024 at 19:05, BassmanPaul said:

Turn down the bass itself to avoid clipping. Nothing needs to be cranked full on for a recording. You could also just go Direct into a mixer channel.

 

Good advice. The input gain on your mixer is your friend. There's usually a switchable pad, too, as stated above. Line level is often marked on the input gain pot to give you a starting point when running line level signals in. If you use a DI box or DI out on an amp, the signal will be stepped down to mic level. DI box transformers are usually around 12:1 and many have switchable pads to attenuate the input signal further. You normally only need those for keyboards, unless you have an active instrument that gives a very hot signal.

 

On the mixer, you should start with the input gain at minimum, set the channel fader to unity/0db and switch in PFL for the channel. Bring up the input gain slowly and you can monitor the level on the meters. If the signal is too hot with the input gain at minimum, switch in the pad.

[agedhorse]

On the Presonus boards they use 2 separate inputs (mic and line). By the spec sheet for the Studio Live 16, the input clip point with the trim control at unity is +12dBu and rotating it counter-clockwise from unity increases the input clip point by 15dB to +27dBu which is 17 Volts RMS and 48 Volts P-P. I believe this is an error in the manual because it exceeds the power supply rails.

 

This is complicated a little bit because the signal block diagram doesn't match the console silk screen values, but even using the -6dB from unity headroom yields +18dBu which is 14dB of headroom on a +4 nominal signal. +18dBu is 6V RMS and 17V P-P

 

Note that it's important not to throw numbers around without understanding the units. Peak, P-P and RMS are all differentfro the same signal.

 

I don't see how you can overdrive the input if you are using the board properly.