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Bass amp as bass monitor also hooked to mixer

Postby MaxTK » Wed Sep 04, 2019 7:33 am

Hi. I’m a rookie. I just bought my first mixer, MG16XU.

My bass guitarist would like to use his bass amp as monitor. Shall I:
Connect bass guitar to amp then amp to Aux 1 of mixer or
Connect amp to Aux 1 then bass to Aux 2 of mixer or
Are there better ways?

Thank you.
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Re: Bass amp as bass monitor also hooked to mixer

Postby Dr R » Wed Sep 04, 2019 8:32 am

Hi MaxTK,

Several questions:

Does the bass player want to hear a combination of his bass playing and the rest of the band from one speaker - ie his amp - rather than have a monitor for the band and his amp as well?
Does he currently plug his bass into the amp, then run a DI out from the amp to the desk, or do you mic up the amp?
What inputs and outputs are on his amp? What make/model is it?

Funilly enough I bought my bass practice amp a few weeks ago with just the first scenario in mind, though I've not used it that way yet. My amp has a DI out and also an aux/line in so you can play along to practice tracks. But handilly the DI output is only the bass guitar signal post eq, which means I could take a monitor input onto the aux, ahear that and the guitar through the bass cab, and sent a clean DI signal back to the desk.

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Re: Bass amp as bass monitor also hooked to mixer

Postby MaxTK » Wed Sep 04, 2019 11:11 am

We currently use one single powered speaker as floor monitor for vocals and instruments. So his bass guitar is connected to the mixer as all other instruments. His problem is he couldn’t make out the sound of the bass from everything else’s from the floor monitor. So we want to try out to use his amp as his own monitor so that it will give out loud bass sound but little everything else. In effect, the band will now have two monitors - his and for the rest.
What’s the best way to go about it?

His bass amp is:

https://shop.fender.com/en-AU/bass-ampl ... l?rl=en_US

My mixer is a MG16XU
https://au.yamaha.com/en/products/proau ... index.html
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Re: Bass amp as bass monitor also hooked to mixer

Postby ef37a » Wed Sep 04, 2019 11:47 am

The Rumble 40 has a balanced XLR line output and that is probably the best way to go with the bass player just getting himself from the amp.

The line out seems to be post everything including the master volume pot which could be a problem. If so the FX out is just post pre amp gain and EQ so once they are set the player can choose his final volume without altering the send level.

However, unlike the XLR out, FX send does not have an earth lift so a DI box might be needed?

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Re: Bass amp as bass monitor also hooked to mixer

Postby Dr R » Wed Sep 04, 2019 12:07 pm

Are you saying the XLR output on the rumble is post master volume? Seems a bit unusual, on my EBS60 (which is an equivalent to the rumble) it's after gain & eq, but before Aux-in and volume, and on the other amps I've used it's post Gain and pre-volume. I didn't see a circuit diagram anywhere.

As Dave says, the first option might be to just try the bass player having his amp, sending the DI out from that to the mixer, and not changing anything else at all. (Except don't send any bass back to the existing floor monitor). If the bass player keeps his volume under control that might be enough, though it will depend on if the DI out relates to his volume pot or just the dialed in Gain.

If you then want to send a second Aux back from the desk to the aux-in on his amp, then we'll need to confirm the amp wiring.

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Re: Bass amp as bass monitor also hooked to mixer

Postby ef37a » Wed Sep 04, 2019 12:29 pm

Yes Doc, according to p25 of the manual the block diagram (why don't ALL audio co's do these?) the line out is picked off at the PA input and goes throught a speaker emulator circuit then an op amp for a Z balanced out.

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Re: Bass amp as bass monitor also hooked to mixer

Postby MaxTK » Wed Sep 04, 2019 1:16 pm

If I connect the bass guitar to the mixer then connect it back via Aux2 of mixer to aux-in of amp, would that work or would it do any damage?
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Re: Bass amp as bass monitor also hooked to mixer

Postby Dr R » Wed Sep 04, 2019 1:59 pm

https://1drv.ms/u/s!AlkBnkq6PtCug_wam6NzvjcMzUPrAA
Link to circuit diagram.
There's no FX loop on the Rumble 40, and it looks like the aux-in is also fed to the DI and power amp.

If you connect the bass guitar to the mixer without using the amp, and then send aux2 of the mixer to the amp, then you're fine.
If you connect the DI of the amp to the mixer, and then feed aux2 from the mixer back to the amp, then if I've read the diagram correctly then it will cause a problem as you'll get positive feedback round the circuit.

Dave is far better at electronics than I ever was or will be, so I'd take his advice!
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Re: Bass amp as bass monitor also hooked to mixer

Postby Music Wolf » Wed Sep 04, 2019 2:13 pm

ef37a wrote:Yes Doc, according to p25 of the manual the block diagram (why don't ALL audio co's do these?) the line out is picked off at the PA input and goes throught a speaker emulator circuit then an op amp for a Z balanced out.

Dave.

Typical Engineer reading all the way to page 25 :D . As a Physicist my natural inclination was to find out how it worked by smashing two Rumbles together at close to light speed and then looking at what bits flew off, however, on this occasion I flicked through to page 9;

LINE OUT — Balanced output to connect to external devices such as PA systems and recording consoles. The level and tone of the LINE OUT signal are affected by all preamp controls, including GAIN. Pressing the GND LIFT button IN may eliminate hum or buzz resulting from connection to improperly grounded equipment.

So I'm pretty certain that the line out is not affected by the master vol. Our bass player also has a Rumble (the 800 head) and I'm sure that the master vol doesn't touch the line-out.
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Re: Bass amp as bass monitor also hooked to mixer

Postby Wonks » Wed Sep 04, 2019 2:13 pm

If the bass is a passive bass, then the input impedance of the line-level inputs (including aux inputs/returns) will be far too low and the bass will lose a significant amount of top-end if the bass is fed first to the mixer.

If an active bass, then the bass should drive into a line input without problems.

With a passive bass, you'd be best getting an active DI box, putting the bass into that and feeding the DI's balanced output into a mic input on the mixer.
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Re: Bass amp as bass monitor also hooked to mixer

Postby Wonks » Wed Sep 04, 2019 2:24 pm

Music Wolf wrote:So I'm pretty certain that the line out is not affected by the master vol. Our bass player also has a Rumble (the 800 head) and I'm sure that the master vol doesn't touch the line-out.

Not according to the manual block digram (which could of course be incorrect but it's the manufacturer's only means if showing how it works). The pre-amp master volume is well before the DI take-off, which is shown right before the power amp stage.
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Re: Bass amp as bass monitor also hooked to mixer

Postby Music Wolf » Wed Sep 04, 2019 2:32 pm

I'm assuming that everything from the mixer is going to the Front of House (FOH) system as well? The way I'm reading it is that presently you have no instrument amps on stage, just the monitor?

I would go: Bass>Rumble>lineout>Mixer.

I would start by not having any bass fed to the floor monitor. Now you have bass amp for bass, floor monitor for everything else (I don't think that you have said what other instruments you have?). Bass is fairly non-directional so everyone on stage will hear it whether the speaker is pointing at them or not. If your bass player just wants to hear more of him (I've met quite a few bass players who like to be much too loud) then you might, diplomatically, suggest that he tweaks his sound to boost the mids a little to make it easier for him to hear himself.
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Re: Bass amp as bass monitor also hooked to mixer

Postby Music Wolf » Wed Sep 04, 2019 2:34 pm

Wonks wrote:
Music Wolf wrote:So I'm pretty certain that the line out is not affected by the master vol. Our bass player also has a Rumble (the 800 head) and I'm sure that the master vol doesn't touch the line-out.

Not according to the manual block digram (which could of course be incorrect but it's the manufacturer's only means if showing how it works). The pre-amp master volume is well before the DI take-off, which is shown right before the power amp stage.

I'll check tonight at rehearsal and report back but I'll be very surprised if it operates that way. It would make it pretty unusual.
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Re: Bass amp as bass monitor also hooked to mixer

Postby Wonks » Wed Sep 04, 2019 2:52 pm

Music Wolf wrote:I'm assuming that everything from the mixer is going to the Front of House (FOH) system as well? The way I'm reading it is that presently you have no instrument amps on stage, just the monitor?

I would go: Bass>Rumble>lineout>Mixer.

I would start by not having any bass fed to the floor monitor. Now you have bass amp for bass, floor monitor for everything else (I don't think that you have said what other instruments you have?). Bass is fairly non-directional so everyone on stage will hear it whether the speaker is pointing at them or not. If your bass player just wants to hear more of him (I've met quite a few bass players who like to be much too loud) then you might, diplomatically, suggest that he tweaks his sound to boost the mids a little to make it easier for him to hear himself.

The whole point of the original post is that the bassist wants to use the amp as a second monitor, therefore it needs a feed in from the mixer.

I don't think it will work well, as the amp is only 40W and isn't one with a HF tweeter.

I doubt if it puts out much energy in the sub 80Hz area, so most of its output will be in the more directional 2nd harmonic-and-above region for the bass. So at 40W, you probably won't be able to hear the bass amp on stage unless you are standing quite close to it; so you'll probably still need some bass in the main monitor. But that's stuff you can play about with.
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Re: Bass amp as bass monitor also hooked to mixer

Postby ef37a » Wed Sep 04, 2019 3:29 pm

Thank you Mr Wonks. I know my eyes are bad but not THAT bad!

The take off for the DI out is clearly at the input of the PA and thus POST master volume. Daft? Yes. Circuit typo? Quite possibly but I can only go by wot i's got. (I also don't like "DI outs" on XLRs at line'sh levels. I reckon a sound tech expects an XLR DI to be mic level? )

Yes Wonks the OP did ask for a monitor but if the bassist goes through the desk first (via a buffer pedal or DI) he will be at the mercy of the desk op for level back to hisself...Where we came in?

Better IMHO that he has control of his local bass level and sends the mixer some?

And, although I am a firm believer in giving people the answers to the questions posed it is not that unusual for them to not really KNOW the right question to ask!

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Re: Bass amp as bass monitor also hooked to mixer

Postby Wonks » Wed Sep 04, 2019 3:57 pm

Were really using the wrong tools to do the job here, which is the basic problem.

Best thing to do IMO is to use the bass amp as just the bass amp (with a DI out to the desk), the monitor as a monitor for everything else and make sure the bass amp is pointing across the stage so that others can hear it with a bit of definition.
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Re: Bass amp as bass monitor also hooked to mixer

Postby Music Wolf » Wed Sep 04, 2019 3:58 pm

Dave

I agree. I was reading the first post as jumping ahead to a possible solution. The problem seemed to be better defined in the OPs second post - the bass player wants more bass than the others.

There's nothing wrong with your eyes but there is, I suspect, something wrong with the block diagram. I quick 'Google' revealed that the question has been asked before and someone contacted Fender to ask. The response that they got was, apparently;

Both outputs are balanced and NOT affected by Master
'Both' being pre and post eq settings on the 800.
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Re: Bass amp as bass monitor also hooked to mixer

Postby Music Wolf » Wed Sep 04, 2019 4:05 pm

Music Wolf wrote:There's nothing wrong with your eyes

Caveat. I'm not a Consultant Ophthalmologist* so please do not take this as being a clean bill of health. If you experience unusual symptoms, consult your Physician.

*I believe that a real one frequents this very parish
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Re: Bass amp as bass monitor also hooked to mixer

Postby ef37a » Wed Sep 04, 2019 9:15 pm

Music Wolf wrote:
Music Wolf wrote:There's nothing wrong with your eyes

Caveat. I'm not a Consultant Ophthalmologist* so please do not take this as being a clean bill of health. If you experience unusual symptoms, consult your Physician.

*I believe that a real one frequents this very parish

Please do not concern yourself, I am getting the very best care at Northampton General with six weekly checks and treatment when required.
I DID however miss the note re FX loop, "not on Rumble 40". So OP does not have that option.

Yes, let the bass player have full reign of his amp. The R 40 is I dare say decent in its class but not I would guess a Walls of Jericho tumbler?

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Re: Bass amp as bass monitor also hooked to mixer

Postby Dr R » Wed Sep 04, 2019 9:20 pm

Oh how I've missed the mad diversions on this forum! Nice to be back.

To the OP. As above, just try the amp as a bass amp, and then run that to the desk. Use the one monitor as before and don't bother putting any bass into that. See if the bass player can hear what he needs. If so then job done and off down the pub at the end of the gig.
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