How might I play two basses through the same cabinet?

#61
PauFerro said:
I often need to bring an upright and an electric bass to gigs.

I notice my cabinet has two inputs in the back (1/4"). And it doesn't seem to matter which of the two inputs I put my speaker cable into from the amplifier,.

Can I have two amplifiers, and run a speaker cable from each amp, to one of the 1/4" inputs in the rear of the cabinet? Each bass would then have its own amplifier, but each amplifier would use the same cabinet.

My understanding is that the two inputs are really there to daisy chain two cabinets. But I wondered if I could use them as two inputs from two separate amps, each going into one of the two 1/4" inputs at the back of the speaker...

I tried using a little mixer, but it really colored the sound of both basses to the point I don't want to use it.
Click to expand...

Okay, I think the OP has received sufficient info regarding the "wrongness" of plugging two separate amps into the two speaker jacks on the back of a cab.

PauFerro: I think what would work well for you is an Ampeg PBSB Amp Switcher. You can plug in two (or more) amps, and have only one cab (or other cabs) connected. So you could connect the one cab you have to the back of this gizmo, and leave the "Speaker Selector" knob alone. You could then connect the outputs of your two separate amps to the back of this gizmo, and just rotate the "Amp Selector" knob to whichever amp you want feeding that cab. See pics:

View attachment 2895613

Ampeg PBSB 2.jpg


EDIT: see agedhorse's post #65. This gizmo may not work for you after all!
 

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#63
DDXdesign said:
Well I will concede the point (and like I said I agreed it would be a Very Bad Idea), but I am now very confused as to those not being one-way streets between head and cab. And I've been playing for ages! Learn something new every day I guess.

(I wasn't trying to be right, I was just trying to be helpful to that one guy)
Click to expand...
Guys, guys, we are arguing feet of accuracy in the placement of a thermonuclear device.
Either way, it is the same electrically.
You are both right. The amps go kablooie!
 
#65
SactoBass said:
Okay, I think the OP has received sufficient info regarding the "wrongness" of plugging two separate amps into the two speaker jacks on the back of a cab.

PauFerro: I think what would work well for you is an Ampeg PBSB Amp Switcher. You can plug in two (or more) amps, and have only one cab (or other cabs) connected. So you could connect the one cab you have to the back of this gizmo, and leave the "Speaker Selector" knob alone. You could then connect the outputs of your two separate amps to the back of this gizmo, and just rotate the "Amp Selector" knob to whichever amp you want feeding that cab. See pics:

View attachment 2895613

View attachment 2895604
Click to expand...

You will absolutely need to verify that there is not ANY common grounds within the switcher. From memory troubleshooting an issue years ago, I recall that these had common grounds either on the input, output or both. VERY BAD (potentially catastrophic) for any BTL amp (bridge tied load).

When these devices were made, Ampeg did not have any class D amps (which are usually BTL), and maybe only a couple amps that were even bridgeable at all.
 
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#67
agedhorse said:
You will absolutely need to verify that there is not ANY common grounds within the switcher. From memory troubleshooting an issue years ago, I recall that these had common grounds either on the input, output or both. VERY BAD (potentially catastrophic) for any BTL amp (bridge tied load).

When these devices were made, Ampeg did not have any class D amps (which are usually BTL), and maybe only a couple amps that were even bridgeable at all.
Click to expand...

Thanks AH! :thumbsup: I added an EDIT comment at the end of my post #61 referring the OP to your post #65.
 
#72
PauFero, you told us a little bit about your amp set up, but nothing about the two basses you plan to use. What is you pickup configuration on your upright? Do you have only a piezo on it; any pre-amp on board?
For several years I did the electric + upright on every gig. Because I ran a fairly big rig, and had a fair amount of stage volume, I ended up getting a magnetic pickup with a built in pre-amp/mixer for my upright. It has a blend control that mixed the piezo I had with the magnetic PU.
I used a ABC box to switch between my passive electric and the upright. I used A for upright, C for electric and B had nothing connected, so it was my mute. This made switching very quick and silent.
The fact that the upright had the built in pre-amp made signal matching easy and I didn’t have any degradation of signal (that I noticed).
 
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#73
Hi there,
Your two 1/4" inputs on your cabinet are most likely in parallel so that you can have a speaker out from your amp to the cabinet, and then add a second cabinet in parallel to move more air with a second speaker cable running between the two cabs. If your second cab is the same impedance as your main cab, your amp will see half of that amount. (Two 8 ohm cabs in parallel make a 4 ohm load to the amp, etc. That math has been covered exhaustively elsewhere here on TB.)

It sounds like you want to be able to switch between two basses. An ideal device for that is the Providence Dual Bass Station. It's extremely cool - you can use it to switch one bass between two amps, OR you can use it to switch one amp between two basses without needing to touch any cables. Simply step on the switch to toggle back and forth - it's that easy. And even better, each bass gets its own dedicated EQ, so if you have two tonally different basses, or one active one passive, or one electric and one acoustic, etc., you can give them each their own EQ, which is AWESOME.
Check it out here:
Providence Dual Bass Station Review | Premier Guitar
There are lots of YouTube videos as well.

If you do want one of those, I have a spare one I'm willing to part with - send me a PM.

Another good device to look at is the Radial Switchbone. Actually, Radial / Tonebone makes all kinds of very cool switches and other goodies, and they are built like tanks. You could probably drive a tank over one of their pedals and it would only crack the knobs. Maybe a slight exaggeration. But only slight.
 
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#76
SactoBass said:
If he is willing to forgo the "two amp" scenario and just go with one amp, then the Lehle is a good option. But if he wants to use two separate amps, then the Lehle is not the tool. :thumbsup:
Click to expand...
No, that's a splitter so it's not intended to take 2 sources and combine to a single output. The reflected impedances between both sources (especially turning onevdown) plus the load would cause very bad loading issues and he wouldn't be able to switch between basses either.

Think this through, it will become obvious why it won't work.
 
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#78
agedhorse said:
No, that's a splitter so it's not intended to take 2 sources and combine to a single output. The reflected impedances between both sources (especially turning onevdown) plus the load would cause very bad loading issues and he wouldn't be able to switch between basses either.

Think this through, it will become obvious why it won't work.
Click to expand...

Yep, you are correct. I had it backwards. That P-split is for receiving one signal and splitting it into two separate signals. That won't help the OP.
 
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#79
Okay, so, let's assume that the OP wants to play bass A into amp A into the one cab, and *ALSO* play bass B into amp B into that same cab (but not at the same time as bass/amp A), then what product on the market is available that would make it safe and convenient for the OP to switch between the output of amp A and the output of amp B, going to the same cab?

(of course, there is the "manual" way of doing it, which is to manually unplug amp A's speaker cable from the cab and plug in amp B's speaker cable into the cab, but I think the OP is seeking a more convenient way to do that)
 
#80
I don't know of any stock amp output switchers that are fully isolated and can also switch high powered amps. There may be some but I am not familiar with any.

This is something that can be custom built by a tech who knows what they are doing.
 
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