Best way to connect 2 instruments to one input jack?

70sJazz · #1 06-16-2011, 09:09 AM

I'd like to connect 2 instruments to my F500 head which only has one input jack. I'm thinking especially the situation where I would plug in both my bass and a synth.

I have an A/B pedal and that works great, but it would be nice to not have to switch, just have them both ON all the time, you know, so I could play a few stabs on the synth & then go back to playing the bass again, without having to stomp on a switch or get a pop through the speakers. But what's the best way to connect them so that the signal remains the best quality? Is this possible to do it the right way?

I don't want to switch to another head that has 2 inputs if I don't have to because:

#1 This head is a really good sonic match for the cab I'm using (for example, I have a Walter Woods that has 2 inputs but it's not a good sonic match for the cab I'm currently using).
#2 I have no need different gain or EQ settings for each instrument.
#3 A dual input head would be twice the size of what I have now just to get the second input jack.
#4 I like the semi-parametric EQ of the F500 & don't want to loose that by switching to something without it.

Dekker · #2 06-16-2011, 09:21 AM

The input impedance on your head would be the issue. Without the A/B pedal separating the two devices, they're basically working together, and affecting each other. The sound being fed into your head may be "unpredictable", based on the settings you have on your two instruments.

That said, I'm sure a bit of DIY can get you a buffered input sum circuit that you can use, powered by a simple 9v... That would isolate the impedance from each instrument, and present the amp with a single stable impedance.

Good luck!

Spinal Tapper · #3 06-16-2011, 09:34 AM

I'm thinking u could start with something as simple as this (with a 1/4" adapter, obviously), but I'm not sure what it could do to your amp if you had too much going on at once...

I'd stick with the A/B box though, probably.

bassman4d521 · #4 06-16-2011, 09:41 AM

how about a little mixer??

BassmanPaul · #5 06-16-2011, 09:45 AM

Get a small metal box and three standard TS phone sockets. Mount all three to the box making sure there is enough room for the plugs you use. Wire the sleeve connections of all three sockets together and connect also to the metal box if the sockets are insulating types. Designate one socket as the common and wire one 47-68KΩ from the tip to each of the other two sockets (two resistors). You now have a passive mixer. Plug the common into your amp and the instruments into the other two.

70sJazz · #6 06-16-2011, 10:14 AM

Quote:

Originally Posted by Dekker

I'm sure a bit of DIY can get you a buffered input sum circuit that you can use, powered by a simple 9v... That would isolate the impedance from each instrument, and present the amp with a single stable impedance.

That's what I was afraid of, people have been telling me you don't want to do the Y cable thing because the sound quality will suffer but I don't understand the technical reasons why (impedance details, etc).

I'm no electronics expert or DIY'er so I'd like to buy a product like this that just works. Can you guys recommend a buffered preamp type device or a tiny 2 channel mixer? Don't want to lug around a full size mixer with all the bells/whistles obviously just to do this!

Dekker · #7 06-16-2011, 10:23 AM

I haven't bought this item, so don't work from experience, however from the description this is exactly what my DIY suggestion does, all for under $15

Ampridge GA101 Jam Cable Dual Guitar Adaptor at AmericanMusical.com

Jam Cables adaptors for two guitars

thedevilisbad · #8 06-16-2011, 10:26 AM

Quote:

Originally Posted by bassman4d521

how about a little mixer??

Ditto, I think this is the best option, you can get a little 4 channel for pretty cheap these days.

PurpleDrank · #9 06-16-2011, 10:45 AM

Quote:

Originally Posted by thedevilisbad

Ditto, I think this is the best option, you can get a little 4 channel for pretty cheap these days.

Right here: Amazon.com: Rolls MX41b 4-Ch Passive Mixer: Electronics

That'll do you right and you can keep a second bass or whatever on it also.

**cheezewiz** · #10 06-16-2011, 11:11 AM

A small mixer is the best option.

BassmanPaul · #11 06-16-2011, 11:22 AM

The problem with the small mixer is that they want to operate at a line level and not at an instrument level which the amp expects.

70sJazz · #12 06-16-2011, 11:25 AM

OK, some decent suggestions here, I'm a little skeptical of how the Jam Cable is different than a regular Y cable but if it's a valid solution it would be the most compact & practical.

I thought of the Radial Bassbone for a second but that has an A/B switch, I don't think you can have both basses active at once.

Perhaps this would work like the Rolls but a little more control.

My Minimark has an aux input and headphones jack, would have been nice if the MB heads had those too. Perhaps this little mixer would be just like adding those 2 jacks to my F500. Looks like it's powered with a wall wart though which probably isn't necessary for this type of use, always some downside I guess.

70sJazz · #13 06-16-2011, 11:30 AM

Oh, here's a passive one they have kinda like the Rolls but a little more flexible, no power supply needed:

seamonkey · #14 06-16-2011, 11:49 AM

Quote:

Originally Posted by bassman4d521

how about a little mixer??

This

Y-cable is like asking "Should I plug the output of my synth into my bass?"
You don't want that. Use a small mixer to isolate the two from each other.

Dekker · #15 06-17-2011, 06:12 AM

The problem with an el-cheapo y-cable is that the impedance from the instruments may change as you change the volume and tone controls on your bass (will change impedance and probably volume level/tone from the other instrument). The premium Y-cable above fixes that.

What the passive (or active) mixer fixes is the line level issue. If your bass is PASSIVE, then most likely you have your amp set to a particular volume level to hear your bass. When you move over to your synth and play a few notes, it is probably outputting at line level, and therefore the volume you hear from the speakers will be about 10db higher (considerable difference). With the mixer, during sound check, you can adjust the levels so they are both "equal", so when you change instruments the volume stays consistent.

If your bass is ACTIVE, you might be able to get away with the premium Y-cable, since both will be pushing out a near-line-level signal, and you can control your bass level to match the synth since they will be close enough in strength.

cchorney · #16 06-17-2011, 06:59 AM

My Morley A/B/C switch allows for on/off of each individual switch. This means with my switch I could run 2 devices simultaneously (or run 1 device to two amps). Maybe your switch can do this too?

Lo-E · #17 06-17-2011, 07:07 AM

Along the lines of what cchorney said, some A/B boxes are available in A/B/Y configurations and some also act as buffers.

Radial is the first brand that springs to mind, but check the offerings of the usual suspects: Whirlwind, Morley, Lehle, ect... I think there are quite a few out there.

It may be referred to as a splitter or an A/B/Y in product literature. I expect you'd have options available at your local big-box music store.

GladToBeBack · #18 06-17-2011, 07:21 AM

Quote:

Originally Posted by bassman4d521

how about a little mixer??

a 2 or more channel mixer would be best. using a splitter on the jack could effect the signal. just like plitting a headphones jack w/o a distribution amp makes the signal to each headset lower. same goes for inputs, less power to each instrument. Running a mixer can help avoid this.

ga_edwards · #19 06-17-2011, 07:41 AM

No one has mentioned the venerable Boss LS-2 yet? Plug one i return A, one in return B and output to amp. You can them mix using the level knobs to taste. I do this with the 2 outputs of my attitude bass.

bassplayer8953 · #20 06-17-2011, 08:40 AM

Quote:

Originally Posted by 70sJazz

That's what I was afraid of, people have been telling me you don't want to do the Y cable thing because the sound quality will suffer but I don't understand the technical reasons why (impedance details, etc).

I'm no electronics expert or DIY'er so I'd like to buy a product like this that just works. Can you guys recommend a buffered preamp type device or a tiny 2 channel mixer? Don't want to lug around a full size mixer with all the bells/whistles obviously just to do this!

This would give you either/or, or both:

Whirlwind Selector A/B Box and more Guitar Effects at GuitarCenter.com.

Edit: there's a Morley mentioned in the ad also, for a somewhat lower price.