Re-wiring Amp for Guitarist

Luke19Boarder · #1 03-16-2009, 11:46 AM

I know this isn't a guitar forum ... but I'm hoping that some of you might have the answer to this:

The lead guitarist in my band uses this amp:

http://www.samedaymusic.com/product--LINSPIII120

Line 6 Spider III 120 watt amp.

It doesn't sound terrible, but with only 2x10 speakers, it really has a hard time keeping up with the rest of the band (i run a full stack, rhythm guitarist has a mesa half stack and drummer hits hard as hell).

Now, we've been pressuring the guitarist to upgrade his rig, but he's always broke. He won't have the cash any time soon to get the tube amp/ half stack we all want him to have.

I was talking to a guy a few weeks ago who mentioned the possibility of re-wiring his amp to include an output that would allow an extension cabinet. It currently does not have such capabilities, as it only has a headphone out.

Does anyone know where I could find a schematic or whatever it's called on doing this? I have a soldering iron and passable skills with it, so I'm hoping to do this for him so he could be running through a 4x12 cab vs. the 2x10s he currently is.

Any help is much appreciated.

BassmanPaul · #2 03-16-2009, 12:07 PM

As with any SS combo amp you are going to have to face the problem of minimum impedance. If you go be low that then the amp will blow. If the amp does not come with a jack for an external speaker then you can almost guarantee that the supplied speakers are already the amps minimum load.

Paul

Luke19Boarder · #3 03-16-2009, 12:12 PM

Ah, yes ... the guy I talked to briefly about this mentioned this. He said that the input jack that I should use would effectively work as a switch ... when the extension cabinet is plugged in, the speakers in the combo would be switched "off," so that the impedance would basically be whatever the cabinet is, not the combination of both.

BassmanPaul · #4 03-16-2009, 12:46 PM

Yes but then you start daisy chaining cabinets and go too low. You also have to consider the impedance of the 4x12. If the impedance is too high you will not get the full output from the amp.I would hazard a guess that the amp is safe to 4Ω (2 x 8Ω speakers in parallel) but you should check with Line 6.

Paul

RickenBoogie · #5 03-16-2009, 04:56 PM

If he's got cash for a 412, why not just wait, and save for a USED head?

lemur821 · #6 03-16-2009, 07:44 PM

Turn down and save your poor guitarist some money.

Luke19Boarder · #7 03-16-2009, 07:55 PM

Quote:

Originally Posted by RickenBoogie

If he's got cash for a 412, why not just wait, and save for a USED head?

he doesn't really have an income. He's got a little bit of money saved up, but doesn't have a job right now (busy college student).

we've been trying to get him to upgrade for a year now, and i feel like this would be the cheapest way.

anderbass · #8 03-16-2009, 09:30 PM

Hey Luke,
I'd try to preform the mod without drilling any extra holes. I did this same mod to a couple of my combos by first locating the 2 wires going to the combos speakers and safely routing the (hopefully) extra slack in these to some location outside the back of the amp. (you may have to extend your wires)
I then simply cut the speaker wires and soldered in a male and female 1/4" speaker plug and jack, making sure to keep each wire connected the same way through the plugs.

So.. when you leave these plugged in, the combo works just like always, but when you'd unplug the male plug going to the speakers you'd suddenly have the female jack (going to the combos poweramp) available to plug in another cabs cable instead.

On mine, I instaled an extra length of wire to plug my combos speaker right into other amp heads, but this extra wire length would probably not be necessary for your situation. I built a home made mounting bracket to secure the female jack. I also made sure the wiring gong to the combos speakers was strongly secured to the combo so any tugging wouldnt unplug the speakers...)

BassmanPaul has a very good point about this amps corect speaker ohm load. I checked the Line-6 Web site and didnt find any specs on this combos speakers or the amps ohm rating. It probably is 4 ohm load like he said but after you cut the 2 speaker wires you could test the wire ends leading back to the speakers to see what ohm rating they are.
(click here for info on how to do that: http://www.google.com/custom?domains...ORID%3A1&hl=en

Many 4x12 guitar cabs are 16 ohm. This would be completly safe for a solid-state amps power section like this but you wouldnt be getting full power, but I'm guessing this rig would still be plenty loud.
You should probably study up on the ohms fact sticky here for more info on this subject: AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links

One more thing, just be aware this mod would probably void his waranty...

black_labb · #9 03-17-2009, 02:49 AM

what about upgrading to some more sensitive speakers? ss amps tend to have pretty insensitive speakers (that dont sound very good quite often). eminence has some very sensitive 10" speakers. going to 2 10's with a sensitivity of 100db@1w1m would be the same volume as going into a 4x12 with greenbacks.

http://www.eminence.com/guitar.asp?speaker_size=10

notice the ragin cajun, ramrod (both 100db@1w1m,75w) and red fang10 (only 50w, but 102db@1w1m, and i doubt the line 6 actually puts out 120w. the extra db means you will have more available volume) any of those 3 would be much more sensitive than whatever is in the line 6. this means he can have better tone at home with the amp, and have more volume at band, and never need an extension cab. make sure to get the same impedance as the current speakers.