Roland Cube 80GX AUX input mod

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thpmink
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Post by thpmink »

I have a Roland Cube 80GX as a portable goto amp for sessions with friends or jazz gigging. It served me well so far, however I want to use it with my Amplifire or other Ampsim pedals, which presents me with a problem: On the GX series, they removed the FX loop, so there is no straight way to bypass the modeler stage and go straight into the power amp.

However, the Cube does have an AUX in, albeit in a weird configuration: What they call “iLink”, basically a headphone-sized TRRS jack giving you stereo in + mono out, so you can hook it up to your phone and use their app to playback a backing track and record yourself at the same time. From the block diagram in the manual, you can see that the input bypasses the modeler/preamp stage and directly goes into the power amp. Voila! So that's cool and the connector would work for the line-input I want, but also happens to be the only not really trustworthy looking thing on this amp. I would feel really uncomfortable using that phoney little phone jack at gigs, or even at home really.

So what I want is basically add a standard 1/4 inch TRS jack at the back. Now before I open it up and present some gut shots (unfortunately there's little information on what jacks they use and I haven't found many gut shots at all really), I wanted to double check in on my noob understanding that it would be as simple as wiring up a switching jack in parallel to the lugs of that little headphone jack?

Could I add a XLR mono / TRS 1/4 combo jack for even more input versatility? (My Amplifire pedal has XLR out, however I'm not sure with all this balanced/unbalanced thing when it comes to XLR)

Thanks!

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apollomusicservice
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Post by apollomusicservice »

You can't do that on simply way just to add couple wires and jacks.
For FX loop, on such kind of amp, You have to engage tech man with experience.

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Post by thpmink »

Hey, thanks for your reply! I'm not going for adding an FX Loop though, just line-in (which already exists, only on a weird mini TRRS jack)

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Post by thpmink »

Maybe my post wasn't clear enough, sorry.

I basically want to add a second AUX in jack to the already existing one, because I want 1/4 inch since the existing one is 1/8 inch.

The existing one is TRRS (Right, Left, GND, Mic), and my noob idea was just to hook up a standard 1/4" TRS to the pads of the already existing one. Would that work?

I'm just not sure if and how it is necessary to use a switching jack. And additionally if one could use something like a Neutrik NCJ9FI-S Combo Connector so you could use an XLR cable for mono input, or TRS cable for stereo.

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Post by apollomusicservice »

OK, here is my suggestion if you want to add another input jack. (Neutrik NCJ9FI-S Combo Connector)
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neutrik mod.jpg
cut.jpg

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Post by thpmink »

Thanks! I'll open it up to get some idea of the internals, where to place the jack, etc.

From what I could see through ventilation holes the Minijack is on its own daughter board, but I'm not sure. I'll report back!

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Post by thpmink »

A quick update: Opened the Cube, very tightly packed, so I didn't dismantle everything until I have the parts.

Here's the input board:
cube80gx-input-board.jpg
On top we can see the normal guitar input jack, the AUX in mini is at the bottom.

Shot here from another angle, and the connections labeled according to the HSJ1594-010110 mini jack data sheet (numbers correspond to the schematic apollomusicservice provided):
cube80gx-mini-jack.jpg
CN14 is the connector going to the main board.

No topside pics at the moment, I didnt have a screwdriver short enough to loosen that board mount (everything is *really* tight in there). Of course everything surface-mount and really tiny etc

— I'm not sure my skills will allow me to cut traces and solder the wires of the new jack in (as per apollomusicservice's suggestion). Hmm. Maybe loosing the mini-jack is a more viable option… I don't use it that much and it would be easier to just desolder it and use its pads to wire up the new jack.

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