Roland Mobile AC line out modification - diyAudio
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Old 22nd March 2014, 01:37 AM   #1
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Default Roland Mobile AC line out modification

Hi all,

New to this forum, hope this is the right place to ask a question about modifying my new Roland Mobile AC.

Like most Cube amps from Roland (Micro Cube, Cube Street etc) this little amp doesn't have a dedicated line out - yet it has a headphone out which disables the main speaker(s) when in use.

As this is an acoustic amplifier - I don't need this 'practice' function and would instead like to use the headphone out as a line out instead while using the amp as a personal monitor.

Whereas modifying the Micro Cube and some others are quite well documented, I can't find anything regarding the Mobile AC (which has quite a different design to the other Cubes - and technically doesn't belong to the Cube family but the Acoustic Chorus family).

Has anyone disassembled this otherwise terrific little amp - or even better modified it so that the headphone jack doesn't switch off the main speaker when in use?

I'm a professional jazz guitarist - not an electrical engineer... any help would be greatly appreciated! :-)
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Old 23rd March 2014, 12:32 PM   #2
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Location: North Derbyshire
Do you have a schematic for the amp?.
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Nigel Goodwin
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Old 25th March 2014, 08:05 AM   #3
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No, I couldn't find any schematic; but my bandmember and fellow guitarist is a bit of a wiz when it comes to doing mods to audio equipment - so we got it done

Whereas most Cubes break the ground circuit when the headphone jack is in use and disable the main speaker - the mobile AC does the opposite, it makes a second ground circuit when a headphone jack is inserted and disables the speaker.

After taking the amp apart carefully we used a multimeter to match the different solder point to the tip, ring and sleeve of the 3,5 jack input and found 3 ground points - 2 of which are activated upon inserting the jack.
By de-soldering one of these points we were able to ensure that both the lineout and main speaker can be used at the same time.

Rough sketch

* Ground
* <-- The solder point that we de-soldered and disconnected from the circuit
* Ground
*** (tip, ring and sleeve)

Mission accomplished - the amp can now be used both standalone and as a stage monitor that passes the sound (and Roland's excellent Reverb) to the PA

Last edited by jazzman81; 25th March 2014 at 08:09 AM.
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