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installing external speaker jack on roland microcube amp

11/6/2005 1:29 PM
Larry Bateman
installing external speaker jack on roland microcube amp
Hi everyone, Has anyone installed a external speaker jack on a roland microcube amplfier?  
All the owners say they love the small practice amp until they turn the volume control past 4 then everything breaks up. I guess the amps 5" speaker cannot handle the power.  
I was thinking if I install and external speaker jack which disables the amps 5"speaker and connect to the proper impedance 8" or 10" celestion speaker I could turn the volume further up than 4.  
Does this sound like a good fix for the problem?  
The reason I picked the microcube is I need a small practice amp for my bedroom. This amp has roland cosm amp modeling and effects for a small price and it produces great sound for its size.  
Thanks to everone who responds.
11/17/2005 2:42 PM
Re: installing external speaker jack on roland microcube
i have one of those micro-cubes --cool little amp.  
I don't see any reason why not- maybe use a switching jack so you disconnect the built in speaker when you plug into the extension cab.
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12/2/2005 1:43 PM
Steve Dallman
Re: installing external speaker jack on roland microcube amp
I purchased the service manual for this little beauty and have done a few mods on mine. They've found their way to a website devoted to this little wonder (with my permission.)  
If you do add a jack for an external speaker, you may be surprised just how good the stock speaker in that little ported box actually is. If you look at the stock speaker and see the ceramic "donut" on the back of it, that magnet is there to control stray magnetic fields.  
Here's the link to the site with the mods for this amp (so far...I'm just getting warmed up.)
12/2/2005 1:55 PM
Steve Dallman

Just some other thoughts...this amp is a real little gem. It not only has a decent DSP chip, but the whole shebang is controlled by an internal CPU. There are two interesting points on the schematic that I'm trying to learn about.  
There is a 3 pin pad marked "For DSP edit." This point has the + voltage on one pin, a connection to pin 21 on the CPU (marked MIDI) and the third pin is ground.  
The second is a 7 pin pad marked "For ONBOARD PROGRAM."  
These two things, called CN1 and CN2 are clearly marked on the schematic, but difficult to find on the circuitboard. If the pads follow similar topology the 3 pin pad could be wired to a 10k pot. Who knows what aspect of the DSP would be controlled. The pin wired to the 3 pin pad says MIDI but it doesn't appear to be a midi in. The ground and power supply connection don't fit.  
I have spoken to some computer geeks about the 7 pin pad but so far no one has been able to figure out the purpose.  
I paid $14 for a hard copy of the service manual, but complained that the schematic was unreadable. They reluctantly sent me the manual on pdf. with indication that they don't want the manual posted publically. I will pass on any info I can as long as it is not posted publically. I have a good relationship with Roland/Boss and don't want to lose that.  
This little amp is a real gem. An amp with 7 amp models, modulation AND delay DSP, etc. and all for just slightly more than a Pignose.  
This ain't your daddy's Pignose.
12/2/2005 2:27 PM
Ray Ivers
FWIW, I recently obtained the Alesis Nanoverb service manual (ATTENTION! DO NOT DISTRIBUTE IN ELECTRONIC FORM! ;)) which has a 10k linear 'EDIT' pot with the top connected to +5V, the bottom grounded, and the wiper connected to pin 61 of the DSP ASIC (labeled 'ADC IN 1'). This pot is labeled 'ADJUST' on the front panel, and controls the depth/intensity of the selected effect, as you can imagine. This unit uses a footswitchable microprocessor defeat for in/out switching, but there's also an unused 'MID' pin on the ADC which may be available for MIDI-controlled ADC (effect) on/off as well (the Nanoverb doesn't have MIDI either).  
The Nanoverb uses a 4-bit rotary encoder for program selection (5-pin pad). The 7-pin pad on your unit may well be a similar situation, but I don't know for sure.  
12/2/2005 2:52 PM
Steve Dallman

Thanks. Say, what did it take to obtain a service manual from Alesis? I have many old, discontinued Alesis boxes, from the original Midiverb and Midifex up through the Quadreverb.  
One that drives me nuts is the "Micro Enhancer." Since day one the level that it takes to trigger the enhancement is way too high. I've tried to get Alesis to part with even a portion of the schematic that would allow me to lower the threshold at which the process operates. They weren't interested in helping.  
I don't want to "copy" the doggoned thing to sell, I just want to fix it so it is actually useful to me. I've already purchased 10 or more of their products and intend to keep all of them. Why they are so adamant to protect the design of a box long obsolete escapes me.  
The possiblility of a rotary encoder makes sense. E-mail me for the manual if you wish to look at it further. I'm sure the DSP edit is done with a 10k linear pot. Several other functions use the same value pot so it makes sense for this one also.
12/2/2005 3:11 PM
Ray Ivers
I E-mailed Alesis regarding a Nanoverb schematic, and Jack Sprague-Hanna replied as follows:  
"Hi Ray,  
A copy of the service manual is $30.00 + shipping.  
To place a parts order I need the following information:  
Name & address  
Telephone number  
Part number & description  
Payment - Visa/MasterCard or Money Order  
Ground or air shipping  
(Please attach all prior email correspondence.)  
Best Regards,  
Jack Sprague-Hanna  
Parts Department Manager  
Email -"  
The price seemed steep at first, but when I received a 100+ page bound plastic-covers service manual with every schematic revision, update, service note, parts list, etc., I felt it was worth it.  
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