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Small 2-channel acoustic-guitar amp (sounds even smaller)


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A buddy of mine just bought himself a very compact 2-channel Roland AC-33 combo amp.(weighs 10 lbs). He brought it over to my place today, to give it a wringing out.

 

His guitar is a Yamaha dreadnought (model ???) with a Martin Thin-Line pick-up (passive). He wasn't too sure about the pick-up, but it sounds to me that this was the likely candidate. We plugged the guitar in, turned up the channel "volume" knob (that's how it's labelled, instead of gain), then turned up the master. Now I know this amp is only rated at 30w, but good God, the output was almost inaudible. They must mean 30w "peak". Geesh. We tried different cables, and it sounded the same. Is there anything that can be done with this? (other than get another amp) From what I gather, the channel1 (HiZ) input impedance is 1M Ohm.

 

Channel 2 of his amp has an XLR input for his vocal mic (Shure Uni-Sphere 565SD) and a 1/4" input. The XLR input has priority when something is connected there, but he's using an XLR->1/4"TS cable that came with his mic.(mic is user selectable dual-impedance)

 

The amp has an aux in (L&R phono jacks).

 

I'm just wondering if there's an accessory available, for coaxing a bit more oomph from this tiny amp.(inline pre-amp?)

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Can't discount the possibility that the amp isn't working but if it's working to spec, and the input sginal is relatively optimized then you just need more watts. IME 30 watts solid state in a budget amp is barely anything. I've found that transistor budget amps of that sort need somewhere around 60 to 100 watts. Tube amps are a different story, but you normally don't want tubes for acoustic guitar.

 

I would suggest you verify that the signal is hot enough by using a different source (or two).... and then get a bigger or better amp. One of AH's perhaps?

 

Of course, having said all that my little 5 watt Vox practice amp is pretty loud for it's size. I've actually gigged with it quite a few times in restaurants and lounges - so it does depend also on the amp.

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Somethings not right. One of the bands I do sound for the lead guitarist plays an accoustic through one of those Roland cubes, when mic'd it sounds pretty good. For practice it should be plenty loud enough. Don't quote me but I think the Martin pickups are made by Fishman, and I've never had a problem with an accoustic with one. Try a DI into the voice channel and see if the volume is still low.

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All of the Roland cube amps I have encountered all seem well underpowered....especially there bass amps.

Not saying there isn't a issue with the one the OP has, but I find there amplifiers to sound good...but just not have any usible output.

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A buddy of mine just bought himself a very compact 2-channel Roland AC-33 combo amp.(weighs 10 lbs). He brought it over to my place today, to give it a wringing out.


His guitar is a Yamaha dreadnought (model ???) with a Martin Thin-Line pick-up (passive). He wasn't too sure about the pick-up, but it sounds to me that this was the likely candidate. We plugged the guitar in, turned up the channel "volume" knob (that's how it's labelled, instead of gain), then turned up the master. Now I know this amp is only rated at 30w, but good God, the output was almost inaudible. They must mean 30w "peak". Geesh. We tried different cables, and it sounded the same. Is there anything that can be done with this? (other than get another amp) From what I gather, the channel1 (HiZ) input impedance is 1M Ohm.

 

 

Something's broken. Did you try another guitar on the same channel? Did you try the same guitar on the other channel? Did you try the same guitar on another amp? Did you try only having one thing plugged in at a time? Can you hear the microphone just fine or is that also quiet?

 

 

but he's using an XLR->1/4"TS cable that came with his mic.

 

 

Why? That's unlikely to be the source of his problems, but that's silly.

 

 

I'm just wondering if there's an accessory available, for coaxing a bit more oomph from this tiny amp.(inline pre-amp?)

 

 

A soldering iron, perhaps.

 

-Dan.

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Something isn't right if the output is "almost inaudible." Are you sure it's a passive pickup on that guitar? Look inside the sound hole and make sure there isn't a 9v battery holder in there somewhere with a dead or dying battery for an internal preamp circuit.

 

To troubleshoot the amp, try plugging in an different guitar. Even an electric guitar should give a healthy output through the amp.

 

If it really is just a straight passive pickup, and there isn't a problem with the amp, then it could just be a very weak signal from the pickup. Sometimes that can happen with a poor installation, especially for undersaddle types if the saddle isn't making good contact with the pickup film. If that's the case, then you could try something like a LR Baggs Para DI to boost the signal. That's a popular preamp in acoustic circles, and it has some other useful functions like a feedback notch filter.

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He's gonna bring the amp over again next week, and this time, I'll try one of my guitars, with an active pick-up.

 

The amp "works", but it's just anemic. We got plenty of volume when we ate the mic, but very little volume if we were more than a few inches away. My old Senn MD-416 U did much better.

 

Dan, The XLR-> TS cable he's using with his mic (UniSphere), is most likely because the mic is set for hi-impedance. It's a dual-impedance mic (Shure UniSphere 565SD). The guy he bought it from, was probably singing thru a combo-amp's guitar-jack,,, or maybe he was using it as an instrument mic (harp?) We tried his UniSphere with a new EWI XLR->XLR cable, plugged into his amps' XLR mic-channel, and there was no difference.

 

The lil' Roland amp is actually a dual 15w/ with twin 5" speakers. Rolands' specs don't specify if that's RMS or Peak, but I suspect it's the latter.

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