RolandAC-33 Acoustic Chorus Battery-powered 30-Watt Guitar Amplifier, Black

Pro quality. Excellent product.

This is brilliant for busking. Mind you, if some opera singer, with his backing tracks blasting out of a boom box and a voice loud as a mill horn, comes along and stands 20 metres from you, well, you'll have to do what I did ... pack up and go elsewhere.It's meant to be an acoustic amp, but I play a National Reso-lectric through it. And it is marvellous, bringing out the 'banjo' in the resonator cone in the guitar, if you see what I mean. An amplified banjo ... my cup runneth over. Mind you, people often stop and say, That's too much like a banjo ... Well, never mind, there's an opera singer just around the corner ...I use Ansmann rechargeable batteries in it (8 AAs), and I get hours of use from one charge. If you were playing close to full volume though, I think you'd go flat a lot sooner.Strictly speaking it's portable. I find though that carrying it and my guitar is just about doable. For about half a mile. But then I'm an old man and I usually have my dog with me, and she pulls a bit on her lead, so get one of these (not necessarily with a dog) when you're young and fit. It weighs around 9 or 10lbs. A great carrier 'bag' is the Accucase AS-AC-130, slightly too big for the Roland, but that leaves room for bits and pieces ... and only £15.I don't have an acoustic guitar with a pick up so I can't comment on how well it performs the task for which the amp is actually made, but going on how well it does whatever I ask of it, I imagine it would be the perfect thing for bringing out the best in an acoustic. And you could use it to perform in a not too noisy venue.I thank the other reviewers who pointed out how good it is for busking. I might never have discovered that otherwise. There's a fancy loop thing on it and you can set up backing tracks (lasting about 40 seconds, but you can make them repeat as often as you want) for you to play like Peter Green over. I never use it since it's all I can do to lurch through what I'm actually 'playing' and I've no idea how I'd ever be able to work up a 'backing'.My only complaint is that I sit when I play, and my guitar lead is short, so the amp is quite close and I sometimes get quite loud feedback. This happens, for whatever reason, mostly when I'm busking. Perhaps someone will tell me how to cure this (without advising me to stop busking ... I've heard all the 'jokes' by now).The other downside, strangely, is that this amp is very well known to the busker's greatest torture ... yes, the pub gigging muso. Wherever you play, these maestros find you, and are drawn inevitably to the well respected amp and my beautiful National. It is hard for these undiscovered Claptons to listen to such a wonderful instrument being played as ineptly as only a busker like me can. Their faces say it all: wonderful guitar, great amp, but you are crap ... ! I inwardly sympathise with them and hope they will leave it at that. Mostly they do. But the odd underrated superstar among them cracks and says something ... you're doing ok (ie god, you are terrible) ... just a little out (ie you can't even tune it) ... I've never played a National, can I just do a quick piece on it (ie I'm going to show people how wasted that guitar is on you) ... and so on. I have found that the best response to these could-have-beens is maximum effing off instantaneously. It's not my fault that no one in the pub listens to them after the first drink ...Other than that, it's five stars for this fantastic amp.

Brilliant little amp, with loop and doubles as a great stereo speaker for your TV!

Great little amp with good sound. The chorus effect might be a little strong for some people but it works great and has good tone. Good well rounded amp.

First, here is a quick summary for those who dislike details. Portability, build quality, and versatility are its major strong points. Price and speaker sound are its major weaknesses. The major disappointment for me is that Roland could have done much better at achieving better sound through the speaker system. The basis for that statement is that I did a comparison to several sets of other self-powered speaker systems of similar size and power and found them all significantly better sounding. For the comparison I used three different sources: a quality acoustic guitar with a quality pickup, voice using a quality microphone, and recorded music through the auxiliary inputs. Possibly, if you use other sources of input, like an electric guitar, for example, you may or may not be as critical regarding sound discoloration. I would characterize the sound of the speaker system as boxy (like the resonance that you hear when you place your ear near a wooden box or near an empty tube). If I were to regularly use the speaker output, I would consider discarding the speaker enclosure and building another box using the existing electronics and more accurate speakers. The electronics portion appears very good. To my ears the special effects (Space, Wide, Reverb, and Ambiance) sound way too harsh when listening using the built-in speakers. However, the effects actually sound good (whether you prefer them or not) when listening through a set of quality headphones. I initially made an attempt to modify the speaker enclosure to improve the sound. And, although it did help, the other speakers that I used for comparison still sounded significantly better. The original speaker/enclosure combination suffers from both a limited frequency range and from uneven response. Measures to improve the sound need to be aimed at improving both. I eventually replaced the original speakers with a pair of medium quality speakers and nearly eliminated the boxy sound. The replacement is described in the update. More details are below.Four Stars: I would likely rate the electronics as worthy of five stars. However, I would also only rate the sound of the speaker system as only worthy of three stars, thereby providing an average or overall rating of four stars. Accordingly, depending on your needs, keep in mind that if you don't need to use the speaker system, the effects, AND the looper, you can buy a headphone amplifier like the Behringer MA400 for around $25 that will allow you to listen to several inputs using headphones. I have even used it for three inputs: two microphones in parallel and my guitar connected to the monitor input.Background: I purchased my AC-33 around five years ago to practice acoustic guitar and singing. I have always used headphones until recently when I decided to play around with the built-in speaker and concluded that it sounded too boxy, characteristic of the enclosure producing standing waves. I initially tried stuffing towels into the enclosure and observed that it helped a little which lead me to take the next step, to remove the towels and line the inside with half-inch soft, dense foam. Although I have a spectrum analyzer and could have made measurements before and afterward, I decided to save time and effort, not make a science project out of it, and simply trust my ears and observations. Although I made evaluations using my guitar and voice, I also relied on prerecorded music because it allowed me greater freedom to experiment. My observations were that the boxy sound was evident using the guitar, my voice, or the prerecorded music.Equipment: This information is probably not specifically relevant, but I will include it for those who might think it is. My guitar is a Martin DX1AE with the Fishman Sonitone pickup replaced by a Fishman Matrix Infinity VT. The voice microphone used was a Shure SM58. The headphones were Sony MDR-V6 and MDR-7506. The speaker systems used for comparison were (1) a Microsoft Digital Sound 80 system (that I use on my desktop computer), (2) a Boston Acoustics Micro Media system, and (3) a Boston Acoustics BA635 computer speaker system. I used the two sets of Boston Acoustics systems because they both use a 12-volt, 1500 mA power supply which is nearly the identical voltage that is used by the AC-33 (13 volts). Although the Power supply for the AC-33 is rated at 4 amps, 2.7 times that of the Boston Acoustics supplies, that factor is not significant when dealing in audio power. For example, differences in loudness are generally expressed as 2 to the log of the ratio of power. Based on that relationship, it requires around 10 times the power to provide a change of loudness perceived by the human ear as being twice as loud. Accordingly, assuming reasonably comparable speaker system sensitivities, either of the two Boston Acoustics speaker systems seemed to provide a good reference for not only sound quality, but also a good reference for sound levels from speaker systems using 12-volt supplies.Instrument Speakers: Instrument speakers are generally distinguished from stereo or audio speakers because they are generally used over a more narrow frequency range. This allows for the design of the speaker (driver) and the design of enclosure to be more efficient in converting electrical energy into sound energy. Traditionally, instrument amplifiers and speakers (including guitar amplifiers and speakers) are designed to somewhat limit the frequency response and thereby do not always provide a full set of harmonics. Historically, this restricted sound became associated with certain instruments, especially electric guitars, and a limited frequency response often became preferred. It may be that you have a similar preference, but for my guitar and for singing and especially when listening to accompanying prerecorded music, I prefer the wider fidelity of full range speakers.Volume (Loudness) Levels: I did not measure voltages supplied to the speakers (drivers) themselves, so I can't provide any information on sensitivity and efficiency. Also, because all three of the speaker systems that I used for comparisons utilized subwoofers and satellite speakers driven with separate amplifiers, this would likely have been an impossible task anyway. However, I did observe that the maximum sound levels that I was able to achieve from the two Boston Acoustic systems (with the subwoofer controls in the neutral position) appeared to have no deficiency in being able to match that of the AC-33.AC-33 Drivers: The AC-33 has two 4-ohm 5-inch drivers with wizzer cones. It is possible that replacing these drivers with other drivers could in itself provide improved frequency response. It is also possible, however, that the frequency response could be worse. And, it is also possible that seemingly higher quality speakers could be less efficient and thereby lower the maximum volume level. I did take a brief look at possible replacements and found that although the speakers are designated as 5 inch, they are smaller than normal. Also, 5.25-inch drivers are too large for the existing 4-inch openings, so installing 5.25-inch drivers would require enlargement of the openings or possibly the use of extension rings. (See update below.)Bass Port: The speaker enclosure uses a 1-1/2-inch diameter unloaded bass port. When designed properly, bass ports are sized to extend the bass below the resonate frequency of the drivers. However, they also allow an opening into the enclosure that can allow standing waves to be audible. To check it out, I removed the front grill and did some simple experimenting with the port. First, I tried plugging the port. As expected, there was likely a slight improvement in vocals at the expense of a slight drop and alteration of the bass. I also applied several different lengths of 1-1/2 -inch tubing to the port, but found no obvious or significant changes or improvements. Obviously, to evaluate and tune the port correctly, this should be performed with test equipment. Also, one can probably assume that Roland engineers likely would have sized the port to match the speakers. In the end, I was inclined to leave it open, but concluded that the port did not provide an obvious major effect. Also, one should be aware that lining the enclosure with foam may slightly decrease the effective volume of the enclosure and could affect the operation of the port, as well. It is also possible to add a fill material that can increase the effective volume.Choice of Lining Material: Standing waves in an enclosure are likely to be in the lower frequency midrange. Regarding lining material, I have read that egg-crate foam is mostly effective at higher frequencies and that high quality carpet foam was supposed to be more effective. I used foam from an exercise mat which appeared superior in that it was closed cell foam yet very soft and flexible to the touch.Installation: I covered all interior surfaces except the upper surface where the electronics are located. Accordingly, you need to avoid foam on the rear 4-1/2 inches of the top and 4 inches on each side below that. I also installed foam on the inside of the battery holder and a 3/4 inch strip on the brace between the electronics unit and the battery holder. I also notched the foam to accommodate the four edge braces.Access: To gain access, remove the battery, remove the eight screws that retain the battery holder, remove the four screws that retain the electronics unit, remove the two screws that retain the carrying handle, disconnect the four speaker wires from the speakers, slide the electronics to the rear, and pass the battery holder through the rear opening and out through the upper opening. To gain access to the drivers simply and carefully pry the grill forward. I used a plastic trim removal tool with rounded edges.Update - Speaker Replacement: I just found the boxy sound a little too annoying so I eventually decided to shop for other speakers. As I mentioned above, the existing speakers are listed as being 5 inch, but are also non-conventional in that their size does not appear to conform to other 5-inch speakers. The cone diameter is 4-1/8 inches and has a functional diameter of about 3-7/8 inches. Mounting hole spacing of opposite holes (which is often used to indicate speaker size) is 4-13/16 inches. Also, as I mentioned above, the existing mounting hole cutout is 4 inches, and I preferred to not enlarge the hole in case a possible future owner might wish to reinstall the original speakers. Accordingly, that decision eliminated a lot of potential 5-1/4 inch speakers. I eventually found two pairs that had the appearance that they would fit if I also incorporated extension rings. The two pairs are Kicker 46CSC54 and Rockford Fosgate R1525X2. I attempted to make a selection from these two pairs by choosing the pair with the more desirable technical parameters (sensitivity, Fs, Qts, and Vas). However, although all four of the parameters are provided by Rockford Fosgate, only sensitivity is provided by Kicker, and even after several emails and phone calls, I still was unable obtain the remaining three. I eventually discovered that Crutchfield has a nifty speaker selection tool that allows the listener to simulate the listening of their speaker inventory using popular headphones (your headphones are also included in the compensation). Both pairs sounded very close in volume (reflective of similar sensitivity) and I slightly preferred the Rockford Fosgate in sound quality. Although I also purchased extension rings, the Rockford Fosgate speakers fit without them making the replacement a 15-20 minute process. I did have to carefully bend the protruding electrical tabs used for the tweeters slightly inward using two pair of needle-nose pliers, but otherwise the concentric rings on the back of the frames allowed the frame to mount in the existing 4-inch cutout hole (though extended outward around 1/4 inch). I drilled new mounting holes precisely 1/4 inch radially outward of the existing holes and when installing the mounting screws, I was careful to not over tighten the screws and bend the mounting tabs on the speakers. The speaker replacement can be performed entirely from the front after removing the grill. The wire connections use the same size spade type connectors, so you can't get them reversed. I found the improvement in sound quality significant. There is more bass, clearer treble, and a reduction in the boxy sound. However, there is also a reduction in sound volume output at a given volume setting which I expected due to the nominally low (88 dB) sensitivity rating of the replacement speakers. Accordingly, there is likely some overall loss in maximum possible sound volume though the amount is likely highly dependent on the type of music or sound. I did not expend the time to make sophisticated sound measurements before and after and I did not have access to a second AC-33 for a side-by-side comparison after the replacement. Obviously, high sensitivity was a major consideration in the speaker selection by Roland, especially in a battery-powered device. And, in general, technical things that improve speaker sound quality also decrease sensitivity. My suggestion is: if you are using an AC-33 at maximum volume and are reasonably content with the sound quality, then do not make the modification. However, I am quite pleased with the improvement. Also, if you do the replacement and for whatever reason change your mind, it only takes ten minutes to reinstall the original speakers.