I really enjoy this site. I thank so many of you for giving such useful, creative, quirky and friendly advice and comments on so many topics about the Gibson SG. I have been visiting everythingSG for some time to learn facts and tricks about the SG. Thanks in part to your hints and ideas, my faded special has become a real dream to play. (Of course the ebony fretboard, the upper fret access, and the light mahogany construction help too!) To date I have not had anything particularly useful to contribute to this bulletin board, but I hope this post might be helpful, or at least interesting. :? The VOX AD50VT is a wonderful amp. It is especially good if you are exploring different styles and tones because serious simulations of amp models can be driven hard at various volume levels. When experimenting with a new style, such as bossa-nova through a dual rectifier, it is not always appropriate to run the amp at full volume, so the level control on the amp is really handy. (Actually, I decided that this style sounded best at zero volume, but perhaps one of you could make it work. :roll: ) After playing the amp for about 2 months, I decided it had two weaknesses that I wanted to fix. Both were anticipated, owing to the low cost of the amp ($360 new, including shipping). First, the speaker was lacking in bass, and I thought the speaker sounded a little bit muddy. The speaker in this amp was made for VOX by Celestion, but it is not a top-of-the-line Celestion product. Its frame is thin, and its magnet structure just looks small. Replacing the speaker was job number 1. Job number 2 was quieting the internal fan. I have never felt any warm air anywhere, so my first thoughts were just to just slow it down, or maybe replace it if this looked easy. The stock fan is low-capacity, but cheap and noisy. Actually, the fan noise did not bother me much when playing, even in the ambient sustain between the notes. When I put down the guitar to read, however, the fan became an annoyance after my hearing recovered. I spent some time looking over the products offered by Celestion and Eminence. Harmony Central has a number of useful reviews of different speaker drivers (located under manufacturers of guitar amplifiers). Many reviews were pretty touchy-feeley, but the overall consensus was that there is a lot to gain by replacing the stock speakers in cheap or mid-priced amplifiers with new products in the $50-100 range. There is also an online Tonequest report about Eminence that will bias you towards their speakers over Celestion: http://www.eminence.com/eminence/pages/products02/pdf/tonequest.pdf Selecting a speaker from written descriptions of its sound was frustrating, sort of like ordering from a menu written in Chinese. I had an email exchange with Dave at Avatar speakers, who suggested that I get a relatively uncolored speaker for this modeling amp. His first suggestion, which I took, was the Eminence Tonker. It cost $69 from Avatar. I thought the name "The Tonker" sounded really dumb, but I learned from wikipedia.com that Tonker is an obscure nickname for a character in the old Doctor Who science fiction TV series. (Will Eminence someday offer a heavy metal speaker called "The Dalek"?) Incidentally, the Eminence "Swamp Thang", which has an even dumber name, might be a good choice too, especially if you like bass. Before installing thenew speaker, I wanted to break it in. Speaker breakin is probably a real effect, but it is not entirely clear to me what it does. Exercising the cone and suspension probably causes mechanical softening of these paper components, at least this seems reasonable to me. A common claim is that the bass frequencies are lowered after breakin, and this would be consistent with such a softening. Finding hard evidence for this is not easy, at least not on the internet. There are a lot of different ideas about what to expect after breakin, but I haven't been able to find speaker response curves measured before and after, for example. I figured that a good breakin would be to drive the speaker cone at large excursions for an hour or so. This takes a lot of power at higher frequencies, so I made the easy choice of 60 Hz. In the garage I plugged the speaker into a borrowed 5 amp variac. I left the speaker face up in its cardboard box, in part to keep it clean. My wife had a social engagement that night, so I was able to run it at 16 V (something like 32 W) for an hour, followed by 20 V (40 W) for half an hour. It was loud. I ended up closing the garage door. Don't try this inside your home. Listening to a continuous 60Hz tone for an hour or two at high volumes is not recommended. The cabinet of the AD50VT was built better than I expected. Okay, the walls, front and back are pressboard, but they are mostly 5/8 inch with some 1/2 inch, and there are a couple of reinforcing ribs on the front. (I am thinking about adding some reinforcement to the sealed back.) The electronics chassis fits nicely across the pressboard cabinet of the AD50VT, and adds a little stiffness. The cabinet tolerances are quite good, so the back fits tightly between the walls. It fits so tightly that it was necessary to loosen the screws to the electronics chassis to remove the back. The screws for the back go into strips of plywood that give much better bite than pressboard, and can take some real force. I liked that. Comparing the Eminence Tonker to the VOX Celestion was interesting. Tapping the cone, the free air resonance of the Tonker was actually a little bit higher than the Celestion, by a bit less than a half-step, I think. Looking into the cones, the two didn't appear very different. The appearance from the back is markedly different. The Tonker was a bit deeper, but the main difference was weight. The Tonker weighed twice as much as the Celestion -- the Celestion weighs 6.6 lbs, and the Tonker is 13 lbs. Both frame and magnet were much more substantial on the Tonker. The VOX Celestion has a slightly larger mounting bolt circle than the Tonker. The four mounting screws for the loudspeaker are tightly captive in the pressboard frame of the AD50VT. They just barely accommodated the mounting holes of the Tonker. Fortunately, they did fit without filing, drilling, or thread damage, and re-assembly was easy. It was not really necessary to remove the grille because the speaker screws were tightly captive. I took off the metal grille anyway, because I was wondering why it didn't buzz. VOX seems to have done a nice trick with some rubber pads for grille mounting. They work well in suppressing buzz, even after I re-installed the grille myself. I was curious about the valve reactor circuit, but I couldn't tell much about how it worked by looking at the analog circuit board in a few minutes. It all seems to be done with conventional components somehow, maybe with capacitor tricks, but there was no reactor to be found. The 12AX7 valve is an Electro Harmonix. It could be replaced easily by opening the back of the cabinet. I wonder what to expect with replacing it with another 12AX7, or perhaps a lower gain twin triode in the same family :?: ) This would be a real guess for me, since I don't know how the biasing and plate loading circuit works in the VOX/Korg circuit, and I am sure that the engineers designed the circuitry around the characteristics of the 12AX7. The fan looked like an afterthought in the engineering design. It blows on the wrong side of the heat sink, and is mounted with standoff screws that seem to require a lot of hand assembly. I cut the wires to it and checked that it ran off 12 V DC, as expected. Its mounting centers are 50 mm apart. I rummaged around for a suitable resistor, and found one that measured 28 ohms. When I put it in series with the fan, the voltage dropped from 10.6 to 8.6 V. The fan noise was diminished considerably, so I decided to leave in the resistor, at least for now. Unfortunately, replacing the fan looks like a pain. Doing it right would require pulling the amplifier analog board from the chassis, and there is some odd routing of wires around the frame of the fan. I think it might also be necessary to break some of the thermal compound to the heat sink and redo it. A better solution might be to clip the power leads to the stock fan and leave it in place. A better fan could be mounted nearby. While this was all exposed, I put in some thicker wire for the speaker leads (but the stock ones are pretty short, so I doubt this makes much difference.) The first few hours of playing the renewed AD50VT were revealing. First, I expected an increased speaker efficiency and a louder sound for the same settings. This was not so obvious, if true at all. The Tonker was just about the same volume as the Celestion it replaced, but this is hard to tell without more care than I gave to it. Second, I expected more bass, owing to the speaker response curves that were available for Eminence and Celestion sites. This was true. The Eminence had more bass, and it was tighter. I am pleased. The biggest change, however, was articulation at any volume level. The Tonker is much more clear. The differences between amp models are now much more obvious than before. I did not expect such a difference in clarity between the two speakers. In the first minutes of playing, I worried that perhaps a muddier speaker was selected by VOX because the electronics would make annoying sounds, perhaps from the digital stages. If this is so, I still haven't noticed it. The 11 amplifier personalities of the AD50VT are now much more distinct, and I can hear effects of my fingering much more clearly than before. Somewhat to my surprise, I now think that the improvement in articulation is more important than the better bass response. I didn't think articulation was such a problem with the original Celestion, but now that I have the Eminence installed, I can't imagine going back. I gave the VOX/Celestion to a college student, who was delighted to get it. Oh yes, the fan is quieter too. I recently found a better one to install sometime. It is bigger and slower, but it really quiet. This is a project for another day, probably after I start getting more serious about recording with this amp.