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Hey guys, as some of you may know, my main amp has been a '71 Vibrolux Reverb for quite some time. It was always a good base clean tone, but I never realized how much I was missing until I started reading up on the circuit differences and trying them for myself. I've read from folks online that the silverface designs are fine as-is, that blackface designs were overrated and, in the case of the Vibrolux Reverb, I haven't found that to be true. I've always just accepted by VR for what it was, which was a lower powered good clean tone with some finicky controls. The blackface circuit it has now has me grinning because it sounds like a completely different amp in a very good way.
Here's what I like about it: warmer amp (the silverface circuit had more of a hi-fi kinda tone), tighter and richer bass (the silverface design had a flubby bass that had to be dialed in pretty carefully), more clarity (I was thinking that if it was "warmer", it was going to lose definition and I'm glad I was wrong), more punch (silverface could get loud, but wasn't as punchy as I was expecting) and an adjustable bias instead of the bias balance configuration which I really think robbed the amp of a lot of the above.
I've never seriously modded a tube amp before (the only previous thing I've done was change the output transformer to a T040). Leave it up to me to choose an amp that I'm sentimental about to experiment on, but it went well the first try thanks to Gerald Weber's (of Kendrick amps fame) videos on vintage Fenders. Gerald breaks it down very well on a component level. Tips like changing a capacitor value and PI tail resistors to redefine the low end and removing things like the caps across the power tubes to open up the high end were invaluable. When you have something that sounds good, it's hard to imagine what it "could" sound like. With all the talk about how scary the voltages are on the power capacitors, I wasn't very motivated to play around with them, but they're actually quite easy to discharge safely without any special tools (for those that didn't know - pin 1 or 6 are the "anode" or "plate" terminations on 9 pin preamp tubes and running an alligator clip to the chassis ground discharges the caps through a network of resistors downstream so they discharge safely).
Best of all, I was able to get all the parts for the mods right from my local Radio Shack for about the cost of a good pack of guitar strings. So, if you're handy with a soldering gun, meticulous with details and want a richer sounding amp for a negligible cost, just give it a try. Save the old parts if you really, really want to put it back to stock. Trust me, unless you want a colder sounding amp with less punch, less bass and treble extension, you'll probably really like it. For those that have one of the later silverface designs with the master volumes and UL transformers I don't think they're necessarily worth converting to blackface, but anything considered relatively early silverface should be a hit. This VR simply blows me away now!
Here's what I like about it: warmer amp (the silverface circuit had more of a hi-fi kinda tone), tighter and richer bass (the silverface design had a flubby bass that had to be dialed in pretty carefully), more clarity (I was thinking that if it was "warmer", it was going to lose definition and I'm glad I was wrong), more punch (silverface could get loud, but wasn't as punchy as I was expecting) and an adjustable bias instead of the bias balance configuration which I really think robbed the amp of a lot of the above.
I've never seriously modded a tube amp before (the only previous thing I've done was change the output transformer to a T040). Leave it up to me to choose an amp that I'm sentimental about to experiment on, but it went well the first try thanks to Gerald Weber's (of Kendrick amps fame) videos on vintage Fenders. Gerald breaks it down very well on a component level. Tips like changing a capacitor value and PI tail resistors to redefine the low end and removing things like the caps across the power tubes to open up the high end were invaluable. When you have something that sounds good, it's hard to imagine what it "could" sound like. With all the talk about how scary the voltages are on the power capacitors, I wasn't very motivated to play around with them, but they're actually quite easy to discharge safely without any special tools (for those that didn't know - pin 1 or 6 are the "anode" or "plate" terminations on 9 pin preamp tubes and running an alligator clip to the chassis ground discharges the caps through a network of resistors downstream so they discharge safely).
Best of all, I was able to get all the parts for the mods right from my local Radio Shack for about the cost of a good pack of guitar strings. So, if you're handy with a soldering gun, meticulous with details and want a richer sounding amp for a negligible cost, just give it a try. Save the old parts if you really, really want to put it back to stock. Trust me, unless you want a colder sounding amp with less punch, less bass and treble extension, you'll probably really like it. For those that have one of the later silverface designs with the master volumes and UL transformers I don't think they're necessarily worth converting to blackface, but anything considered relatively early silverface should be a hit. This VR simply blows me away now!
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