Warren0728 asked elsewhere about the possibility of dropping the power on a Valve Jr from the stock 5W down to 1W or so. I thought the response really belonged here in the Mods forum, so am tacking it on to this thread.
Interesting question. Since it's only 5W to begin with, most people are interested in mods that add MORE gain or output to the VJr, rather than less. But since even 5W can be deafeningly loud in a small area, this power reduction could be very useful to the home player.
Several large amps that let you drop the output substantially do this by "subtracting" power tubes from the circuit. The Mesa Lone Star series amps are a good example of this approach. They have 4 power tubes, but give you the ability to run with only one or two of them, dropping the output wattage accordingly. But since the Valve Jr. only has a single tube to begin with, this is obviously not an option. Zero power tubes is a little too quiet!
Some of the potentially useful power reduction options would include the following:
1) Add the capability to switch the EL84 power tube from pentode to triode mode. Not sure exactly what would be involved as far as the actual circuit modification, but this is a stock feature on the newer Blackheart Little Giant amps. But this only drops the output from 5W to 3W, which really doesn't make that big a volume impact. It also changes the tone somewhat, though not in a bad way--just different. But to truly quiet the amp and let you push the preamp & power stages at "bedroom" volume levels, I don't think this approach is gonna get you there.
2) You could conceivably convert to some lower output power tube type. Not sure what that would be, since the stock EL84 is already at the low end of commonly used power tubes. But there are certainly a boatload of more exotic tube types, and I have to believe there would be something useable available in the 1W range, though some type of adapter might be needed to make it pin-compatible with the VJr power tube socket. The downside with this approach is that the tone would almost undoubtedly be affected. Plus, the EL84 output tube is an integral part of the characteristic VJr tone. I really don't see a 1W tube getting close to duplicating that sound.
3) A well-known modification for the VJr is the installation of a "master volume" pot between the preamp & power stages. This would be a kind of "halfway" solution, as it would allow you to run the preamp gain up high to generate some crunch there, but would allow you to keep the actual output volume down. The problem with this approach (as with any master volume type amp) is that you don't get that nice creamy power tube saturation until the master volume is also dialed up, and that's the distortion that most folks think sounds the best. But this is certainly a partial solution to the volume issue, and one that is quite easily & cheaply done.
4) I think the best overall solution for getting the good saturated tone for which the VJr is known & loved at low volume levels doesn't involve modifying the amp at all. My recommendation would be to look into a good low-wattage attenuator, like the Weber MiniMASS or MicroMASS. These units are quite reasonably priced ($70 - $75), are very well made, and have a reputation for altering an amp's tone very little. So you can maintain the VJr's fundamental tonal character, drive the preamp and power stages to saturation, and still keep the final volume level at very manageable levels. Sure, the cost is more with this approach, but you also end up with a stand-alone attenuator that you can use on other low-wattage amps.
There may be other viable approaches to this issue, though, so I invite anybody else to chime in here....
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Originally Posted by just strum
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