RJ Guitars wrote:
Dana - for the benefit of all who do not know, can you give us the info on what the VVR is and how to get it? If that request has too much commercial action going on inside the forum, could you post an info link where we could get to the info.
I think the Rocket Crew as well as the entire AmpGarage forum would like to hear about it... sounds like it's very Trainwreck friendly.
rj
VVR is just an acronym for Variable Voltage Regulator. Basically it works just like KOC's "Power Scaling" but uses a much simpler circuit that only requires 6 parts. I posted the schematic for cathode biased amps that I have been using since 2005 to regulate my own amps last winter. I will post it again at the bottom of this post. You don't need to buy anything from me to implement it on a cathode biased amp. It has been built by people using terminal strips, small turret/eyelet boards and their own handmade PCB. I do have a version that I came up with that can be used on fixed bias amps like the Express that regulates the bias along with the B+. I haven't posted the schematic for that but I have made a high quality PCB available that can be used/configured for either cathode or fixed biased amps just by populating it with the parts needed for the particular amp you have.
There are two different camps when it comes to adding "Power Scaling" to an amp. You can regulate the voltages on the whole amp or just make the voltages variable on the power section and leave the preamp running at normal voltages. No matter which way you go you have to add additional circuitry to the amp. If you regulate just the power tubes then you need to install a MV to compensate for the preamp running at normal voltages overdriving the power tubes running at reduced voltages. If you regulate the whole amp then it is possible for the signal coming from your guitar to overdrive the 1st preamp stage running at reduced voltages. At that point your vol on your guitar becomes your MV so to speak. You will need to install some blocking caps to keep DC that leaks onto the grids of the pream tubes running at extremely reduced voltages from causing a scratchyness on the guitar vol pot and amp vol pot.
If you do a search on this forum for "VVR" you will see a few threads where myself and others have implemented the VVR or KOC's power scaling. My circuit has been used on amps from 5 watts (EVJ) to 50w Komets and amps running a pair of KT88s . By running your amp at reduced voltages you drop you power levels down but keep a lot of the character of the amp intact, like the gain structure. Ken's amps are a little different in the way the gain structure is set up and IMHO I think regulating the whole amp keeps the gain structure of the amp closer to the way it was designed at full voltages. YMMV
Nothng is perfect when it comes to getting a cranked tone at very very low volumes. Attenuators require you to crank the amp up to full power levels and then attenuates the signal going to the speakers. One of the big drawbacks to atenuators is that they are hard on your power tubes while the VVR is actually prolonging the life of your power tubes. A MV by itself without some kind of voltage reduction will allow you to overdrive the preamp but not the power amp.
I don't intend for this to be a sales pitch and if someone wants to buy a board from me then that is great. If you want to take the schematic I have provided and build your own then that is cool too. I guess we are all tinkerers at heart or we wouldn't be here. I am a hobbiest and don't have an "amp company" I had boards made because a lot of people wrote me asking if I could provide them. I am not getting rich selling them and don't know how long I will keep supplying boards. I have plenty at the moment and can get more made if people still want them but I have no plans on starting a webpage or amp business so if you want them just shoot me a PM or email and I will give you particulars on pricing. I only sell either blank boards or preassembled boards for either fixed or cathode biased amps. (NO Kits you assemble yourself) They all come with instructions and BOM. There are hundreds of amps out there that are running my version of the VVR and most people love it and some find the technology just isn't their cup of tea. My best advice is to try it for yourself and form you own opinion.
Sorry to deviate from the Rocket thread but hopefully this will answer a few questions and provide you with enough info to build it into your Rocket. I have personally tried the 1/2 power switch on my first Liverpool (the Ginger clone) and found it to be pretty much useless IMO. If you just need an extra bell or whistle to add to your front panel or have an extra hole you need to fill up then go for it.
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They would be a bargain at twice, dare I say three times the price 
He has shared with the DIY amp community a mechanism for volume control (and divorce prevention, disturbing the peace violations, etc.) that is simple to install and does what it says it will do. A less charitable person might have gone commercial, and Dana would have been within his rights to do so without apology. The gentleman from West Virginia has given us a gift we can all use that can cure that age-old debate about "Which attenuator won't screw up my tone?" 
