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This is a retrospective post from a procedure I undertook about five years ago. \u00a0I originally\u00a0documented it on the Amp Garage\u00a0forums, but you had to be a member to view the documentation, so finally got around to sticking it in a publicly accessible post.<\/p>\n
WARNING<\/strong>: \u00a0The voltages found inside tube amplifiers can and do kill people. \u00a0If you’re not comfortable working\u00a0with very high voltages, find someone who is. \u00a0Seriously, implementing this modification can kill you. \u00a0Proceed accordingly.<\/span><\/p>\n I went\u00a0down the route of Dana Hall’s VVR power scaling module. \u00a0From memory it cost about $20 AUD in 2011’ish. \u00a0At the time of the install, my amp was still under warranty, so wanted an installation that could be reversed with next to no evidence that I’d played inside.<\/p>\n There are two\u00a0lines\u00a0the VVR module needs to intercept. \u00a0The B+ and bias voltage lines.<\/span><\/p>\n The simplest way to hook into the B+ line was via two points that already have connectors on the circuit board. \u00a0In the schematic we see it at the B+ and SP1 points. \u00a0Note that although they are separate points, they are directly connected.<\/p>\n Here we can see the traces on the back of the board, just to prove that B+ and SP1 are directly connected, as in 0\u2126 between them.<\/p>\n The photo below shoes the front of the board. \u00a0because B+ and SP1 are connected, we only have to feed one of them to the VVR board. \u00a0The B+ marked connector wire therefore goes to the B+ IN\u00a0<\/strong>on the VVR board. \u00a0Below the black and white image is a colour shot of the same area. \u00a0The red wire goes to\u00a0B+ IN<\/strong>, and the yellow comes from\u00a0B+ OUT<\/strong>, which splits into two and takes the connectors which were originally connected into the amp’s B+ and SP1 points. The intercept point here is C- as shown in the schematic below. \u00a0Lucky for us at this point the line is moved to another board via a ribbon cable, so easy to hook into.<\/p>\n To break into C-, I slit the end line of the ribbon, to allow it to be isolated. \u00a0Red goes to BIAS IN <\/strong>on the VVR board, yellow comes from\u00a0BIAS OUT\u00a0<\/strong>on the VVR board.<\/p>\n The board was mounted with the B+ MOSFET onto the base of the chassis as a heat sink, with a mica insulator. \u00a0The BIAS MOSFET was lifted and isolated, so that it didn’t earth on the chassis. \u00a0From here lines run up to the potentiometer, mounted in what was the standby switch hole (I hold firmly to the view that\u00a0the standby switch in guitar amplifiers is a triumph of marketing over engineering). \u00a0Since the photo below was taken, the standby switch has been removed, and the switch lines jumped with some cable and spade connectors.<\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n It’s been a good five or six years since I installed the VVR, and I remain exceedingly happy with it. \u00a0Not only would I do it again to my Hot Rod Deluxe, but would also certainly install it into any tube amp I may buy in the future.<\/p>\n Sadly it appears as though Hall Amplifiers who made the VVR module are no longer around. \u00a0Fortunately London Power still appear to offer kits<\/a>.<\/p>\n Feel free to leave any questions in the comments.<\/p>\n","protected":false},"excerpt":{"rendered":" It’s common knowledge that the Rod Rod Deluxe is a fantastic amp, it’s also LOUD. \u00a0I play live a lot, but almost all my playing is with my amp mic’d and run through a PA, so really need to maintain a manageable stage volume without loosing the sound of driven tubes, especially the sound of … Continue reading Taming the Fender Hot Rod Deluxe with VVR power scaling.<\/span> Finding the B+ intercept point<\/strong><\/h2>\n
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\n<\/a><\/p>\n<\/a><\/p>\nFinding the BIAS intercept point<\/h2>\n
<\/a><\/p>\n<\/a><\/p>\nMounting the VVR board<\/h2>\n
<\/a><\/a><\/p>\nThe result<\/h2>\n
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