David Allen and I have been working on a premium-quality output transformer for well over a year. We have developed a new bifilar-wound unit (the center tap is not only the center of the number of turns but also exactly one half of the total resistance) with improved bass response. We’re calling it the TO20B because its specs are the same as the TO20, but it is a different design internally. It is a more “hi-fi” approach than our old school/vintage style TO20. Like the TO20, it uses the more-efficient, grain-oriented M-6 lamination steel, has pretinned leads, and, of course, is made in the U.S.A. The TO20, with its more vintage-oriented layered winding, stays in the lineup.
The TO20B features an electro tin plated finish. Rated 6,600 ohms primary to 8 ohms secondary, it is ideal for a 2xEL84 or a 2x6V6 amplifier using an 8 ohm speaker load. It’s the same physical size and weight as the current TO20 unit. With 2-13/16″ mounting centers it is a perfect upgrade for many popular amps and drops right into the Blues Junior, Princeton Reverb, Pro Junior, the Excelsior, some old Gibsons and others. Read more…
Billm Audio’s ongoing collaboration with David Allen of Allen Amplification pays off again–a real upgrade power transformer! The new TP24 power transformer fits exactly and addresses a number of Blues Junior modification issues:
More heater power for octal conversions. While it’s not necessary for 6V6 output tubes, it’s essential for getting full power from the 5881 or 6L6GC.
More plate voltage. An additional 30-40 volts of B+ provides more headroom without exceeding the 400 volt rating of the coupling capacitors.
More reserve power. There’s lots of current on tap for a powerful, effortless sound.
Designed for the Blues Junior’s bridge rectifier power supply and includes the bias/solid state winding.
Cooler running under load, no overload or sag issues, as you would get with the stock PT and 5881s or 6L6s.
Click for larger image.
As you can see, the TP24 has nearly twice as much core as the stock power transformer and has an internal bell end for maximum hum protection. The TP24 benefits any Blues Junior, but it delivers the most with 5881s or 6L6s when paired with the TO26 output transformer.
New video: Here’s a link to a demonstration of the TP24 with EL84s. The higher voltage brings out the glassy nature of the EL84s, which the Blues Junior otherwise masks. The presence and sparkle controls help you dial back if you find it a bit too aggressive: Billm Blues Junior with TP24 and EL84s
New! The bias board gives you proper bias regulation for all octal tubes with the higher voltages produced by the TP24.
With the Series III, introduced in September, 2010, Fender implemented a “sparkle mod,” which means that they removed a voicing capacitor, C9 on the cream board, which limited the amp’s high-frequency brightness. The Series III is definitely brighter than previous BJrs, but it can also be harsh and strident, even irritating. The Sparkle Control makes the amount of sparkle reduction adjustable from zero (stock Series III) to the same as the series II, to even darker, like the old green board (1995-2000) Blues Juniors. When you pull up on the knob, it defeats the control and gives you the stock BJr III amount of sparkle. Read more here: Sparkle Control.
Back on September 1, 2010, when the Blues Junior Series III was introduced, I went to Guitar Center and bought the first one they’d been shipped. I promptly took it home and had in pieces on my bench. Fender claims a bunch of improvements, but only two of them affect tone: the “sparkle” mod and the new Lightning Bolt speaker. continue reading…
This brilliant new output transformer, co-developed with Allen Amps’ David Allen, is a breakthrough for the Blues Junior, Pro Junior, Princeton Reverb Reissue, and Super Champ XD. Designed from the ground up to provide big-transformer performance in the least possible space, the TO20 is built by respected US manufacturer Heyboer, fits the stock mounting holes in all of these amps and has the same height as the stock transformer. The “widebody” core is made of premium M6 steel, which has superior magnetic properties, allowing maximum efficiency and power transfer from primary to secondary. The low-profile TO20 outweighs the stock OT by at least half a pound! Continue reading.
By popular demand! People have been asking me for years for a standby switch on the Blues Junior, and here it is.
There isn’t room inside the chassis for another switch next to the power switch, even if you relocate the pilot light. Yes, you could cram a cheesy little switch in there, but we’re talking high voltage here, and only a heavy-duty switch will do. Fortunately, Carling, the same company that makes the power switch that’s in your Blues Junior, makes a clever progressive switch. It has three positions: off, standby, on–very logical. In standby, the high voltage supply is cut off. The filament and bias supplies receive power.