We are introducing a new service in support of the DIY kits. Read more here!
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.
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.
Would your Blues Junior look infinitely cooler with one of these? See here for how it’s done: http://billmaudio.com/wp/?page_id=1035
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.
This is the 1000th Billm-modded Blues Junior.
New! I finally added some sound files so you can hear what it sounds like.
Or as close as I can figure, given the number of components I’ve ordered over the years, shipping records, etc.
I decided to pull out all the stops on this one. I started with a basic black Blues Junior, the perfect platform for a stealth amp that can blow away some much more expensive hardware.
With 5881s, it puts out 25 watts and sounds awesome!
Read more about it here.
June 17, 2011, Added Installing a Jewel Light
June 13, 2011, Added Installing Blues Junior Tilt-Back Legs
April 22, 2011, Added Removing Rusted Screws, Relic Blues Junior
April 3, 2011, Added Pro Junior and Pro Junior Adjustable Bias, with video
March26, 2011, Added 1967 Princeton Reverb Refurb
March 4, 2011, Added Tracking Down Hum in a Blues Junior
January 20, 2011, Updated Re-tension Your Tube Sockets, Resolder Output Sockets
September 6, 2010, Added video to Removing the Circuit Board
September 1, 2010, Added Series III Blues Junior: What’s Different?
April 6, 2010, Added “Fixing Simple Printed Circuit Board Mistakes”
July 16, 2009, Updated “Aftermarket Knobs: Bad Idea” with a cure for shaft wobble.
May 19, 2009, Added “EL84 vs. 6V6 vs. 5881”
May 11, 2009, Updated “The TwinStack Mod”
May 1, 2009, Updated, added speaker reviews. “The Right Speaker for your Blues Junior”
April 26, 2009, Added standby power switch to available Mods and Services
April 16, 2009, Updated, added speaker reviews. “The Right Speaker for your Blues Junior”
April 2, 2009, Added “The Right Speaker for your Blues Junior”
April 2, 2009, Added “Footswitches for Fat/Clean Boost Footswitch Option”
March 31, 2009, Updated “Blues Junior Revision History” with speaker basics
March 27, 2009, Added ECC88 info (very bad idea), “What About Tubes?”
March 15, 2009: Added “Bad Caps in New Blues Juniors”
February 19, 2009: Interviewed at the 5th Fret blog
February 8, 2009: Added “Aftermarket Knobs: Bad Idea”
February 7, 2009: Updated “Warning”
February 6, 2009: Added “Blues Junior Revision History”
February 1, 2009: New information and photo, “What About Tubes?“