Sparkle Control for Blues Junior III (and others)
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.
The Sparkle Control operates much like a tweed-era tone control, rolling off harsh highs gently, across a spectrum that covers the treble control and steadily declining through part of the high midrange. Instead of the usual tone control location in the preamp, the Sparkle Control is positioned just before the output stage, so it “seasons” the tone regardless of your bass, mids, and treble settings.
Why not just turn down the treble control? The treble control actually has a “balance” function built into it. When you turn up the treble, it reduces the input from the bass and mids controls, and vice versa. When you turn down the treble, it increases the bass and mids, which is why your amp will distort more easily if you back off on the treble. With the Sparkle Control, the ratio stays the same, but the highs are tamed.
You can make a Series III sound like a series II, a Series II (2001-2010 cream board) sound like a Series III, and either of them sound like the old 1995-2000 green board. It will also brighten the green board, giving it a high-end sheen that you didn’t know was there.
It works well with the presence control and gives you a wide variety of additional tones and inflections.
In this picture, the small knob on the left is the presence control. The one between the Middle and Master is the new Sparkle Control.
I’ll have recordings up shortly.