Catalinbread Formula No. 5 User Manual

FORMULA NO. 5 USER GUIDE
INTRODUCTION
The Catalinbread Formula No. 5 was inspired by the old tweed amps from the 1950's, most notably
the 5E3 circuit. The character of the 5E3 is very unique. It has very minimal power filtering, low plate
voltages, elemental tone stack, and does next to nothing to control the low end between gain
stages, not to mention the under-rated output transformer and speaker. The entire system runs
inefficiently resulting in a loose bass, greasy mids, cutting treble, and incredible grit – none of these
qualities were ideal or intentional back in the day. In spite of this, over the past five decades the amp
inspired some of the coolest, most sought after guitar tones ever recorded. It's practically a fuzz
pedal with a built-in speaker!
We've captured the unique qualities of these amps in the Formula No. 5. For this circuit we felt
cascaded JFET gain stages yielded the most authentic sounding result. They have a softer sound
than MOSFETs. JFETs also have much more natural attack/decay behavior than diode clipped rigs
which are pingy on the attack and fizzy on the decay. We chose capacitor types that enhanced the
midrange and burnished the treble. And perhaps most importantly, we paid specific attention to the
input sensitivity of circuit so that it feels and behaves just like the amp it is seeking to emulate. The
attack characteristic at the pick, the clean up at your guitar's volume knob - all of these things are
absolutely crucial to capturing the 5E3 vibe and when combined make for a very dynamically
sensitive playing experience.