Tools, Tones and Toys for Guitarists
This was long overdue – I finally got around to making a half-decent wiring rig. I’d been using cardboard from pizza boxes (yes really), which worked, but it was pretty ordinary to say the least. Once the parts were laid out and the enclosure marked up, I drilled the pilot holes in the chassis, then … Read more
Another great contribution by Chris Stelloh! This is a layout drawn from the Madbean Oracle project, which is, essentially the Boss CS-3 compression sustainer. I really like the sound of VCA-driven compressors, especially on sampled drum sounds. This Boss pedal has been around for about 40 years, and the Madbean version makes a few slight … Read more
GIBSON GA-30 GUITAR AMPLIFIER SCHEMATICS This is one of the GA-30 amps – there were a few by the sounds of it. While they share a similar topology, there are clearly some differences from the one above. Apart from changing the circuit, their appearance also varies over time – I’m not going to try and … Read more
6SJ7 preamp, 6SN7 paraphase inverter, 2 x 6V6 with local negative feedback. GIBSON BR6-F GUITAR AMPLIFIER SCHEMATIC Clearly a bit of work has been done on this one – just using the pic as an example of circuit construction. Low impedance input 6SJ7 PRE Ra 220k Rk 2k2 20u bypass Screen 2m2, 50n bypass 10n … Read more
5879 pentode premap, which is an improved version of the E8F6 – uses a Vox style cut control across the plates of the phase inverter. Paraphase inverter, driving 2 x cathode biased 6V6. GIBSON GA-40 GUITAR AMPLIFIER SCHEMATIC
Ignoring the gigantic and overly complicated trem section – this is one of my favourite sounding AC amps, which is most likely the inspiration for the Matchless DC30 pentode channel. VINTAGE VOX AC-15 SCHEMATIC Version: NO V-1-5 / OA/031 Apparently this schematic is a v3, redrawn by Thomas Organ, with some different component numbering. … Read more
The Vox AC6 is a departure from the Vox AC2 & AC4, in that it has a 12AX7 preamp, negative feedback, no trem, and for some reason, the tone control is before the first triode – it’s a bit of an odd-ball in the Vox lineup from the time. The 12AX7 preamp arrangement would give … Read more
Another early Vox model is the AC2. It’s often described as being the same as an AC4, but there is one key difference — the tone control. Instead of sitting in the preamp like the AC4, the AC2’s tone control is wired in the power stage, between the EL84 plate and the B+ supply (effectively … Read more
Despite the name – and even the familiar look – the original Vox AC4 has very little in common with the modern “AC4” amps wearing the same badge. The cabinet and the single EL84 output stage are about all they share. The AC4 started life as the AC2 in 1958. Fair to say that the … Read more
Schematic is avaiable HERE. Note that the electrolyctic caps have been oriented in the correct direction in the layout.