Top jimmy bias amp 2 patches serial numbers#

Moving through the circuit, the Super LeadвЂ™s volume one control has a 500pF bright capacitor wired across it and there are some minor component value differences in the tone stack вЂ“ notably a 500pF capacitor on the treble control rather than 250pF. Turning a Super Lead into a Super Bass, and vice versa, is relatively simple.Д«roadly speaking the differences are as follows: the Super BassвЂ™ first preamp tubeвЂ™s cathodes share a cathode bias resistor and capacitor but the Super LeadвЂ™s V1 cathodes each have their own. Why did the likes of Paul Kossoff, Eric Johnson, Jimi Hendrix, Jimmy Page and John Frusciante chose to use a Super Bass rather than a Super Lead? Super Bass enthusiasts will no doubt mention less aggression, warmer tones and a more pedal-friendly front end.Д¬onsequently, the Super Bass has developed something of a cult following, but the differences between a Super Lead and a Super Bass amount to little more than a handful of components. Two of the filter caps, two signal caps and V1вЂ™s cathode bias cap are replacements, and one of the speaker output jacks has been changed, but other than that, the amp is surprisingly original.

Almost all of the carbon film resistors look original and rather than the fabled вЂmustardвЂ™ signal capacitors, this amp has grey RS types that appear factory fitted. Relatively little work has been done on the circuit board over the years, but it can be tricky to identify the components that have been replaced because Marshall used whatever they could get hold of.

Having one would provide some physical protection for the valves, but these amps run hot, and keeping the back open is probably advantageous in a home or studio environment. All the evidence suggests this amp was made in 1967 and is almost certainly one of the very earliest JMP Super Bass 100 amps that Marshall made.ДЄlthough the original handle, black Tolex and gold piping remain in decent condition for their age, the back panel is missing. Marshall later shifted the diodes closer to the power transformer, just before changing the model designation to JMP. The JTM rectification diodes were located centrally between eight sideways-mounted 32mF RS filter capacitors. The earliest JMP Super Bass models inherited the JTM 45 Super 100вЂ™s larger power supply board. More clues may be gleaned by looking at the circuit. Large rubber cabinet feet replaced smaller grey feet in 1969, and even though the feet on this amp are modern, grey residue from the smaller originals can still be seen when theyвЂ™re removed. Marshall also transitioned from aluminium to a steel chassis in late 1967. The model designation was soon changed to JMP with black lettering on the front panel, but Super Bass 100 was retained. By 1967 there was a black flag JTM logo on the front panel with a gold Plexi rear panel adorned with вЂSuper Bass 100вЂ™. MarshallвЂ™s earliest 100-watt bass head was the JTM 45/100 model with вЂSuper 100 AmplifierвЂ™ on a white rear panel and the word вЂbassвЂ™ adjacent to the speaker impedance selector.

ThereвЂ™s an вЂSBвЂ™ stamp on the rear of the chassis вЂ“ no prizes for guessing that stands for Super Bass вЂ“ followed by a number that closely corresponds to other Super Bass examples we found that have been identified as 1967 models. Instead we have to look at the ampвЂ™s features for clues.

Top jimmy bias amp 2 patches serial numbers#

This Super Bass вЂ“ the JMP 1992 Super Bass 100, to use its full model name вЂ“ is a very early example and comes courtesy of Vintage Tone Factory, a boutique guitar recording studio specialising in remote reamping that can be found via /vintagetonefactory.Дating 1960s Marshalls accurately can be problematic because there was no coherent system of serial numbers until July 1969. MarshallвЂ™s bass amps were arguably more popular with A-list bassists than the Fender Bassman ever was вЂ“ Jack Bruce, Chris Squire and Lemmy were fans вЂ“ but the Super Bass has always been revered by guitarists too. The Fender Bassman provided the early inspiration for Marshall amplifier designs but, both sonically and in terms of their circuit architecture, they soon evolved into something entirely their own.