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Marshall JTM45 vs Marshall 1959 Super Lead
Circuit differences, stage by stage, from Gridleak’s verified redraws of both schematics: 17 differences, 30 the same.
What’s different, and why it matters
The preamp layout carries over: two channels into a shared second stage, a cathode follower, then the tone stack. Nearly everything around it changes. The 1959 runs four EL34s instead of two KT66s, silicon diodes instead of a GZ34, a 33 kΩ slope resistor and 500 pF treble cap instead of 56 kΩ and 270 pF, and a 0.005 µF bright cap where the JTM45 has 500 pF.
- The JTM45 runs two KT66s and the 1959 Super Lead runs four EL34s. KT66s are usually described as full and smooth, with a softer breakup; EL34s are usually described as forward in the upper mids, with an earlier, grittier breakup. With four output tubes to two, the 1959 Super Lead makes more power (the JTM45 is rated 45 W, the 1959 Super Lead 100 W), so it stays clean to a higher volume than the JTM45.
- The JTM45 rectifies with a GZ34 tube, the 1959 Super Lead with silicon diodes. A tube rectifier lets the supply voltage dip when the amp is played hard (the 'sag' that softens the pick attack); diodes hold the voltage up, for a tighter, faster response.
- Same tone-stack layout, different values: slope resistor 56 kΩ vs 33 kΩ; treble cap 270 pF vs 500 pF. In practice the smaller slope resistor in the 1959 Super Lead gives a less scooped midrange and more level out of the stack, and the larger treble cap in the 1959 Super Lead lets the treble control reach further down into the upper mids.
- Negative feedback: 27 kΩ (16 Ω tap) in the JTM45, 47 kΩ (8 Ω tap) in the 1959 Super Lead.
What they share: a long-tail pair phase inverter, the same tone-stack layout and a cathode follower.
At a glance
| Marshall JTM45 | Marshall 1959 Super Lead |
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| Years | 1962–1966 | 1965–1981 |
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| Origin | UK | UK |
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| Rated power | 45 W | 100 W |
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| Channels | 2 | 2 |
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| Preamp tubes | 3 × ECC83 | 3 × ECC83 |
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| Power tubes | 2 × KT66 | 4 × EL34 |
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| Rectifier | Tube (GZ34) | Solid-state (silicon diodes) |
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| Phase inverter | Long-tail pair | Long-tail pair |
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| Master volume | none | none |
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| Effects loop | no | no |
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| Reverb | no | no |
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| Notable players | Eric Clapton | Jimi Hendrix, Eddie Van Halen, Angus Young, Jimmy Page, Eric Clapton |
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Stage by stage
Inputs and channels
| Marshall JTM45 | Marshall 1959 Super Lead |
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| Inputs | 4 | 4 |
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| Channel switching | front panel only / none | front panel only / none |
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| Voicing / power switches | none | none |
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Preamp
| Marshall JTM45 | Marshall 1959 Super Lead |
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| Preamp tubes | 3 × ECC83 | 3 × ECC83 |
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| Triode gain stages (all channels) | 3 | 3 |
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| Most gain stages in series | 2 | 2 |
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| Gain stage 1 | ECC83 · plate 100 kΩ · cathode 820 Ω, 250 µF bypass (shared) (×2: Ch. 2 first stage, Ch. 1 first stage) | Normal channel: ECC83 · plate 100 kΩ · cathode 820 Ω, 250 µF bypass; High-treble channel: ECC83 · plate 100 kΩ · cathode 2.7 kΩ, 0.68 µF bypass |
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| Gain stage 2 | ECC83 · plate 100 kΩ · cathode 820 Ω, unbypassed | ECC83 · plate 100 kΩ · cathode 820 Ω, 0.68 µF bypass |
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| Cold-biased stage (clipper) | none | none |
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| Cathode follower | yes | yes |
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| Bright cap(s) | 500 pF | 0.005 µF |
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| Coupling caps (preamp) | 0.02 µF | 0.0022 µF / 0.022 µF |
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| Diode clipping | no | no |
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Tone stack
| Marshall JTM45 | Marshall 1959 Super Lead |
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| Type | Treble / bass / middle stack with a slope resistor | Treble / bass / middle stack with a slope resistor |
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| Position | after gain stage 2, driven by a cathode follower; no gain stages after it | after gain stage 2, driven by a cathode follower; no gain stages after it |
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| Slope resistor | 56 kΩ | 33 kΩ |
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| Treble cap | 270 pF | 500 pF |
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| Bass cap | 0.02 µF | 0.022 µF |
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| Middle cap | 0.02 µF | 0.022 µF |
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| Pots | treble 250 kΩ · bass 1 MΩ · middle 25 kΩ | treble 250 kΩ · bass 1 MΩ · middle 25 kΩ |
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| Master volume | none | none |
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Effects
| Marshall JTM45 | Marshall 1959 Super Lead |
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| Effects loop | no | no |
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| Reverb | no | no |
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| Tremolo / vibrato | no | no |
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Phase inverter
| Marshall JTM45 | Marshall 1959 Super Lead |
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| Type | Long-tail pair | Long-tail pair |
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| Tube | ECC83 | ECC83 |
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| Plate loads | 82 kΩ / 100 kΩ | 82 kΩ / 100 kΩ |
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| Tail / cathode load | 10 kΩ | 10 kΩ |
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| Cathode bias resistor | 470 Ω | 470 Ω |
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| Input coupling cap | 0.02 µF | 0.022 µF |
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| Coupling to power tubes | 0.1 µF | 0.022 µF |
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Feedback
| Marshall JTM45 | Marshall 1959 Super Lead |
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| Negative feedback | yes | yes |
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| Feedback resistor | 27 kΩ | 47 kΩ |
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| Feedback taken from | 16 Ω tap | 8 Ω tap |
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| Presence | yes (5 kΩ pot, 0.1 µF cap) | yes (5 kΩ pot, 0.1 µF cap) |
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| Resonance / depth | no | no |
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Power amp
| Marshall JTM45 | Marshall 1959 Super Lead |
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| Power tubes | 2 × KT66 | 4 × EL34 |
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| Configuration | Push-pull | Push-pull, 2 tubes per side in parallel |
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| Bias | Fixed bias | Fixed bias |
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| Screen resistors | 470 Ω | 1 kΩ |
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| Grid stoppers | none | 5.6 kΩ / 56 kΩ |
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Power supply
| Marshall JTM45 | Marshall 1959 Super Lead |
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| Rectifier | Tube (GZ34) | Solid-state (silicon diodes) |
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| First filter (reservoir) | 32 µF | 100 µF + 100 µF in series |
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| Filter nodes, in order | 32 µF → 32 µF → 16 µF → 16 µF | 100 µF + 100 µF in series → 100 µF + 100 µF in series → 100 µF (2 × 50 µF) → 50 µF → 50 µF |
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| Filter choke | yes (20 H) | yes |
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| Highest DC voltage printed on the drawing | not printed | not printed |
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| Printed bias voltage | not printed | not printed |
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