History · Fender-style

The Champ line

Fender's smallest student amplifier and its longest-lived circuit idea: a single-ended power tube, no phase inverter, no tone stack. The line begins with the late-1940s Champion student amps, passes through the tweed 5-series revisions that swapped an octal pentode preamp for a 12AX7, reaches its most copied form as the 5F1, and continues under blackface (AA764) and silverface cosmetics into the early 1980s. Throughout, the output stage stays a single cathode-biased 6V6 — the defining constant of the family.

1948–1968 8 models 5 documented 4 verified 3 history-tier

Era timeline — each bar spans a model's production years; the chain from top to bottom is the line's succession.

Verified circuit — operating point checked against a published chart Draft circuit — drawn and sourced, verification not complete History entry — placed & sourced, circuit not drawn yet Succession within the line

The models

Designation	Years	Watts	Output stage	Key change	Circuit
800	1948–1949	4 W	single-ended 6V6	The first entry in the line and Fender's earliest student amp: a single octal pentode preamp driving one single-ended 6V6, in a TV-front cabinet with an 8-inch speaker (the "800"). Output rating is approximate — these were never formally catalogued with a wattage figure. Sources for 800 (1) Wikipedia, Fender Champ — Champion 800 era, cabinet, speaker and single-ended 6V6 output — en.wikipedia.org	history entry Open requests for 800 ↗ Suggest research for 800 ↗
5B1	1949–1953	4 W	single-ended 6V6	Same single-ended 6V6 recipe stepped down to a 6-inch speaker (hence "600") in a two-tone cabinet, carrying a 6SJ7 pentode preamp, 6V6 output and 5Y3 rectifier. Dating is soft: the Champion 600 name spans roughly 1949 into the mid-1950s and overlaps the wide-panel tweed 5C1 revision. Sources for 5B1 (1) Wikipedia, Fender Champ — Champion 600, 5B1 designation, 6SJ7/6V6/5Y3 complement and 6-inch speaker — en.wikipedia.org	history entry Open requests for 5B1 ↗ Suggest research for 5B1 ↗
5C1	1953–1955	4 W	single-ended 6V6	The Champion 600 circuit carried into a wide-panel tweed cabinet as the model name shifted toward "Champ." Topology is essentially unchanged from the 5B1 — still a 6SJ7 pentode front end into a single-ended 6V6. Tweed-era dates are approximate. Sources for 5C1 (2) EL34World schematic archive, Fender Champ 5C1 sheet (indexed by designation; drawing prints the circuit number) — el34world.com Wikipedia, Fender Champ — Champion 600 tweed / 5C1 wide-panel transition — en.wikipedia.org	5C1 circuit ↗
5D1	1954–1955	4 W	single-ended 6V6	A short-lived component revision within the wide-panel tweed era, still built around the 6SJ7 pentode preamp and single-ended 6V6. It sits between the 5C1 and the 12AX7-based 5E1; exact start/end dates overlap its neighbours and are not firmly documented. Sources for 5D1 (1) Wikipedia, Fender Champ — tweed 5-series revision sequence preceding the 5E1 — en.wikipedia.org	history entry Open requests for 5D1 ↗ Suggest research for 5D1 ↗
5E1	1955–1957	5 W	single-ended 6V6	The pivotal revision: the octal 6SJ7 pentode preamp is replaced by a 12AX7 twin triode used as two cascaded gain stages, in a narrow-panel tweed cabinet. This is the two-triode, single-ended 6V6 architecture the rest of the line keeps. Sources for 5E1 (2) AmpBooks classic-circuit analysis, Fender Champ 5E1 — stage values and 6V6 operating point — www.ampbooks.com EL34World schematic archive, Fender Champ 5E1 sheet (indexed by designation) — el34world.com	5E1 circuit ↗
5F1	1958–1964	5 W	single-ended 6V6	The definitive tweed Champ and the most reproduced circuit in the line: the 5E1's two-stage 12AX7 into a single-ended 6V6, with an 8-inch speaker and revised power-supply filtering. Topology is a light refinement of the 5E1 rather than a redesign. Sources for 5F1 (2) Fender 5F1 published drawing, read directly for values and node structure (archived at EL34World, indexed by designation) — el34world.com Rob Robinette, 'How Amps Work' — 5F1 component roles and B+ structure — robrobinette.com	5F1 circuit ↗
AA764	1964–1968	5 W	single-ended 6V6	Blackface cosmetics, and the first Champ with tone controls: a 250 kΩ treble-and-bass stack between the two 12AX7 stages. The supply also stiffens (+360/+350/+330 V against the 5F1's +340/+295/+250) and the feedback loop moves onto a 47 Ω divider leg, but the output stage stays a cathode-biased single-ended 6V6. The AA764 designation is shared with the tremolo-equipped Vibro Champ sibling below — same audio path, same designation, a different drawing. Sources for AA764 (2) EL34World schematic archive, Fender Champ AA764 sheet (indexed by designation) — el34world.com Wikipedia, Fender Champ — blackface AA764 / Vibro Champ tremolo introduction — en.wikipedia.org	AA764 circuit ↗
AA764	1964–1967	5 W	single-ended 6V6	The AA764 drawing's tremolo-equipped sibling: the plain Champ's audio path (two-stage 12AX7 preamp, treble-and-bass stack, cathode-biased single-ended 6V6, 5Y3GT rectifier) carries over component-for-component, plus a second, dedicated 12AX7 running a bias-vary tremolo oscillator (Speed and Intensity controls) ahead of the same output stage. Fender's own drawing prints "VIBRO-CHAMP AA764" — the identical designation the plain Champ sheet carries, so the two circuits are filed apart by model: the plain Champ under the bare AA764, the Vibro Champ under an AA764 qualified by the model name. Sources for AA764 (3) EL34World schematic archive, Fender Vibro Champ AA764 sheet (indexed by designation; two print runs exist under Fender Electric Instrument Company and later CBS-era letterheads, both AA764 and both read for this entry) — el34world.com Mojotone/Ampwares Fender field guide, 'Blackface Vibro Champ' — AA764, 1964-1967, cathode-biased 6V6GT/5Y3GT, single 8-inch Oxford 8EV speaker — mojotone.com Wikipedia, Fender Champ — blackface AA764 / Vibro Champ tremolo introduction — en.wikipedia.org	AA764 (Vibro Champ-style) draft ↗

The circuit column says how far this model has been documented, in three states. A circuit ↗ badge links a verified circuit: redrawn schematic, parts list, and a simulated operating point held against the published voltage chart under a maintainer's sign-off. A draft ↗ badge links a circuit that is drawn, sourced and published, but has not completed that chain — its own page states what is unresolved. A history entry is placed, dated and sourced here, but its circuit isn't drawn at all yet.

Dating & notes

The AA764 designation covers two drawings in this family: the plain Champ, which keeps the bare designation, and its tremolo-equipped Vibro Champ sibling, whose own drawing prints the identical AA764 and which is therefore filed under a designation qualified by the model name. Both rows above share that designation deliberately; it is not a duplicate. Tweed-era production dates (5B1 through 5D1) are fuzzy and overlap between revisions; the ranges given are the defensible spans, not firm year-by-year boundaries. Wattage figures for the pre-5E1 Champions were never formally catalogued and are approximate. After the AA764, the Champ and Vibro Champ continued under silverface cosmetics from 1968 into the early 1980s (with a brief blackface reissue near the end) — the single-ended 6V6 output stage unchanged throughout. Marketing names are used descriptively.

Sources

Each model's own citations are listed in its row above, under “Sources for …”. The complete data behind this line — every model's fields as stored, including those the page doesn't print — is in history/families/champ.yaml.

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