A short and unusual line. The tweed 5F10 Harvard is the only true member: a compact single-channel amp that, unlike its Champ and Princeton stablemates, ran a fixed-bias push-pull pair of 6V6s driven by a cathodyne phase inverter — more power stage than a student amp but with a deliberately spare front end. The later 6G10 shares the Harvard name in cosmetics only; it was a leftover-parts oddity built on single-ended tweed Princeton chassis, not a continuation of the 5F10's push-pull design.
| Designation | Years | Watts | Output stage | Key change | Circuit |
|---|---|---|---|---|---|
| 5F10 | 1955–1961 | 10 W | push-pull 2x6V6GT | The Harvard proper: a two-stage single channel with only a volume and a treble-cut control, feeding a 12AX7 cathodyne phase inverter and a fixed-bias push-pull pair of 6V6GTs (a selenium rectifier supplies the negative bias). Rated at 10 watts, it is the push-pull middle ground between the single-ended Champ/Princeton and the larger Deluxe. The preamp valve is listed as 6AV6 or 6AT6 across the run; the corpus's documented 5F10 carries the 6AT6. This row spans the whole 5F10 run. The front end changed inside it — early chassis open on a 6AV6, later ones on the 6AT6 — and the documented circuit is the 6AT6 revision, so its own entry dates from that change rather than from the designation itself. Sources for 5F10 (2)
| 5F10 circuit ↗ |
| 6G10 | 1962–1963 | 5 W | single-ended 6V6 | Not a push-pull Harvard at all. This rare model reused leftover tweed 5F2-A Princeton chassis and cabinets after the brown Princeton launched, so it is a single-ended 6V6 circuit — essentially a rebadged tweed Princeton wearing the Harvard name (some shipped with 5F2-A tube charts, the Princeton name struck out). It breaks the 5F10's push-pull identity rather than continuing it; no derivation from the 5F10 is claimed here. Sources for 6G10 (2)
| history entry Open requests for 6G10 ↗ Suggest research for 6G10 ↗ |
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.
The Harvard is effectively a one-model family: the 5F10 is the only amp built as a Harvard from the ground up. The 6G10 is a name-only continuation on single-ended Princeton chassis and is included for completeness, flagged as such — the two do not share a power-stage topology. 6G10 wattage follows the single-ended 6V6 5F2-A chassis it was assembled from and is approximate. Marketing names are used descriptively.
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/harvard.yaml.