History · British-style

The Hiwatt line

Dave Reeves trained in electronics in the Royal Air Force and worked at Mullard; made redundant in 1966, he set up Hylight in September of that year and built amplifiers under contract for Ivor Arbiter's Sound City shop. When the Who's management fell out with Marshall in 1967 and John Entwistle and Pete Townshend took up Sound City amps, the customised heads Reeves was building for them became the basis of his own badge: the DR103 Custom 100. What followed was one circuit at four sizes. A single four-valve preamp — two cathode followers, a tone stack and a master volume — sits in front of 50, 100, 200 and 400 watts of EL34s across the DR504, DR103, DR201 and DR405, and one factory-lineage sheet says so on its face, heading itself "HIWATT PREAMP AND DRIVE" over the model list "DR504 DR405 DR103 DR201 ALL COMBO'S". Partridge transformers and, from 1971, Harry Joyce's standardised wiring gave the line its reputation for headroom and for being built like equipment rather than like instruments.

1964–1995 8 models 1 documented 7 history-tier

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

Documented circuit — links to its page History-tier — placed & sourced, circuit not yet drawn Succession within the line

The models

Designation	Years	Watts	Output stage	Key change	Circuit
Hiwatt (1964 one-off)	1964–1964	—	—	The name appears on an amplifier two years before the company existed. The general reference used here records it as a single project rather than a product, and no circuit or specification for it was found, so nothing is claimed beyond the date and the fact of it.	history entry
L100	1966–1969	100 W	push-pull 4×EL34	Not a Hiwatt, but the amplifier the first Hiwatt was. Reeves founded Hylight in September 1966 after being made redundant at Mullard and contracted with Ivor Arbiter's Sound City music store to build Sound City-branded guitar amplifiers; the L100 was the 100-watt head of that range. The customised versions he built became the DR103. The bracket here runs from the founding of Hylight to the point the Hiwatt badge takes over, and is a bracket rather than a production record — no dated Sound City drawing was read for this entry, and no valve complement is claimed.	history entry
DR103	1969–1981	100 W	push-pull 4×EL34	The model the badge is built on, and the circuit this corpus documents: four inputs across a Brilliant and a Normal channel, a four-valve preamp with two cathode followers and a master volume, an ECC81 long-tailed pair and four EL34s over a silicon bridge. From 1971 the certified government wirer Harry Joyce standardised the schematics and eliminated the variations that had accumulated in a hand-built run, capping his own output at forty amplifiers a month to hold the standard. The bracket ends at Reeves's death in 1981; the model itself continued under later owners in revised form.	DR103 circuit ↗
DR504	1969–1981	50 W	push-pull 2×EL34	The same amplifier at half the output valves. Its factory-lineage sheets share the preamp and driver page with the DR103, the DR201 and the DR405, and change only behind the phase inverter: two EL34s on 22 kΩ grid stoppers and 1 kΩ 5 W screen stoppers, a Partridge output transformer TG 6556 / TH 7551, and a supply whose sheet prints 460 V at the HT node and −36 V of fixed bias. The introduction year is not pinned by the sources read here, so the row is bracketed to the Reeves-era run; the July 1979 sheets are dated evidence of production inside it.	history entry
DR201	1969–1981	200 W	—	One of the two high-power heads the general reference credits to the urging of the bassist Glenn Cornick, who wanted more than a 100-watt head could give. It runs the same preamp and driver page as the DR103. No introduction year and no valve complement are claimed: neither was found in the sources read, so the row is bracketed to the Reeves-era run.	history entry
DR405	1969–1981	400 W	—	The largest head of the line, and the other of the two Glenn Cornick asked for. Like the DR201 it sits behind the shared preamp and driver page. Its introduction year and valve complement are likewise not pinned by the sources read, and are not claimed.	history entry
DR103 (Biacrown era)	1981–1984	100 W	push-pull 4×EL34	Reeves died in 1981 after a fall down a staircase. Several Hiwatt employees incorporated as Biacrown Ltd and carried the amplifiers on "with minor circuit changes until 1984, when the company folded for financial reasons". What those changes were is not documented in the sources read here, so nothing is claimed about the circuit of this period beyond the fact that it moved.	history entry
DR103 (Issue 3/4 sheets, S/No. AB0309 onwards)	1994–1995	100 W	push-pull 4×EL34	The revision the surviving factory title blocks actually describe, and a different amplifier from the four-input head: one jack per channel, 470 kΩ volumes with a 220 kΩ lin master and a 100 kΩ lin middle, 10 kΩ preamp droppers in place of the 47 kΩ and 22 kΩ of the earlier chain, and printed working voltages of +160 V at the input plate and +140 V at the second stage. The years given are the DATES ON THE DRAWINGS — 22/11/94 for the supply sheet, 25/04/94 for the output stage, 19/05/95 for the preamp — not a production bracket, which the sources read do not give. The sheets carry no serial-number end, only a start: "S/No. AB0309 Onwards". The accompanying specification page and the preamp drawing contradict each other on the phase-inverter valve, the page calling it an ECC81 and the drawing lettering all four preamp valves ECC83.	history entry

A circuit ↗ badge links a fully documented circuit — redrawn schematic, verified operating point, parts list. A history entry is placed and sourced here but its circuit isn't drawn yet; contributions are welcome.

Dating & notes

This family carries a documentation problem the Fender and Marshall lines do not, and it is stated rather than smoothed over: the DR103 that people mean — the four-input Reeves-era head — has no factory drawing among the documents read for this corpus. The sheets that carry a proper factory title block are all dated 1994-95 and describe a later two-input revision. The four-input circuit entry therefore rests on published redraws and is published as a draft. Three further gaps are left open rather than filled. Introduction years for the DR504, DR201 and DR405 were not found, so those rows are bracketed to the Reeves-era run instead of dated. What Biacrown's "minor circuit changes" were is not documented in anything read here. And the dating of the last row sits oddly against the row before it: the general reference has Biacrown folding in 1984, yet the manual bearing the 1994 and 1995 drawings names Biacrown Ltd as its distributor — no source read here reconciles the two, so both are recorded as they stand. Only the DR103 has a documented circuit entry in this corpus at present; every other row is history-tier (circuit_ref: null) until one is built.

Sources

Every model above carries its own citations in the corpus data file. Browse the full source list for this line: history/families/hiwatt.yaml.

← All family lines · See the full lineage tree ↗