The Sansui AU-111 rewards careful documentary research. Original advertising, service information and an individual amplifier's present condition answer different questions. This guide starts with a visually checked original catalogue page and explains what a collector or owner should establish before selecting parts or planning restoration.
What the original 1969 catalogue documents
The AU-111 appears on page 11 of the scanned Sansui 1969 stereo catalogue. It describes a 6L6GC output stage operating in class AB with fixed bias, negative feedback and output transformers. The page presents the amplifier as usable with its preamplifier and main-amplifier sections separately.
The prose refers to 40 W × 2, while the specifications list 45/45 W continuous and 96 W IHF music power, each with its own stated conditions. Those are different catalogue labels, not interchangeable measurement standards or a promise about a surviving amplifier. The page lists 8 Ω and 16 Ω output impedances, 12 valves, two transistors and three diodes. Catalogue inclusion establishes availability in that document, not an exact production start date.
Build a document record for the actual amplifier
Record the full model marking, serial number, market version and voltage information visible without opening the unit. Photograph external labels and controls with the equipment safely disconnected. Keep purchase history and previous service invoices together with the documentation. Do not assume that every online AU-111 schematic or later model bearing a similar name represents your particular unit.
Valve complement in the original service manual
Pages 3–6 of the scanned Sansui AU-111 service manual describe a push-pull class AB1, fixed-bias 6L6GC output stage. Page 6 lists the following complement:
| Valve type | Quantity |
|---|---|
| 6L6GC | 4 |
| 12AX7 | 5 |
| 12BH7A | 2 |
| 6AQ8 | 1 |
The manual also describes a silicon-transistor head amplifier: describing every circuit as valve-only would be inaccurate. Its power table distinguishes 96 W IHFM music power, 45/45 W RMS left/right and 40 W × 2 RMS stereo. Preserve those labels and their measurement context.
The scan’s revision date is not established. This is a type-and-quantity list, not a valve-position map or proof of an individual unit’s present circuitry. Match the applicable manual and market version to the actual amplifier before ordering valves. A fitted valve is not proof of the intended type.
Why transformer identity matters
For a restoration assessment, ask a qualified technician to identify the fitted mains and output transformers, compare their connections with the appropriate service documentation and record evidence of replacement or rewinding. The output transformer forms part of the output-stage load and feedback relationship. Physical fit alone cannot establish an electrically suitable replacement.
An undocumented transformer substitution can change the questions that need answering before use. Original-looking covers, paint and labels do not demonstrate winding condition or safe insulation. Avoid buying a replacement solely because a seller calls it an “AU-111 transformer”; establish the applicable electrical specification and intended circuit first.
Ageing components and restoration scope
A valve test is only one part of assessing an old amplifier. The technician's evaluation should address the power supply, bias system, capacitors, resistors, wiring, sockets, switches and protective arrangements as a complete system. A noise symptom or a failed channel does not, by itself, identify a faulty valve.
Ask for a written scope that distinguishes observations, measurements, proposed changes and completed work. Keep a record of component values and circuit changes. Where preservation matters, document original parts and agree how removed components will be retained. Replacing everything indiscriminately can lose useful historical evidence; retaining every aged component without assessment is not a safety strategy.
Original and modified units
Separate cosmetic condition, circuit originality, measured performance and electrical safety when comparing amplifiers. A careful service history can be more informative than an unsupported “fully restored” description. A modified unit should be described with its modifications; originality alone does not establish fitness for use.
Before buying valves, establish the exact type required in each position and whether the original circuit remains intact. Ask about the required quantity, matching criteria and bias procedure. Do not select an arbitrary 6L6-family substitute from its base arrangement or a single maximum rating.
Questions from owners and collectors
Does a 96-watt catalogue heading mean 96 watts per channel?
No. The checked page labels 96 W as IHF music power and gives separate continuous-power figures. Preserve the complete label and conditions when discussing the specification.
Does the catalogue prove a particular amplifier is original?
No. An individual unit needs its own provenance and technical assessment.
Can I open the chassis to check the bias or transformer wiring?
Valve amplifiers contain potentially lethal voltages and may retain stored energy after unplugging. Internal inspection, diagnosis, electrical measurements and adjustment require a qualified technician. This guide provides no internal repair procedure.
Does Glass Audio offer AU-111 restoration services?
This article documents public-source research. It does not advertise an amplifier repair service or claim restoration experience.
Sources and related reading
The historical observations above refer to page 11 of the original 1969 catalogue scan, visually reviewed on 15 October 2026. The scan remains with its external publisher; no redistribution permission is claimed. The service-manual observations refer to visually reviewed pages 3–6 of the linked original manual scan; no manual files are reproduced here.
For valve selection, read how to interpret a valve datasheet and explore the manufacturer datasheet library. Contact Glass Audio with the exact valve designation and equipment documentation for a product enquiry. This public guide contains no unpublished book manuscript or proprietary restoration research.