Audio Research Reference 80S Stereo Power Amplifier

The Audio Research Reference 80S is a fully balanced vacuum-tube stereo power amplifier delivering 70 watts per channel from 20Hz to 20kHz from two KT150 output tubes per channel. Designed as the most accessible stereo amplifier in Audio Research’s Reference series, the REF80S combines the company’s fully balanced differential topology with automatic tube bias, switchable Pentode/Triode operation, 4/8/16-ohm output taps and dual GhostMeter displays. Audio Research

Hand-built in Maple Grove, Minnesota, the Reference 80S is intended for listeners who want Audio Research’s Reference-series tube architecture without requiring the greater output capability of the Reference 160S or Reference monoblocks. Audio Research

70 Watts Per Channel

Audio Research rates the Reference 80S at:

70 watts per channel continuous from 20Hz–20kHz

with 1kHz total harmonic distortion typically reaching 1% at 140 watts per channel in Pentode operation. In Triode mode, Audio Research specifies approximately 33 watts per channel at 1% THD. Audio Research

This is an important distinction for the listing: the REF80S is officially a 70W-per-channel amplifier, while its measured short-term capability at 1kHz extends considerably beyond that continuous rating.

Four KT150 Output Tubes

The Reference 80S uses:

4 × KT150 output tubes — two per channel
2 × 6H30 tubes — gain stage

Audio Research specifies the KT150s as two matched pairs, with the 6H30 tubes handling the gain stage. Audio Research

This comparatively compact tube complement allows the REF80S to deliver Reference-series performance from a smaller output stage than the Reference 160-series amplifiers.

Fully Balanced Differential Design

Like Audio Research's larger Reference amplifiers, the REF80S uses a fully balanced differential circuit architecture.

This isn't simply an amplifier with an XLR connector added to an otherwise single-ended circuit. Audio Research designed the amplification topology itself around balanced operation to reduce distortion and noise throughout the signal path. Audio Research

A four-layer circuit board provides a dedicated ground plane, improved circuit layout and fewer point-to-point connections that could introduce additional noise. Audio Research

Pentode & Triode Operation

One of the REF80S's most useful features is switchable Pentode/Triode operation.

Pentode mode provides the amplifier's full output capability and greater dynamic headroom. Triode mode changes the operation of the output tubes and reduces available power, with Audio Research specifying approximately 33 watts per channel at 1% THD. Audio Research

This gives the owner two operating characteristics from the same amplifier and allows the system to be optimized around loudspeaker sensitivity, room size and listening preference.

Importantly, Audio Research describes this specifically as Pentode/Triode operation, distinguishing it from the Triode/Ultralinear modes used in the Reference 160-series amplifiers. Audio Research

Automatic Tube Bias

The Reference 80S incorporates Audio Research's proprietary automatic bias system.

The circuit continuously compensates not only for normal output-tube aging but also for variations in AC line voltage. This removes one of the traditional maintenance requirements associated with high-performance tube amplifiers. Audio Research

There is no need for the owner to periodically measure and manually adjust output-tube bias.

For a Reference-level tube amplifier, this significantly improves day-to-day usability.

Individual Output-Tube Protection

Audio Research also provides output-tube fusing for improved safety and operating stability. Audio Research

Combined with automatic bias and output-tube monitoring, the design makes the REF80S considerably easier to own than a traditional manually biased tube power amplifier.

Dual GhostMeters

The front of the Reference 80S features Audio Research's distinctive dual GhostMeter displays, visually positioned in front of the four KT150 output tubes. Audio Research

The transparent meter design allows the tubes to remain visible through the front of the amplifier rather than hiding them behind conventional opaque meters.

The REF80S shares its basic physical dimensions with the larger Reference 160M monoblock, giving it the unmistakable contemporary Reference-series appearance. Audio Research

Balanced XLR & Single-Ended RCA Inputs

The REF80S provides both:

Balanced XLR inputs
Single-ended inputs

Input sensitivity is:

1.4V RMS balanced for rated output
0.7V RMS single-ended for rated output

with 25.5dB gain into 8 ohms. Audio Research

Input impedance is exceptionally high:

300kΩ balanced
75kΩ single-ended. Audio Research

The high input impedance makes the amplifier relatively easy for a partnering preamplifier to drive.

4Ω, 8Ω & 16Ω Output Taps

Dedicated speaker connections are provided for:

4Ω
8Ω
16Ω

loads. Audio Research

Multiple transformer taps allow the REF80S to be matched more appropriately to different loudspeaker impedance characteristics rather than relying on a single universal output.

Audio Research specifies approximately 1.0dB output regulation from a 16-ohm load to open circuit, corresponding to a damping factor of approximately 8. Audio Research

0.7Hz–94kHz Frequency Response

The Reference 80S has extremely wide small-signal bandwidth.

Frequency response: 0.7Hz–94kHz (-3dB at 1W)
Power bandwidth: 7Hz–68kHz (-3dB) Audio Research

Bandwidth extending well beyond the audible spectrum reflects the wide-bandwidth design of the amplifier and its output transformers.

Low Distortion at Normal Listening Levels

Audio Research specifies:

THD below 0.04% at 1 watt

while the 1kHz distortion figure reaches approximately 1% at the much higher 140W output level in Pentode mode. Audio Research

Those figures help illustrate the REF80S's operating behavior more clearly than quoting its nominal wattage alone.

15dB Overall Negative Feedback

The REF80S employs:

15dB overall negative feedback

with a specified:

10V/µs slew rate
4.0µs rise time. Audio Research

These are useful technical specifications for shoppers comparing the circuit architecture of Audio Research amplifiers rather than simply comparing output ratings.

Adjustable Cooling Fan

Tube amplifiers generate considerable heat, and Audio Research integrates a shallow, low-noise fan into the amplifier's bottom plate.

Fan speed is switchable, giving the owner control over thermal management based on installation and operating conditions. Audio Research

Adequate open space around the amplifier remains important. The REF80S should not be treated like a cool-running solid-state component when planning an equipment rack.

Tube Hour Meter

A built-in tube hour meter tracks operating time. Audio Research

This is particularly useful on a reference tube amplifier because output tubes are consumable components. Rather than estimating tube age based on ownership time, the user can monitor actual operating hours.

12V Trigger & RS232

For integration into a sophisticated two-channel or automated system, the Reference 80S includes:

12V trigger input
12V trigger output
RS232 input. Audio Research

The trigger connection allows compatible Audio Research preamplifiers and other control components to power the amplifier on and off as part of a coordinated system.

The amplifier also includes a defeatable automatic shutoff function. Audio Research

62-Pound Aluminum Chassis

The Reference 80S uses an all-aluminum chassis with structural extruded panels.

Dimensions are:

19" W × 10.5" H × 18.5" D at the faceplate/chassis depth

and:

21" total depth including handles and connectors.

Net weight is:

62 lb / 28.2 kg

with shipping weight of:

73 lb / 32.7 kg. Audio Research

The chassis itself is 18.5 inches wide, while the front faceplate measures 19 inches. Audio Research

Power Requirements

For U.S. operation, Audio Research specifies:

105–130VAC / 60Hz

Power consumption is:

420W at rated output
280W in Triode mode
221W at idle
3.6W when off. Audio Research

The 221W idle consumption is worth considering when planning ventilation and equipment placement, because the amplifier produces meaningful heat even when no music is being reproduced.

Hand-Built in Minnesota

The Reference 80S is built by hand at Audio Research's Maple Grove, Minnesota facility. Audio Research

Audio Research continues to list the REF80S in its current Reference power-amplifier range alongside the Reference 160S, Reference 160M MkII, Reference 330M and Reference 750SEL. Audio Research

That distinction matters because Audio Research has recently introduced the D-80, but the D-80 does not replace the Reference 80S. Audio Research states that the D-80 is built on the REF80S platform and replaces the VT80SE; the Reference 80S remains a current Reference-series model. Audio Research

Technical Specifications

These specifications follow Audio Research's current REF80S product page and official specification sheet. Audio Research

Reference 80S vs. D-80

This distinction is worth addressing because both amplifiers are now in Audio Research's lineup and the specifications can make them appear closely related.

The D-80 is built on the Reference 80S platform and is also rated at 70 watts per channel with two pairs of KT150 output tubes. However, Audio Research positions the D-80 as the successor to the VT80SE, while the Reference 80S remains part of the Reference series. The REF80S additionally provides its Reference-series feature set, including switchable Pentode/Triode operation and dual GhostMeters. Audio Research

For SEO, I would keep the two products clearly differentiated rather than allowing their descriptions to become near-duplicates.

Audio Research Reference 80S at The Grid HiFi

The Audio Research Reference 80S delivers the essential architecture of an Audio Research Reference amplifier in a more approachable stereo format: 70 watts per channel, four KT150 output tubes, fully balanced differential circuitry, automatic bias, switchable Pentode/Triode operation and 4/8/16-ohm output taps. Audio Research

The Grid HiFi can build the complete system around the Reference 80S, including Audio Research preamplification and source components, reference turntables and digital front ends, loudspeaker matching, cabling, power management and equipment support. Because tube-amplifier and loudspeaker matching involves more than nominal wattage alone, we can help select the appropriate output tap and determine whether the REF80S has the right power and load characteristics for a specific speaker and room.

Considering the Audio Research Reference 80S? Call The Grid HiFi at (713) 218-8120 to arrange a private audition and build the complete system around it.