LP125sa Vacuum-Tube Stereo Power Amplifier
The latest in the highly regarded series of conrad-johnson vacuum-tube power amplifiers, the LP125sa represents a compelling combination of the audio excellence one expects from conrad-johnson, the convenience of a single stereo chassis, and, at 125 watts per channel, sufficient power for the majority of high-end speaker systems. This is an amplifier capable of capturing the delicate textures and subtle nuances of live music while maintaining control with the authority that comes with ample power.

The LP125sa audio circuit consists of three stages. The input signal is amplified by a single-ended triode amplifier designed for wide bandwidth. The signal is then direct coupled to a cathode coupled phase-inverter. This high current, triode phase-inverter stage provides a balanced, low impedance drive to the output stage. Output power is developed by two pairs of KT120s per channel, chosen for their excellent sonic character, high power, and reliability. The output tubes are operated in ultralinear configuration which offers a desirable combination of high power and low distortion. Massive output transformers with intricately interleaved windings afford extended bandpass and high phase linearity. A small amount (about 12 dB) of loop negative feedback reduces distortion and achieves a sufficiently high damping factor to control reactive loudspeaker systems.

Power supply design is every bit as critical to the performance of an audio component as the audio circuit itself. In the LP125sa, separate, low impedance, discrete dc power supply regulators are provided for the input and phase-inverter stages, preventing the output stage from modulating these stages through the power supply.

These amplifiers require no complicated adjustments or specialized equipment to maintain. To assure continued peak performance, the owner need only make a simple bias adjustment when new tubes are installed. Built in LED bias indicators allow the user to make this adjustment using only the supplied screwdriver.

ART Amplifier
The ART Amplifier is our first limited edition power amplifier, and only the third of these very special limited edition products that we have offered in our more than thirty years in business. It is designed to be a reference amplifier for the use of industry professionals as well as dedicated audiophiles. Like its companion GAT Preamplifier, the ART Amplifier will be offered in an edition of just 250 units (125 pairs) to be sold through selected Conrad-johnson dealers and distributors.

At conrad-johnson, our approach to circuit design is predicated on the principle that the surest path to both state-of-the-art musicality and exceptional reliability is to keep the circuits simple and build them with the finest available parts. The ART amplifier exemplifies this basic principle. The audio circuit has just three elements, each as simple as possible, and each essential to the operation of the amplifier. A voltage gain amplifier (a single triode) is direct-coupled to a cathode coupled phase inverter (each phase handled by a single triode), which in turn drives the output stage. Power is developed by 6550 output tubes, chosen for their musical accuracy, high power, and reliability. Four pairs are used to comfortably and reliably achieve the 275 watt power rating. A small amount (about 12 dB) of loop negative feedback reduces distortion and achieves a sufficiently high damping factor to control reactive loudspeaker systems. To assure continued peak performance, the owner need only make a simple bias adjustment when new tubes are installed. Built in LED bias indicators allow the user to make this adjustment using only the supplied screwdriver.

Separate, low impedance, discrete dc power supply regulators are provided for the input and phase-inverter stages, thoroughly isolating these stages from the power demands of the output stage. These power supplies are designed to maintain a rock solid supply at all audio frequencies.

ET250S Amplifier
The conrad-johnson Enhanced Triode (ET) Amplifiers are power amplifiers designed to capture the best attributes of both fine vacuum-tube designs and of the best solid-state designs. The ET250S is a 250-watt per channel stereo power amplifier, the MET150 a five-channel amplifier rated at 150 watts per channel. These sophisticated zero-feedback amplifiers offer the refinement of a vacuum-tube amplifier with the guts and control of a solid-state amplifier.

Zero Feedback. Negative feedback is an engineering technique used to reduce measured distortion. While feedback does achieve this goal, it also introduces aberrations in the tran­sient response characteristics of the circuit. We have found that eliminating loop negative feedback can result in much finer gradations in dynamic response (micro-dynamics) and more accurate decay on musical transients. But eliminating negative feedback requires much more care in the design of the circuits - both in choosing devices and in power-supply design, and places greater demands on the parts.

The Right Device for the Job. A power amplifier has two distinctly different functions. First, a voltage gain stage must increase the amplitude of the input signal by a factor of about thirty. The distortion characteristics of the amplifier are dominated by this stage. No device is better suited to accurately amplifying signals at high amplitude than triode vacuum tubes. For our enhanced triode amplifiers, voltage gain is provided by a 6922 vacuum tube, selected for its ability to track a high amplitude signal accurately. Theory and 30 years of experience have taught us that the voltage gain stage of a power amplifier dominates the sonic character of the critical mid-range of a power amplifier, and indeed these amplifiers exhibit the smooth, lucid midrange for which tube amplifiers are so highly esteemed.

The high amplitude signal produced by the voltage gain stage must then be efficiently coupled to the loudspeaker system through an output stage to produce the power and control needed for a musically accurate response – basically to provide current gain and a low output impedance. High-current bi-polar devices have been specified for the output stages of these amplifiers, based on their extremely low output impedance and their ability to handle a great deal of current. This contributes the fast, weighty bass and seemingly limitless power reserve that are notable in these amplifiers.

Solid Power Supplies. Rock solid power supplies are needed to enable the audio circuits to reach their potential on musical transients. The ET amplifiers feature oversized main power transformers (so that the circuits are not starved for current), and massive power storage reservoirs with high-speed capacitor shunts to deliver quick, even startling transient response. Carefully designed DC voltage regulators isolate the critical voltage gain stages to prevent demands of the output stage from modulating the input signal.

Quality Parts. Conrad-Johnson components are internationally known for the quality of their parts, and the ET amplifiers are no exception. The audio circuits and their related power supplies utilize precision low inductance laser-trimmed metal foil resistors. The circuits employ polypropylene, polystyrene and Teflon capacitors extensively, except in the main power supply storage, where high-speed electrolytics are used because of the extremely high capacitance required. Precision-machined input/output connectors have been carefully selected for optimal sonic performance. Even the internal wiring is chosen on the basis of its sound quality in its specific application.

Thoughtful engineering, specification of top quality component parts, and painstaking care taken in production make the MET150 and ET250S capable of extraordinary performance in music reproduction. We invite you to arrange an audition with your conrad-johnson dealer to confirm for yourself the extraordinary musicality of these amplifiers.

LP125M Amplifier
Consistent with conrad-johnson's design philosophy that circuits should be kept as simple as possible, these amplifiers work their magic with a minimum of vacuum tubes (seven in the stereo LP66S, and six in the mono LP125M). A composite triode input stage is direct coupled to a cathode-coupled phase inverter. The output stage is comprised of 6550s operated in ultralinear configuration (one pair per channel for the LP66S, two pair for the LP125M) for an optimal combination of high power and low distortion. Limited negative feedback is applied to the circuit to reduce distortion and provide a sufficiently high damping factor to control most real-world speaker systems. Discrete dc power supply regulators are provided for the input and inverter stages, in order to isolate each stage from the output signal.

As with all conrad-johnson tube amplifiers, these amplifiers require no complicated adjustments or specialized equipment to maintain. To assure continued peak performance, the owner need only make a simple bias adjustment when new tubes are installed. Built in LED bias indicators allow the user to make this adjustment using only the supplied screwdriver.

Component parts quality is a signature strength of any conrad-johnson product. The audio circuit and related power supplies feature precision metal film resistors and high-performance polypropylene capacitors. There are no electrolytic capacitors in the audio circuit or in the related power supplies. Proprietary wide-bandwidth output transformers contribute to excellent high frequency performance. Even the input/output connectors and internal wiring have been carefully selected for optimal sonic performance.

Conservatively rated at 60 watts per channel, the LP66S offers sufficient power for most applications. Users who have not previously experienced the dynamic range and lifelike timbre of tubed components will find the LP66S an ideal introduction to the joys of modern tubed amplifiers. For those who do require more power, the LP125M mono-block delivers a solid 125 watts. Along with the tonal integrity and faithfulness to the music that are embodied in these amplifiers, their ease of use, low maintenance costs, and reliability will be a revelation for those who have only experienced "entry-level" tube gear.

We invite you to visit your conrad-johnson dealer to audition an LP66S or LP125M and rekindle your passion for enjoying great music in your home.

Classic Sixty SE Amplifier
The new Classic Sixty SE amplifier has once again demonstrated the conrad-johnson design team's commitment to adapting the advances from our state-of-the-art pursuits to more affordable offerings accessible to a wider range of music lovers. Borrowing heavily on the technology of its big brother, the ART amplifier, the Classic Sixty SE preserves the distinctive tonal character of individual instruments and voices, with each clearly located within the overall acoustical environment of the original recording. Musical transients are reproduced with realistic impact, but without artificial enhancement. Like its more costly siblings, the Classic Sixty SE captures the emotional impact of the live event, never getting between the listener and the musical performance.

There really is no mystery to the basis for outstanding musical performance: best results come from simple circuits executed with quality parts. The Classic Sixty SE amplifier circuit design is about as simple as possible, employing just seven vacuum-tubes. Single-ended triode voltage gain and inverter stages are coupled to an output stage comprised of a single pair of ultra-linear operated KT120 tubes for each channel. As it is critically important that the DC voltage supplied to the gain stages be absolutely rock-solid stable, these voltages are provided by simple but highly effective discrete voltage regulators. And speaking of simple, maintenance of the Classic Sixty SE could hardly be easier: the owner need only make a simple bias adjustment using the built in bias indicators when installing fresh output tubes.

The use of premium quality component parts is the other half of our underlying design mandate. In this area as well, the Classic Sixty SE is a leader in its class. Ultra high-performance metal foil resistors in strategic locations and precision, metal-film resistors elsewhere yield low noise performance for greatest clarity. Teflon CJD inter-stage coupling capacitors, along with polypropylene and polystyrene capacitors specified for both the audio circuits and the regulated plate voltage supplies assure a high degree of temporal accuracy. The result is an exceptional range of dynamics – reproducing both subtle variations in level as well as dramatic loud crescendos. Our proprietary trans-spectral wide-bandwidth output transformers contribute importantly to the extended, "airy" highs that help distinguish the Classic Sixty SE from ordinary tubed amplifiers.

The Classic Sixty SE offers low maintenance costs, notable reliability and near state-of-the-art performance at a relatively modest cost. Install one in your audio system and prepare to rekindle your passion for enjoying great music in your home.

GAT Triode Preamplifier
The GAT Preamplifier embodies conrad-johnson’s latest advances in line-stage preamplifier technology. We believe that it will quickly be recognized as the new industry-wide reference standard for line-stage preamplifier performance, a role filled for more than a decade by its legendary predecessor, the ART preamplifier. Like the ART, the GAT Preamplifier will be available in a numbered, limited edition of 250 units which will be sold through selected conrad-johnson dealers.

The GAT Preamplifier is a vacuum-tube, line-stage preamplifier that looks as good as it sounds. It is also notable for convenience and ease of use. The unit features input selection and level adjustment by microprocessor-controlled relays. Level and balance can be adjusted in 100 steps of approximately .7 dB per step. All functions can be controlled by the hand-held wireless remote control.

The circuitry of the GAT Preamplifier is elegant in its simplicity. The audio circuit consists of a single amplifier stage incorporating one composite triode comprised of paralleled sections of a high-transconductance miniature dual triode vacuum tube. This amplifier stage is coupled to the preamplifier outputs through a high-current MOSFET buffer, which achieves a very low output impedance, making the GAT extremely flexible in the choice of interconnect cables and amplifiers. DC voltage is supplied to the circuit by our latest discrete voltage regulator that isolates the audio circuit from the power line by maintaining negligible impedance across the audio frequency band. Infrasonic noise is minimized by operating the tube filaments (heaters) on a dc voltage supplied by another discrete regulated power supply.

Considerable care and attention have been paid to the physical aspects of the design as well. Microprocessor controlled relays, used for selecting sources and level setting, are located right at the input connectors, keeping signal paths short to minimize crosstalk between channels and inputs. The vacuum-tubes are isolated by a suspension system designed to minimize microphonics. The dramatic casework features attractive clear Lucite tube guards outside the chassis, allowing for easy access for tube replacement.

At conrad-johnson we have long appreciated that the full potential of any circuit can only be realized by using the finest available parts. Each part for the GAT has been selected on the basis of both sonic performance and durability. The audio circuit (including the level control) is executed entirely with precision metal foil resistors and proprietary CJD Teflon capacitors. Tubes have been carefully hand selected for minimum noise and microphonics. The dc regulated power supplies use the same quality resistors as the audio circuits. Capacitors for the power supplies are exclusively polypropylene and Teflon – there are no electrolytic capacitors in the audio circuits or their related power supplies. All signal switching is done by special relays designed for signal applications. These relays are sealed and have gold plated silver contacts. Input and output connectors are machined from oxygen free copper, and are gold plated. The GAT is built without compromise to achieve a new standard in musical performance, and it is built to last.

ET5 Enhanced Triode Preamplifier
Introduced in 2009, the GAT Preamplifier continues conrad-johnson's dominant position atop the rankings of reference preamplifiers. An important benefit of pursuing state-of-the-art designs is that the circuits and techniques developed in our flagship products are frequently directly applicable to out entire line of products. In this instance, we have embodied the technology of the GAT Preamplifier in the more cost effective ET5 enhance triode line-stage preamplifier at a more affordable price.

The circuitry of the ET5 follows closely that of the GAT line-stage preamplifier. The audio circuit is elegant in its simplicity. An audio amplifier stage consisting of a single-ended triode amplifier provides the voltage gain. This amplifier stage is connected to the preamplifier outputs through a high-current MOSFET buffer, which achieves a very low output impedance, making the ET5 extremely flexible in the choice of interconnect cables and amplifiers. DC voltage is supplied to the circuit by our latest discrete voltage regulator that isolates the audio circuit from the power line by maintaining negligible impedance across the audio frequency band. Infra-sonic noise is minimized by operating the tube filaments (heaters) on a dc voltage supplied by a separate regulated power supply. The ET5 is also notable for convenience and ease of use. The unit features input selection and level adjustment by microprocessor-controlled relays, with controls available both at the front panel and via a full-function remote. All control functions of the ET5 operate through microprocessor-controlled relays. For the level control, the relays select combinations from a network of precision, low-noise metal foil resistors to effect loudness and balance changes in 100 steps of approximately .7dB per step. All switching and adjustment can be controlled by the unit's remote control. A Theater Mode, which passes the input signal through at unity gain, makes it simple to incorporate the ET5 into a high quality home theater system without compromising its two-channel performance.

Like its bigger brother, the GAT, the ET5 is constructed from the highest quality, carefully selected parts for unrivaled sonic performance and reliability. Tubes have been carefully hand selected for minimum noise and microphonics. The same CJD Teflon capacitors that distinguish the GAT are used in the ET5 for output coupling and post-regulator power supply storage. All other capacitors in the audio circuits and related power supplies are polypropylene or polystyrene – there are no electrolytic capacitors in the audio related circuits. The resistors in these circuits (including the two dozen level control resistors) are special low inductance, high-precision laser-trimmed metal foil resistors. Switches are sealed relays with gold-plated silver contacts. Input and output connectors are premium quality custom machined parts.

For more than three decades, we at conrad-johnson have been dedicated to creating audio components that do credit to music performances. Through meticulous engineering, careful specification of only the finest available component parts, and a painstaking attention to construction, we have created what we feel is a line-stage without rival in its class. We invite you to arrange an audition of the ET5 with your conrad-johnson dealer to experience the extraordinary musical performance of this remarkable preamplifier.

ET3 Vacuum-Tube Preamplifier
At conrad-johnson, development of our flagship products has traditionally led to important enhancements of our entry-level offerings. The ET3 preamplifier is a case in point. The ET3 line-stage is a “baby” version of our flagship line-stage preamplifier, the GAT. The family resemblance is much more than skin deep. With voltage gain provided by a triode vacuum-tube, the zero-feedback line-stage circuit of the ET3, along with its DC voltage regulators, closely replicates the circuit of the GAT. Finally, and especially noteworthy, the ET3 features a relay operated discrete stepped attenuator level-control circuit of the type found in the GAT and CT5, absent only the balance control function found in those more costly models.

Functionally, the ET3 provides highly flexible I/O facilities with six separate line-level inputs (including one “tape” loop), plus a theater loop that facilitates use in a home theater system. In addition, the ET3 offers the convenience of infrared remote control of all functions.

For vinyl enthusiasts, the ET3 is optionally available with a vacuum-tube phono stage that borrows its zero-feedback audio circuit from our reference quality TEA1 phono stage. Customers can choose between high gain (recommended for cartridges with a rated output of 1.0 mV or less) and low gain (recommended for cartridges with rated output greater than 1.0 mV) versions of the phono stage. Input resistive loading is switch selectable over a range from 47 kOhms down to 200 Ohms. The ET3 phono stage is built to the same high quality standard found in the ET3 line-stage

It would be fair to say that the only thing “entry-level” about the ET3 is its price. Arrange to audition one at a conrad-johnson dealer to find out for yourself – you’ll be surprised at just how affordable true high-end performance can be.

TEA1 Phono Preamplifier
The TEA1 triode equalization amplifier is a phono stage available in four different versions to meet a wide range of needs – all designed to satisfy the expectations of the most demanding music lovers. All versions share a common circuit approach featuring a zero loop feedback circuit with passive RIAA equalization. All feature two phono inputs, one with switch selectable resistive and capacitive loading allowing the user to fine-tune performance to the chosen phono cartridge. With the exception of capacitors in the audio circuits and related power supplies, parts quality is identical in all four versions. All resistors are top quality precision metal foil types. I/O connectors are custom made gold-plated machined oxygen-free copper. The TEA1b is the base model TEA1. In the TEA1b, the two phono inputs each provide 54.5 db of gain. Resistive and capacitive loading can be adjusted by toggle switches on the PHONO 2 / Variable Load input. The base model uses CJD Teflon capacitors for all but the highest value capacitors (2.0 micro Farad and higher) in the audio circuit which are polypropylene bypassed by Teflon. A capacitor upgrade is incorporated in the otherwise identical TEA1bc, replacing a number of high value polypropylene capacitors with multiple 2.0 micro Farad CJD Teflon capacitors. The TEA1bt upgrades the base model by adding premium wide-bandwidth audio transformers to the PHONO 1 input to provide the higher gain and very low noise required by low output moving coil cartridges. The active circuit is modified to reduce its gain to 45 db, offering the user one HIGH GAIN transformer coupled input (PHONO 1) with 63 db of gain and one LOW GAIN direct input (PHONO 2) with 45 db of gain. The fully configured TEA1 includes both the transformer option and the capacitor upgrade.

Designed to precisely track the prescribed RIAA equalization curve, the TEA-1 assures absolute tonal accuracy. The low-gain audio circuit of the TEA-1 is comprised of two cascaded single-ended triode amplifiers. The circuit is a zero-feedback design, to eliminate the temporal inaccuracies that negative feedback introduces. RIAA equalization is established by a passive network between the two gain stages. Careful implementation of this fundamentally simple circuit results in extremely wide bandwidth, and low distortion, without resorting to negative feedback. Precision wound input transformers provide the additional 18 dB of gain for the high-gain inputs.

The ideal dc power supply circuit is simply a zero impedance path to ground. Any deviation from this ideal is fully reflected in the audio circuits. Thus the power supplies are as important to audio performance as the audio circuits and must be accorded equal attention in design. In the TEA-1, each stage has its own discrete regulated DC power supply. These power supplies have been carefully designed for minimum impedance, even at the highest audio frequencies, to prevent the power supplies from degrading music reproduction. The full potential of any circuit design can only be realized if executed with the highest quality parts. The audio circuits of the TEA-1 use only conrad-johnson's proprietary Teflon capacitors. In the power supplies, all capacitors are polypropylene and Teflon composites - there are no electrolytic capacitors anywhere in the audio circuits or their dc power supplies. The audio circuits and related power supplies both use high-precision laser trimmed metal-foil resistors, designed for ultra-low inductance. All parts in the TEA-1's RIAA compensation network are 1% tolerance, to assure precise tracking of the RIAA curve. Input and output connectors are gold-plated, machined oxygen free copper. Even the hookup wiring has been carefully selected for optimal audio performance.

Thoughtful engineering, specification of the finest available component parts, and painstaking care taken in production make the TEA-1 a phono equalization preamplifier without peer in music reproduction. We invite you to arrange an audition with your conrad-johnson dealer to confirm for yourself the extraordinary musical performance of these products.

TEA2 Phono Preamplifier
The TEA-2 triode equalization amplifier is a vacuum-tube phono stage offering an extraordinary degree of musical accuracy at a moderate price. The audio circuit of the TEA-2 is comprised of two cascaded single-ended triode amplifiers. The circuit is a zero-feedback design, to eliminate the temporal inaccuracies that negative feedback introduces. RIAA equalization is established by a passive network between the two gain stages. This network has been carefully designed and has been implemented with precision (1% tolerance) parts to precisely track the prescribed RIAA equalization curve assuring absolute tonal accuracy. Careful implementation of this fundamentally simple circuit results in extremely wide bandwidth, and low distortion, without resorting to negative feedback. A high-current MOSFET buffer stage follows the second gain stage to achieve a low output impedance (less than 200 Ohms).

In the TEA-2, discrete regulated power supplies, carefully designed for minimum impedance, even at the highest audio frequencies, isolate the amplifier stages from the ac line and from each other to guarantee that power supply irregularities do not degrade the audio performance.

The TEA-2 is available in high-gain (55 dB) and low gain (40 dB) versions to match a wide range of modern phono cartridges. The high gain version is recommended for use with cartridges with a rated output of 1.0 mV or below. The low gain version is best suited to higher output cartridges. Both versions offer switch selectable resistive loading allowing the user to fine-tune performance to the chosen phono cartridge. The performance of any audio component is only as good as its component parts. The audio circuits and the related regulated power supplies of the TEA-2 use polypropylene and polystyrene capacitors and precision metal film and metal foil resistors exclusively. All parts in the TEA-2's RIAA compensation network are 1% tolerance, to assure precise tracking of the RIAA curve. Input and output connectors and even hook-up wiring have been carefully selected for audio performance. Thoughtful engineering, specification of quality component parts, and painstaking care in production make the TEA-2 a phono equalization preamplifier of remarkable musicality.