TEST: Koch ATR-4502

So dear children, take good care, I've brought you something! Uncle Axel again tells anecdotes from a decade when the hair was still toupeed, the skirts were short, the heels were high and in Los Angeles anyone who could hold a guitar the right way round (he didn't even have to know how to play it) was a superstar. Once again, it's all about the wild times of the eighties, when, in addition to some very questionable color schemes in the instrument area, one or the other concept was developed, which had to be classified at least in the area of innovative, but sometimes also in the drawer of trend-setting.

To the last mentioned area must be counted in any case the burgeoning 19-inch concept, which is based on the fact that not only the rapidly growing effects area should be screwed into a suitable rack, but also the upstream preamps, along with downstream power amplifiers find a new home in it. The advantage was obvious: complete flexibility in the choice of components, freely configurable and optimally protected for transport in an appropriate case. The fact that the practice did not always turn out so simple even with meticulous signal routing, in particular with regard to persistent hum loops, we leave here once generously under the table. The diametrical fashion wave of vintage amps in the nineties abruptly ended the presence of refrigerator-sized racks on the stages of this world, but did not change anything about the logical and practical concept, which still holds its own today, especially in the second stage row.

So it is not surprising that some renowned manufacturers continue to carry one or the other product of this series in their catalog, respectively develop it further. One of these companies is the Dutch company Koch Amps around mastermind Dolf Koch, which is gaining more and more followers in the scene due to its long breath and outstanding products.


Construction

The Koch ATR-4502 requires only a single height unit in the rack and also has a 2-fold fan construction, which makes it possible to keep no height unit free both above and below the housing for overheating reasons. As an operating concept, a hybrid technology was chosen, which is already used in the very popular Jupiter series. The speech is of 2 pieces 12AX7 double triodes, which take over the sound behavior of a tube, with a transitor output stage switched behind it for the power output.

The power amplifier is designed in stereo and can supply in stereo mode any speaker between 4 - 16 ohms, in mono mode between 8 - 16 ohms with juice. As power data in mono mode 90 W (8 ohms), 70 W (16 ohms), in stereo mode 2x 50 W (4 ohms), 2x 45 W (8 ohms), 2x 35 W (16 ohms) are mentioned. According to the transistor design, the power output decreases with increasing number of ohms, but the transformer does not blow when no load is applied. Unfortunately you can't have everything. The weight of the Koch ATR-4502 turns out to be very pleasant due to the output transformers saved by the hybrid design with only 5.5 kilograms, which is just about one fifth of the weight of a 19 inch power tube.

On the front side, in addition to the On/Off switch and 14 angled ventilation slots, there are 2 volume controls for the two power blocks and 2 voicing controls per channel, which can be used to boost the bass (Depth) or the treble (Presence). On the rear side, the Koch ATR-4502 has 2 input sockets, which can be individually lowered by -10dB each in the input sensitivity, in addition to the cold device plug and the input openings of the fans. A total of 6 output sockets allow any conceivable speaker combination in mono and stereo, here maximum flexibility is announced. The product is supplied with 2 screwable rack brackets and 4 self-adhesive rubber feet for stand-alone operation.


Practice

The practical part of this test is quickly dealt with. The power amplifier sounds very good indeed! Through the intelligent use of the 12AX7, the product manages to reproduce the compression behavior of a tube power amplifier over large parts 1 : 1, only at high volumes you notice due to the different reaction to the return current of the speaker that it is not the big bottles a la EL34 or similar. The response is lively, the tonal orientation open with a touch of compression.

Depending on the preamp connected in front of it, one can still influence the personal tuning somewhat with the two voicing switches. One or the other will miss the execution in the form of resonance or presence knobs, I for my part could not determine any impairment in this regard.


Conclusion

With the Koch ATR-4502, the Dutch manufacturer carries an absolute top product in its catalog. Equipped with low weight, very good workmanship and a sound that maintains the attributes of tube compression, the product finds its place between various cheap homes on transistor basis and the 30 kilogram monsters in full tube construction.

A very strong product for the musician who wants to combine minimum weight with maximum sound. Highly recommended!

Additional informations:

- Koch Amps stands as a renowned and revered brand in the world of guitar amplification, acclaimed for their dedication to crafting exceptional tube amplifiers that capture the essence of vintage tones while incorporating modern features. In this comprehensive review, we will delve into the history, craftsmanship, innovative technologies, and notable product offerings of Koch Amps, showcasing their significant contributions to the realm of guitar amplification.
History and Legacy: Koch Amps was founded in the Netherlands in 1988 by Dolf Koch, a passionate guitarist and engineer. With a vision to create amplifiers that reproduced the classic tones of iconic vintage amps, Koch embarked on a journey that would establish the brand as a leader in the industry.

Craftsmanship and Quality: Koch Amps is renowned for its unwavering commitment to craftsmanship and quality. Each amplifier is meticulously handcrafted using premium components, ensuring exceptional durability and reliability. From the circuitry to the cabinet construction, Koch Amps exemplify the highest standards of craftsmanship, delivering products that are built to last and inspire musicians for years to come.

Innovative Technologies: Koch Amps has consistently pushed the boundaries of innovation, incorporating cutting-edge technologies to enhance their amplifiers' performance and versatility. Some notable advancements include:

a. Power Attenuation: Koch Amps was among the first to introduce built-in power attenuators in their amplifiers. This technology allows players to dial in the desired power output, enabling them to achieve coveted tube amp tones at lower volume levels, making them suitable for both studio and stage use.

b. Dynamic Valve Reactor (DVR): The patented DVR technology implemented in Koch Amps' amplifiers ensures that the power amp section faithfully replicates the response and dynamics of classic tube amplifiers, even at lower volume levels. This innovation captures the organic, touch-sensitive feel that guitarists crave from vintage amps.

c. Switchable Channels and Voicings: Many Koch amplifiers offer multiple channels and voicings, allowing players to seamlessly switch between clean, crunch, and high-gain tones. This versatility makes Koch amps suitable for a wide range of playing styles, from blues and rock to metal.

Notable Amplifier Models:
a. Jupiter Series: The Jupiter series represents the flagship line of Koch amplifiers, delivering a harmonically rich, vintage-inspired sound with modern versatility. Models like the Jupiter Junior and Jupiter Combo offer a range of power outputs and features, allowing players to dial in their desired tone and volume.

b. Studiotone Series: The Studiotone series embodies the perfect balance between power and portability. These compact amplifiers pack a punch, offering tube-driven tones suitable for studio recording and smaller gigs. The Studiotone Combo and Studiotone Head exemplify the versatility and high-quality sound that Koch Amps is known for.

c. Twintone III: The Twintone III is a dual-channel amplifier that combines classic British and American voicings. With its versatility and lush, harmonically rich tones, the Twintone III has become a favorite among players seeking a wide range of tonal options.

Artist Collaborations and Endorsements: Koch Amps has earned the respect and admiration of numerous renowned guitarists who have chosen to endorse and use their amplifiers. Artists such as Greg Howe, Paul Gilbert, and Scott Henderson, among others, have collaborated with Koch Amps to create signature models that reflect their tonal preferences and musical styles. These artist partnerships further validate the quality and performance of Koch amplifiers.
Impact on the Music Industry: Koch Amps has made a significant impact on the music industry by providing musicians with amplifiers that faithfully capture the timeless tones of vintage amps while incorporating modern features. Their dedication to craftsmanship, innovation, and versatility has empowered guitarists to shape their signature sounds and express their musicality across a wide range of genres.

Conclusion:
Koch Amps has established itself as a respected and influential brand in the realm of guitar amplification. Through their commitment to craftsmanship, innovative technologies, and collaborations with renowned artists, they have consistently delivered amplifiers that capture the essence of vintage tones while providing modern features and versatility. With their exceptional build quality and unwavering dedication to authentic tube amplification, Koch Amps continues to inspire and empower guitarists worldwide.

- 19-inch guitar power amps have revolutionized the world of professional guitar amplification, providing guitarists with a dedicated solution for delivering high-quality, powerful, and reliable amplification on stage and in the studio. In this comprehensive review, we will explore the features, benefits, applications, and notable models of 19-inch guitar power amps, highlighting their significance in achieving optimal guitar tone and performance.
Overview and Benefits: 19-inch guitar power amps are rack-mounted units designed specifically to amplify the signal generated by a guitar preamp or processor. They offer several key benefits, including:

a. Power and Headroom: 19-inch power amps provide ample power to drive guitar speakers, delivering clean headroom and the ability to produce loud, dynamic performances without distortion or loss of tone.

b. Signal Fidelity: These power amps are engineered to faithfully reproduce the tonal characteristics of the preamp or processor, ensuring accurate representation of the guitarist's desired sound.

c. Durability and Reliability: Built for professional use, 19-inch power amps are constructed with robust components and reliable circuitry, allowing them to withstand the rigors of touring and regular live performances.

d. Rack Integration: Being rack-mountable, these power amps can be easily incorporated into a professional rig, providing a streamlined and organized setup.

Power Ratings and Configurations: 19-inch power amps come in various power ratings, typically ranging from 50 watts to 1000 watts or more. They are available in different configurations, including mono, stereo, and multi-channel options, allowing guitarists to adapt to different performance setups and speaker configurations.

Connection Options: These power amps offer a range of connection options, including balanced XLR, unbalanced 1/4-inch TS, and Speakon connectors. This versatility enables seamless integration into different setups and ensures compatibility with various audio systems.

Applications: 19-inch guitar power amps find application in a wide range of scenarios, including:

a. Live Performances: These power amps provide the necessary amplification for live performances, enabling guitarists to project their sound to larger audiences with clarity, power, and reliability.

b. Studio Recording: 19-inch power amps are utilized in professional recording studios to capture the pure tone and dynamics of a guitar signal, delivering pristine audio quality for recordings.

c. Integration with Modeling Systems: Guitarists using digital modeling systems or software-based guitar rigs often pair them with 19-inch power amps for amplification, combining the flexibility of digital processing with the authentic power and feel of a dedicated power amp.
Notable 19-Inch Power Amp Models: Several notable manufacturers offer exceptional 19-inch guitar power amps, each with its own unique features and sonic characteristics. Some prominent models include:

a. Mesa/Boogie 2:90: Renowned for its legendary tone and robust build quality, the Mesa/Boogie 2:90 power amp offers stereo or mono operation, delivering 90 watts per channel.

b. Peavey Classic 50/50: The Peavey Classic 50/50 power amp is highly regarded for its reliability and warm tube-driven sound. It provides 50 watts per channel in stereo mode.

c. Marshall EL34 100/100 Dual Monoblock: This power amp from Marshall offers two independent channels with 100 watts per side, utilizing EL34 power tubes for that classic British rock tone.

d. EVH 5150III EL34: Designed in collaboration with Eddie Van Halen, the EVH 5150III EL34 power amp delivers the iconic high-gain sound associated with Van Halen's signature tone.

Future Trends and Advancements: As technology continues to advance, 19-inch guitar power amps are expected to evolve further, incorporating features such as digital connectivity, built-in effects, and advanced power management options. Additionally, advancements in power amp design, including Class D amplification, may offer more compact and lightweight options without compromising on sound quality and power.

Conclusion:
19-inch guitar power amps serve as an essential component in professional guitar rigs, delivering the necessary power, tone, and reliability required for live performances and studio recordings. With their robust construction, versatile connectivity options, and compatibility with various preamps and processors, these power amps empower guitarists to unleash their creativity and achieve their desired sound with precision and authority.