Yamaha Tn amplifiers Engineers Interview

In December of 2006, Yamaha introduced the new Tn series amplifiers. Consisting of three models varying in output power, the flagship series gives you everything you would want from a touring amplifier; True two ohm operation capability with enough power to drive large-scale concerts, exceptional sound quality and reliability you would expect from a Yamaha amplifier, and remote monitor/control features. To give you an insight of the development process of the Tn series and to give you a better idea of what the amplifiers have to offer, Yamaha's own Tim Harrison interviewed the Tn Development team at Yamaha Corporation headquarters in Hamamatsu, Japan.

Ken Iwayama- "Chief Producer" of the Tn Series.
Toshiro Mayuzumi- "the Amp expert", Electronic designing.
Tomoyuki Tsujimura- Electronic designing, protection circuits.
Yoshikuni Kitamura- Mechanical designing.
Seiji Kurauchi- Sales & Marketing

How did you come about developing the new

Iwayama: The year 2006 marked the 30th anniversary of Yamaha professional power amplifiers. (*P2200 was introduced in 1976. See below.) This project started from our desire to create a legendary amplifier to live up to the history of 30 years that we have in this industry. Until now, Yamaha has had a wide range of amplifiers in its lineup, from under 100W to 1000W output. What we didn't have was an amplifier that could drive line array speakers with ease. With line array speakers making their appearances in increasing number of applications, we were set to create a line of flagship amplifiers that can easily handle line array speakers.

What makes these amplifiers unique? What sets them apart from other amplifiers available today?

Iwayama: Not only do the Tn amplifiers deliver higher output than we had before, but they are capable of easily maintaining its high output power even in torturous two ohm drive conditions. As we have announced in our press release, the Tn series' compliance with Underwriter Laboratories Inc.'s and Intertek SEMKO's safety requirements at 2 ohms prove the amplifiers' reliability in low impedance drives. Stable 2 ohm drive will not only reduce the number of amplifiers required for driving speakers, but assures no-compromise sonic quality in tough conditions. There are already many amplifiers in the market with catalog specifications under two ohms, but we were taken by surprise to find out through thorough testing that many of these amplifier are in reality not truly capable of driving 2 ohm loads. Knowing that even top name amplifiers with great market recognition are weak in low impedance conditions, our minds were set to accomplish a true 2 ohm low impedance drive with sufficient power to always maintain finest sound quality. To have the amplifier recognized for its stability and safety even at 2 ohms, by an internationally recognized standards organization, independent from our industry, we began development with intent to qualify with UL and SEMKO's safety standards at 2 ohms.

What was the development process like?

Mayuzumi: The first issue we had, was to provide sufficient power supply. But to get an idea of where our technology was, we started by thorough and comprehensive testing of industry standard high power amplifiers. None of these amplifiers were able to meet our standards, and we observed various "malfunctions" such as noise and distortion and sudden activation of limiters during low impedance operation. We also put our existing line of amplifiers to test to see what kind of work we need in order to achieve truly stable operation at 2 ohms.

I understand that meeting safety requirements at 2 ohms is not an easy task. What were some of the difficulties you faced in development of the amplifiers?

Kitamura: One important factor of the safety requirements at 2 ohms is dealing with heat/temperature.
Yamaha already had technology called "EEEngine", a high-efficiency amplifier topology, so in terms of amplifier temperature, we were better off than competitors to begin with, Even then, there was a lot of work that had to be done to bring heat level down to meet safety requirements with considerable margin. We conducted countless simulations and experiments to efficiently dissipate heat by modifying cooling fans, heatsinks etc, until we finally found our answer.

Mayuzumi: Of course, cooling can be accomplished by bring fan power up, but then you run into another problem, fan noise. When output level is high, fan noise is not very noticeable but a stack of amplifiers emitting high fan noise is not acceptable when output is low, or when there is no signal. The low-volume fans on the Tn amplifiers operate at varying speeds corresponding to input signal level. While Kitamura dealt with efficiently dissipating heat, I concentrated on minimizing heat generation.
Operating at 2 ohms means dealing with large currents of electricity. As electric current increases, transformer coils heat up and efficiency is lost. One newer technology we used was copper plates rather than wire in the transformer coil giving reduced resistance, thus being able to draw larger currents of electricity. We have also incorporated the latest transistor technology. Thinning semiconductors is a very difficult technology and was not available until very recently. Thin film transistor chips give reduced heat resistance, allowing greater heat liberation. Because of this, the transistor chip is capable of handling larger power that is suitable for low impedance operation. We have also modified our own "EEEngine" amplifier technology, in particular the FET drive circuit within the high efficiency current buffer, in order to achieve stable performance at low impedance.

Tsujimura: We also put a tremendous amount of work into the protection circuit on the Tn amplifiers. Without protection, output current is theoretically infinite (I=V/RL), instantly destroying the power transistors in case of a two ohm output short (RL1=0 ohms). The amplifiers are designed to operate at up to 1.5 ohms, so detecting abnormality is very important. Tn amplifiers are also equipped with thermal protection which limits output when heatsink temperature rises above a certain point. This circuit limits output signal before temperature rises to a point where muting becomes unavoidable. Also new on Tn amplifiers is the Very High Frequencies Protection function, reducing unwanted stress on the amplifiers caused by very high frequencies of over 20kHz. Amplification of frequencies of over 20kHz is also limited to protect speakers.

What did you aim for in the sound of Tn amplifiers?

Mayuzumi: Many think of the YAMAHA sound as "being true to the original sound with a clear, natural and a musical tone." This is true not only for our amplifiers, but for our complete lineup of professional PA products. The Tn amplifiers maintains this signature sound, but with stronger low-end and midrange to drive large touring speakers with impressive power. Outstanding sound quality of the Tn amplifiers, fine and delicate yet powerful, is the best I have achieved in the many years I have spent developing amplifiers. The Tn series truly represents YAMAHA's wealth of knowledge and experience from 30 years in this business. When we took these amplifiers to our testing hall for internal reviewing, I myself was astonished by the sheer power in the sound. It was apparent that we had brought power amplifiers to a new level.

With high power amplifiers being an area of unfamiliarity, how did you overcome the technical difficulties you may have encountered during product planning and development?

Iwayama: Yamaha's North American sales subsidiary, Yamaha Commercial Audio Systems, is the US distributor of world renowned line-array speaker manufacturer, NEXO. That is why our engineers have relationships with NEXO and received feedback from them during development. Because the Tn amplifiers were designed for use in large scale concerts for driving large speakers such as line array speakers, we asked NEXO to conduct a thorough review of the amplifiers. After a series of extensive testing, the Tn amplifiers were found to be very much capable of large scale concert use, and received an exceptional review for their performance. In North America, we plan to promote a combination of NEXO speakers with Yamaha amplifiers.

What is in the naming of the amplifiers? What is the reason for dropping Yamaha amplifiers' traditional "P" or "PC" model names?

Kurauchi: As mentioned earlier, we wanted to create a new amplifier, something completely new, to mark the 30th anniversary. Although many users have come to love our "PC" and "P" series amplifiers, the new naming shows our will and commitment for a "new" amplifier.

Yamaha's recent lineup of PC1N, XP, XM, XH and the P series all share a common design concept, but the Tn amplifiers looks different.

Kurauchi: Because those series were mainly for installations, we designed them to have a uniformed appearance when different models are installed in the same rack. We also felt that the delicate appearance of these existing line of amplifiers were not suitable for touring. The Tn amplifiers cut down on fancy appearance and went for a robust and durable look. It is also a design that reminds you of the old Yamaha amplifiers. The rugged appearance represents the tradition of reliability and durability of Yamaha amplifiers.

Iwayama: The high power cooling fans on the front panel make quite an impression on the overall design. The filters on these intake fans can be easily exchanged, making maintenance easier on these touring amplifiers.

Any comments to add before we wrap up this interview?

Iwayama: The height of success that Yamaha's digital mixers have established has overshadowed presence of Yamaha amplifiers, but our amplifiers have a longer history than our digital mixers. We have complete confidence that current and old users of PC2002 and P2200 will not be disappointed by the Tn amplifiers. The Tn series amplifiers are by far the best sounding professional amplifier yet; hear the sound for yourself.

About P2200
P2200, Yamaha's first professional power amplifier was introduced in 1976. With an output power of 240W per channel, the P2200 started Yamaha amplifiers' tradition of excellence in sound and well thought out design. P2200's design allowed access to the inside of the amplifier via the front panel. This design made maintenance and exchange of components parts possible without taking the amplifier out of the rack in case of failures. Uncoated binding posts were used on speaker output terminals to improve sonic quality. P2200 was replaced with the introduction of PC2002 in 1982, which soon became a global standard in professional amplifiers.

Written by: Tim Harrison from Yamaha CA Support Centre Europe.
Tim is the "output side" product specialist, specializing in loudspeakers, amplification, signal processing, control and digital audio networking. He joined Yamaha in 2005 after working in installation sales, project management and distribution.