An Interview with Esoteric's development team on F-03A and F-05

Esoteric's new integrated amplifier F-03A and F-05 had evolved greatly in performance and functions from the traditional "I Series" and emerged with drastic changes. In this interview, we talked to Mr. Tetsuya Kato, Mr. Hiroyuki Machida and Mr. Hiroyuki Suzuki, the development team, about the direction and development behind "F series".





■ The proper sense of size and arrangement of the internal configuration is the point of F series development 

Interviewer: When did you start development?

Mr. Machida: This is about a year ago. The lineup of class A and class AB, both of which were decisions of the full balance circuit at an early stage, assumed the lower one as the price range.


Left: Mr. Tetsuya Kato, Director of Esoteric Development Co., Ltd.,

Right: Mr. Hiroyuki Machida Sales Promotion Manager

Interviewer: I think the interior is tightly packed impression.

Mr. Kato: How to make the input switching circuit and preamplifier circuit proper, making the sense of size proper, and where to place it was actually a highlight in the design. Since the power amplifier can follow the flow from the S series, in the configuration around that, the power stage was inevitably decided next to the power transformer. The internal layout at such a place was decided smoothly.


The right is the amplifier module of the separate amplifier S series, the left is the F series amplifier module. Despite the difference in scale, the arrangement and configuration of parts, wiring, etc. are almost equal.

Interviewer: The tone control which can adjust 3 bands is also impressive.

Mr. Kato: It was dual mono, and it had to be made in full balance. It was serious if you tried doing it.

Machida: The degree of fulfillment of the pre-division is amazing. As well as pre-out, there is also a buffer between each section, bringing in the design philosophy of the C series preamplifier as it is. I also do not compromise anything about the accessory function.


Interviewer Hiroshi Suzuki receives explanation of full balance circuit from Mr. Tetsuya Kato

■ It is the best basic of the amp to convey energy without escape

Interviewer: Did you have any difficulty with noise countermeasures?

Mr. Kato: As it condenses, it approaches physically and it becomes a factor that sound mixes approaching electrically. On the other hand, it is necessary to use a 4-layer board to strengthen the power ground, pre-amplifier circuit section, power supply, ground pattern thickness, distance between circuits between L and R channels, signal line spacing, Although it was harsh in terms of space, thoroughness did not cause great difficulty for noise.


In order to thoroughly countermeasure vibration of the heavyweight body, F-03A adopts pinpoint foot (left), F-05 adopts steel insulator (right), and it supports at four points

Machida: Also, the control system is inside the front panel, the main body of the preamplifier is in the vicinity of the back panel itself, but since it is connected via all what is called isolator, the configuration that does not propagate microcomputer noise etc. at all is.

Mr. Kato: It is easy to understand that audio signals are connected at the shortest in terms of sound quality, but in the case of amplifiers, how to prevent loss by supply of power to drive amplifier circuits is considered an important factor.


Internal structure of F - 03A. The pre-section and the power amplifier input stage are splendidly arranged symmetrically, and you can see that the parts etc. are tightly packed. He said that there was considerable difficulty in putting the idea of eparate into an integrated type

Machida: It is a rugged construction (laughs)

Mr. Kato: It does not change when it is circuit diagram. Even with a normal connector connection or with a screw fastener. But, if you actually listen to music, you will soon see the difference. I absolutely will notice when pulling out my hand. Somewhere up to where we convert the electric signal from the speaker to the energy of the sound expressing the energy, it is the most basic of the amp to say not to leak energy or to convey without letting escape .

■ Also developed an optional DAC board. This is also a dual mono configuration

Interviewer: This time, we designed "OP-DAC 1" of the DAC board as an option, the type that users insert and remove by themselves.

Machida: Esoteric's digital player has a USB input and can use the DAC function, but I developed a DAC board considering how to use only the pre-main amplifier and the PC.

Mr. Kato: It is now time to be able to listen to music by connecting USB directly to the USB DAC from the NAS for audio, so it is about trying to deal with such things as well as PC. The DAC device I use is AKM's "AK4490" which uses dual mono, that is, one channel at a time. Of course, this is also a full balance circuit, passing the audio signal to the amplifier main body with balance output.

Interviewer: It is thorough.

Mr. Kato: I thought that I had done something serious

Interviewer: Please give a message to the readers at the end.

Machida: I think the best thing that was made is the Integrated Amp. Customers using Esoteric SACD / CD players please try it, as they are by the same design team and can expect the same tendency of sound.

Mr. Kato: Please enjoy it as a richness of playing stereo from the speaker, sound by the body in various places. Among them, I think of the Esoteric's amplifier as how much goodness of stereophonic can be produced, so I would like to experience that point.

(Structure: Audio Accessory Editorial Department)

■ True charm of "F-03A / F-05" found in audition and interview

Directly bring in new flow, thorough design. Dynamic F-05, deeper in hi-fi, F-03A

After hearing the development story and actually listening to it, I felt that this F series is not a successor model of the I series, but rather the flow of Esoteric's new amplifier directly starting with Grandioso's separate amplifier. Although it is the design of the image with the pre-function attached to the power amplifier "S-03", actually the EI transformer of the power supply part has the same capacity, the transistor used is the same specification, or the full balance circuit.


Adopted "3D Optimized Chassis" which is a solid internal structure and each circuit block is dedicated compartmentalised and arranged in three dimensions. Unified amp achieves exceptional heavy construction of 32 kg total weight

Those who are interested would like to listen to them at shops, events, etc., they will receive the impression that a pretty Integrated Amplifier has appeared. It is a direction of dynamic F-05 and more hi-fi and deep F-03A, but it may be better to regard it as a grade difference rather than AB class and A class operation.

Original article and interview by Hiroshi Suzuki