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Technical Aspects of Hashimoto Products
1. Product and Product Design Philosophies The goal of Hashimoto Electric is to provide the best sounding and the highest quality tube audio transformers with the 21st technologies based on over sixty years of accumulated experiences. As if (actually is) a fine musical instrument, every Hashimoto transformer is literally hand crafted by experienced employees. As if (is) a fine musical instrument, every part of Hashimoto transformers is carefully selected and inspected. Finally, as if (is) a fine musical instrument, the most important aspect of Hashimoto production is how it's being built rather than what is being used to build. The chief engineer at Hashimoto Electric, Mr. Takao Ishiguro, has proudly mentioned to me that reverse engineering is almost impossible with Hashimoto products, "Could anybody rebuilt a Stradivarius by just taking its apart and finding out what it's made of?"
Hashimoto engineers prefer the total approach for its product design - examining every possible part to use, testing the optimum measurable characteristics of its products, and finally auditioning the sonic results - the most critical criteria. Even if a new product displays the best measurable characteristics, this product could be rejected if it is sonically inferior to other possible products. In other words, the top priority of Hashimoto transformer design is to obtain the most real-life-like music sound based on their accumulated technologies and proven methodologies. Hashimoto engineers prefer the step-by-step approach rather than putting too much emphasis on merely expensive or exotic material. For example, Hashimoto engineers intentionally avoid using silver wire because they have discovered that it actually worsens the sound compared with the traditional copper wire. Another good example is Hashimoto does not use permalloy cores. This is because permalloy cores are weak in lower frequency, thus the final sound tends to be unbalanced even though permalloy cores yields beautiful high to mid-range sound. Hashimoto's sonic orientation has been a long term goal and tradition from the Sansui era. Mr. Ichiro Ohshima who was a high-end product manager at Sansui from mid 1980's to 2000 mentioned to me that "It's easy to design an amplifier that has excellent measurable characteristics. But, it's very difficult to build an amplifier that sounds good under the same technical characteristics." Because of this pursuit in "good sound" philosophy, Sansui put so many efforts to eliminate two major sources of sound distortions; physical vibrations and grounding issues throughout the 1990's. As Sansui engineers has pursuit, Hashimoto engineers put great emphasis on eliminating the physical vibrations and shutting-off the external electrical noises. Hashimoto engineers believe these are two major elements of making significant differences into the better sound. For example, Hashimoto output/input transformer cores are filled in pitch rather than stored in the solid plastic or epoxy because Hashimoto engineers discovered that the oil based pitch is better material to absorb the physical vibrations. Another good example is Hashimoto MC transformers consist of three layers of internal insulations with two different density of micro-wax to minimize the absorption of external vibrations as well as electro-magnetic noises. Even before Hashimoto started its branded tube transformer business, Hashimoto has been producing the hospital-grade power transformers that require the lowest noise level in order to supply the cleanest power to the sensitive medical equipments. The essence of this technology is so called "Multiple Balanced Shield," and Hashimoto took advantage of this technology to design its choke coils and power transformers to yield very low hum and noise level. As the result, the combination of Hashimoto power supply transformers and signal pass transformers yield the optimum sound quality with the lowest hum, noise, and vibration inferences. This is the exact reason why Hashimoto recommends to use all Hashimoto transformers in an amplifier.
2. Output Transformers Two of the most significant issues on output transformer design are the core selection and the winding techniques. Most of Hashimoto's main output transformers, excluding smaller transformers, such as 15W in PP or 7W in SE, are constructed with a parallel twin Cut-Core to form a shell type core. The core material is 0.27mm Orient Core Hi-B, which is the enhanced directional silicon steel, from Nippon Steel Corporation with 1.10 W/Kg Material iron Loss at 1.7T/50Hz (for the comparison, the thickness and Material iron Loss of popular M3, M4, M5, M6 are 0.27mm/1.3, 0.27mm/1.4, 0.3mm/1.5, 0.3mm/1.65 at 1.7T/50Hz respectively).
As being previously mentioned, Hashimoto engineers intentionally avoid to use permalloy or amorphous cores. This is because they have determined that the Oriental Core Hi-B would yield better and more balanced sound quality if other important factors; such as the core windings, the isolation and filling material, and the overall case design, are designed correctly. Hashimoto core winding techniques which have been accumulated over 60 years of experiences should be the ultimate asset for Hashimoto engineers. Hashimoto inherited the top quality transformer technologies from Sansui in the late 1970's, then Hashimoto has further fine tuned the skills for the last thirty some years. In essence, the core winding techniques are the result of numerous tries and errors. This is the place where accumulated experiences should count the most, and this is the place where subtle sonic differences will appear depending upon the depth of engineers skills. The ultimate goal of core winding technique is to determine the best scheme of minimizing the leakage inductance and the stray capacitance. The leakage inductance can be reduced by alternatively mixing the primary and the secondary windings in several layers; this is called the horizontal dividing method. However, too many horizontal layers will increase the stray capacitance. In order to reduce the stray capacitance, the secondary windings can be divided into sections in each layer; this is called the vertical dividing method. However, at this time, too many vertical dividing will increase the leakage inductance. Therefore, Hashimoto engineers have to determine the optimum point of mixing the horizontal and the vertical dividing methods. Especially for a high-primary-impedance transformer, too many horizontal dividing will increase undesirable stray capacitance; thus, the technique of vertical dividing becomes an essential factor to design a high quality high-primary-impedance transformer.
Another issue which makes the core winding more complex is the fact that Hashimoto output transformer secondary has 4, 8, and 16 Ohms outputs. These three independent output windings could slightly increase the leakage inductance due to the unused section of output windings. Hashimoto engineers solve this issue with further elaborated core winding techniques. Beside the core winding technique itself, there are many other issues Hashimoto engineers need to give their attentions to. For example, in order to secure the horizontally and vertically divided coil, Hashimoto has adopted the custom made paper for the insulation material. For Single-Ended transformers, Hashimoto engineers uses polyester films for a core spacer (SE transformers need a core spacer to avoid the magnetic saturation caused by B+ DC current). The reason why Hashimoto uses pitch for the filling material has been mentioned in the previous section. Finally, Hashimoto engineers have designed the outer case and chosen its material in consideration of minimizing the external physical vibrations and magnetic interferences. As being described before, Hashimoto transformers are the result of the total efforts to obtain the best possible sonic performances after the optimum measurable characteristics have been archived. In this sense, Hashimoto transformers require the highest attention to the details to build, and they are nothing but an art created by skilled craftsmen.
3. Input / Interstage Transformers The basic construction of Input / Interstage transformers is very similar to that of output transformers except these transformers have a single Orient Core Hi-B in the core type construction. This is because Input / Interstage transformer require the low-noise characteristic rather than the power efficiency. Because Hashimoto Input / Interstage transformers allow users to configure in different impedance settings, the internal windings become extremely complex.
4. Power Transformers Hashimoto power transformers adopted a cold rolled, 0.5mm Hi-Light Core, which is non-directional silicon steel, to form the I-E core. As being already described, Hashimoto power transformers are the direct result of experiences obtained by developing the larger / higher-powered hospital-grade power transformer technologies. The significant benefit of the "Multiple Balanced Shield" technology is the minimization of both the normal mode and the common mode noises. These noises are caused by the stray capacity being generated between the transformer and the ground. According to the data from Hashimoto Electric, the noise improvement with the "Multiple Balanced Shield" shows a significant 35dB difference compared with transformers without the "Multiple Balanced Shield".
Besides the "Multiple Balanced Shield" that insulates between the primary and the secondary windings, both a copper short-ling and a silicon steel hum-proof belt around the coil and the core prevent from its own noise leakages. To improve the electrical insulation, Hashimoto engineers adopted the hospital-grade insulation materials. Finally, to minimize the chance of over-heating, every Hashimoto power transformer contains an internal 130C heat fuse.
5. Choke Coils The materials being used in Hashimoto Choke Coils are very similar to those of Hashimoto Power Transformers; the same core and the same insulation materials. One unique feature that should be mentioned here is Hashimoto Choke Coils can be set at one of two selectable inductance levels.
Last changed: 02/01/15 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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