DOGMA 600 MonoBlock Amplifier - OTHER --

During the prototype test period of the DOGMA 600 MonoBlock Power Amplifier, we conducted field tests in North America and Japan. We have prepared a list of items that were most frequently asked about during this period.

QIt says that the DOGMA has eight parallel output stages. Are these 8-parallel push-pull?
(i.e. 16 output elements) Or, are they just simply parallel?

The N-ch, P-ch push-pull configured circuit is 8-parallel.

QIt can be implied that the output elements are FETs. Do you use regular MOS-FETs?

Yes. They are regular plastic molded MOS-FETs with a power dissipation of 100W.

QIs the output stage in a SEPP or BTL configuration?

In terms of sound quality, it is best to have one of the speakers grounded, and the policy for the whole of the circuit is to amplify the voltage to ground. This is why we do not adopt BTL but use a single-end amplifier.

QIt says that a non-return design is adopted. Isn’t even local feedback applied at all?

Overall return is not applied to the input stage from output at all.
100% local return (voltage-based) is applied to the output stage, and power generated on the speaker coils is controlled. This cancels out not only drive distortion of the speakers but overall distortion including the speakers (speaker cables, enclosure, etc.) and reflection from the room. We do not think of speakers as being external items but as incorporated and driven powerfully as part of the output circuit. Nevertheless, we believe that when that is brought to the input stage, alternatively, input signals become distorted and the music information or delicacy needed for music playback is missing. As a result, one starts to observe a sound that, lacking dynamism, seems stuck to the speakers and spreads only over a flat plane, as well as a thin quality about the sounding body.

QIs there an order of priority in sound quality between unbalanced input and balanced input?

The amplification circuit is purely unbalanced amplification (in-phase amplification), so balanced input is provided for the connectors. There is no order of priority, and no difference in sound quality occurs whichever connection is used.

QThe indentation of the exclusive legs and the spike on the main unit are out of position. Why is this?

The resonance in the room and acoustic pressure emitted from the speakers is transmitted to the DOGMA main unit. These positions have been shifted so that enclosure vibration is dispersed and attenuated. Objects, not just audio equipment, always have a natural frequency dependent on material and shape. Ideally, during development, information on resonance points over a wide vibration frequency should be collected while performing low-temperature vibration testing with the main unit still turned ON. However, by just that alone, the equipment would just be an industrial machine made to satisfy ultimate statistical specifications only, and would no longer be classed as audio equipment. This is why we eventually developed exclusive legs by audibility-based selection while taking the vibration coefficient into consideration.
As a result of this, we attenuated vibration energy by adopting the concept of viscoelasticity and slightly shifted the positions of the stainless steel legs of the DOGMA main unit and the receptacles for these legs. Viscoelasticity appears in polymers such as plastic and rubber. However, since the legs of the DOGMA main unit are made of stainless steel, we obtained the value of the viscoelastic properties when the main unit is installed in the indentations of the exclusive legs made from a combination of SUS403 stainless steel and No.4032 aluminum plate, and adopted this technique since we found, while we were measuring these positions, that we could further attenuate vibration by shifting the positions.

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