Extract from Mr Ohashi's Blog June 30 2024
Power Amp with Hashimoto HW40... P1616D
Translated By Google Translation.
You will notice that the output transformer has been replaced by Hashimoto HW-40. It is still in the evaluation stage, but if there are no problems electrically or in terms of sound quality, it will be exported to Canada/USA.
It would be premature to think that anyone can just change the OPT... The output transformer affects the overall characteristics as much as a car engine. In cases such as a single triode with no feedback, it may be possible to replace it by checking the impedance and core capacity, but in the case of a push-pull amplifier with a large amount of feedback, in the worst case scenario, the amplifier may oscillate and be damaged, so careful consideration in advance and detailed measurements after replacement are required.
The original output transformer is a custom-made product (made in Japan) optimized for the SV-P1616D and has KNF (cathode NF) windings, but the OPT to be installed this time does not have KNF windings. NFB is established based on the delicate balance of the amplifier, so the design is very delicate and design changes are required.
According to the report of the craftsman who was commissioned to make the prototype, the default NF resistor and phase compensation capacitor capacitance caused oscillation outside the audible range. This is something that cannot be detected by ear and can only be detected by measurement, so special care is required. As a result, integral compensation was added to the secondary side of the OPT to ensure stability and the project was completed.
These are the frequency and phase characteristics of the EL34 model with integral compensation and Hashimoto OPT. The results are impressive: gain 29dB/8Ω, output 40W+40W, frequency response 10Hz~160kHz/-3dB. With KT170, the output will increase by about 15%~20%. If you convert it to a MONO BLOCK and make it a parallel PP, as I wrote in my previous entry, an output of close to 100W will become a reality.
https://www.diyaudio.com/community/threads/double-the-output-power-of-set-amp.412884/
Power Amp with Hashimoto HW40... P1616D
Translated By Google Translation.
You will notice that the output transformer has been replaced by Hashimoto HW-40. It is still in the evaluation stage, but if there are no problems electrically or in terms of sound quality, it will be exported to Canada/USA.
It would be premature to think that anyone can just change the OPT... The output transformer affects the overall characteristics as much as a car engine. In cases such as a single triode with no feedback, it may be possible to replace it by checking the impedance and core capacity, but in the case of a push-pull amplifier with a large amount of feedback, in the worst case scenario, the amplifier may oscillate and be damaged, so careful consideration in advance and detailed measurements after replacement are required.
The original output transformer is a custom-made product (made in Japan) optimized for the SV-P1616D and has KNF (cathode NF) windings, but the OPT to be installed this time does not have KNF windings. NFB is established based on the delicate balance of the amplifier, so the design is very delicate and design changes are required.
According to the report of the craftsman who was commissioned to make the prototype, the default NF resistor and phase compensation capacitor capacitance caused oscillation outside the audible range. This is something that cannot be detected by ear and can only be detected by measurement, so special care is required. As a result, integral compensation was added to the secondary side of the OPT to ensure stability and the project was completed.
These are the frequency and phase characteristics of the EL34 model with integral compensation and Hashimoto OPT. The results are impressive: gain 29dB/8Ω, output 40W+40W, frequency response 10Hz~160kHz/-3dB. With KT170, the output will increase by about 15%~20%. If you convert it to a MONO BLOCK and make it a parallel PP, as I wrote in my previous entry, an output of close to 100W will become a reality.
https://www.diyaudio.com/community/threads/double-the-output-power-of-set-amp.412884/
