Thanks!

Hello. This modification was made by order of my friend. He has high impedance STAX electrostatic headphones and this amp didn't have enough gain to fully drive it. According to my friend. Also, my friend is very demanding on sound quality and to improve the resistors in the signal circuits and feedback circuits were replaced with Vishay metal foil ones and high-quality high-capacity capacitors were installed in the power supply of each channel amplifier. This modification was made for certain headphones and may not be suitable for another type. In this case, the values ​​of the input resistors were reduced . feedback resistor value 15 kOhm, input resistor value 2.15 kOhm. We selected them by preliminary audition.

@@arenaengineering8070 thank you for answering. If i change the resistors in the signal circuit and feedbak circuit with metal foil resistors of high quality with same value as the originale resistor, can i the expect an increes in sound quality?

And hove many farads did the capasitors have?

@@robertmollan7054 First of all, you should know that this amplifier contains good resistors from Vishay. And replacing with expensive Vishay metal foil resistors may not give the increase in quality that you expect compared to the cost of the resistors themselves. My friend was completely satisfied with the result. But he is a musician, an audiophile and he has a high-end signal source and high-quality headphones - with such a system he got the result he expected. There was also a preliminary audition before this upgrade.

@@robertmollan7054 According to the diagram, 100 µF capacitors were placed in these places. They were replaced with 1000 uF Elna Silmic 2 capacitors. As was seen in the video, their size turned out to be quite large and it was necessary to change the location of some of them.

Здравствуйте! Не могу ничего сказать про плеер, но по описанию он очень требователен к качеству записи для хорошего воспроизведения высоких частот( уж не знаю почему, возможно связано с питанием от литиевого акб и особенностей встроенного преобразователя питания). Внешний усилитель будет подключаться через линейный выход плеера( это важно). Вы не озвучили бюджет и пожелания так что предложу для начала усилитель beyerdynamic A 20.

Так же можете попробовать BURSON Audio Soloist SL MK2. Тоже дискретный усилитель для наушников,который в состоянии работать на высокоомные наушники.