Take a look at this shell, everyone? Not bad, right? This was an extra protective measure added last time when I purchased the LCD accessories for the 180TC from Dudu to prevent the LCD from being damaged during transportation! This box is indeed small and cute, and I plan to use it as the shell to make a super mini tube headphone amplifier. Let's get started. I'm busy making a super mini tube headphone amplifier myself. Since it's positioned as mini, it should be portable. So the voltage cannot exceed 12V. Finally, through a related search on Google, I found a tube headphone amplifier circuit that can work normally at an ultra-low voltage of 12V. Job Recruitment, especially suitable for friends who like tube headphone amplifiers to make themselves. After tinkering for N minutes, with tools like electric drills and soldering irons being put to work, the mini tube headphone amplifier finally came out. This tube headphone amplifier can be powered by a 12V battery. If using 10 nickel-metal hydride rechargeable batteries with a capacity of 2300mAh, it can work continuously for about 7 hours. Because the filament working current requires 300mA. So the original idea of making it work with a 9V rechargeable battery as a portable headphone amplifier is not feasible. Because the current highest capacity of a 9V nickel-metal hydride rechargeable battery is only 250mAh, which would give this tube headphone amplifier less than an hour of working time. The circuit uses one domestically produced tube 6N11, which is relatively cheap, around 20 yuan, and easy to buy. This model can be interchanged with 6922, 6DJ8, and ECC88. Changing different tubes can produce different tones, and the effect is immediate. Since the filament working voltage of the tube is generally around 6V, a 7805 three-terminal voltage regulator IC is needed to stabilize the 12V voltage to get a 6V filament working voltage. And this packaged 7806 chip can output a maximum current of 500mA, which is more than sufficient for the 300mA filament working current. However, due to the relatively large power consumption, the 7806 voltage regulator chip must have a heat sink added. Of course, you can also fix the 7806 to the iron shell with screws, which can save some space. Since the output impedance of the tube is relatively high, it cannot be directly used to output to the headphones. An OP must be added to handle the headphone output circuit. I used OPA2604 as the BUF output for the headphones. The OP can also use dual op-amps like 5532, OPA2134, AD827, etc. This circuit can also use the BUF634 dedicated buffer chip for headphone output, but the 634 is not easy to buy, so I had to use an OP for headphone output. The original intention of making this headphone amplifier was to match the LINE OUT audio output of the iPod dock, which gives much better sound quality than the iPod's own headphone output. During testing, I found that the sound from the iPod's own headphone output was hazy, as if covered with a layer of sand. After going through the headphone amplifier, the overall soundstage widened significantly, and the low, mid, and high frequencies all received a certain boost, with very obvious effects! Of course, to experience these effects, you definitely need a good pair of headphones or earphones. I use ER4P and Shure E5C earphones, so matching them with the headphone amplifier is a must. Christmas is here, thinking about what to give you, not planning to give you too much, only giving you fifty million: be happy! Be healthy! Be safe! Be content! And never forget me! It's not that I only think of you on such days, but it's on such days that I can legitimately bother you, telling you, Merry Christmas! Happy New Year! Be happy every day! I offer a heart of blessings, on this special day, may happiness, satisfaction, joy, flowers, and all good wishes be with you. Merry Christmas! Seeing you gives me an electric shock; not seeing you, I need to recharge; without you, I'll lose power. Loving you is my career, missing you is my business, hugging you is my specialty, kissing you is my profession! First, to be with you in this life; second, to be with you in the next life; third, to never be separated from you for three lifetimes. Crystal Love wishes you a happy New Year. When I hardened my heart and turned away, you cried helplessly behind me. This pain made me realize how much I love you. I turned around and hugged you: this pig is not for sale. Crystal Love wishes you a happy New Year. The wind is gentle, the rain is soft, the moon is full, the半岛铁盒 (Peninsula Iron Box) is by your side, showing a happy face every day! Winter goes, spring comes, like water and smoke, in the busy life, enjoy yourself! Listen to a light song, say a word of safety! New Year's auspiciousness, all wishes come true. Legend has it that lavender has four leaves: the first leaf is faith, the second leaf is hope, Customer Cases! The third leaf is love, and the fourth leaf is luck. I give you a lavender, wishing you a happy New Year!