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NP-100v12: 12AU7 (ECC82) / IRF510 Headphone Amp
12AU7 (ECC82) Tube Pinout Diagram
circuit
A Bipolar Junction Transistor (BJT) can be used in place of the MOSFET, but MOSFETs tend to be more stable with temperature and current shifts. Use caution when handling MOSFETs as they are very static sensitive.
The signal enters the grid via a coupling capacitor, it leaves the plate (anode) amplified and 180 degrees out of phase, it is then directly coupled to the gate of the MOSFET and leaves the source. The signal is then coupled to the headphones via a electrolytic capacitor, which blocks the DC from your headphones. Since the sleeve of your headphones is common it completes the circuit.
The MOSFET is biased into class-A operation and will be constantly conducting at approximately 125 mA. The LM317 regulator is configured as a constant current source and regulates at 125 mA in the given configuration. You can use the online LM317 regulator calculator to determine the current through the regulator by adjusting the program resistor. It is suggested that a 10 ohm 1/2W program resistors is used for R4 (you can use two 1/4W 20 ohm resistors in parallel). Note that the regulator and MOSFET devices will heat up and radiate heat. There are some real in depth calculations for heat, but know that the MOSFET can dissipate at least 1.6 Watts and the LM317 2 Watts to air, at room temp. I tested a prototype over a continuous 24 hours period in a 150 cubic-centimeter (about 9 cubic-inch) enclosure and there were no thermal stability issues. You can add heatsinks to the devices, just ensure that if you gang the FETs together to use mica and silicone washers to prevent the 12V supply from transferring to the heat sinks.
The schematic above shows only one channel, you will have to wire the the tube for both channels using different pins. The only wiring that is common for the 12AU7 tube between the two channels is the heater.
PCB Files
> NP-100v12 PCB Image - (PNG 50kB)
> NP-100v12 Components-Layout - (PNG 23kB)
> NP-100v12 PCB Image - (PDF 13kB)
> NP-100v12 EAGLE Circuit Board File - (BRD 16kB)
> Potentiometer Routing PCB Image - (PDF 3kB)
> Potentiometer Routing EAGLE Circuit Board File - (BRD 5kB)
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เค้าเริ่มทำตั้งแต่ปี2008 ปรับปรุงล่าสุดapril 2010
วงจรใช้ไฟแค่12โวลท์ เอาไปใส่Sound Cardก็ได้ หรือ ใส่ในเคสเครื่องคอมก็ได้ หรือ ทำแบบExternalก็ได้
ไฟล์PCBก็มีให้ครบทุกอย่าง หรือที่เค้าทำมาไม่ถูกใจ จะเขียนPCBใหม่ ในเวปก็มีคนทำได้หลายคน
ตัววงจรก็ยังสามารถปรับปรุงต่อยอดได้อีก ยังโมเพิ่มได้อีก
NP-100v12: 12AU7 (ECC82) / IRF510 Headphone Amp
12AU7 (ECC82) Tube Pinout Diagram
circuit
A Bipolar Junction Transistor (BJT) can be used in place of the MOSFET, but MOSFETs tend to be more stable with temperature and current shifts. Use caution when handling MOSFETs as they are very static sensitive.
The signal enters the grid via a coupling capacitor, it leaves the plate (anode) amplified and 180 degrees out of phase, it is then directly coupled to the gate of the MOSFET and leaves the source. The signal is then coupled to the headphones via a electrolytic capacitor, which blocks the DC from your headphones. Since the sleeve of your headphones is common it completes the circuit.
The MOSFET is biased into class-A operation and will be constantly conducting at approximately 125 mA. The LM317 regulator is configured as a constant current source and regulates at 125 mA in the given configuration. You can use the online LM317 regulator calculator to determine the current through the regulator by adjusting the program resistor. It is suggested that a 10 ohm 1/2W program resistors is used for R4 (you can use two 1/4W 20 ohm resistors in parallel). Note that the regulator and MOSFET devices will heat up and radiate heat. There are some real in depth calculations for heat, but know that the MOSFET can dissipate at least 1.6 Watts and the LM317 2 Watts to air, at room temp. I tested a prototype over a continuous 24 hours period in a 150 cubic-centimeter (about 9 cubic-inch) enclosure and there were no thermal stability issues. You can add heatsinks to the devices, just ensure that if you gang the FETs together to use mica and silicone washers to prevent the 12V supply from transferring to the heat sinks.
The schematic above shows only one channel, you will have to wire the the tube for both channels using different pins. The only wiring that is common for the 12AU7 tube between the two channels is the heater.
PCB Files
> NP-100v12 PCB Image - (PNG 50kB)
> NP-100v12 Components-Layout - (PNG 23kB)
> NP-100v12 PCB Image - (PDF 13kB)
> NP-100v12 EAGLE Circuit Board File - (BRD 16kB)
> Potentiometer Routing PCB Image - (PDF 3kB)
> Potentiometer Routing EAGLE Circuit Board File - (BRD 5kB)
เห็นหลายคนพูดถึงอยากให้มีDIY Group Buyในเวปนี้กัน ผมว่าตัวนี้ก็น่าสนใจไม่น้อยน่ะ
ถ้าจะทำDIY Group Buyกันจริงๆ ตั้งกระทู้ใหม่ แล้วพูดคุยกันในนั้นได้เลย
เค้าเริ่มทำตั้งแต่ปี2008 ปรับปรุงล่าสุดapril 2010
วงจรใช้ไฟแค่12โวลท์ เอาไปใส่Sound Cardก็ได้ หรือ ใส่ในเคสเครื่องคอมก็ได้ หรือ ทำแบบExternalก็ได้
ไฟล์PCBก็มีให้ครบทุกอย่าง หรือที่เค้าทำมาไม่ถูกใจ จะเขียนPCBใหม่ ในเวปก็มีคนทำได้หลายคน
ตัววงจรก็ยังสามารถปรับปรุงต่อยอดได้อีก ยังโมเพิ่มได้อีก
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