The price is the kit, without power mosfet, other originals are included.

The price includes: 2-channel pcb board, a full set of resistors and adjustable components, K170 and J74 that are precisely matched according to the circuit characteristics, (the kit does not include the power mosfet), the kit needs to be soldered by yourself,

You need to contact us in advance to make a reservation for the finished board.

Feature sharing:

1. PCB size, 29.5cm*3.5cm.

2. DC power supply: +/-21V to 24v, AC power supply: dual 16V to 18v.

3. Circuit index:

Input impedance: 10Kohms (RCA input)

Output power: 15 to 20 watts

Gain: 14.5DB

Input voltage at maximum output: 2.7volts

Frequency response:-3 dB @ 100 KHz

Power consumption: 175 watts

Fuse: 3AG slow blow, 1.25A (240 VAC)

4. The power mosfet recommends the use of high cost-effective Hitachi: 2sk1058 and 2sj162 (need to be paired, or other audio-specific power mosfets with low turn-on voltage and negative temperature characteristics can be used, the pin definition is: 1 is G pole, 2 is S pole , Pin 3 is D pole)

5. When the power mosfet uses Hitachi 2sk1058 and 2sj162, the power supply voltage is +-24v, the single tube current should be controlled below 800ma, the power supply voltage should be +-21v, and the single tube current should be controlled below 900ma. Please ensure good heat dissipation.

6. In the actual test, no noise and self-excitation caused by poor PCB design were found.

7. Actual listening experience: There is really some doubt before the sound, can it make a good sound? But when the music played, these questions disappeared It has excellent musicality, good damping and driving force (Need to use pre-amplifier)

8. The recommended power of the power transformer: 400W to 500W.

(Notes: 1. The Class A power amplifier generates a lot of heat, and the radiator is recommended to be above 2.8 kg per channel.

2. If you need a speaker protection board, please install it yourself. The board does not have speaker protection function.

3. The kit provides installation and commissioning instructions, please be sure to operate according to the instructions.

4. Power supply filter capacitor (shared by two channels), please use a single channel with a total capacity of 90,000uf and above, and a positive and negative power supply with a total capacity of 180,000uf and above. This can ensure a pure power supply and also a good sound for the F7 amplifier Good foundation.

Introduction:

FirstWatt F5, conceived in 2007, is a push-pull Class A amplifier that uses 8 semiconductors and 23 resistors to achieve 25 watt output, and has good specifications and good sound. You can make articles in the user manual and DIY, both of which are posted on the www.firstwatt.com website. F5 has received good reviews and sales, and has received a lot of attention from the DIY audio community (as of this writing, F5 has been viewed 3 million times on www.diyaudio.com). Like other golden first watt amplifiers, this is a limited release and will be discontinued after the 100 sets are sold. Later, a more powerful version was released to DIYers, F5 Turbo, which provided more power and multiple options for the experiment. The sound performance of the First Watt F5 power amplifier lies in the details and neutrality of the music. This is the characteristic of a simple Class A amplifier, wide bandwidth, and a lot of negative feedback. For some audio sources and equipment, the F5&x27;s sound is exquisite, but the amplifier also tends to highlight faults in the recording and the rest of the system. For a bad recording project, a second-rate DAC, or the peak of the speaker, the amplifier is again Looks so ruthless

Since then, I have spent a lot of time exploring other types of amplifier design methods, but I always want to go back to F5 and see how it can be improved. Mainly I am looking for two things: better sound and even simpler circuit. The desire for simpler circuits is self-explanatory-apart from aesthetics, I think simpler circuits often sound better. (Because I built them myself, it would be cheaper. I envisioned a circuit with only four transistors and four resistors (it seems to be the smallest model of this type of amplifier, in which all Fets work in common source mode, providing both voltage and Current gain. The complementary input Jfets drives two complementary power supply Mosfets, and the output voltage is fed back to the source pin of Jfets, usually called "current feedback" (CFA).

A little explanation: Amplifiers and speakers are a bit like dancing. Both sides have their own complexities, but

The key is to get them to get along well. The amplifier designer does not generally control what speakers are used, and usually chooses the amplifier as a superior partner to make it a pure voltage source. Negative feedback in a typical voltage source amplifier is used to define the speaker regardless of the current passing through the speaker. This represents a "my way" method of amplification, and big hardware has a lot of feedback to be good at this. Most speakers are designed around the assumption of a low impedance voltage source.

FirstWatt F7, is a nice small class A amplifier, there is hardly any feedback

The advantage of brute force. It resorts to a strategy that makes the dance a bit more like tango. Appropriate amount of negative feedback and positive current feedback form a balanced impedance close to zero in the output, which improves the transient response and frequency response. Of course, you can achieve a similar effect by using a lot of negative feedback, but I think this is more elegant and sounds better For the sake of brevity, I will call it "PCF". In addition, I used more filter capacitors in the power supply, and found a clever way to further reduce the effects of high-frequency DAC noise and environmental RF. FirstWatt F7 This is a different amplifier. What is the diversity of audio flavors, and not everyone will like it. I think some audiophiles will like it.

In conclusion

If you haven&x27;t noticed, I like amplifiers with personality. They don&x27;t have to measure perfection, they just have to sound good. This is a very simple small class A amplifier with many personalities, I hope you like it

aThe price includes: 2-channel pcb board, a full set of resistors and adjustable components, K170 and J74 that are precisely matched according to the characteristics of the circuit, (the kit does not include the power mosfet), you need to solder it yourself,

Introduction:

FirstWatt F5, conceived in 2007, is a push-pull Class A amplifier that uses 8 semiconductors and 23 resistors to achieve 25 watt output, and has good specifications and good sound. You can make articles in the user manual and DIY, both of which are posted on the www.firstwatt.com website. F5 has received good reviews and sales, and has received a lot of attention from the DIY audio community (as of this writing, F5 has been viewed 3 million times on www.diyaudio.com). Like other golden first watt amplifiers, this is a limited release and will be discontinued after the 100 sets are sold. Later, a more powerful version was released to DIYers, F5 Turbo, which provided more power and multiple options for the experiment. The sound performance of the First Watt F5 power amplifier lies in the details and neutrality of the music. This is the characteristic of a simple Class A amplifier, wide bandwidth, and a lot of negative feedback. For some audio sources and equipment, the F5&x27;s sound is exquisite, but the amplifier also tends to highlight the recording and the rest of the system failures. For a bad recording project, a second-rate DAC, or the peak of the speaker, the amplifier is again Looks so ruthless

Since then, I have spent a lot of time exploring other types of amplifier design methods, but I always want to go back to F5 and see how it can be improved. Mainly I am looking for two things: better sound and even simpler circuit. The desire for simpler circuits is self-explanatory-apart from aesthetics, I think simpler circuits often sound better. (Because I built them myself, it would be cheaper. I envisioned a circuit with only four transistors and four resistors (it seems to be the smallest model of this type of amplifier, in which all Fets work in common source mode, providing both voltage and Current gain. The complementary input Jfets drives two complementary power supply Mosfets, and the output voltage is fed back to the source pin of Jfets, usually called "current feedback" (CFA).

A little explanation: Amplifiers and speakers are a bit like dancing. Both sides have their own complexities, but

The key is to get them to get along well. The amplifier designer does not generally control what speakers are used, and usually chooses the amplifier as a superior partner to make it a pure voltage source. Negative feedback in a typical voltage source amplifier is used to define the speaker regardless of the current passing through the speaker. This represents a "my way" method of amplification, and big hardware has a lot of feedback to be good at this. Most speakers are designed around the assumption of a low impedance voltage source.

FirstWatt F7, is a nice small class A amplifier, there is hardly any feedback

The advantage of brute force. It resorts to a strategy that makes the dance a bit more like tango. Appropriate amount of negative feedback and positive current feedback form a balanced impedance close to zero in the output, which improves the transient response and frequency response. Of course, you can achieve a similar effect by using a lot of negative feedback, but I think this is more elegant and sounds better For the sake of brevity, I will call it "PCF". In addition, I used more filter capacitors in the power supply and found a clever way to further reduce the effects of high-frequency DAC noise and environmental radio frequency. FirstWatt F7 This is a different amplifier. What is the diversity of audio flavors, and not everyone will like it. I think some audiophiles will like it.

in conclusion

If you haven&x27;t noticed, I like amplifiers with personality. They don&x27;t have to measure perfection, they just have to sound good. This is a very simple small class A amplifier with many personalities, I hope you like it

Feature sharing:

1. PCB size, 29.5cm*3.5cm.

2. DC power supply: +/-21V to 24v, AC power supply: dual 16V to 18v.

3. Circuit index:

Input impedance: 10Kohms (RCA input)

Output power: 15 to 20 watts

Gain: 14.5DB

Input voltage at maximum output: 2.7volts

Frequency response:-3 dB @ 100 KHz

Power consumption: 175 watts

Fuse: 3AG slow blow, 1.25A (240 VAC)

4. The power mosfet uses EXICON 10N20 10P20, the pin definition is: 1 is G pole, 2 is S pole, 3 is D pole

(Remarks: The actual hearing sense using Hitachi 2sk1058 and 2sj162 cannot be compared with the original EXICON tube)

5. Please ensure good heat dissipation.

6. In the actual test, no noise and self-excitation caused by poor PCB design were found.

7. Actual listening experience: There is really some doubt before the sound, can it make a good sound? But when the music played, these questions disappeared It has excellent musicality, good damping and driving force (Need to use pre-amplifier)

8. The recommended power of the power transformer: 400W to 500W.

Precautions:

1. The Class A power amplifier generates a large amount of heat, and the radiator is recommended to be above 2.8 kg per channel.

2. If you need a speaker protection board, please install it yourself. The board does not have speaker protection function.

3. The kit provides installation and commissioning instructions, please be sure to operate according to the instructions.

4. Power supply filter capacitor (shared by two channels), please use a single channel with a total capacity of 90,000uf and above, and a positive and negative power supply with a total capacity of 180,000uf and above. This can ensure a pure power supply and also a good sound for the F7 amplifier Good foundation. (It is recommended to use a special filter board with 12 capacitors, which is available in our shop.