This item has a new version, which provides more rich and mellow vacuum tube sound!

**One update on Jan. 2018: Attached AC/DC adaptor voltage changed from 12V to 9V. The sound quality is same as original but more stable operation even for lower impedance speaker.

**Small "hum noise" issue is solved in the current version.

Precaution before ordering: The AC/DC adaptor included in this kit produces small (subtle) amount of "hum noise". You will notice it in the case of no audio input but during playing music, it is ignorable. If you prefer "perfect", please try battery drive by 8-series AA or AAA (not included in this kit)

Precaution (2) for REV.1 From this kit, Nutube is directly soldered on PCB (socket is NOT included), since the lifetime of Nutube is enough long (much longer than general vacuum tube). (for REV.1) When soldering Nutube, PLEASE ATTACH plastic foot before soldering Nutube. After Nutube soldering, one of the plastic foot cannot be attached with PCB

What is it?

Now my Nutube amplifier has an evolution. My previous one was a headphone-driving application but it will be very fun if we can have "Nutube sound" through speaker!!! Here comes the next one! Nutube Pre/Main amplifier!

Why did you make it?

Speaker driving is more fun to use than headphone amplifier because everyone can enjoy Nutube sound simultaneously!

What makes it special?

Basic design concept is, "as much as, as is from Nutube". The sound from Nutube is transfer to speaker out as is, and additional component would not have additional "color" to sound. It consists of three stage. The first stage is made of Nutube, working as a kind of "analogue signal processor", generating rich "vacuum tube second harmonics sound". The second one is an impedance converter by JRC MUSES 8920. We may omit this stage if input impedance of the next stage is enough high (it requires more than 100 kOhm) but the next stage amp has that of tens of kilo-ohm so I inserted as well. MUSES is a high-end brand of JRC Japan, for high fidelity amplification. The third one is Class-D amplifier by Texas TPA3110. This tiny chip provides 15W x 2 output. By nature, class-D produces a wonderful sound by very simple circuit. As a whole, it is working a "21st century amplifier supported by lots of modern technology".

What is included in this kit? All the parts to complete amplifier (PCB, Nutube, ....), including 100-240V universal 12V AC/DC adaptor. As shown in the picture, some of SMT parts are pre-soldered for your convenience.

What is NOT included in this kit? Speaker, and AC-plug shape converter if your country is not compatible with US shape.

Precaution before ordering: The AC/DC adaptor included in this kit produces small (subtle) amount of "hum noise". You will notice it in the case of no audio input but during playing music, it is ignorable. If you prefer "perfect", please try battery drive by 8-series AA or AAA (not included in this kit)

Precaution (2) From this kit, Nutube is directly soldered on PCB (socket is NOT included), since the lifetime of Nutube is enough long (much longer than general vacuum tube). When soldering Nutube, PLEASE ATTACH plastic foot before soldering Nutube. After Nutube soldering, one of the plastic foot cannot be attached with PCB