Elekit TU-8900 300B/2A3 DIY Tube Amp Kit
The Elekit TU-8900 300B/2A3 DIY Tube Amp Kit offers total flexibility for the serious audiophile who loves the magical sound of a great single-ended tube amp, with 300B or 2A3 tubes. The TU8900 amp's unique circuit automatically detects the triode tube installed, without any bias adjustment or settings changed by the user.
Directly-heated triode tubes like the 300B and 2A3 enjoy an enduring popularity among audiophiles. The 300B with its rich midrange and extended bass - and 2A3 with its delicate expression and gentle tone - they offer a very special sonic experience. These 2 tubes, similar in appearance but very different in characteristics, can both be used in the Elekit TU-8900 Tube Amp Kit without any special changes in amplifier settings. Many manufacturers are make 300B and 2A3 tubes so users can enjoy trying the various versions available in the market.
See our tube packages for this amp here
We also offer Mundorf coupling capacitor upgrades for the TU-8900 amp. You can order a 4-pack of caps below:
■ Automatic detection of 300B and 2A3 tubes
“300B” and “2A3” tubes look similar but their respective filament voltages and operating parameters are totally different. Their supply voltages need to be adjusted depending on which of these tubes are used in the same amp. In TU-8900, the tubes installed are detected automatically and the correct filament voltage and voltage of B-power are automatically set. When 300B tubes are installed, the LEDs on the sides of the volume knob will light up in blue. If 2A3 tubes are installed, the volume knob LEDs will light up in green. Additionally, these LEDs on the right and left side of the volume knob will turn red when there is excessive current due to defective tubes, etc., and the current is shut down to protect the amplifier. The red LEDs will also diagnose the problematic tube- the right side of the volume knob turns red when excess current occurs in the right channel, and vice versa.
■ 12BH7A also usable instead of 12AU7
TU-8900 is designed to use 12AU7 as voltage amplification tubes. However, 12BH7A, with high driving ability, can also be used instead of 12AU7.
■ Matching headphone impedance/volume levels
You can change the headphone impedance/volume levels by simply removing the front panel and change the position of a short pin.
■ Tube-friendly design
Warm-up time for directly-heated tubes and indirectly-heated tubes are different. In most designs, directly-heated tubes warm up faster than indirectly-heated tubes. So directly-heated tubes are often overloaded. With TU-8900, the voltage is gradually raised and reduces the level of overload to the directly-heated tubes.
■ Newly designed circuitry
The power transformer has independent windings for the right and left channel to minimize the interference between channels as much as possible. The filament power uses the latest DC-DC converter with extremely low noise and high efficiency. Schottky barrier diodes and fast recovery diodes are used as rectifying diodes that reduce even the most negligible noise spikes. Listeners can enjoy music free from noise even when using a pair of high efficiency headphones. The main circuit of the power unit is unitized per channel as a module.
■ Easily change the feedback setting to NON-NFB
Many triode tube amps use negative feedback in their design. The TU-8900 has an option for listeners to hear the triode tube sound without negative feedback. In TU-8900, changing the position of a short plug on the PCB can change the setting to NON-NFB. The gain level increases by approx. 8dB when NON-NFB setting.
■ Updated more reliable tube sockets
After brainstorming with our manufacturer, we have come up with more reliable 4-pin sockets for 300B/2A3. Tubes are mounted safely and securely when installed in these sockets. ■ High heat-resistant polycarbonate tube cage
The IEC (International Electrotechnical Commission) sets guidelines on thermal limits on materials and parts, such as a chassis and the tube cage. The TU-8900 tube cage top can heat up to 100 degrees Celsius due to the heat from the output tubes. A robust polycarbonate tube cage with high heat resistance is used to meet the IEC standard. Directly-heated triode tubes like the 300B and 2A3 enjoy an enduring popularity among audiophiles. The 300B with its rich midrange and extended bass - and 2A3 with its delicate expression and gentle tone - they offer a very special sonic experience. These 2 tubes, similar in appearance but very different in characteristics, can both be used in TU-8900 without any special changes in amplifier settings. Many manufacturers are producing 300B and 2A3 tubes so users can enjoy trying the various versions available in the market. * NOTE- TUBES ARE NOT INCLUDED
■ Ample space for larger coupling capacitors
Coupling capacitors can have a big effect on the sound quality. For the TU-8900, high quality conductive polymer electrolytic caps and polypropylene film caps are provided. However, exchanging for other coupling capacitors is also possible. The maximum size of the caps that can fit in the space is 22mm in diameter x 44mm in length.
●Tubes ：300B (or 2A3) x 2pcs, 12AU7 (or 12BH7A) x 2pcs (Tubes not included)
* Specifications below are with the 300B and 12AU7, with NFB, 8Ω loaded
●Rated output ：8W+8W (300B) / 3.5W+3.5W (2A3), THD 10％
●Rated input : 1Vrms (300B) / 650ｍVrms (2A3)
●Residual noise : 15μV (IHF-A)
●Frequency response : 7Hz-90kHz (with NFB) / 12Hz-45kHz (Without NFB)
●Input impedance : 50kΩ
●Output impedance : 4-6.3Ω, 8-16Ω (Switch on backside)
●Input terminal : LINE x 1
Headphones: 6.3mm headphone jack
Speakers (L/R channel) : Gold-plated screw type terminal (Banana plug usable)
●Power voltage : AC110-120V or AC220-240V 50/60Hz (3 Prong inlet)
●Power consumption : 95W (300B) / 65W (2A3)
●Measurement : W 356 x H 214 x D 320mm (including projections)
●Weight : Approx. 11.4kg (excluding a power cable)
Additional Information and Downloads
Elekit (EK Japan Co. LTD) has been producing electronics kits since the early 1970's. While their main focus has always been educational kits, more recently they started to offer hifi audio amplifier kits. Included are some fantastic DIY vacuum tube amps and headphone amplifiers.
Warranty Information and Return Policy
Since this is an electronic product that is assembled by the user, we cannot provide a warranty like those found for regular pre-assembled electronics. Instead, Elekit can provide a counseling service. If there is a problem in the product please contact ELEKIT. However, throughout the instruction manual there are many check points, and we kindly ask you to make sure to pay attention to those check points as most of the time your problem can be solved if you follow them closely. We can not accept returns of any kit that has been started.
EK JAPAN CO., LTD Tofuro-minami 2-19-30, Dazaifu-shi, Fukuoka, 818-0105 Japan Phone: +81-92-923-8235 Fax: +81-92-923-8237 Website: http://www.elekit.co.jp Email: firstname.lastname@example.org
Ratings & Reviews
Elekit TU-8900 300B/2A3 DIY Tube Amp Kit | Awesome and easy to build amp.
This is the second tube amp kit I've built. Great instructions and all parts included plus they seem to have added additional pieces for some small parts in case I lost something. It sounds great and I'm using 300B tubes but would like to try some 2A3 in the future.
Very pleased with this purchase! DIY-EK-TU-8900