300B/2A3 SE POWER AMP KIT
TU-8900* TUBES NOT INCLUDED

Directly-heated triode tubes like the 300B and 2A3 enjoy an enduring popularity among audiophiles. The 300B with its richmidrange and extended bass - and 2A3 with its delicate expression and gentle tone - they offer a very special sonic experience. These2 tubes, similar in appearance but very different in characteristics, can both be used in TU-8900 without any special changes intubes so users can enjoy trying the various versions available
amplifier settings. Many manufacturers are producing 300B and 2A3 tube
TU-8900!
in the market. * NOTE- TUBES ARE NOT INCLUDED with THE TU-89
U-8900!

With 2A33

With 300B■ Automatic detection of 300B and 2A3 tubes■ Newly designed circuitryi“300B” and “2A3” tubes look similar but their respective filament voltages andoperating 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 ofB-power are automatically set. When 300B tubes are installed, the LEDs on the sides ofthe 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 thevolume 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.

The power transformer has independent windings for the right and left channel tominimize 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 reduceeven the most negligible noise spikes. Listeners can enjoy music free from noise evenwhen using a pair of high efficiency headphones. The main circuit of the power unit isunitized per channel as a module.

■ Tube-friendly design
Warm-up time for directly-heated tubes and indirectly-heated tubes are different. In mostdesigns, directly-heated tubes warm up faster than indirectly-heated tubes. Sodirectly-heated tubes are often overloaded. With TU-8900, the voltage is gradually raised
and reduces the level of overload to the directly-heated tubes.

■ Easily change the feedback setting to NON-NFB
Many triode tube amps use negative feedback in their design. The TU-8900 has an option forlisteners to hear the triode tube sound without negative feedback. In TU-8900, changing theposition 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

■ 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.

■ Ample space for larger coupling capacitors

The IEC (International Electrotechnical Commission) sets guidelines on thermal limits onmaterials and parts, such as a chassis and the tube cage. The TU-8900 tube cage top can heat up
to 100 degreesC due to the heat from the output
tube cagep tubes. A robust ppolycarbonateyg withhigh heat resistance is used to meet the IEC standard.

Coupling capacitors can have a big effect on the soundquality. 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 thespace is 22mm in diameter x 44mm in length.

■ Matching headphone impedance/volume levels
You can change the headphone impedance/volume levels bysimply removing the front panel and change the position of ashort pin.
With a tube cage

TU-8900 SPECIFICATIONS●Tubes ：300B (or 2A3) x 2pcs, 12AU7 (or 12BH7A) x 2pcs (Tubes not included)* Specifications below are with the 300B+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 (SW on backside)●Input terminal : LINE x 1●Output terminal
Headphone terminal : 6.3mm headphone jackSpeaker output terminals (L/R channel) : Gold-plated screw type terminal (Banana plug usable)●Power voltage : AC110-120V or AC220-240V 50/60Hz (3P inlet)●Power consumption : 95W (300B) / 65W (2A3)●Measurement : W356xH214xD320mm (including projections)●Weight : Approx. 11.4kg (excluding a power cable)