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.
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.
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 22 mm in diameter x 44 mm in length.
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.
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. 8 dB 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 °C due to the heat from the output tubes. A robust polycarbonate tube cage with high heat resistance is used to meet the IEC standard.
Available versions or TU-8900E vs TU-8900VK
There are two available versions of this kit – TU-8900E and TU-8900VK. Version E is a full kit prepared for european power lines with standard output transformers. TU-8900VK is a kit WITHOUT output transformers, or with Lundahl output transformers. Except output transformers both kits are exactly the same.
TECHNICAL SPECIFICATION
| CIRCUIT CONFIGURATION |
Single ended tube amplifier |
| TUBES |
300B x 2 or 2A3 x 2
12AU7 (ECC82) x 2 or 12BH7A x 2 |
| Below specs are for 300B + 12AU7 (ECC82), with NFB, 8Ω load if not set otherwise |
| RATED OUTPUT |
8W + 8W (300B) / 3,5W + 3,5W (2A3) (THD 10%) |
| RATED INPUT |
1 VRMS (300B) / 650 mVRMS (2A3) |
| RESIDUAL NOISE |
15 µV (IHF-A) |
| FREQUENCY RESPONSE |
7 Hz – 90 kHz (with NFB) / 12 Hz – 45 kHz (Without NFB) |
| INPUT IMPEDANCE |
50 kΩ |
| OUTPUT IMPEDANCE |
4 Ω – 6,3 Ω / 8 Ω – 16 Ω
Selectable by the rear switch |
| INPUT TERMINAL |
LINE x 1 |
| OUTPUT TERMINAL |
Speaker terminal gold-plated screw (banana plug usable), headphone terminal 6,3 mm jack |
| POWER VOLTAGE |
AC 110-120 / 220-240 V 50/60 Hz (3P inlet) |
| POWER CONSUMPTION |
90 W |
| DIMENSIONS |
W 365 x H 214 x D 320 mm |
| WEIGHT |
Approx. 11,4 kg (excl. power cord) |
