TU-8600R 300B SE tube power amplifier kit.
Power circuit enhancement
A high efficiency, low magnetic flux leakage R-core
is used. The rectifier consists of schottky barrier
diodes that require shorter recovery time. This results
in a reduction in even negligible noise spikes. The
windings of the power transformer include individual
windings for the filament heater (A- Power), high voltage
(B-power), and bias to stabilize the Negative Feedback
(NFB) circuitry (C-Power). In addition, all power is
stabilized to reduce residual noise as much as possible.
This results in the noise level as low as less than
1/10 of that of TU-8300R.
Stable NFB circuit for great audio quality
To make the most of the 300B tubes, the characteristics
of various parts and circuits, including OPT, have been
improved. The NFB is applied to the cathode of the 300B
by the third winding of the OPT as well as to the voltage
amplifying stage. Consequently, the overall NFB is minimized
as well as the chance for the transient response.
New active automatic bias adjustment adopted
For the 300B tube bias, the power supply is equipped
separately, and a ”New active automatic bias”
is used where the amp detects plate current and automatically
adjust the grid voltage. This design earns TU-8600 the
priviledges of both self-bias and fixed bias. In addition,
current detecting circuit is moved from the cathode
side to the B-power side resulting in even better sound
Driving 300B tubes to full power
A very orthodox design is used for the voltage amplifying
stage to bring out the outstanding characteristics of
the famed 300B tubes. Of special note is that 12AU7(ECC82)
is used in parallel for the 2nd stage to drive the 300B
tubes to full power- resulting in 200Vp-p without clipping.
Warm-up time for directly-heated and indirectly-heated
tubes largely differ. In most designs, amp power-up
starts heating both the directly heated 300B tubes (fast
warm-up) as well as the indirectly-heated 12AU7 and
12AX7 (slower warm-up). In TU-8600R, the 300B tubes
are heated after the indirectly-heated tubes have warmed
up. A very tube-friendly design that will not overload
tubes that have not warmed up fully.
Output level selection for headphones
For the headphone, you have 4 selections of output level
to match your headphone.
Ample space for larger coupling capacitors
Capacitors can have a big effect on sound. TU-8600R
use high quality conductive polymer hybrid electrolytic
caps and polypropylene film caps. For those who wish
to use other higher quality caps, there is ample space
provided on the PCB for mounting larger caps.
Special version with Lundahl's transformers
Besides the standard version, the kit will be also available
with special adjustments for using a highest quality
Lundahl LL2770B transformers for even better sound quality.
This is the TU-8600RVK model.
• Circuit configuration, Single ended tube amplifier
• Used tubes (not included), 300B x 2, ECC83 x
1, ECC82 x 1
• Rated Output, 9,2 W + 9,2 W
• Rated input, 320 mV
• Residual noise, 36 µV (IHF-A)
• Frequency response, 7 Hz - 40 kHz (-3 dB)
• Input impedance, 50 kOhm
• Output impedance, 4 -
6,3 Ohm / 8 - 16 Ohm, Selectable by the rear switch
• Input, line x1
• Output, Speaker terminal gold-plated screw (banana
• Power voltage, AC 100/110-120/200/220-240 V
• IEC Standard inlet
• Power consumption, 90 Watt.
• Dimensions, 385 x 217 x 325 mm
• Weight, 12,8Kg
by Herb Reichert, Stereophile.
Elekit TU-8600R may look like a generic, old-school,
single-ended 300B integrated amplifier, but its sonic
character is clean, neutral, and precise in a distinctly
21st-century way. It doesn't sound at all warm or soft,
but fast and vigorous, as transparent as any amplifier,
and extremely captivating. My many months of auditioning
it suggest that, with the right speakers, this humble
amp kit could please discriminating listeners as much
as any amplifier at any price. Bravo, Yoshitsugu Fujita.."
With Lundahl C-core output transformers.
Remember that this is a DIY kit. It means that YOU will
have to build it yourself using the assembly manual.
The kit includes all electronic and mechanical parts
(including housing) required to build a ready to work,
high quality tube amplifier. It should take 5-6 hours
to construct and it will need soldering. You should
have some tools and soldering skills. Interconnects
are not inclueded and the power cable is Japanese type,
you will need a proper cable for your country.
multimeter is not required but is really useful.
Detailed visual assembly kit instructions in Japanese
language are included in package. An English language
instruction will be send to you in pdf format after
for bigger coupling capacitors