Elekit TU-8600S & TU-8600SVK 300B Single Ended Tube Amplifier kit
The TU-8600S is a 300B single-ended integrated valve amplifier kit, pushing out a little over 9 watts output per channel. The kit can receive a single RCA input pair controlled by the front-located volume control. The on-off switch is located on the left side of the front panel. The power indicator, also situated at the front, can be either a green or blue lead, your choice while constructing.
One of the most intriguing things is that the kit supports a 1/4-inch stereo headphone socket. Once you insert your headphones, the RU-8600S becomes a dedicated headphone amplifier - brilliant. On the rear panel above the speaker binding posts, the output impedance is switchable - either 4 to 6.3 ohms OR 8 to 16 ohms. The main input is via an IEC socket.
The kit is universal, it can feed off all mains voltage variations of the world from 100Vac to 230Vac. Just make sure you use the correct power input board. The kit is built on a sturdy printed circuit board. I noticed that most of the solder tabs are not put-through-hole, so this helps if you wish to upgrade components later.
The kit is not supplied with valves as people generally have their opinion on valve selection. The output valves are 300Bs, with 1 x 12AX7 and 2 x 12AU7s making up the full complement.
There are two versions of the kit - we stock both. The TU-8600S features Elekit's standard E, and I core output transformers, whereas the TU-8600SVK uses Lundahl LL2785B C-core output transformers. This version is more expensive but worth the extra amount.
Power circuit enhancement
A high-efficiency, low magnetic flux leakage R-core is used for the mains transformer. The rectifier consists of Schottky barrier diodes that require a 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 the earlier TU-8600R version.
Stable NFB circuit for great audio quality
To make the most of the 300B tubes, the characteristics of various parts and circuits, including the output transformer (OPT), have been improved. The NFB is applied to the cathode of the 300B by the third winding of the OPT and to the voltage amplifying stage. Consequently, the overall NFB has minimized the chance of the transient response.
A new active automatic bias adjustment system
The power supply is equipped separately for the 300B tube bias, and a ”New active automatic bias” is used where the amp detects plate current and adjusts the grid voltage. This design earns TU-8600S the
privileges of both self-bias and fixed bias. In addition, a current detecting circuit is moved from the cathode side to the B-power side, resulting in even better sound quality.
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.
Tube-friendly design
Warm-up times 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-8600S, the 300B tubes are heated after the indirectly-heated tubes have warmed up. A very tube-friendly design will not overload tubes that have not fully warmed up.
Ample space for larger coupling capacitors
Capacitors can have a big effect on sound. TU-8600S uses high-quality conductive polymer hybrid electrolytic caps and polypropylene film caps. For those who wish to use other higher-quality caps, ample space is provided for mounting larger caps on the PCB.
SPECIFICATIONS
- CIRCUIT CONFIGURATION: Single-ended tube amplifier
- VALVE SET: 300B x 2, ECC83 x 1, ECC82 x 1 - valves not included
- POWER OUTPUT: 9.2 W + 9.2 W (THD 10%)
- MAXIMUM INPUT VOLTAGE: 270 mV
- RESIDUAL NOISE: 36 µV (IHF-A)
- FREQUENCY RESPONSE: 15 Hz - 40 kHz (-3 dB)
- INPUT IMPEDANCE: 50 kΩ
- OUTPUT IMPEDANCE: 4 Ω - 6,3 Ω / 8 Ω - 16 Ω Selectable by the rear switch
- INPUT TERMINAL: RCA LINE INPUT x 1
- OUTPUT TERMINAL: Speaker terminal gold-plated screw (banana plug usable)
- POWER VOLTAGE AC: 115Vac ' 235Vac 50/60 Hz (IEC inlet)
- POWER CONSUMPTION: 90 W
- DIMENSIONS: W 385 x H 217 x D 325 mm
- WEIGHT Approx. 17kg TU-8600S, 18kg TU-8600SVK
PRICE (1 off, excluding vat & p&p) not supplied with valves or IEC lead
TU-8600S - £1035.00
TU-8600SVK (with Lundahl OPTs) - £1375.00
For those who wish to buy the component upgrade kit, you will need to add the following to your cart when purchasing your kit.
As featured on the VK Audio's video, please note that some of Takman Carbons' values are no longer available, so we have listed alternatives above.
Elekit Volume Control Upgrade PCB for TU-8600 Series & TU-8800 (SOLD SEPARATELY)
Can be used with the following Elekits, TU-8600R, TU-8600RVK, TU-8600S, TU-8600SVK and TU-8800
Allows for high-grade pots such as the TKD 2CP-601(S) 50K.
This kit contains:
- Printed Circuit Board (PCB)
IT DOES NOT INCLUDE A POTENTIOMETER
Compatible potentiometers are available to purchase at the links below below
PRICE (1 kit)
£5.00 +vat +p&p
Elekit TU-8200S Lundahl Transformer Upgrade Kit (SOLD SEPARATELY)
This Kit Includes:
- 1 pair of Lundahll LL2785B output transformers
- 1 pair of fitting harnesses (PCBs + leads)
PRICE (1 kit)
£475.00 +vat +p&p
See our three instructional Youtube videos below on how to construct the Elekit TU-8600RVK kit (prior version)