Elekit TU-8600R 300B Power Amplifier / Headphone Amplifier Kit
>>> Please note that tubes are not included in this kit <<<
"A world-class, four-star 300B tube amp that should cost $20,000 but will cost you only about $2,000 because you've assembled it yourself"
Herb Reichert Stereophile Magazine March 2019
The TU-8600R is a 300B single ended audio power amplifier kit. This is a special edition for the diyAudio store that includes upgraded 2% REX50G Takman resistors.
The 8600R has been reviewed by Stereophile and is now a Stereophile recommended component.
- TU-8600R Product Leaflet
- Review of TU-8600R in March 2019 Stereophile magazine
- Stereophile recommended components list
It's available as a SE version for $1,229 (TU-8600R with Takman resistors) or a deluxe version including the Lundahl transformer, for $1,785.
The Lundahl transformer is also available separately (including wiring harness and everything you need to perform the upgrade on a stock 8600R), for $650.
Power circuit enhancement
- High efficiency, low magnetic flux leakage R-core transformer
- Schottky barrier diodes for shorter recovery time
- Individual windings for the filament heater (A power), high voltage (B power), and bias to stabilize the negative feedback circuitry (C power)
- All power stabilized to reduce residual noise as much as possible, resulting in a noise level as low as 1/10th of the TU-8300R
Stable NFB circuit for high quality audio
- Improvement to various parts and circuits including OPT to make the most of 300B tubes
- NFB applied to cathode of 300B by the third winding of the OPT as well as to the voltage amplifying stage
- NFB is minimized as well as transient response
New active automatic bias adjustment
- Bias power is supplied separately
- New "Active automatic bias" used where the amp detects plate current and automatically adjusts the grid voltage, rendering the TU-8600 both self-biasing as well as having fixed bias.
- Current detecting circuit moved from cathode side to the B power side for better sound quality
Full power use of 300B tubes
- Orthodox voltage amplification stage to make the most of the 300B's outstanding sonic characteristics
- 12AU7 (ECC82) used in parallel for 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 differ. Most designs warm up both at the same rate.
- The TU-8600 heats up the directly heated 300B tubes after the indirectly heated 12AU7 / 12AX7 indirectly heated tubes have warmed up.
- This is a very tube friendly design that will not overload tubes that have not warmed up fully
Output level section for headphones
- There are jumpers on the board to allow for headphone impedance matching
DIY friendly design
- The TU-8600 comes with high quality polymer hybrid electrolytic caps and polypropylene film caps, however extra space has been designed into the PCB for audiophiles to add (larger) after market caps
- The TU-8600 operates at very high voltages, and includes a safety cover
- Tubes: 300B x 2, 12AX7x1, 12AU7x2 (TUBES ARE NOT INCLUDED)
- Rated output: 9.2W + 9.2W (10% THD)
- Rated input: 320mV
- Residual noise: 36uV (IHF-A)
- Frequency response: 7Hz-40kHz (-3dB)
- Input impedance: 50kΩ
- Output impedance: 4-6.3Ω, 8-16Ω selectable
- Input: Line1 (2 x RCA)
- Output: Gold plated speaker output terminals (banana plug compatible)
- Power input: 100/115/200/230V 50/60Hz (IEC inlet)
- Power Consumption: 90W
- Dimensions: 385x217x325mm (including projections)
- Weight: ~12.6kg assembled
I've always been intrigued by 300B SET amps. Over the years I've built a number of kits from AudioNote Kits and Bottlehead. Herb's Stereophile review made me commit. This is the best packed, picked, instructed kit I have made. Like Herb's, mine is the upgraded version, but I built it myself. It was an easy and fun build. My only caution is for newbies with little soldering experience. Watch some YouTube videos and practice first. In places the PCB is densely populated and the solder pads are close together.
Now for the best part. As Herb stated in his review, pair the TU-8600R with the right speaks and they sing. It's just mind boggling. You just built a $20,000 amp $2,000. There's nothing else to say!!!!!!
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