Description

>>> 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.

Features

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

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

Safety

• The TU-8600 operates at very high voltages, and includes a safety cover

Specifications

• 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