Conrad-Johnson ART108A Power Amplifier – Quick Look
All Image Credit: Conrad-Johnson
I always loved the sound from my pair of Leak TL50 Plus, ultra-linear, mono power amplifiers. They use 2 x KT88 vacuum tubes operating as beam tetrodes in Class AB providing 50 watts into 8 ohms, and I always found their mid-range and top, smooth, open and detailed.
So if you love the vacuum-tube sound, needs lots of Class A power and have deep pockets, then you may want to take a peak at the the Conrad-Johnson flagship ART108A mono-block power amplifier. This beautiful, vacuum-tube, class A high power amplifier was a new addition to their range of ART amplifiers back at the beginning of 2022. If the ART108A is a little too challenging for you pocket or you require a little less power then take a look at their other lower cost ART or Classic range of vacuum-tube power amplifiers. If you are also in the market for a valve preamplifier, control amplifier or phono pre-amplifier Conrad-Johnson manufacture those too.
Their design philosophy is based upon the culmination of more than 40 years of research and development. Conrad-Johnson products are executed with simple circuits and constructed with the highest-quality custom components. Proprietary components include: CJD film capacitors, audio and power transformers, military-grade parts like precision audio resistors, and in-house designed elements such as circuit boards, chassis and dress metal.
The ART108A is capable of 160 watts when driven into 4 ohm loads (may be configured for either 8 or 16 ohm loads). The power is developed by four pairs of Genelex Gold Lion KT88 beam tetrodes that are configured for triode operation. Precision, laser-trimmed bulk metal foil Vishay resistors are used in all crucial positions in power supplies and voltage gain audio stages. CJD proprietary PTFE (Teflon) dielectric capacitors are used throughout both to couple the inverter stage to the output stage, as well as to bypass the high value (also proprietary) PP (polypropylene) capacitors in the fully regulated power supplies. A custom mains transformer supplies the independently regulated power supplies for the output stages, input amplifier and inverter stages, providing plenty of headroom for full output power. The proprietary output transformer that is optimized for Class A operation is a custom designed Translinear wide-band model.
Optimal biasing of the 8 KT88’s is not automatic but manual and is simplified by the use of an adjacent LED and pot next to each vacuum tube. KT88’s will typically provide about 2,500 hours of worry free operation during which they should only be required to have their bias checked about every 6 months with moderate use.
Technical Specifications:
- Type Mono valve power amplifier
- Power 160 Watts rms into 4 ohms from 30 to 15KHz at no more than 1.5% total harmonic distortion
- Tube Complement 3 × 6922, 8 × KT88
- Sensitivity 1.0V rms to rated power
- Small Signal Distortion less than 0.25% at mid-band
- Frequency Response 20 Hz to 20 kHz, ± 0.25 dB
- Hum and Noise less than 200 microVolts
- Phase phase correct
- Input Impedance 100 kOhms
- Dimensions (W×H×D) 48 × 22 × 53cm each
- Weight 40.4kg each
Warranty: 3 years (excludes tubes)
MSRP: $52,000.00/pair
For more information visit: conradjohnson.com
Want to know more about amplifier classes. Take a look at this post.
Want to know how Tubes work? Then take a peak at: Valves or Tubes To You – An Introduction
