Johari Audio System

Johari Audio System.

I met Johari almost 8 years ago. I went to listen to Johari's audio system when I had my 2 months business trip in Singapore. He was using the Oris horn with 45 SET tube amplifier previously. His setup really opened the eyes of a novice DIYer like me. His system has evolved since then, but still, the 45 direct heated triode remained in the system. Read more about direct heated triode here:

Go to Direct Heated Triodes.

Let’s dig deeper into Johari audio system.

Digital Front End: Sony XA50ES CD player is used as transport. This is from the Sony “ES” series, the premium category for Sony gears. This CD player is built like a tank! The weight of this monster is ~15 kg by itself!

DAC: Zhaolu D2 (above is not the actual picture) with LME49720HA Op-Amp at output stage. The Zhaolu D2 is one of the best bang for the buck DAC in the market. High end DAC chips are used. Good quality components are employed everywhere in the DAC. One cannot complain with the price paid for this DAC and it can easily beat DACs costing many times the price.

Quote from Op-Amp manufacturer: Some details on the Op-Amp: LME49720 is part of the ultra-low distortion, low noise, high slew rate operational amplifier series optimized and fully specified for high performance, high fidelity applications. The LME49720 combines extremely low voltage noise density (2.7nV/ √ ^Hz) with vanishingly low THD+N (0.00003%) to easily satisfy the most demanding audio applications. The LME49720 has a high slew rate of ±20V/μs and an output current capability of ±26mA. Further, dynamic range is maximized by an output stage that drives 2kΩ loads to within 1V of either power supply voltage and to within 1.4V when driving 600Ω loads. The LME49720's outstanding CMRR (120dB), PSRR (120dB), and VOS (0.1mV) give the amplifier excellent results.

Analog Front End in Johari Audio System

• Thorens TD124 MkII Turntable
• Micro Seiki MA88 tonearm
• Expert Stylus re-tipped DL103 with Midas aluminum body

DACT CT100 phono stage with customized shunt regulated PSU in Johari Audio System.

Quote from manufacturer: The CT100 is a two-channel phono preamplifier module with very accurate RIAA equalization and many features. It is realized with the best semiconductors available and non-inductive, low noise, SMD metal film resistors. The circuit is designed to accept both moving coil (MC) and moving magnet (MM) transducers/cartridges directly in order to eliminate the need for an external MC step-up transformer or amplifier. MC/MM input loading and input nominal level values are easy to select with high resolution by DIP-switches.The CT100 is ideal for the most demanding applications requiring accurate RIAA equalization, very low noise, extremely low distortion and superior sonic performance. The high output voltage from CT100 makes it equivalent to other signal sources like CD-players.

Pre-amp in Johari Audio System: 5687 with Lundahl 1660 output transformers – it is a simple single stage WOT (with output transformer) minimalist pre-amp. This removes the need of coupling capacitors that colors the sound no matter how good the capacitor is. Of course, the output transformer would need to be of certain quality to sound good.

Power amps for midrange in Johari Audio System: 45 SET mono-block. 45 direct heated triode needs no introduction! You can look at the below link to understand more about 45 vacuum tube and direct heated triodes.

The 45 SET mono-block is a minimalist design as well – it is a 2 stage amplifier with 12AT7 driving the 45 vacuum tube using Lundahl output transformer.

Power amps for bass in Johari Audio System: UcD180AN mono-block – “UcD” stands for “Universal class D amplifier”. This is a module from Hpyex, Netherlands. Quote from Hypex:

“The UcD180™ amplifier module is a self-contained high-performance class D amplifier intended for a wide range of audio applications, ranging from Public Address systems to ultrahigh-fidelity replay systems for studio and home use. Chief distinguishing features are flat frequency response irrespective of load impedance, nearly frequency-independent distortion behavior and very low radiated and conducted EMI. Control is based on a phase-shift controlled self-oscillating loop taking feedback only at the speaker output.”

Output power: 180W at THD = 1% with power bandwidth of 20-35 kHz and 10 – 50 kHz +/0 -3dB at all loads.

This is more than enough to drive the 15” Usher 15HM x 2 with ease. I owned the UcD400HG myself and I can never be happier using it in driving the subwoofers. I’ve tried it on my Tannoy Edinburgh copy with DCC 3149 and it was doing a fantastic job when partnered with a tube pre-amp.

Speakers for midrange in Johari Audio System: AH204 Azurahorns with 2" throats – this is a horn with mouth diameter of 800mm, with a throat of 170mm and an axial length of 310mm when made for 8” Lowthers. The throat size is customizable too for drivers down to 2” from a one piece mould. The Le Cleac’h flare rate is 204 Hz at 0.8T factor calculated from a 168mm throat size. You can find more details on the Azurahorn website.

Midrange driver in Johari Audio System: Radian 950pb compression drivers.

Quote: “The 950PB 2" exit neodymium compression driver with ultra-low distortion produces extremely clean high-frequency sound. The 950PB's wide frequency response range & 125 watt AES/250 watts program rating make it ideal for recorded & live sound applications that require clear transparent high frequencies at extreme SPL levels.”

Specifications:

• Frequency response: 500 Hz to 20 kHz
• Sensitivity: 111 dB
• Impedance: 8 or 16 Ohms

Bass - Onken style custom enclosures with 15" Usher 15HM per channel.

Quote from Parts-Express on Usher 15HM bass driver: “This item has been discontinued. The Usher 15" studio woofer is designed to offer a value-based alternative to other premium large-format studio monitor and PA drivers. The 15HM has a low Qts, making it play well in smaller vented enclosures. While excellent for high sensitivity studio monitor designs, this driver can also be horn loaded for higher-power, higher-output systems. Don't let the conservative 150 watt power rating fool you, this driver can produce a big, clean sound that will compete with other woofers in its price range.“

Crossover is a hybrid with the Behringer DCX2496 (DCX2496 again! This is one famous piece of active crossover in the DIY world!) working in conjunction with a customized passive line filter.

The sound is big and transparent but smooth and slightly on the warm side.

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