JD-9A MK2 Phono Stage Level-1 mod
The following details the Level-1 modification for the Jolida JD-9A Phono Stage ($480 + freight retrofit:
- We install 2 Auricap signal path metallized polypropylene coupling capacitors.
- 8 Riken Ohm ½ and one watt signal pat" 1% carbon comp. resistors with gold-plated leads are installed.
- 4r International Rectifier Hexfred ultra-fast soft recovery, diodes are installed in the power supply.
- We replace the two stock preamp tubes with a pair of Electro Harmonix Gold pin tubes.
- We Install 4 small EAR brand Sorbothane isolation feet.
- 2 sheets of SoundCoat chassis damping material cut & applied where applicable.
- WBT high silver content (4%) solder used throughout.
- The mod takes a total of 3 hours labor.
The unt has a more liquid midrange and more neutral presentation from bass to treble. It is quiter. Blacks are blacker, resolving more low level detail and ambiance. It is more dynamic and micro dynamic contrasts are much improved. Transparency is improved and you can now look farther into the soundstage. Images are sized better and are more defined. Stage width and depth improve.Bass slam and extension are improved with fuller weight and authority in the critical midbass region. It now competes with much more expensive units in this important area.
Our basic Level-1 mod is $990 for new units and offers exceptional value. Our Level-2 & 3 mods take it to the next level and allow it to compete with world-class phono stages that sell for up twice what these modified units sell for. These mods were designed by Chris Johnson, the founder and former president of Sonic Frontiers.
JD-9 MK2 Level-2 mod
- We replace the two stock preamp tubes with premium matched milspec Russian Electro Harmonix gold pin 12AX7s, designed for 10,000 operation. These are ultra low noise with ultra low microphonics.
- We add two Auricap metalized polypropylene coupling capacitors in the output signal path
- We install four hi quality coupling, bypass and power supply capacitors
- Eight Riken Ohm ½ and one watt 1% carbon com. resistors (gold-plated leads) are added in the signal path
- Four International Rectifier Hexfred ultra-fast soft recovery diodes are installed in the power supply
- One pair of premium Vampire direct gold plated over copper body RCA female connectors on the input
- Two additional 1000uF/25V upgraded capacitors are used in the phono power supply
- We replace the stock $4.00 Burr-Brown OPA-2604 dual op amps in the output driver section with two adapter PCBs, allowing the use of the world's finest op amp, the $25.00 Burr-Brown OPA-627 single surface mount op amp. W use two modules with 4 opamps in total.
- We Install four large EAR brand Sorbothane isolation feet
- Two sheets of SoundCoat chassis damping material are cut & applied where applicable to the chassis.
- WBT high silver content (4%) solder is used throughout
- 4.5 hours total labor
JD-9 MK2 Level-3 modIn the Level-3, we do the following additional mods to the Level-2 ($1,300 retrofit plus shipping):
- Replace four additional $4.00 single op amps with the world's finest op amp, the Burr-Brown OPA-627
- We add 10 additional top quality 220uf 6.2V Power supply capacitors
- Two more Auricap metalized polypropylene coupling capacitors are added to the input signal path
- We install fourTelefunken SF4007 ultra-fast soft-recovery diodes in other sonically critical power supply positions
We replace the stock tubes with RFT (German) 1970’s vintage ECC83’s. (12AX7’s)
- Total install labor – 6 hours