Friday, March 23, 2012
Onix OA-21s Amplifier and OA-22 SOAP power supply
Wow. Wow. Wow. Yes there are three there and there should be more. At 60WPC coupled with it's SOAP power supply it just sounds amazing. From it's minimalism design, to it's stunning blue circuit board, quality components and it's absolutely spectacular sound. All this unit would need is some incandescant ambient lighting and a cameo in a Ridley Scott 80's sci-fi movie and it would have it all!
This particular unit belongs to a customer who had brought it to me for a service and repair. Prior to being with the current owner these two units had actually been review units for HiFi Choice or What HiFI magazine in the UK (I can't remember which one!).
This unit is beautifully built, I cannot stress it enough, Solid anodized knobs, ALPS pot for volume and nice and heavy toroidal power supplies. The pre-amplifier for the phono stage could be removed and replaced with either a moving magnet or moving coil pre-amplifier. This unit was fitted with a moving magnet preamp.
The idea of the two units is that you could use the amplifier as a stand alone unit. Using it's toroidal power supply and on-board capacitor bank (originally consisting of 4x 4700uF capacitors a total of 18,800uF) to power the unit. If you added the SOAP or Special Onix Audio Power and connected it through it's umbilical cord to the OA-21 it would provide a dedicated power supply for the power amplifier stage as well as providing an additional 44,000uF worth of capacitors in the form of 2x 22,000uF capacitors. In simple terms you could drive the amp harder, louder and and not have distortion due to the capacitor bank being unable to supply clean DC power instead of 'dirty' power through the bridge rectifier directly. Very very cool!
OA-21 Amplifier unit:
It had two faults with it, the first being intermittent sound out of the phono stage, and the second being a lose input selector knob. The owner also wanted my opinion on giving it a full restoration, in the end we opted to also replace all the electrolytic capacitors in the OA-21s unit, however left the ones in the SOAP power supply alone as they were still in exceptional condition.
The phono sound issue was from the input switch selector having some dirty contacts. In order to do a proper job at cleaning them the switch selector was disassembled and all contacts cleaned individually. The switch selector moving freely was due to a worn collet on the shaft of the input switch selector. A new collet was machined and fitted in, now it switches between all inputs with no 'play'.
Replacing the capacitors was pretty straight forward. The unit could fit my star performers the Panasonic TS-HA filter capacitors rated at 6800uF were fitted in place of the original 4700uF capacitors.
Electrolytic capacitors were replaced with Panasonic AM series, some tantalum and film capacitors were also replaced with Panasonic film capacitors.
Rebuilt phono board:
I also ran into a small issue with the power connector on the OA-21 unit. It was producing some small amounts of arcing when powering on. The surface area of the plug going into the main board wasn't enough to supply the power across without arcing, so I opted to remove the plug completely and solder the power connector from the toroid directly to the board.
Overall the repair and restoration process was pretty straight forward, all solder joints were painfully redone as there were signs of cracked or partially cracked joints, the mica film and thermal paste were also replaced on the main output pairs. A couple of resistors were replaced that had shown signs of heat fatigue with resistors that could handle a bit more power.
The sound is phenomenal. Very clear with just the right amounts of bass and treble applied. My testing speakers were a pair of JBL 240Ti and Marantz HD880s. This is when the SOAP power supply really could show it's stuff. Without the SOAP, the sound is pretty damn fine, turn it up a bit too much though and you can hear a slight drop off in the deeper and more complex pieces. Plug the SOAP in and fire her up, wow! It doesn't even break a sweat! As always though, sound is subjective :) Results may vary from person to person but I certainly was extremely impressed at what this unit could deliver.
Modeling pictures as always, comments and questions always welcome!