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Part 2: Mr. Cable TPX Capacitors plus T20U DIY mod special report
Upgrading the capacitors is often the first step in DIY modifications. Procedures are usually easy to carry out as long as the size of the capacitor is suitable and the PCB accessible. Before-and-after results are usually not difficult to notice after a reasonable run-in period especially with smaller caps. This was exactly my experience with the KingRex T20U upgrade. Tommy Wu of JohnBlue tempted me with his JB version of the Tripath amp, which has received critical acclaim in Taiwan. However the Taiwan version is not for export due to regulatory issues. The JohnBlue website gives no specific information on what's upgraded. However, Tommy gave me a private crash course on the subject and sent out the required parts, which included the 2.2 uF/100v Mr. Cable TPX Teflon capacitors to replace the original Bennic XPP polypropylene capacitors and some audio-grade copper wires (branded KEL Fox Audio) also used for internally wiring his JB3 speaker. Tommy was so thoughtful as to also pack some WBT 4% silver solder. I should have told him that I always keep some solder stock and saved him the trouble. Here's the upgrade in 4 steps:

1. Volume pot. Christine Wu of KingRex also sent me some 50K A type Noble volume pots for upgrade. She told me that the higher quality and better sounding pots are now featured in current productions of the international versions of the T20 and T20U. This part turned out to be the most time consuming mod as the Noble pot is much smaller than the original and the contact pins would not line up with the soldering points of the PCB. I had to solder six very short pieces of audio-grade copper wires (also kindly provided by Christine) onto the 2mm spaced contact pins and then fit them onto the PCB within a very tight space so the shaft would clear the pre-drilled hole of the front panel. The production version has a tailor-made sub-PCB to make the connection neat and tidy. But my soldering skills weren't too shabby.

2. Coupling capacitors. The T20U has two of those, the T20 none. This upgrade is strictly for the T20U. Removing the PCB was a breeze. Replacing the caps was just as easy. A piece of Tommy advice: "Keep the lead-in wires long. They will sound better." That's why they stick out like curious emus. They are the parts that won't pass RoHS.

3. Twist the wires. Replace the copper wires connecting the AUX input RCA sockets to the PCB with multi-strand twisted wires. Tommy recommended silver for hot (+) and high purity copper for return (-).

4. Cut the beans. The beans refer to the tiny black EMI beads connecting the PCB and speaker binding posts. Tommy gave these instructions:

"Unsolder them and reconnect with the JB3 internal wires." James Lee of KingRex provided me with a thorough technical explanation. "The presence of the EMI bead cores is to satisfy ECC/CE requirements. Many of the switching type audio amplifiers emit a frequency within the 200KHz to 1MHz bandwidth depending on the chip used. This frequency will be transmitted with the output signal through the speaker binding posts. Although such ultra-sonic frequencies are beyond the audible bandwidth and won't have any effects on the loudspeakers, they do pose an interference threat to electronic gear in proximity. By adding EMI bead cores to the output terminals, we reduce to a considerable extent the potential for interference."

Asking questions is second nature to me. I wanted to know what I was cutting out and what electronic equipment might be affected and how serious that could be. James was as patient and accommodating as always. "The beads in the T20U are from Jantek Electronics and the model is RH Series 3.5*6*0.8M/M. In theory, any equipment that utilizes a fundamental oscillator frequency within the 200KHz-1MHz range stands a chance to be affected. CE and FCC set very stringent quality approval tests to make sure that certified products don't cause interference while simultaneously the products themselves are nearly immune to such interference." I had just one last question before I cut the beans. What would happen to the KingRex warranty? Null and void was the obvious answer.

Audition
The frequency response pushed outwards on either end. The highs became clearer without thinning out, bass even deeper without any rough edges while the midrange grew warmer and more enriched. The volume pot only needed to be set to 12 noon vs 1:30 or 2:00 with the original version. The valve-like character was even more pronounced. The sonority was warm, organic and utterly analog. The best yet was bi-amping, each amp powered with a KingRex SLAP! battery unit driving the Klipsch F2. When I closed my eyes and listened to the Rubinstein Piano Works played by Zora Mihailovich [Centaur 2235], I had to ask myself the most cliché question of all time: "Is this a recording or is it real?"