So, after having a good experience with my Motorola EL84 SE, I decided to deconstruct the Mr. Liang's KT88 and use the components to build a new SE amplifier. The parts that I could use were the Jensen coupling capacitors, Jensen electrolytic capacitors, some 6DJ8s, EL34s, KT88s, 6L6s, ALPS potentiometer, RMG resistors, etc.

I then bought a pair of 20W EI 2.5K / 3.5K local Hong Kong made single-ended output transformers, an EI power transformer and a Chinese made chassis. That was my second SE amplifier with no negative feedback. I tried using paralleled 12AX7, 1/2 12AT7, 1/2 6DJ8, 6C45PI to drive the power tube including KT88, EL34 and 6L6.

The results were not very satisfactory. Then, I swapped the pair of trannies with a pair made by a Chinese tranny guru. Since then, I started to realize how important the role of the trannies is in a tube amplifier. The difference was so obvious that the machine sounded completely different! What an open sound stage that was.

At that moment, I was using the 6C45PI with a lot of driving current. The only thing that I didn't satisfied was the dynamic.

Therefore, I started thinking maybe one stage of amplification was just not enough to drive the power tube good. With this idea in mind, I changed the driver stage from one to two, using 1/2 6DJ8 to drive 1/2 6CG7 and then coupling to the power tube. And the result was just good. And that is the circuit I'm still using at the moment to drive my pair of Klipsch Heresy. And the power tube that I like most in this machine is KT88.

I got two pair of 6B4Gs in hand and the project would start in the near future. I have quite high hope towards 6B4G.

Push-pull vs Single-ended

Before I used the Mr Liang's KT88 PP amplifier, I was using Musical Fidelity A2 to drive a pair of Dali Royal Menuet. I didn't satfisfy with the bass performance of MF A2. I thought the KT88 PP could give me better bass response but it didn't.

After listened a while, a net-friend motivated me to do some mods. He said the output transformers of my amp were the weakest links. As a newbie, I didn't believe him. And I decided to do my own way. Firstly, I removed the PCB and completely rewired the machine with point-to-point soldering, as I read from the web that point-to-point would make the sound better.



Secondly, as told by the net-friend that RMG carbon composite resistor was the best choice for tube amplifier, I changed all the resistors to RMG. Thirdly, all the red WIMA coupling capacitors were changed to Vitamin Q. The first phase of mod was basically done.


And the sound... not much different. Why?

Then, I suspected the stock Chinese tubes were not up to par. So, bidded some GE 6DJ8s and 6CG7 to replace the Chinese 6N11 and 6N6. The sound "changed". It's a little diffrent, but not necessarily in a good way. Was that because of the push-pull design?


In the mean time, I kept reading tube related websites, and started to have fantasy towards single-ended amplifier. And I acquired an ugly small SE Motorola EL84 console amplifier from eBay. Each channel used 1/2 6DJ8 to push an EL84. And the sound was just amazing! The mid and the high were just so seductive that just blowed my KT88 off.


From that moment, I was convinced that SE was my cup of tea.


My tube journey started from a cheap Chinese KT88 amplifier

That morning, I logged on to the audiophile forum as usual and I watched the discussion about a Chinese manufacturer called Mr Liang's Audio. They said the KT88 push-pull amplifier was okay for a price under US$200. So, I bought it. Since then, I was addicted to vacuum tube!