mewrei
Head-Fier
- Joined
- Jul 23, 2009
- Posts
- 87
- Likes
- 0
Ok, so its not very pretty inside. And I pulled a redneck DIY deal and added some extra shielding to the transformer in the form of some aluminum foil. Its grounded out though.
Actually the build is probably pretty laughable to someone who knows what they're doing, but this was probably only my 3rd build to date.
The story behind this one is long and tedious. I opted to build the CKKIII back in January as a stepping stone to other amplifiers. Fortunately, I got exactly what I wanted out of this amp's build, experience.
I ordered all the parts in February, and immediately got to work. First round was a colossal failure. The quiescent current on each channel had a LARGE delta and the trim pots couldn't manage this back down. I also managed to lift a couple pads when I was desoldering the old transistors and putting new ones in. I also had an issue where there was a large fidelity difference between the left and right channels. I ended up getting the plug for my headphones stuck in the headphone jack as well so I literally had to use a hammer and chisel to get it out of there (no damage to the headphones I'm pleased to report).
So I opted to just rebuild the board from scratch. This time I put a little more effort into selecting capacitors and internal parts, focusing on low-ESR. After the board was completely rebuilt, I noticed the quiescent current was still off by a little bit but this was managable. However I was still having the same issue with differing audio fidelity in each ear. I poped out the good ol' multimeter and started going over every point with a fine-toothed comb. I noticed that the test points (+/- 15v) differed by about a volt, so I ordered a new set of higher quality voltage regulators. Once these were installed, the test voltages read identical now. I rebiased the quiescent current and went to test again.
Still I had the same issue with differing fidelity. Long story short, turns out my issue was I had the outputs mixed up on the headphone jack (so I basically did all that work because I had a few wires mixed up).
But onto the fun details.
This version uses mostly Panasonic FM capacitors except where the bipolars are needed in the feedback loop (Panasonics), and the power stiffening caps, which are Nichicon HE's. The film caps are Wima's except in the power supply stage and near-output stage. The heatsinks are all Aavid-Thermalloy; and the opamp in the feedback loop is a TI OPA2134, and the output transistors are Toshiba 2SC2238/2SA968 units.
I ordered the panels from Front Panel Express. Original design was by [size=small]steinchen, I modified it a bit to suit my parts.[/size]
The end result is extremely good. I'm having a minor problem with ground channel saturation but that's a power source issue, not any of the amp internals. The music is incredibly detailed and accurate. Bass is plenty, and there's a really good soundstage.
All in all, I can't wait to have the unit broken in.
