Someone pointed out that it's interesting to see all the components in a system, rather than discuss them individually. I liked the idea - I think it also shows what projects ended up actually useful - so here are my systems (I have four with diy components).

The music I listen to is an eclectic mix of classical music (such as Rachmaninov and Tchaikovsky), opera (mostly arias), jazz (Armstrong) and some pop music.

The first system is the one I listen to the most:

• exposure 2010S CD player with Tentlabs low-jitter clock
• B1 clone preamp
• F5 clone
• Vintage Celestion DITTON 15XR speakers

The second system is the testbed for whatever project I may be working on:

• Audio Analogue Crescendo CD player
• B1 clone preamp
• Zen V4 with SiC power JFET in the gain stage
• Klipsch Heresy III speakers

The third is the best sounding so far, has the highest WAF and is likely to stay around for some time:

• Sony CDP-XB920 CD Player
• Elekit TU-879S integrated amp

...

Built from a kit. Sound lacks finesse.

Built from a kit. I don't like the sound at all.

Built from the kit from Bruce Rozenblit. Very nice one, but is not being used - it has too much gain for any of my systems. I will probably sell it.

Unsatisfied with the sound of my gainclone amplifier, I re-used the enclosure and the power supply for a gainclone along the lines suggested by Bob Cordell, whose implementation of an LM3886 based amp was praised by at least one member on the NJ audio society.

I skipped both the Klever Klipper and the toroidal air core output inductor, and kept only 10,000 uF per rail in the PSU. The schematic can be found in Chapter 27 of Cordell's Designing Audio Power Amplifiers. The PCB was designed to re-use the existing mounting holes of the ChipAmp's PCB.

The result? Better than with a plain vanilla chip amp, but still not good enough for music. Perhaps I should not have limited myself to re-use of the PSU et al. but should have taken all the details of my implementation seriously.

I posted some time ago a note about my Velleman K4040 amplifier. The sound of the amp as built from the kit was unremarkable and definitely not in line with the price. Lacking experience with tubes, I was looking for some time for well documented mods to the kit.

I found two 2006 posts here and here and implemented them rather directly. The only difference is that I used IXCP10M45S instead of a pair of J508 current sources in each channel and replaced the 1N5408 rectifiers with UF5408 instead of adding noise suppressing capacitors in parallel to them.

The mods did not leave much of the original Velleman design in place; the result, however, is a remarkable improvement in sound!

However, two problems remain: (1) I got hum that wasn't present before the mods; and (2) a two-year old running around doesn't get along with eight hot, attractively glowing tubes. The project is shelved until a better time.

For future reference: The toroidal...

To try out Class D without working too much, I picked two ready-made Class D amplifier modules: one is the $45 2*100 Watt Class-D Audio Amplifier Board from Sure Electronics with the optional $10 volume control board, the other is the $199 IRAUDAMP7S from International Rectifier.

The Sure Electronics module is based on Tripath's TK2050 chipset. Powered from a 150W 24V SMPS from Mean Well, it predictably puts out about 22W RMS to a 8 ohm load. (The declared 2*100W requires a 30V supply and a 4 ohm load.) The sound and the measurements are decidedly mediocre, although at the $45 price, the module still may be a good value. Also, the volume control board feels odd, as the knob only adjusts volume after a push; another push disconnects it again.

The IRF module requires dual rail supply, for which I chose an SMPS400A180 by hypex. With +/-40V rails, the amplifier delivers 100W RMS into a 8 ohm load. The measurements are good, and the sound is very interesting for...

I wanted to build a Class D amp based on TI's PurePath chips - e.g. TAS5086 PWM processor and a few TAS5162 power stages - until I read Bruno Putzeys' "The Truth About Digital (Class D) Amplifiers". He makes a convincing argument that digitally controlled class D is a dead end street. I also noticed that very few people around here have been writing about PurePath. Shall I look at the UcD patent and application note, as well as ready made Hypex modules, instead?

I just built a Distortion Cancelling Push Pull (DCPP) amplifier designed by Peter Millett. It sounds very nice, was fairly easy to build, and is rather inexpensive. Thank you Peter for the great design!

To get warm and comfortable on long winter evenings, I built myself a Burning Amplifier 1. With its 300W quiescent dissipation and ineffable ((c) Nelson Pass) sound, it is a nice winter time companion.

I used four heatsinks, each holdings two IRF250 MOSFETs in TO-3 packages and a PCB. Each pair of heatsinks is cooled by a quiet 140mm fan. Power supply uses a 400W toroidal transformer and 2x40,000 uF per channel; it is a dual mono configuration. The amplifier is housed in a 5U 400mm deep enclosure from modushop. Their "pierced base" was very handy to keep all the parts together without sacrificing the looks. Total weight is 23 kg (about 50 pounds).

The knob on the front panel was designed as volume control, but it looks ugly, so I will remove it.