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.

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?

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.

This is an implementation of National's reference design for LME49830 with two matched pairs of 2SK1530+2SJ201 per channel. The PCBs were made using National's gerbers (thus National's logos). Sounds surpisingly good, but it has just been completed; I did not have a chance to listen to it carefully yet.

Update: I rebuilt the amp as a pair of monoblocks, each delivering healthy 200W into 8 ohms. It now looks tidier.

Update: the original Gerbers from National are nowhere to be found since national.com was merged into ti.com. Attached are the original archives downloaded from the national.com.

This was unavoidable, I guess. Dual mono LM3886 kit from ChipAmp.com with Avel Lindberg's transformers in a wonderfully compact enclosure from Design Build Listen. I liked the simplicity but not the sound. Why is everyone so excited with gainclones? IMHO, Papa's Zen V4 is not much more complicated to build (although no kit is available), but is so much more an interesting experience!

Last year I got an Lm60 kit from AmpsLAB. This year, I finally got an enclosure from Design Build Listen and a power supply and built it. Each channel is built on a small (120x60mm) one-sided PCB and uses one 2SK1058+2SJ162 pair in the output stage. With proper biasing, the sound is good, esp. for such a simple and compact design. I should have started with this one, rather than with the (equally inexpensive) K-8LS.

One of the more interesting projects for me was building a tweaked clone of Creek 4330. It was designed for Creek by diyAudio member x-pro; the schematic is available on his web site. The tweak was the topic of x-pro's paper and was discussed in this forum. Last year, this design generated enough interest on one of Russian DIY forums for a group buy of PCBs and some components. I used a PCB from that group buy, a compact chassis from modushop, and a K4700 speaker protection kit from Velleman. Today it is this amp that I use most often for music, and I am very pleased with its sound. Thank you x-pro for sharing the design!

Nelson Pass' Penultimate Zen (aka Zen V4) proved trickier to build than the simple schematic suggested. I used a chassis from designbuildlisten and PCBs made with the gerbers posted on passdiy.com. Initially I used some Chinese electrolytic capacitors that were easily available, but the sound was not good at all. I replaced them with ELNA for Audio, and things improved greatly. I found that the apparent simplicity of the schematic belies the difficulty of making it right.
Update: I replaced the gain stage MOSFET with a SemiSouth SiC JFET and got a noticeable improvent in both the sound and the measured performance, see a separate post.