Posted 8th February 2011 at 07:24 PM byalexcp (My DIY projects)
Updated 17th December 2011 at 01:24 PM byalexcp
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?
Posted 9th October 2010 at 06:52 AM byalexcp (My DIY projects)
Updated 16th March 2013 at 02:40 PM byalexcp
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.
Posted 4th September 2010 at 06:02 PM byalexcp (My DIY projects)
Updated 8th October 2012 at 10:26 AM byalexcp
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.
Posted 4th September 2010 at 05:58 PM byalexcp (My DIY projects)
Updated 5th September 2010 at 07:59 PM byalexcp
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!
Posted 4th September 2010 at 05:54 PM byalexcp (My DIY projects)
Updated 7th July 2011 at 12:33 AM byalexcp
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.
Posted 15th August 2010 at 01:50 PM byalexcp (My DIY projects)
Updated 15th August 2010 at 04:18 PM byalexcp
This handy instrument is a version of the design published in Australian Silicon Chip (a subscription is required to view the details of the article). It is based on a dsPIC33 microcontroller, has TOSLINK and S/PDIF digital outputs (44.1k, 48k and 96k sample rates) and a stereo analog output. Output frequency, phase, attenuation, and other parameters are set by the keyboard. It produces sine, square, triangle, and sawtooth waves and has a variety of modes. It can be powered by an external DC source or a battery. The article claims low distortion for sinewave (less than .06%) and even lower with a good external DAC, but I did not have a chance to verify that just yet. Highly recommended.
Posted 15th August 2010 at 11:05 AM byalexcp (My DIY projects)
Updated 18th August 2010 at 08:24 PM byalexcp
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!
On first power-on the amp oscillated at 12 MHz when connected to headphones. The oscillation was inaudible but clearly visible on a scope. A quick look at head-fi.org showed that PPA instability is not a new problem. I reduced the value of R11 (see PPA's schematic), which eliminated the oscillation and improved the sound. I replaced the recommended OPA627 with LME49710.
PPA is positioned as a high-end DIY headphone amp, and it is in this project that I felt how subjective "high-end" is. PPA is a nice amp, but a true high-end device like Musical Fidelity X-CANv8 simply blows it away.
Posted 12th August 2010 at 07:57 PM byalexcp (My DIY projects)
Updated 15th August 2010 at 11:09 AM byalexcp
ezDAC lacked a USB input, so I leveraged my newly acquired SMD soldering skills building BantamDAC from a kit. While PCM270x-based USB DACs are rather common, BantamDAC is a compact (1" x 2"), neat version.