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Archive for the 'DIY' Category

More hi-fi – a remote controlled preamp

2013-09-08 12.33.18
Building and learning about electronics remains one of my favorite pastimes. When I can connect it to music, so much the better.

I’m building a new preamp – this one with a microcontroller and a pile of digital hardware to provide remote control and switching. The best place for this kind of project is www.diyaudio.com – a huge set of forums for people involved in building their own equipment. I’ve been involved in the forum for almost ten years, building speakers and amplifiers.

My build thread is here: all the information about what I’m building and why. The goal is both to stimulate discussion (not much yet), and to document the process so others can benefit. And to take some pleasure in explaining myself – always a good thing.
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A new amplifier

F4 (4).jpgI’ve been away from the world of hi-fi and DIY for a long time. Before I went back to school I started building a power amplifier designed by Nelson Pass, but I never finished it. Until now.

I feel as though I finally have my commute worked out, and the work routine under control more or less, and so I pulled out the bits a couple of weekends ago and got it all finished off.

F4 (1).jpgMetalwork (the enclosure and heatsinks) are always the hardest part. In this case I used a mix of plywood and redwood strips, combined with a cheap extrusion and a couple of surplus heatsinks (originally one piece: cut in half on the table saw).

It came together pretty quickly. Self-tapping screws to hold the transistors down, and wood screws or machine screws for much of the rest. The amplifier draws a lot of current, and I was pretty nervous turning it on, but with some great advice from online, and a lightbulb as a current limiter, it all worked out fine.

The sound is great. It’s super-clear, and a pleasure to rediscover a lot of music. It’s also completely quiet: no audible hum or noise at all. If you want to learn more, Nelson provides information on another of his websites: www.firstwatt.com.

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Music is more than…

I came across this (thanks, Stephanie!) this afternoon: it’s a group of people who get together to explore home-made musical instruments, many of them combinations of mechanical and electrical or electronic components. Some of them are played in conventional ways, some make music under computer control, and some combine multiple techniques. 


What’s nice about this is that it describes a group of people who get together to share their ideas, and to have a good time together. It’s a long way from a conventional concert, but just as rewarding, and perhaps more so.

There’s a lot going on in electronic music—tonight the Stanford Laptop Orchestra (that’s right) is playing and I’m hoping to go. There’s also a group in the Bay Area that get together regularly to learn about electronics, computing and music. A week ago I went to a talk at UC Santa Cruz that presented some algorithmic music—I’ll try to post separately about that.

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DIY furniture

I’ve always enjoyed woodwork – ever since I was introduced to it at school, building simple things like a pencil case and a tray. True craftsmanship is a discipline I find hard, however, so I’ve tended to find quick and efficient ways to make things. I enjoy the puzzle-solving aspect of design as well.

ShoeRackBookCase
These are two recent pieces – a shoe rack for the front door (we tend not to wear shoes inside), and a long, low bookcase that’s also big enough to store records.

They are built from 3/4″ birch ply – reasonably good quality at $40 / sheet, but tricky to cut without splitting. I use mitred joints for the look – without dowels or biscuits these were the very devil to glue up – and double thickness for the carcass to create a strong outline. The shelves of the shoe rack are 1/4″ marine ply (oukoume), and everything is finished in clear lacquer.

Lacquer turns out to be a very easy finish to apply – brush it on and it dries almost instantly. Use steel wool (very fine – 0000 grade) to polish the surface and keep on adding coats until you’ve had enough.

The downside of lacquer is that it is easily damaged by water – not a good surface if people are going to put damp glasses down, as I have already sadly discovered. At least with a DIY piece I don’t feel bad about sanding it down and putting on more lacquer.

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New speakers in the living room

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I’ve spent the past couple of months building a new set of speakers based on a design by Wayne Parham (Pi Speakers). They are three-way horn-loaded speakers, using high quality PA (public address) drivers that are a lot more efficient than the speakers they are replacing.At the weekend I finally was able to install the new Pi Sevens in the living room. Here’s a first set of impressions.

My system is as follows:

  • Townshend Rock III turntable with Grado MM cardtridge.
  •  EAR 834P phono stage
  •  Naim CDP8i CD player
  •  First Sound passive “preamp”
  • Music Reference RM9 tube amplifier
  • Mixed cables – DIY solid silver, Cardas speaker cables

The speakers replace my Thiel CS3.6 floor-standers, in roughly the same locations (corners). The room is sub-optimal in that the speakers are in corners that also house bookcases, and there’s a baby grand piano between the speakers along the same wall. However, there’s no sign yet of any piano-contributed vibration.

I’ve been listening to lots of stuff: Beatles, Tom Paxton, King’s Singers, Lieder (Brahms, Schubert), Wagner, Gilbert & Sullivan, Dave Brubeck, and a mix of CDs and records.

The first impression is of a very delicate and accurate mid-range. The King’s Singers have never sounded better. The mid-horns seem solid and unfussy. The treble is clear, but I think a bit recessed, and definitely less audible than with the Thiels. The bass I’m not quite sure about yet. Clearly the power of the woofer is exciting a couple of room modes, and I will need to build some tube traps or something, and possibly alter the room layout a bit (I’m sitting against the back wall, which is probably not ideal). The most obvious effect is on plucked bass lines, and also some coloration on male voices. But except for the notes that are too loud, the bass seems clear and unobtrusive. I don’t know if I’m really getting all the extension I was expecting – this may be because of the bookcases, or (and I hope not) it’s possible the cabinets leak. I have been unable to detect much port action so far.

The other major change is the increased level of dynamics. I find I have to adjust the volume for every recording separately – I never needed to do that before. Popular recordings with lots of compression need to be turned well down. Classical recordings with wide dynamic range can be turned up and I still get good pianissimo, with exciting climaxes. The bass excitation limits my ability to listen loud – especially with bass or baritone voices.

I should mention Marina’s view – she has expressed three opinions:

1. “They are bigger than you led me to believe”
2. “They are uglier than I thought”
3. “They sound much better than the old speakers.”

…so I guess I get to keep them, but I will need to finish the veneering and clean up the wiring etc.

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