HiFi

OK, so it stretches the definition of 'hobby' but you clicked the link ...

Image not foundMy hifi. Part bought, part home-made, has been built up over many years, and many many hours of critical listening. The house is littered with various amplifiers and loudspeakers. Some I am trying to sell, some to give away. Here's the details of the current 'main system', and a brief outline some of the unusual (and sometimes controversial) technology involved.

Source (digital, my turntable is for occasional nostalgia only).

Main source: FLACs. My CD collection has been ripped to FLACS (Free Lossless Audio Compression files), which are on my PC upstairs. Software used was Fairstars CD Ripper: free, and painless to use.

Image not found FLAC files are bigger than MP3s, but have the same sound quality as CDs. MP3s simply don't - though the sound quality at high bitrates can be very good indeed.

The data in the files is fed to a media streaming device in the main listening room. This is a Squeezebox Classic - which is a little hardware receiver, with accompanying software for your computer. It communicates over ethernet (a standard computer networking technology), and I use Homeplug ethernet-over-mains for this which uses the household mains wiring as the network cabling. It works very well - most of the time.
The network supplies the data - still digital - to the Squeezebox, where it is read into a memory buffer. The Squeezebox remote control communicates back to the PC, and playing music is a bit like using an iPod. Assuming all the digital bits have arrived in the Squeezebox buffer, sound quality is completely unaffected by this part of the audio chain. If they haven't - then the music simply stops until the network catches up. It works, or it doesn't.

Converting the digital stream into an audio signal

The digital bits need to be converted in to a continuously variable audio stream. From now on every step of the process is critical, and you will find thousands of webpages and discussion over even the smallest minutiae of the process. This is a viral obsession!

The device which initially converts the digits to audio is called a Digital Audio Converter (DAC). There is one built in to the Squeezebox - and they proudly boast in their sales pitch that it is a 'Burr-Brown'. This is therefore one of a family of DAC chips, of varying but generally high quality. Sadly, it is not one of the better members of the family. It will sound good - but you can do better.

Image not found Fortunately you can intercept the digital signal from the Squeezebox, and use your own DAC. There is now a range of reasonably priced DACs. I went - for no particular reason - with the Beresford TC7510 Mk6/4. A lot of talk (hype?) about this, and it got good magazine reviews. Personally I have been pretty impressed - it clearly improves on the SB3's Burr Brown. So now I've got my audio signal.

Setting the volume

This section must seem odd, but believe it or not there are options here. Technically, more than 2 options now, but realistically either a potentiometer (pot, variable resistor), or a Transformer Volume Control (TVC). TVCs are generating a bit of interest, and have some advantages over a simple pot. They work by using a fixed primary winding on a transformer, then having a range of taps (leads out) from the secondary winding. The control knob selects different taps to set the volume. The audio signal is a varying voltage. Instead of converting waste voltage to heat a TVC converts it to current. However, perhaps more importantly, it acts as an impedance buffer allowing source and amp to work with optimum efficiency. A pot will present the same impedance both ways, so will always be a compromise.

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A/B-ing between the two (using an Alps Blue pot) shows a clear advantage to the TVC for all aspects of the sound. This may well be rather system-dependant.

Sadly, the transformer windings are labour-intensive so TVCs do cost. I went with the well received Promitheus TVC. I have not been disappointed.

Amplifying the signal

Big choices here ... solid state or valves, Tripath chips, Ice-power chips, single-ended triodes, many choices - and to suit every pocket. My current amp is a Charlize. This comes as a low-priced little circuit board, and you build your own case and wire up the various connectors. The actual amplification is performed using a Tripath chip. It is low powered (about 10 Watts), but has phenomenal sound quality.

Image not found Poor old Tripath, having introduced low-cost high-quality amp chips to the world somehow got their business strategy all wrong and ended up going bust. Fortunately there are loads of chips out there, so amps are easy to come by. The original stir was caused by a plastic 30$US amp which gave many expensive amps a run for their money. The Charlize is one of the better implementations.

I recently changed the input capacitors from the OK Blackgate, to a US brand - Auricaps. The improvement was marked (if you find yourself with a Charlize 1 - don't hesitate).

This part is now out-of-date, my curiousity and Decware's new kit amp finally resulted in me building a Single Ended Triode. This has replaced the Charlize - and you can read about the build process here:

Decware SE84-DIY Kit Build

Loudspeakers

Image not found First - ALL loudspeakers are some sort of compromise. Personal preferences rule here. The lower-powered Tripath chip amplifiers need efficient speakers and you don't need to look too far on the web to find folk advocating a design called a Back-Loaded-Horn (BLH). These are huge, but do many things uniquely well. Buying them is a very expensive option (if you can find any), but there are many tried and tested DIY plans, and that is the route I went down.

But first - having bought my drivers (Fostex FE206) I discovered the huge controversy over a process called EnABL (Enhanced Auditory Boundary Layer) patented by an American guy called Bud Purvine. This involves painting a special pattern of tiny rectangles onto the speaker cone. These appear to disrupt wave reflections inside the cone material, and significantly clarify the sound. The mechanism is under intense scrutiny in some long-running web forums, but the technique is published for hobbyists to use. So I did - and it is pretty impressive!

The actual speaker design is the Sachiko. They are huge cabinets (full-range horns have to be) and took me 3 weeks to build. They sound superb - I have never heard a more enjoyable hifi loudspeaker. The designer is Scott Lindgren (Scottmoose) in Yorkshire, who was good enough to answer some of the questions I had.

Wires

Another debate which I have also participated in, performing my own double-blinded testing of different cables. My opinion is they make a difference - it's an acrimonious debate!

So ... Van den Hul D102 III RCAs (a copper/silver/carbon hybrid), Solid silver in teflon RCAs, and JPS Labs Superconductor speaker cables (made of a copper-aluminium alloy claimed to conduct audio frequencies better than silver !?!) to join the bits together.