Articles & Essays

 This section of the Audio Crafters Guild site is dedicated to presenting articles and essays related to audio in general and Do It Yourself audio in particular. With our special interest in hi-fi digital audio reproduction the first set of articles deals with the technical aspects of digital audio. If you have an article you would like to submit or an idea for one contact me at ntracy@galstar.com. We will also welcome your comments on the following articles and their usefulness and are just curious to know who is visiting so send us some e-mail!

I am very excited to get this part of the ACG WWW site up and running as it serves the ideal upon which Audio Crafters Guild was founded, a free and open sharing of ideas (and better yet, results!) between members of 'The Guild'. Special thanks to all the authors who have made this possible and especially to Erland Unruh who not only contributed articles of his own but also converted all the PDF articles into that format.

Several of the following articles are in Acrobat 'PDF' format. These are flagged with the symbol. You will need Acrobat Reader in order to view these documents. Clicking on the link will take you to Adobe's site for a free Acrobat Reader download, the reader is free the PDF creation s/w is not, clever chaps at Adobe 'eh?!

If your Acrobat reader fails to open our articles check which version you have, versions 2.x fail on the following files and should be upgraded to 3.x or 4.x.

Supply Decoupling by Guido Tent (28 KB) was first published in HiFi World magazine in 1999. Guido is an Electro Magnetic Compatibility engineer for Philips so his article is based on daily real world professional experience in the field. Guido is also an avid designer of audio circuits so this article is a great resource for anyone trying to manage the tricky coexistence of digital and analog electronics. E-mail Guido at EvaGuido@iaehv.nl.

CD Jitter by Paul Winser (290 KB) first appeared in the newsletter of The London Live DIY HiFi Circle. In the article Paul presents a CD player clock upgrade for Philips based players aimed at improved jitter performance. It also provides excellent background on jitter and its effects on CD playback. An important article that introduced us to the wonders of ECL based clocks.

DOO by Erland Unruh (879 KB) In this article Erland presents a S/PDIF modification he calls DOO (Digital Output One) applicable to CD, MD, DAT, or LD (even DVD?) players used as transports providing data to external DACs via the S/PDIF (Sony/Philips Digital InterFace) link. An extension of Winser's work aimed specifically at improving clock jitter and the electrical characteristics of the S/PDIF coax link. Complete with PCB layouts and parts lists.

DOO 1.1 Rev1 by Erland Unruh (6 KB) The latest updates to DOO.

Re-clocking TEAC VRDS-T1 and TEAC VRDS-7 by Lars-Erik Wedin (933 KB) An application of DOO to an acknowledged excellent transport. All the details of installing DOO in the TEAC VRDS-T1 CD transport. Includes color photographs detailing the install process and oscilloscope displays showing the results. Also valuable added information on selecting and optimizing crystals for use in ECL based clocks.

See also Erland Unruh's new project DIO in the Guild Craftsmen Projects page of this web site. E-mail Erland at erland.unruh@telia.com.

Combo by Erland Unruh (30 KB) is a short article detailing his adapter board allowing a combination amplifier made up of AD797 and AD811 to replace the AD811 used in X-DAC 3.0. Pictures of an earlier Combo adapter are here in the Guild Craftsman Projects section.

Taking X-DAC 3.0 One Step Further by Erland Unruh (666 KB) details his extensive rework performed on his third X-DAC 3.0. Strong emphasis on reduction of power supply and ground noise using SMT parts and advanced grounding scheme.

A prototype DAC to evaluate Crystal Semiconductor's CS4329 by Lars-Erik Wedin (511 KB) DAC built to evaluate the CS4329 DAC chip and other technologies. Lars-Erik's craftsmanship is such his 'prototype' features better fit and finish than many commercial products.

On Jitter, the S/PDIF Standard, and Audio DACs by Norman Tracy (9 KB) a short 1996 essay on jitter and S/PDIF interfaces.

Sample Rate Converters in DACs by Norman Tracy, (24 KB) the designer of X-DAC 3.0 discusses his experiences with AD1890 and the controversy surrounding its use in DACs.

References (6 KB) a list of references to articles and standards related to digital hi-fi audio.

A Tube DAC, Norman Tracy; Glass Audio 1/94 will appear here when I get permission from Audio Amateur and have time to convert it into HTML or PDF. This article's value is as a tutorial in the operation of RsquaredR DACs and its introduction of the use of simple resistor based current to voltage converter. The R-to-ground I/V converter idea makes the use of tube based analog stages much simpler as explained in the article. The popularity of tubes in audio encouraged others to refine and extend the original 'Tube-DAC' circuit. Sheldon Stokes was first updating the circuit with the CS8412 input receiver, better regulator implementation, and a tube stage of his own design. He also designed a PCB to hold it all. Jukka Tolonen's version is very interesting in that he first modeled the various tube stage types using SPICE and added passive anti-aliasing filtering. Jukka also developed a two PCB board set with a DAC board and seperate tube stage board. The DAC board allows for the use of op-amp analog stages for those who prefer silicon over thermonic emmisions.

Jukka Tolonen's DAC and tube audio articles several of which have been published in Glass Audio magazine.

An Enlighting DAC-project by Arjen Verhoeff (22k) first part of a series on his experiences building Tolonen's tube DAC. This series aims to document both the DAC project along with the procedures and considerations when one does a DIY project via the Internet.
 
 

Sheldon's Audio Designs by Sheldon Stokes with DAC, tube amp, and Quad ESL information.

Digital Domain with articles on CD mastering and digital audio by mastering engineer Bob Katz. This site is great if you are involved in the recording side or curious about how a great master tape becomes a great CD. His article 'The Digital Detective' is very applicable to digital audio DIYers, a great tutorial if you are hooking your oscilloscope up inside a CD player or DAC for the first time. Also be sure and read Bob's jitter and dither articles.

Jitter-Free DAC by Richard Lim shows his design of a CS8412/AD1893/SM5842/PCM63 DAC.

Triode Amps and Stereophile Trojan Horses and Illusion Engines by Lynn T. Olson while on the surface dealing with the zero feedback triode amplifier and the reasons it finds such favor of late really go much deeper. Why in 1998 is there still disconnect between measured performance and musical enjoyment? Has the once vital 'high end' audio movement become itself another establishment? Is there still a place for independent research? Perhaps Lynn's take on these issues can be summarized in his own words from a reply to my e-mail asking permission to post his articles here:

>Would you grant permission for me to HTML it and place it in the 'Articles & Essays' section of the ACG web site?

" Sure, no problem at all. You should have seen the Illusion Engines post before I toned it down! I was quite vexed at the appalling condition of the US mainstream press because I had just finished reading the extraordinary 1/1998 issue of MJ magazine, with the *entire* issue devoted solely to the 300B tube. They visited the new Kansas Westrex factory (many photos and assembly-sequence diagrams), reprinted all of the 300B projects over the last 20 years, compared 300B's from ancient to modern with lots and lots of plate curves, and had a ten-page round-robin discussion amongst the editors about the tube and MJ magazine. Wow!!!"

" And for comparison, we lucky US readers get ... wait for it ... a front-cover feature on the latest 40" Toshiba TV for Fi (or Fie!) magazine. What editorial courage! A mass-market color TV on the front cover! That must have taken real guts! Watch out, Popular Mechanics, here comes Fi magazine, with a cover feature about the Chevrolet Suburban!"

" To top it off, *then* I came across the self-indulgent, self-referential 'Pile brushoff by Martin Colloms, whose idea of good triodes is Cary and Russian 6DJ8's ... talk about heavily loading the dice against triodes. By this point, I was so *cranked* at the patronizing tone and willful ignorance of the US mainstream press I couldn't take it anymore ... thus the Illusion Engines piece."

" Here's the missive that preceded it (more reflective, more technical, and written before I read the Colloms column). Feel free to reprint both as companion pieces if you like." L.T.O.

I suppose my interest in Lynn's postings comes not from triode vs. transistor but rather from my experience in digital audio. Here was a medium that measured essentially perfect from day one yet early consumer format digital audio sounded horrific. It was only when we zoomed in from the macro view of THD to the micro view of a technologies interaction with the music that we began to understand what had gone wrong and how to begin fixing it. N.P.T.