Pete Millett's DIY Audio pages
of information and still growing!
Data from this site is now available on DVD-ROM from www.theoscilloscopestore.com!
Last update: 4/30/08 - Posted "Audio Design Handbook" by H. A. Hartley. Posted some interesting audio amplifier papers by Dr. Alexander Bereskin, including a 3,000 watt tube amp, and detailed instructions on building an amplifier with feedback from a tertiary winding on the OPT. Posted spec for the HA-1 custom power transformer.
4/21/08 - Posted file downloads for "The Mighty Midget" (audioXpress 5/08) and the "Starving Student" hybrid headphone amp design. Posted the Heath W4-AM manual on the vintage page.
PLEASE READ - Commercial usage of information on this site:
I consider all the information that I post here to be in the public domain. So, you can use it however you want, for commercial or non-commercial use.
That said, I would appreciate it if you at least let me know if you are going to use any of the circuits or especially PCB Gerber files to make commercial products, or to sell bare PCB's.
There are some cases where products are being sold not only with my permission, but active involvement. The "Millett Hybrid" effort and others at HeadFi are examples (and excellent models of how the DIY community should work, in my opinion). There are other cases where I have asked vendors to sell PCB's as a service to hobbyists - the boards that Euphonia Audio and others sell are examples. And there are other cases where companies are manufacturing and selling PCB's, chassis, etc. without contacting me at all.
In ALL of these cases, I make no profit from any of the sales. Zero, zip, nada. I have a normal "day job" that pays the bills, this is strictly a hobby with me. So please do not expect me to provide the level of technical support that you might expect when buying a product. I try and help, but it sometimes takes me days - even weeks if I'm traveling for work - to respond.
Thanks for your indulgence in reading this!
The Mighty Midget (from AudioXpress 5/08) (left) and the Starving Student hybrid headphone amp (right)
This is a depository for various audio designs and projects - mostly tube - that I've put in the public domain, as well as additional info to support magazine articles that I've written, and an ever-growing amount of technical data archives relating to vintage and tube audio. I'm constantly adding and updating things, so come back every once in a while and see what's new. Remember: you may have to hit the "refresh " button to to see the updated versions of pages!
Follow the links below for detailed info.... Most pictures are hyper-linked to full-size pictures, so you can zoom in if you click on them.
If you have questions please feel free to e-mail me at:
Please, if you send me e-mail, make sure that there is a logical "subject", or your mail will get dumped along with all the junk mail (spam) that I get - it's up to about 100 junk e-mails per day now. If I don't respond within a few days, try again, just in case I missed your message. I try and return everybody's mail within a week, though I travel quite a lot for work and find I get very behind at times. Please be patient...
Standard disclaimer: This info is provided with no guarantees as to accuracy, usefulness, etc. There's no guarantee that if you try and build anything like this stuff that you won't electrocute yourself, the kids, or your cat, or burn your house down... especially if you don't know what you're doing. Be careful!
I'm posting tons of scanned old data, including full books, to fellow tubeheads free of charge. I have a bandwidth limit of 1,000 GB per month. Believe it or not this site has approached this limit in the past.
Hopefully I won't have any issues like excessive traffic, so at least for now feel free to download any or all of the data; if you expect to want to see it again, save it locally so I don't get hit with excess traffic charges. If you want to copy data and post it on another web site please contact me for permission.
Many files on this site, especially scanned documentation, are in Adobe Acrobat (PDF) format. I recommend that if you don't already have it you download the latest version of Adobe reader. Some files have compressed images that may not work correctly with older versions of Acrobat reader.
Scanned vintage books, manuals, catalogs, papers...
NEW 4/30/08 - Technical books ONLINE! - Full image scans of old technical books related to tube audio and pre-silicon electrical engineering and technology
NEW 4/30/08 - Vintage audio info and articles - Everything but books: magazine articles, schematics, catalogs, brochures...
McIntosh service data - Schematics and other service data for classic McIntosh products
Transformer data and schematics from Tango, UTC, Thordarson, Acrosound, Chicago...
Tube Data, including some data from RCA, Western Electric, GE, Tung-Sol, etc.
1951 and 1959 Sylvania tube manual
Audio projects and experiments:
NEW 4/21/08 - "The Mighty Midget" (from audioXpress 5/08)
NEW 4/21/08 - The "Starving Student" hybrid headphone amplifier
Low-voltage Hybrid amplifier with adjustable damping
Wheatfield Audio HA-1 tube headphone amp
"A Single-Ended E-Linear Amp" (from audioXpress 4/05)
Push-pull 6B4G class-A amplifier
Push-pull KT88/6L6/EL34/2A3/300B amp with "universal" driver / power supply PCB
Low-voltage tube hybrid headphone amp (from AudioXpress 11/02)
813 single-ended triode amp with microprocessor-controlled power supply
Wheatfield Audio HA-4 headphone amp (solid-state, with crossfeed and EQ!)
SRPP ECC99 tube headphone amplifier (drives AKG K1000's!)
2-8 watt push-pull amp using 7044 computer triodes
"A Low-mu preamp" (from AudioXpress 2/04)
High-Frequency filament converter for DHT's
EL802 push-pull single-stage "spud" amp experiment
EL34 active-loaded (SRPP) parafeed amp experiment
Speaker projects:
MLTQWP speaker using the Jordan JX-92S driver
Bert Doppenberg's TQWP project
Downloadable drawings for "An Affordable Full-Range Speaker Project", AudioXpress 6/03
Glass Audio and AudioXpress articles:
Ed Dell at audioXpress has been gracious enough to allow me to reproduce here some of the articles that I've written for Glass Audio and AudioXpress magazines in their entirety:
"A Low-Mu triode Preamp" (1.3MB PDF file) from AudioXpress 02/04
"Build A Low-Voltage Tube Hybrid Headphone/Line Amp" (612kB PDF file) from AudioXpress 11/02
"Power Transformers For Audio Equipment" (1.3MB PDF file) from AudioXpress 6/01
"All About Wire" (476kB PDF file) from AudioXpress 8/01
"The Power Line Interface" (1.3MB PDF file) from Glass Audio 6/00
Miscellaneous technical information:
Tektronix power transformer information - Info I've collected on classic tube-type Tektronix power transformers
ResCalc, a cool utility program you can download that calculates combinations of standard resistors to get a particular value.
"The James- Baxandall Passive Tone-Control Network", a paper by Ramon Vargas Patron (753kB PDF file)
"The Sound of Distortion" presentation from ETF.04
High-Gm driver pentode test data
Ixys current regulator as a CCS plate load
Other non-audio stuff:
A picture collection of interesting old QSL cards that I received in the early 1970's.
Who I am:
I've been an electrical engineer for twenty-some years, doing mostly computer and consumer electronics work. I own(ed) and operated Wheatfield Audio, which made tube headphone amps. I've transitioned this business to HeadRoom corporation (good guys, see them if you need headphones or a headphone amp), so I have more time and money to waste on my own amusement. I also write for articles AudioXpress magazine (formerly Glass Audio) on occasion.
I do some commercial audio design work. Some of my more recent projects are sold by TTVJ (Todd the Vinyl Junkie).
I'm currently living near Dallas, Texas, and work for a large semiconductor company.
These are the HA-1 and HA-2 tube headphone amps, which I designed a few years ago:
I've put some info from the old Wheatfield Audio web site here that might be useful, especially if you own an HA-1 or HA-2.