Pete Millett's DIY Audio pages

Fortechnical books, tube data, vintage data, transformer data, and McIntosh data,go to:

Last update:  4/9/19 - Added aNutube balanced (differential) amp for headpohone or line amp use

10/28/28 - Added the NuClassD amplifier, a 50-watt hybrid class D power amp using the Korg Nutube

PLEASE READ - Commercial usageof information on this site:

i consider all the information that i post here to be in thepublic domain.  so, you can use it however you want, for commercial or non-commercialuse.

that said, i would appreciate it if you at least let me know ifyou are going to use any of the circuits or especially pcb gerber files to make commercialproducts, or to sell bare pcb's.  

there are some cases where products are being sold not only withmy permission, but active involvement.  the "millett hybrid"effort and others at are examples(and excellent models of how the diy community should work, in myopinion).  there are other cases where i have asked vendors to sell pcb'sas a service to hobbyists.  and there are other cases where companies are manufacturing andselling pcb's, chassis, etc. without contacting me at all.

in all of these cases, i make no profit from any of thesales.  zero, zip, nada.  i have a normal "day job" thatpays the bills, this is strictly a hobby with me.  so please do not expectme to provide the level of technical support that you might expect when buying aproduct.  i try and help, but it sometimes takes me days - even weeks ifi'm traveling for work - to respond.

600彩好的thanks for your indulgence in reading this!

All that said... I do sellthings, including projects I no longer need, PC boards for my designs, andoccasionally parts and tubes.   I do this through eBay - I maintain an eBay store "pmillett".  You can clickhere to see what I may be selling at the moment.

Nutube Balanced Amp


The NuClassD Amp

This is a depository for various audio designs and projects -mostly tube - thatI've put in the public domain, as well as additional info to support magazinearticles that I've written, and an ever-growing amount of technical data archivesrelating 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 see the updated versionsof pages!

600彩好的follow the links below for detailed info....  most picturesare 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", oryour mail will get dumped along with all the junk mail (spam) that i get - it'sup to about 100 junk e-mails per day now.  if i don't respond within a fewdays, try again, just in case i missed your message.  i try and returneverybody's mail within a week, though i travel quite a lot for work and find iget very behind at times.  please be patient...

standard disclaimer:  this info is provided with noguarantees as to accuracy, usefulness, etc.  there's no guarantee that ifyou 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!

Many files on this site, especially scanned documentation, arein Adobe Acrobat (PDF) format.  I recommend that if you don't already haveit you download the latest version of Adobe reader.  Some files havecompressed images that may not work correctly with older versions of Acrobatreader.


Scanned vintage  books, manuals, catalogs, papers...

Pleasego to for thismaterial.

Audio projects and experiments:

Power amps

NEW 9/7/18 - A hybrid (SS driver) class A2 DHT amp

A 50 watt monoblock version of the "Engineer's Amp"

A PL177 single-ended amplifier

"La Luxuriante" stereo R120 SE amp

"Fatboy", a low-distortion zero-feedback push-pull 300B amp

A compactron triple-triode driver for push-pull amps

"Mr. Potatohead" 815 amp - 50W from 2 tubes in class AB2

The "807" Push-Pullamp600彩好的 using driver boards below

Push-pull driver PCB600彩好的, a (nearly) universal driver for push-pull amps

"Jonokuchi", a single-ended tube headphone / speaker amp

Class-A2 1636 amp using a power opamp driver

The "Engineer's Amplifier"600彩好的, an affordable, high-performance push-pull TV pentode amp

The "Unnecessarily Complex 300B Amplifier" (from audioXpress 2009) 

The 307A tube, and a push-pull 307A amplifier

The "Glowing Hybrid" amp

"The Mighty Midget"600彩好的 (from audioXpress 5/08)

Low-voltage Hybrid amplifier with adjustable damping

"A Single-Ended E-LinearAmp" (from audioXpress 4/05)

Push-pull6B4G class-A amplifier

Push-pullKT88/6L6/EL34/2A3/300B amp with "universal" driver / power supply PCB

813single-ended triode amp withmicroprocessor-controlled power supply

829Btriode-mode SE amp

2-8watt push-pull amp using 7044 computer triodes

EL802 push-pull single-stage "spud"amp experiment 

EL34 active-loaded (SRPP) parafeedamp experiment


Preamps / Line Stages

NEW 4/8/19 -A Nutbe Balanced Amp - a true diferential amp for line stage or headphone amp use

A buffer PCB using the Korg Nutube 6P1 low-voltage DHT

"el escorpion", a simple line stage in a cigar box that runs off of 12VDC

A solid-state LR phono preamp600彩好的 (no caps in the EQ) from ETF.13

A high-end Tube Microphone Preamp

"ALow-mu preamp" (from AudioXpress 2/04)

Pentode phono preamp


Headphone Amps

The NuHybrid headphone amp, a hybrid headphone amp using the Korg Nutube

The DIY "Butte" solid-state headphone amp

"Jonokuchi"600彩好的, a single-ended tube headphone / speaker amp

The "StarvingStudent" hybrid headphone amplifier

WheatfieldAudio HA-1 tube headphone amp

Low-voltage tube hybrid headphone amp600彩好的 - the original "Millett Hybrid" amp (from AudioXpress 11/02)

WheatfieldAudio HA-4 headphone amp (solid-state, with crossfeed and EQ!)

SRPPECC99 tube headphone amplifier (drives AKG K1000's!)


Test equipment

A breakout board for banana cables

An audio dummy load

A "Sound Card Interface / AC RMS Voltmeter" you can build

Tube-regulated high-voltage bench power supply 

Softwarefor the HP 8903 audio analyzer - Make professional plots from thisaffordable audio test system!


Other stuff

Voltage selector PCB for transformers like the Hammond 300-series with multi-voltage primaries

A power supply PCB for B+ supplies using the Tentlabs MEC Mini Electronic Choke

A linear "USB adapter", a 5W power supply

A power (AC) sequencing  board600彩好的 for big amplifiers

A 10W B+ flyback supply (switching power supply) that runs off of low-voltage DC (5-20V)

Muting relay PCB to eliminate the "thumps"

A two-channel shunt-regulated adjustable bias supply

High-voltage regulator600彩好的 ("Maida" regulator) that fits Landfall Systems heatsink

Tube amp power supply PCB with bias supply

An isolated current sensor board to measure plate current using a PanelPilot meter

 MOSFET follower buffer for class-A2 grid drive

an Opamp experimenter board

Asimple regulated DC power supply /  filament supply

Tubeactive crossover

High-Frequency filament converter for DHT's


Speaker projects:

MLTQWP speaker using the Jordan JX-92S driver

AdireKIT281 experiences

BertDoppenberg's TQWP project

Downloadable drawings for "An AffordableFull-Range Speaker Project", AudioXpress 6/03 (uses Fostex FE-164)


Glass Audio and AudioXpress articles:

audioxpress has been gracious enough to allow me to reproduce heresome of the articles that i've written for glass audio and audioxpress magazinesin their entirety: 

"A Low-Mu triodePreamp" (1.3MB PDF file) from AudioXpress  02/04

"Build A Low-VoltageTube Hybrid Headphone/Line Amp" 600彩好的 (612kB PDF file) from AudioXpress 11/02- the original "Millett Hybrid".

"Power Transformers For Audio Equipment"(1.3MB PDF file) from AudioXpress 6/01

"All About Wire"(476kB PDF file) from AudioXpress 8/01

"ThePower Line Interface" (1.3MB PDF file) from Glass Audio 6/00


Miscellaneous  technical  information:

"LR Phono Preamps" presentation from ETF.13 (PDF or PPT)

Whereto get stuff - an assorted list of some of my suppliers

Tektronix power transformerinformation - Info I've collected on classic tube-type Tektronix powertransformers

ResCalc, a cool utility programyou can download that calculates combinations of standard resistors to get aparticular value.

Parts shopping in Asia (sorry, getting a bit out of date)

"The Sound of Distortion"presentation from ETF.04

High-Gm driver pentode test data

Ixyscurrent regulator as a CCS plate load

CADprograms for the DIY'er


Other non-audio stuff:

A picture collection of interestingold QSL cards600彩好的 that I received in the early 1970's.  


Who I am:

a lifetime electronics geek, i got a ham radio license at the age of 8 and afirst-class commercial radio license at 14.  i'm just old enough that iactually build and used tube some stuff when it was still in production.  i've been an electrical engineer fornearly thirty years, doing mostly computerand consumer electronics design work.  i owned and operated wheatfield audio,which made tube headphone amps (but no money!) for a few years.   i alsohave written articles for audioxpress magazine (formerly glass audio) on occasion.

600彩好的i do some commercial audio design work outside of my "day job".  some of mywork includes the product line,which is sold by (todd the vinyl junkie).

i'm currently living near fort collins, colorado, and work for a silicon valley semiconductor company.  

these are the wheatfield audio ha-1 and ha-2 tube headphone amps, which i designed a long time ago:

I've put some info from the oldWheatfield Audio web site here that might be useful, especially if you ownan HA-1 or HA-2.

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