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Richard's Stuff

Welcome:  I hope you enjoy my vacuum-tube hobby show-case.  You will see from my photographs that I enjoy the visual aspect of tube electronics as much as the design and performance.  To me, I have not "seen" an amp until I have turned it upside down.  I love to design & build tube Hi-Fi equipment.  It is a wonderful way to fulfill my passions for both engineering & music.  Perhaps you will  find some things of interest?  Can I build anything for you?  Email me from the home page.

Acknowledgements  In this crazy world of rush, rush, we sometimes don't take the time to think about those around us who really contribute.  To this end, I want to say a special thank-you to Kevin Kennedy and Steven Spicer both of whom were tremendously forthcoming in responding to my numerous and lengthy technical emails while I was getting my mind re-aligned with this subject after 25 years.

Serious Stuff:

YOU MAY NOT USE THE DESIGNS FOR ANYTHING OTHER THAN PRIVATE PURPOSES.  UNAUTHORIZED USES INCLUDE, BUT ARE  NOT LIMITED TO, COMMERCIAL USE AND PUBLICATION ON ANY OTHER FORUM OR MEDIA WITHOUT MY (Richard F Sears)  WRITTEN PERMISSION. 

You will need Adobe Acrobat Reader to display the schematics.

BE WARNED!  The voltages present in vacuum tube equipment are LETHAL.  Furthermore, I cannot accept responsibility for any damage to person or property than may result from use of any designs published on these pages. 

And now, The Tubes

Current project:  I am in need of a new 'summer amp' because though I may love the 845, it puts out in excess of 600W of heat.  My previous summer amp (EL34 PP Integrated) has been put out on permanent loan to a friend, as have the KT88 PPP mono blocks.  I am now a fully vested SE loony.

Massive two-chassis 25wpc amp built as my first foray into SE!  Intended for use with the speaker project below

Triode connected KT88s make BIG sound, excellent for electrostatics.  Novel drive topology with lengthy narrative (yawn!) as to why and how I designed it

10WPC class A stereo amp using one 6AS7 per channel.

Intended for use with the KT88 PPP amps.  It accompanies a CD player modified using Sowter 8347 DAC mu metal cored step-up transformers.  (The line stage design was published in Vacuum Tube Valley magazine number 17, Christmas 2001.)

'Switch-on the fly' triode / ultra linear integrated amp incorporating a quality phono-stage.

Two high quality phono-stage using the WE 416 planar triode for the input.  The Mk1 has 'conventional' series power supply regulation while the Mk11 uses separate (active) tube shunt regulation for each stage.

A 'quick and dirty' phono stage to tide me over as I developed and built the 416Mk11 design....

My first (serious) foray into speaker design and construction.  I think I got lucky!  A truly great match for the 845 SE.

A four channel line stage.  The line output channels have a high pass filter to remove sub energy while the sub channels are full range, relying on the sub-woofer low pass filter.  The transformer coupled inputs can accept balanced (XLR) and single ended (RCA) inputs.

Other Projects

jfet phono-stage. with passive equalisation, suitable to drive a computer sound card.

Guitar practice amplifier.  PP EL84 with output attenuator and Baxandall tone controls intended to enable the user to get the desired tonal character at apartment friendly levels.

DV 563 Mods.  Linear DAC PSU, and transformer coupled XLR output stage direct from DAC:

Test Bench

Audio bench with KT88 mono-block on test.  Equipment includes a function generator, B&K multimeters, HP dual channel CRO, Heathkit IM 5248 IMD analyser and a HP 339a distortion analyser.

In addition to this, I use the demonstration version of MCap7 extensively for simulation and drawing schematics.  This, while not entirely intuitive is quite easy to use once you have figured out how to enable the tube models (or somebody has shown you how).  While a bit limited in the number of nodes it will analyse, it is good for filter and network design, also for "getting on the page" with DC coupled stuff e.t.c. It may be downloaded free at www.spectrum-soft.com

A synopsis of the basic mathematical relationships governing audio transformer electrical design with an example of the design for a 300B direct feed (DC current) and presentation of underlying theory. 

My thoughts on power supplies.

Some recommendations (and .pdf downloads) on tube literature.  (This area continues to be sorely neglected by me.)

Links to audio web sites, parts suppliers, tube data search and more.