Valve Audio

[My System]
[Single Ended]
[Push Pull]
[Phono Stages]
[SACD Player]
[Other Projects]
[Tube Links]
[Transformer Math]
[Tube Literature]
[RFS Tube Data]

Serious Stuff:  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. 

PLEASE NOTE:  In a spirit of sharing, I have made schematics of all projects directly available (in PDF format).  All designs are copyright Richard F. Sears, all rights reserved.  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 without my (Richard F Sears) written permission.

My System:  Some off-the-wall philosophy followed by a chronology of system "development".

Power Supplies:  Discussion of passive and regulated PSUs, notes on operation and performance of series and shunt regulators, where to find examples of various regulator types on this site.

Single Ended amplifiers and line stages:  L-C-L coupled 0-300B with switchable operating conditions for 50 or 300B, 845 with transformer coupled 45 drive and "Super mu Follower" input stage also a 2A3 transformer-input line stage.

Push Pull amplifiers and line stage:  6AS7G, triode connected KT88 and 6BM8, triode / UL EL34, 6AQ5 pentode with cathode coupled feedback, also a 6SN7 PP transformer-output line stage.  Two of these are integrated designs incorporating phono stages.

Phono stages:  Five phono stages designs, two using the type 416 planar triode intended for low Z, low output cartridges (MC) and three for high output cartridges (usually MM), two of which feature a hybrid cascode front end specifically developed for the Sumiko Blue Point Special.

SACD Player:  Pioneer DV563a SACD/CD/DVD hot-rod featuring transformer coupling direct from the DAC with a 'no capacitor' tube output buffer, featuring constant current feed to isolate the buffers from the plate supplies thereby getting very close to true 'no capacitor topology.

Other Projects:  

  • jfet battery phono stage

  • guitar practice amplifier 

  • restored Bush table radio 

  • high quality two way speaker project

Test Bench:  Showing 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


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

Transformer Math:  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. 

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


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.