Bespoke Audio Products

and Reference Materials

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Redstone Electronics is a custom electronics design, construction and modification service focused on high end audio.  We design & build new equipment and modify older high end equipment for both improved reliability and for improved sonics. 

This webpage documents some of my work and contains reference materials for those technically inclined.


I wanted a woofer to augment the low frequencies of the LS3/5a project below, and I decide to build the woofer section of the vintage KEF 104 and experiment with crossovers.

LS3/5a project    New 10-2019
This LS3/5a Project involved building this vintage speaker using all new components from Stirling Broadcast and Falcon Acoustics, including new Falcon-made drivers.  Includes lots of crossover examination/tweaking measurements.

Continuum speakers  New 7-2018
Jeff Bagby designed mini-monitor to continue the tradition of the famous BBC designed LS3/5a.

Designed to work with my Kairos 3 ways speakers (below).

Frequency response measurements of RS Minimus 7, ADC 404, Fried B2, JR149 and LS3/5a speakers.

Kairos speakers  New 11/2016

Jeff Bagby's quasi-transient-perfect 3 way design using Satori and SB Acoustics drivers.

Bastanis Prometheus   New 7/2016

High efficiency dipole speaker system with active woofer.

CAOW1   New 9/2009

Mini-monitor, designed by Dennis Murphy, built as floorstanding version.  Uses the Hiquphon OW1 tweeter and Seas CA15RLY woofer in a vented enclosure. 

Fried Model H

This landmark 3 way speaker system designed by Irving Fried in 1978 consists of two small satellites plus a large common dual channel transmission line subwoofer, using classic KEF drivers.  

Fried Model B/2  New 6/07

This mini-monitor speaker was an evolution of the satellite of the Model H, and competed with the Rogers LS3/5a and JR 149 among others.  With the Model T subwoofer (below), it formed the Model H/2 system.   Lots of reference material here.

Fried Model T subwoofer  New 3/09

Reference materials, including plans and crossover schematic, on this dual transmission line woofer.                 

   Satterberg woofers  New 5/08


Digital Audio (USB DACs)

    Scott Nixon USB DAC  New 3/08


Peter Daniel USB DAC  New 3/08

      Power Supply for Wavelength Brick USB DAC  New 2/09


Sequerra Model 1 FM Tuner  Updated 6-2017



DaySequerra Tuners - reference information  Updated 6-2018


Kenwood KT-7500



Kenwood KT-8300


Magnum Dynalab FT-101a


 Dynaco FM-3

Amplifiers, Preamps and Crossover

    Pass B1R2 Buffer  New 12-2017

  Gainclone Lab Amp  New 4-2017

    Gaincard Amp  Webpage added 8-2015

                        in Audio Research D-150 chassis Updated 6-2017


Audio Research SP-3 preamp  Updated 10/07


Audio Research ST-70-C3 amplifier  

Updated 10/2008 with Bill Johnson mod suggestions



 MPB's Electronic Crossover  New 9/07



  Audio Research VT-100: Adding a tube timer 

  New 5/07


  Gainclone Integrated Amp with USB DAC  New 10/08

   Levinson LNP-2 preamp  New 5/2011
New 10/2011

Reel to Reel

  Studer A80 RC - Refurb & Maintenance tips

 New 4/2015

Phono Systems

     SP-10 Mk2 Power Supply, New 1-2020

Panasonic SP-10/ SME 3009/ ADC XLM  New 5/07



    Michell GryoDec regulated Power Supply  New 1/09

Peter Daniel Phono Preamp (VSPS Variant)  New 4/09



Misc Scans of Interesting Audio Materials

New 5/2015:

New 9/2012: Amplifier Test Clinic brochures (both from mid-late 1970s):

Above: Ad for Technics RS-1506 from Audio January 1979.  Click to enlarge.


20000 Watt Home Hi-Fi System article from Audio magazine, April 1976.  This is also a PDF file. The cover of that magazine is shown below.


Cover photo (in color) from the above Audio, April 1976. 


Hewlett Packard 339A Distortion Analyzer review from Audio magazine, July, 1979.   PDF file.

RIMO FM Tuner Filters article by Richard Modafferi from Audio magazine, January 1979.  PDF file.

Kill FM Interference With Two Antennas article by Richard Modafferi, Audio magazine, January 1980.  PDF file.