Welcome to the former home of Kennedy Tube Audio.
The very first of three 300B SE Stereo Basic Amplifiers constructed is shown. These units were hand built in my shop between 1999 and 2000.
This is part of a two piece amplifying system that was intended to be as good as I knew how to make at the time. (power supply unit not shown).
Tamura Amorphous Core output transformers and WE 300B are just two features of this custom amplifier. (Design and built amplifiers not available for purchase)
These amplifiers featured: Full Dual Monaural Construction, High Purity Copper Chassis, SE operation, Western Electric 300B, fixed biased outputs, SRPP driver, RC coupled input stage. All triode audio path, DC heated filaments, and choke decoupling on the 300B filaments.
Output transformers were Tamura Amorphous Core, and the fully tube regulated power supply unit featured custom built
power transformers by Tamura. Gain: 23dB Hum & Noise: 0.5mVrms unweighted Bandwidth: 20Hz - 40kHz -1dB
Power Output: 10Wrms max. out into 4, 8 or 16 ohms.
Many of the project pages have been updated with pdf archives, and there are many projects to build here.
Please note that other than books, and licensing older designs I am NOT offering any services to design, construct, repair or modify equipment. There is no current product line
on offer here. KTA - the business has been closed since 2001. Recent serious health issues mean that for the time being my custom design service is closed.
ST-70 Driver Board Upgrade
Currently available ST-70 pcb may be ordered from:
This is the same design I originally sold until used up in the early 2000's. Tube complement is a single 12AX7A and a pair of 12AU7A. This is fresh PCB spin and represents a significant improvement in ease of construction.
Details can be found on the ST-70 pages under Amp Pages below. These can be used in conjunction with widely available transformers and chassis to construct an entirely new amplifier quickly
Dynaco® MKIII Driver Board Upgrades
Not Available at this time.
Custom Design Service
Due to recent health issues I am not currently accepting custom design work.
Currently available Designs (Schematics and Bills of Material ONLY):
A variety of new and custom designs using all manner of DHT and beam power/pentodes are available. Both IT and battery bias options available where appropriate.
I have decided not to make the 300B SE design featured on this page available for the time being. (If ever)
Licensing for an improved version is available.
A 120Wrms two Chassis mono-block design. A quartet of 6550/KT88 are used per channel in UL connection with cathode feedback. Driver stage is differential using 12AX7A
and 12BH7. Power supplies are fully regulated and tube based.
A 2A3 SE Stereo Amplifier, direct coupled design, choke loaded mu follower driver, 5 tubes. Low gain for use with line stage. Easy to build.
IT coupled 50 DHT.
Several 45, and 2A3 SE Stereo Amplifiers, two chassis design, fully regulated tube based supplies.
2A3 SE Stereo Amplifier, two chassis design, fully regulated. IT based driver stage with 6CK4 and 27 input stage.
Transformer Coupled Line Stages based on 01, 10(Y), 12(112), 26, and 6J5/6SN7. All feature tube regulated supplies, and DHT's feature
constant voltage or constant current filament supplies.
SRPP Line Stages using a pair of 6CG7, 12AU7A, 6SN7, single or dual chassis. Regulated or unregulated tube power supplies.
Several designs based on 5751 for use with HO moving coil or MM cartridges. Higher performance custom designs available.
Integrated Amplifiers and complete Pre-Amplifier designs are available. Some studio electronics as well.
Tubes currently used in my designs include:
DHT: 01, 10(Y), 12, 26, 45, 50, 2A3, 300B, GM70, 211, 845
Others: 6BY5, 5U4, 5AR4/GZ34, GZ37, 6CK4, 27, 56, 76, 12AX7A, 12AU7A, 5751, 5687, 5842/417A, D3A, 6BQ5/EL84, 6L6, EL34, 6550, KT88.
In many cases existing designs can be adapted to suite, and expense will generally be minimal. Fully custom designs are also
available on either a flat fee basis, or an agreed upon hourly rate. (Generally $50/hr) Licensing is available for commercial use.
DIY Mods For Sony SACD Players Models SCD-777ES and SCD-1
These first generation SACD players are still capable of surprisingly good performance compared to many comparably priced recent models.
They really shine when modified. In fact there is a whole industry that has grown up around modding these players, but this site has nothing
to do with that.
These players respond well to a lot of different sorts of modifications, but the ones discussed here all required considerable skill with a solder iron, and
some ability to carefully follow instructions, read schematics, etc. I. E. These are not external tweaks of things like line cords, and cables but wholesale changes
to internal circuitry and components.
Stock photo of SCD-1 SACD Player
Link to SCD-1/777ES Mod Pages
Check out the project pages (links below) for updated files for many different power amplifier and pre-amplifier projects. Several
designs feature 45 and 300B DHT. Archives have been updated to pdf format. Designs vary in complexity, but use commonly available parts.
Phono stages, line stages, and various power amplifier designs are featured. New material will be added periodically. Even more information
may be found in my recently re-released line of project books.
A variety of amplifier projects can be found here including a 45 based SE amplifier, a 30W pushpull amplifier using 300B's, a triode pushpull amplifier with 6CK4 triodes as outputs, and the ST-70 project on which the ST-70 driver PCB is based. Most designs avoid the use of negative feedback and feature tube regulated supplies in some instances as well.
This is where you will find the Transformer Coupled 26 DHT based line stage featured in PFO a few months ago. Two simple phono stages, and a 417/5842 line stage are also featured. No feedback is employed in any of these designs, and tube regulated supplies are featured.
Older articles published in OTS' Positive Feedback Magazine. Varied Topics, and a few projects.
Vintage output transformers can often be a source of useful and high quality iron for D.I.Y projects, see what I have used in some of my projects. Note that the iron in all cases was reclaimed from basket cases, no mint or clean units gave their lives for this cause.
Here are my LULU book offerings
More offerings coming in the future.
Currently available for purchase:
Downloadable versions of my books start at just $7.70. Hard copies are a little more. There is a wealth of useful information both for the newbie and the seasoned
veteran. If you are a collector/restorer you will find "A Guide to Vintage Audio Equipment.." a useful adjunct to your hobby.
A collection of three phono stages, three line stages, and the power supplies that run them. These designs feature the
ubiquitous 12AX7A or 5751, passively equalized, 0 fdbk phono stages, simple to complex, and line stages of varying complexity, several
with long tailed pair based gain stages and augmented cathode follower outputs. Active voltage regulation is used.
Three amplifier designs are featured, two are pushpull triode designs, one with IDHT's, cross-coupled differential driver
stage and no feedback, the other with triode strapped EL34 reminscent of the Mullard 5-20. The third design is a 45 SE amplifier
operating with fixed bias, SRPP based driver and tube regulated supplies.
A collection of descriptions, useful notes, and tips on how to get the most out of vintage tube hifi, targeted at music lovers and
audiophiles alike. Introduction to basic tube electronic terms and topologies is included. Lots of information on fixing, modding,
and improving performance and reliability.
Hundreds of copies sold during the last print runs of all three of these books. Now nicely bound for the first time, still as relevant
as when they were first published.
LS-1 SRPP Line Stage project with fully voltage regulated supplies. Simple and easy to build design. (3 tubes)
P -1 Phono Stage project intended for use with the above line stage. Low noise, 0 fdbk design with passive eq, with fully regulated psu.. (5 tubes)
Both the LS-1 and P-1 were commercial products produced in small quantities when KTA was still active.
300B PP amplifier with updated boms, and notes. Same design originally published in VTV 10yrs ago.
More than slightly off topic is the story of my Jeep CJ-7 ground up rebuild project. If you like old Jeeps check this out!
**If you wish to sell any of these books in your store whether brick and mortar or online please contact me for a possible discount.**
(10 copy minimum)
Useful Tube Audio Links
Useful links for tube audio enthusiasts.
Links to online vendors for tubes and other assorted parts.
Help preserve the stereo (2 channel) format which I believe still provides the most musically involving listening experience.
Your help is much appreciated and will help to defray the cost of maintaining this site. Thankyou!
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Disclaimer of Liability for information contained on this site: The author accepts no liability whatsoever for the accuracy of presented information, the ability or inability to apply the information contained herein, or for any consequential damages that may arise out of the use or attempted use of any of the designs presented herein.
Legal Rights: Right to use information contained herein is granted solely for non commercial (i.e. individual) use only, and its possession in no way confers any other rights without exclusion. Commercial licensing is available for any design on this site as well as for prior KTA products on a royalty or absolute fee basis.
This is the only official Kennedy Tube Audio (KTA-HIFI) site, please note that the old site name is no longer under my control.
In an unfortunate lapse of judgment I allowed the domain name registration for the original site to expire, not realizing that the site
might have value to a potential cyber-squatter. Attempts to re-acquire the domain name resulted in a request for an exorbitant payment and
since this is just a hobby now the funds to do so are not available.
Find me also at just look for kevinkr
Latest Updates: 2014.04.04 Home Page.
© All Contents of this site are Copyright 1999, 2000, 2001, 2002, 2003, 2005, 2006, 2007, 2008, 2010, 2012, 2014 by KTA/Kevin Kennedy
Registered trade marks are the property of their respective owners.