Welcome to the former home of Kennedy Tube Audio.
Thanks for stopping by
The very first of three 300B SE Stereo Basic Amplifiers constructed is shown.
This is part of a two piece amplifying system (power supply unit not shown) of exceptional quality.
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 fresh pdf archives, and there are many projects to build here!
Please note that other than books, a design service, and licensing older designs I am NOT offering any services to construct, repair or modify equipment. There is no current product line
on offer here either. KTA - the business has been closed since 2001. Based on some recent inquiries and negative comments by email I feel compelled to spell this out.
MODS FOR DYNACO® TUBE AMPS
ST-70 Driver Board Upgrade
Currently available ST-70 pcb may be ordered from: Classicvalve.ca KTA ST-70 PCB
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
and easily.
I am looking for dealers to assemble and sell built up versions of this PCB worldwide. Generous licensing terms apply. If interested in carrying this product please contact me at the
email address at the bottom of this page.
Dynaco® MKIII Driver Board Upgrades
Coming soon is both a Noval version of my old MKIII driver board and an Octal version as well. These are mechanically direct drop in replacements.
This design is based on differential long tailed pairs, utilizes a 12AX7A or 5751 in the front end, and a 12BH7A/5814/6189 in the driver stage. This design does not require the use of very closely matched tubes in the driver circuits. Drive is sufficient for a quartet of 6550/KT88 in UL
with powers in excess of 120Wrms being achievable in a custom application. Widely available chassis and transformers can be used to construct a very high performance version
of the MKIII quickly and easily.
I am looking for dealers to handle assembly and sale of these boards worldwide.
Generous licensing terms apply. If interested in carrying these products please contact me at the email address at the bottom of the page.
Custom Design Service
Custom designed projects to meet your needs. Includes full schematics, parts lists, recommended components where critical.
Phono Stages, Line Stages, Power Amplifiers both Pushpull and SE using a variety of tubes, Tube regulated high voltage, low noise
power supplies, and Filament supplies both constant voltage and constant current. Pricing upon request. Design hourly rate is $50.00/HR
unless flat rate has been agreed. (Generally $100 minimum)
Currently available Designs (Schematics and Bills of Material ONLY):
Power Amplifiers
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.
Line Stages
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.
Phono Stages
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
Project 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.
Hobbyist Section
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.
My books are back! Now available at Lulu.com
Several recently added new titles now available!
GO TO MY BOOKSTORE
Now available for the first time in years:
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.
The Little Book of Vacuum Tube Pre-Amplifier Projects.
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.
The Little Book of Tube Amplifier Projects.
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 Guide to Vintage Audio Equipment for the Hobbyist and Audiophile.
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.
Recently Added:
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!
You are the 
person to log into this website.
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.
Regarding the old www.kta-hifi.com Domain Name
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 diyAudio.com just look for kevinkr
Latest Updates: 2012.03.01 Home Page.
© All Contents of this site are Copyright 1999, 2000, 2001, 2002, 2003, 2005, 2006, 2007, 2008, 2010, 2012 by KTA/Kevin Kennedy
Registered trade marks are the property of their respective owners.