kauffman AMPLIFIERs
What if the transistor was invented 10 years later than it was? In the late fifties, industrial vacuum tube equipment was reaching considerable heights in performance and reliability, but tube research and development was mostly abandoned when the transistor started advancing. Tube equipment was built so well that during the Gulf War, fifties vacuum tube equipment had to be brought in quickly to replace the solid-state gear that was failing. Apparently, the electric fields stirred up by blowing sands were too much for the modern, superior equipment.
When I started this project almost 16 years ago, I tried to build an amplifier as if it were in an alternative history. Having in mind that thought, where would audio have gone with more time for tube development? In the sixties, market forces led the manufacturing of tube gear to be cheaper and smaller. These amplifiers are my attempt at answering that question. What would have been designed if tube gear kept advancing?
The last thing the world needs is another guy and his audiophile tube amp. What makes these amplifiers different is that I’m a musician and an audio technician, with 23 years of repairing tube gear. This is not a hobby for me, but a life purpose. I can easily navigate between the snake oil and legit sound reproduction. Also, a life interest in radio brings in a different knowledge base, perspective and frankly, beauty. Built like an old piece of military gear, these units are optimal and serviceable for generations. Aesthetically I drew inspiration from industrial designers like Raymond Loewy and Walter Teague (look up Walter Teague today). I wanted an amplifier that looks as good as it sounds. High art, serviceability, and a simple signal path are missing in too many audio products today.
In the preamp section of my design, I tried well over 25 tube types, searching to find the type that best reproduced the feel of live sound. Days and days were spent listening to drum tracks and picking tube types that gave the feel of stick bounce and wood resonance. I tried four different output transformers from three manufacturers before picking the best one. All caps and crucial resistors were sound tested and compared. For example, copper foil capacitors were night and day the winner for coupling. They added depth and instrument separation in this circuit. For resistors, a military-spec metal film type was chosen. These amplifiers can run on different power tube types, rectifier tube types, and classes. KT88s in pentode operation is my personal favorite. And here’s a little nugget: 12AX7s, while great in a guitar amps, are terrible in Hi-Fi. The Hi-Fi world and guitar amp world are opposites.
One problem with engineering a high power tube amplifier is the need for feedback. To keep frequency response flat and distortion low, feedback from the output is injected into the input. I believe in user-control of feedback, so you can dial in your preferred sound. You get a flat response by increasing feedback. If you want more dynamics and open up the sound stage, you reduce the feedback. You see a slight increase in distortion under measurement this way, but your ears will be thankful, as you’re finding your sweet spot. I feel the same way about tube rectification versus solid state. If you want a faster sound, use solid state diodes, and if you want more warmth, flip the switch for tubes. One feature of the PKM120 is that you can operate it in a mode where ultra-linear and triode modes are operating in parallel at the same time. The resulting sound is what you would expect, a perfect combination of the two. As far as I know the PKM120 is the only commercially available amplifier ever that can do this.
It’s about your music. Maybe it’s Howlin’ Wolf thrown off the needle or Pacific Ocean Blue. Teenager-headphones-Loveless? Exile, Nilsson, Blonde On Blonde, Tusk, Mingus, Billie Holiday, Eno, Neko Case. It’s about “hearing the Jack Daniels in Lemmy’s voice” as we joke in the shop. There is something magical about vacuum tubes. I think it has to do with purity and longevity. It’s fitting to fashion tubes into a luxury product, which can then be passed down for generations. From a historic aspect, a front dial on the units gives a nod to early radio with its classic look. Thin illuminated glass sits between the transformers so that in evenings, a light is cast, reaching towards the shore. I put all I had into these amplifiers. Excellence will endure. Reconnect with your music and write your favorite artist name on a dirty bathroom wall.
Coltrane lives.
Ken Micallef swings by to take a listen…
120 Watt Mono Power
Amplifier
Features and specifications with KT88s:
Selectable output between three modes: ultra linear, triode, and combination mode. This is the only amplifier made which uses a combination of UL and triode modes paralleled at the same time, giving you the sonic benefits of both modes.
120 watts pentode (ultra linear mode), push pull AB
63 watts (triode mode)
91 watts combination (combination of triode/pentode mode).
Tubes: (4) KT88 (2) 7N7’(2) 866 (1) RK24
Power tube options: KT88, KT66, EL34, 6L6GC, 7027, 6550
Selectable rectification: Choose between solid-state or tube
Rectifier Tube Choice #1: Mercury Vapor 866
Rectifier Tube Choice #2: Mercury Vapor 966
Rectifier Tube Choice #3: Non-Mercury 3B28
Frequency response: 20Hz ~ 20Khz (-.5db). Tested from 5Hz ~ 40Khz for stability
Total harmonic distortion: <.5% (20Hz ~ 20Khz)
Total max gain: 45dB
All units wired point-to-point using copper silver plated Teflon wire
100K input impedance. 500mV ~ 1.8V for full output, depending on volume and settings
Total unit weight: 49 lbs
Paint finish: Custom, high-quality car paint sprayed by a body shop
(custom colors available)Illuminated front dial volume control
Illuminated glass between transformers indicates standby or operate modes
Coupling capacitors: copper foil, paper in oil
Overbuilt choke filtered power supply
55 Watt Integrated Stereo Amplifier
Features and specifications with KT88s:
55 watts (ultra linear mode), push pull AB
Tubes: (4) KT88 (2) 7N7 (2) 866 (1) 6F8G
Power tube options: KT88, KT66, EL34, 6L6GC, 7027, 6550
Selectable rectification: Choose between solid-state or tube
Rectifier Tube Choice #1: Mercury Vapor 866
Rectifier Tube Choice #2: Mercury Vapor 966
Rectifier Tube Choice #3: Non-Mercury 3B28
Frequency response: 20Hz ~ 20Khz (-.5db). Tested from 5Hz ~ 40Khz for stability
Total harmonic distortion: <.5% (20Hz ~ 20Khz)
Total max gain: 40dB
All units wired point to point using copper silver plated Teflon wire
Three selectable inputs, 100K impedance
Sensitivity: 400mV ~ 950mV for full output depending on volume and settings
Total unit weight: 53 lbs
Paint finish: Custom high-quality car paint sprayed by a body shop
(custom colors available)Illuminated Front Dial volume control
Illuminated glass between transformers indicates standby or operate modes
Coupling capacitors: copper foil, paper in oil
Overbuilt choke filtered power supply
