The Krohn-Hite story and my search for the ultimate in sound & music.

Have You Ever wondered why such super companies as H.P., Western Electric, Altec, RCA, Gates, Tektronics or General Radio, never made a Super, Super, tube Amp? What I am talking about is using the Big & powerful resources that a major company has, the BEST, most famous engineers, and the most sophisticated no compromise design to make a truly advanced, superior amplifier. One that is far, far, above & beyond the entire world of the Hi-Fi consumer universe & it’s so called “luminary’s”. Even beyond everything ever done in Japan!

Well, there were such unit’s made. As with the building of Vintage Tube Services, I did much long hard research & by sheer grit, drive & some luck found them. When looking back, EVERYONE ((especially when they find out who the designer is, will think, How did these get missed!!!))

Now after quietly collecting every unit I could find over the last 30 Years ((and again, as with V.T.S., 30 YEARS of learning, studying & perfecting techniques)) I have now mastered them & have enough of them to put together nice fully matched pair’s for the ultimate enjoyment of music!

These Historic amp’s will only be available until the dozen or so set’s are sold.

Who would be interested in such amp’s? Those interested in hearing & enjoying the finest, most refined, & yet at the same time the fastest & most vivid, music machines ever made.

Far beyond just a sound stage, when supplied with a good enough analog source, and TRULY high quality speakers these amp's supply a very solid & consistent sonic envelope or bubble that is simply bewitching.

I will spare You any more audiophile blather words, however I will share an odd effect that I have NEVER had with any other amplifier in 40 Years of collecting & auditioning amplifiers. I still say to myself each time when playing these amps (mostly, I think because of their speaker damping & massive lack of inter-transit noise.) "Is this the same recording I have been hearing for years that I just put on? It sounds so different it must be a different record!"

If You are interested in auditioning them call me.

Sincerely,

Andy Bouwman

Ultra-Fidelity Audio (616) 794-9680

Vintage Tube Services (616) 454-3467

 

 

Who Is Khron-Hite?

The Krohn-Hite corp. has been & is still a world leader in "state of the art" Precision Calibration, Precision Phasemeters, Distortion Analyzers and Ultra Low Distortion, Wideband Power Amplifiers. You probably would not want to spend an evening listening to their current solid state offerings but the tube unit’s that were designed by the famous Mr. Richard Burwen in 1953 at the age of 26, just graduated out of Harvard University (( once properly re-built )) will put a smile on your face, year after year, for life!

---

Technical

• The most technically advanced circuit ever developed for an audio amplifier, not designed as a home entertainment product but a true "state of the art" scientific instrument!
• Frequency bandwidth ±3 db 0.08 cps to 80k! (Bass Anyone)
• Phase Distortion/shift less than ±2 degrees max. deviation from linear phase shift (0.5 cps to 30kc.)
• Input and Driver Circuit: Conservative values of gain and phase shift at all frequencies up to 20 megacycles (20,000,000 cycles).
• Dynamic range 110 db
• Distortion ratings that look more like a dry solid state amplifier than a juicy tube unit!
• Output rise under 5 microseconds
• Load Impedance for maximum power output: 1, 2, 4, 8 ohms, selected by the MATCHED LOAD IMPEDANCE switch.
• Output Regulation (No load to full load): Less than 1% from 20 cps to 1 kc, rising to about 10% at 20 kc with MATCHED LOAD IMPEDANCE switch on 1, 2, 4, or 8.
• Internal Impedance (expressed in percent of setting of MATCHED LOAD IMPEDANCE switch): Less than 1% from 20 cps to 1 kc, rising to about 15% at 20 kc with MATCHED LOAD IMPEDANCE switch on 1, 2, 4, or 8.
  

Recommended Use

• To drive very high quality, ultra hi flux density, moving coil loudspeakers and Reproducers.

Construction Details

• All parts made in USA and Germany by the all time classics.
• Main Electrolytic's are all computer grade by CD, Mallory & Sprague from 1988 to 2004 (Pre-changeover).
• All signal caps are vintage glass seal oil.
• Main buckets are vintage oil hi-power and hi-current transmitting capacitors & high current wired.
• Power Switch is a true industrial Electroswitch Corporation unit, it is still made at the original factory in Weymouth MA. It nows costs $138.00!
• DOUBLE choke & cap in series on power supply. (I have never seen this in any other power amp in my 40+ years.)

Richard Burwen Condensed History Timeline 

1940's Early Years

When the government shut down ham radio for security reasons during World War II Dick became interested in hi-fi sound reproduction. In college and graduate school at Harvard, Dick’s adviser was F. V. Hunt, inventor of the first low-pressure phono pickup.  Dick was inspired to spend every afternoon in the Physics Library reading every article in every publication that had anything to do with acoustics and music recording and reproduction.

1949

During the summer of 1949 between semesters, at Bell Laboratories, he designed a tracking band-pass filter.

1954

Krohn-Hite Corp. Ultra-Low distortion Power Amplifier, model UF-101. 50 watts at 0.005% distortion from 4 - type 6550 output tubes produced for 20 years as a laboratory instrument, designed by Dick.

1961

In September 1961 Dick quit his job at Honeywell to become a full-time circuit design consultant, working at his well equipped home laboratory for more than 60 different companies during the next 42 years. The following are just a handful out of 100's!

1963

Pioneer Spacecraft Magnetometer. In 1963 there were no low-power integrated circuits. His spacecraft magnetometer circuits successfully measured the magnetic field of the moon from orbit for several years.

1970's/80's

As a consultant Dick helped Mark Levinson with the first products of Mark Levinson Audio Systems and Cello LTD’s Audio Palette.

Burwen Laboratories Modules MP202, UN201, and VU306. These epoxy potted modules were designed for use in the Burwen Laboratories model 10001. They were the heart of Mark Levinson's famous LNP-2 Pre-Amplifier. Dick's 20,000 watt sound system featured in the 1986 Audio magazine still uses more than 250 of these modules.

1984

Mark Levinson's Cello Ltd. product, the Audio Palette tone control system was a remarkable success and manufactured for many years. Dick submitted this schematic, description, and tentative specifications and features of a program equalizer to Cello Ltd. on March 3, 1984 and it became the basis of the Cello Audio Palette.

1990

About 25% of the worlds hospital MRI systems used Dicks circuits in their Copley Controls model 264 MRI gradient amplifiers.