Lafayette KT - 600 Tube Preamplifier - - Hegeman Design - - Marantz 7C Killer




Item History & Price

Information:
Reference Number: Avaluer:19277354Brand: Lafayette
Country/Region of Manufacture: United StatesModel: KT-600
Original Description:
For Sale is One 
Lafayette KT-600 Preamplifier "Master Stereo Audio Control Center" 
If you are reading this, you probably know the KT-600 is widely considered one of the finest tube preamplifiers ever made. It was designed in the late 50's by Stewart Hegeman for Lafayette, and has been a widely sought after classic ever-since -- famous for its bold, authoritative sound. 
In its Winter 1998 Review of vintage tube preamplifiers, The Absolute Sound gave the L...afayette Kt-600 their highest vintage rating, and said it possessed "...Out of this world accuracy, solid imaging, and a certain odd allure akin to the Marantz 1." 
In addition to sounding incredible, this preamplifier is unique for several reasons: First, it can play back any record properly by virtue of its 28 combinations of roll-off and equalization settings. Second, it employs a stereo balancing circuit based the null principle, allowing you to perfectly balance each stage of the preamp. Third, and crucially, its frequency response is flat from 5Hz to 40kHz for unconstrained, clean playback. It represents one of the first implementations of Hegeman's wide bandwidth approach to audio design, the principle that served as the foundation for all his later work: the KT-550 amplifier, Citation I and IV pre-amps, and Citation II and V amplifiers. 
(Note to other sellers: stop stealing my descriptions. Write your own) 

Condition  
Aesthetically, the preamp is stunning. It is probably the cleanest example you will ever see. Use the photos to judge for yourself. Please note: some of the knobs were cracked and have been repaired. They are all stable, perfectly functional, and show well. But they are not flawless. Electrically, this preamplifier has been subject to judicious electrical restoration. It is in excellent working condition. And while the KT-600 was never the quietest preamp, this one outperforms the original specification.The restoration work was done by me, as follows: 
Power Supply Work 
All the electrolytic "can" capacitors were re-stuffed with premium modern electrolytics: (1) Mundorf MLytic AG MLGO, (2) Mundorf MLytic HV MLAL, (1) JJ C-EC47-385, and (1) Nichicon CY series capacitor. On photo shows one of the Mundorf caps with its "can" removed so you can see it. **  The selenium bridge in the filament supply was replaced with (4) MUR860 diodes  The selenium rectifier in the B+ supply was replaced with (1) UF5608 rectifier All <=1 watt resistors in the PSU were replaced with Takman Rey metal film resistors*** The 2 watt 10K resistor in the power supply was replaced with a NOS Mills MRA-5 non-inductive wire-wound resistor*** The 0.1uF heater supply bypass capacitor was replaced with a high quality polypropylene capacitor Some of the red B+ wiring, which was damaged, was replaced with silver plated copper wiring with Teflon insulation 
** The Nichicon CY capacitor was used in the reservoir position because it can handle tremendous stress (it's rated at 12000 hours) and the cap in the reservoir position sees a lot of it, especially at startup. The JJ capacitor was used as the filter capacitor for V7, which is active only when calibrating the channels, or when using the "blended" output jack. The Mundorf HV MLAL caps were used as the filter capacitors for tubes V1, V2, V3, and V4 (the tubes that are in the audio circuit during normal use). The Mundorf AC MLGO was used as the filter capacitor for the filament supply. 
 ***Takman Rey resistors are subject to exceptionally high quality control standards, are extremely quiet, and are considered great sounding by those who believe resistors have a tone. I used matched pairs for each position in each channel. I used an oversize Mills wire-wound (not the Vishay version, an original Mills) in the highest current spot to make sure the supply is as quiet as possible.  

Audio Circuit Work 
All the original carbon composition anode and cathode resistors (4 per tube) -- which carry the most current and, therefore, produce the most noise -- were replaced with Takman Rey metal film resistors. This made the preamp significantly quieter. Their use is also entirely appropriate to the preamp. Hegeman used metal film resistors for the anodes/cathodes of  V1 and V4 to keep the phono section as quiet as possible. He did not not use them elsewhere on account of their astronomical price. The whole kit cost $75 in 1960, and metal film resistors retailed at close to $1 each at the time. There's no doubt Hegeman would have used metal film resistors on all the tubes if it wouldn't have cost nearly half the price of the entire kit to do so. All other resistors were checked, and those that did not meet specification were replaced with new Ohmite "Little Demon" carbon composition resistorsThe multi-section cathode bypass capacitor was replaced with individual Elna Silmic II capacitors mounted directly on the underside of the PCB board. Doing so not only freed up space in the power supply "cans, " but significantly reduced the noise associated with the long lengths of wire that connected the original can capacitor to the PCB. All the original "tubular molded capacitors" tested out of specification and were allowing significant amounts of DC current to pass. They were all replaced with NOS, tested, matched pairs of Russian K40Y-9 paper-in-oil capacitors**** 
**** Yes, you may find some people selling supposedly "working" examples of this preamplifier with the original coupling capacitors still installed. I have news for you: none of them are functioning as designed. Pyramid capacitors were bargain-bin parts to begin with. None of them are working at specification 60 years later. When kept in place, they allow DC current to "leak" between stages, altering the operation point of the tubes and destroying the preamp's fidelity. If you want to hear this preamplifier operate as-designed (like the people at TAS did), then those caps need to be replaced, and these have been.  

General Work I re-routed all the wires according to the original build instructions. A lot of people think the routing indications were just for looks, but they are in fact designed to produce the lowest noise result.  I checked for and and re-flowed all suspect solder joints. I cleaned all the switch contacts with Deoxit products, and lubricated all the wafer switches. Lubricating the wafer switches is key to preserving the knobs. Most of them crack because the wafer switches, when their factory lubricant dries up, become extremely difficult to turn. You will find the wafer switches in these move quite well. 
All the original parts that I replaced above were retained. I will ship them with the unit if you like. With the exception of the parts listed above, all other resistors, wires, and capacitors are originals. So are the power transformer and choke.  

Shipping 
I will pack this with extreme care and fully insure it. International buyers, please contact me for an accurate quote.  

Payment 
I accept payment by PayPal. Payment must be made within 48 hours of purchase. Please contact me if you need more time.

Questions 
I'm happy to answer! Please ask before bidding 



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