kenwood kw-1100

  The largest, heaviest and most powerful tube receiver made by Trio / Kenwood. The only one that could compete with the SANSUI 1000A. Produced only for two years 1965-66, because at the same time Kenwood launched transistor models which were replacing tube devices. Very classic look, aluminum front with bakelite and aluminum knobs. When it comes to BASS / TREBLE regulation, such a construction of these knobs allowed separate regulation in each channel. Bakelite was for "R" regulation and aluminum is for "L" channel adjustment. The receiver also had an indication system shown which input was used. While worked with a tuner, the tuning indicator was illuminated in green, which went out when switching to another input. The other AUX, PHONO and TAPE HEAD inputs were coupled with "juvels" illuminated in different colors on the right side of the scale. The KW-1100 tuner in the FM part was the most advanced in terms of automation and at the same time the most modern among TRIO / Kenwood products. The FM head had, in the first stage, the "fashion scream" of the electronic miniature nuvistor lamp. A typical old 6AQ8 / ECC85 tube cooperated with it. In addition, the same type of lamp regulated the automatic frequency stability of the FM head -  AFC. It was interesting that the constructors at the front placed an additional potentiometer to adjust the width of the AFC, instead of a switch as usually. The MPX decoder was also an interesting design. It included two 6AW8 and 6AN8 tubes. The triode part of the 6AW8 double tube was responsible for the automatic switch-off of the stereo. It just turned off the decoder when the signal was weaker. The stereo indicator has been solved in an interesting way. It was an ordinary light bulb hidden behind a window with the word STEREO. Unfortunately, its brightness depended on the FM signal, i.e. the better the signal, the brighter the STEREO sign was illuminated. The radio part was complemented by the AM track with the medium wave range.
The KW-1100 model was sold both under the Kenwood and Trio brands, except that sometimes the letter "U" was added to the numbers 1100. It meant the possibility of being supplied with 115 or 230V and an extended FM range from 80 to 108 MHz.
The power amplifier in the KW-1100 was built on 7591 tubes working in the Push & Pull arrangement. This particular model still featured the original Hitachi 7591 tubes. All four were measured like new. 6AN8 tubes were typical Japanese driver tubes. The standard 12AX7 / ECC83 tubes handled the entire preamplifier. The receiver had a Mono / Stereo switch on the front (mainly for external signals because the FM signal used the FM MONO / AUTOMATIC switch) and a high-cut filter as MPX NOISE FILTER and a low-cut filter as LOW FILTER. And of course the LOUDNESS switch as standard for the company
In SANSUI 1000A, the power tubes were coupled through capacitors with a capacity of 300 nF (currently available value is 330nF). The Kenwood 1100 had 100 nF coupling capacitors. As a result, the amplifier "did not extend" very low, but also the bass signal was more "fast" and the power tubes suffered less.
A unique design feature that distinguished the KW1100 from all other tube receivers was the use of potentiometers with the values ​​used in transistor devices. While each receiver (tube amplifier) ​​had a voice potentiometer with a value of 470 kOhm to 2.2 MOhm, in this KENWOOD product the volume and balance were regulated by potentiometers with a value of 100 kOhm. Nowadays, it makes servicing much easier in the event of damage to these elements.
The KW1100 receiver had siblings. The brother was the KW-220 power amplifier, and the sister was the KW-550 tuner. The KW-220 was practically a clone of the KW-1100 power amplifier. Minor functional modifications were made and the BIAS voltage balance control system for the end lamps was added. The tuner with the KW-550 symbol was also a clone of the radio part of the 1100 amp. It was advertised as "Automatic FM Stereo Tuner" which obviously referred to the automatic switching off / switching on of the MPX decoder depending on the strength of the MPX signal.
The copy of the KW-1100 presented on the website was purchased in the USA. It was very well modified which prevented the lamps from working outside their regime. All oil capacitors were replaced with other types. The voice potentiometer was replaced, but the problem was the balance potentiometer. It was replaced with the NOS Telpod 100k A with MN characteristics.
You would rarely listen to the amplifier using the original 7591 HITACHI tubes with 100% emission. > One of the photos shown a multimeter reading of 25.7 mV. After conversion, it means a lamp current of 25.7 mA, which exactly corresponded to the designed factory parameters. The other vacuum components were also in excellent condition.


 

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