stereo power amp  ('88-'89)   $500
150 WPC 

In excellent cosmetic condition, fully bench serviced and thoroughly tested, this NAD 2600A monitor series stereo power amp is a rare and heavy duty brute. 
NOTE: We have several preamps available at extra cost.  Examples are shown in the photos.

The back story:
The NAD 2600 series was an evolution of the NAD 2200. The 2600 can have “B” or “C” series main amp boards but the best of the 2600 series is the one we have here, the 2600A. That's primarily because it has “C” series amp boards. Some 2600’s and all 2600A’s have an upgraded input board with additional transistors regulating the 18v supply rails. This is the SW 692 board. These upgrades included providing front panel volume controls for each channel and replacing the metal front panel of the 2200 series with a plastic panel. The main power rails have been raised to 72v, from the 65v of the 2200 series, enabling NAD to claim a power output of 150 watts per channel compared to the claimed 100 watts of the NAD 2200. This additional voltage is provided by a different transformer, which has switchable taps for different impedance speaker arrangements on the rear.

Specs:
Power output: 150 watts per channel into 8 ohms (stereo)
Frequency response: 20Hz to 20kHz
THD: 0.05%
Speaker load impedance: 4 ohms (minimum)
Dimensions: 17.2"W x 5.5"H x 15.5"D
Weight: 29 lbs

About NAD...
Based in London, NAD is a great audio company and has made a number of very notable, and now vintage, amplifiers. Their philosophy has been driven by making their amplifiers sound “musical”, though at a price point that us mere humans can afford. One of their key innovations is using a dual rail power supply with two voltages, with the higher rail providing a reserve of power that is used for musical transients.
It's well known throughout the vintage HiFi community that NAD makes very good amplifiers. The circuits are well thought out and the core components are well considered. In some of their models their choice of components has been driven by cost, and as such replacing these with modern components does return a noticeable benefit.

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integrated amp /  tuner ('75-'77) 40 WPC  $500 / set only

Obtained locally from the original owner, this Kenwood KA-3500 integrated amp is beautifully simplistic in design and very well built indeed.  After our intensive bench servicing and testing, it's literally in mint cosmetic condition and performing perfectly.  Both the amp & tuner cabinets feature a unique and very attractive graystone mineral textured finish.

There's something special about these mid-70's Kenwood integrated amps;  they are one of our favorites among the hordes of mid-size amps available during the frenzied 70's marketplace.  Even today they are extremely desirable for their durability and smooth exterior designs.  As some have stated (and we definitely agree with) "the Kenwood KA-3500 has the aesthetics and build quality that simply oozes '70s vintage class."

The KA-3500 was positioned as a mid-level component amplifier in Kenwood’s '75-'77 product lineup.  The very conservative power rating of 40 watts per channel into 8 ohms (45 WPC into 4 ohms) put the KA-3500 in direct competition with the Pioneer SA-7500 (which was also powered at 40 WPC).   This great looking "Kenny" is really one of the sweetest sounding amplifiers from the era, with plenty of detail and enough power to drive most mid-level systems with ease.  Features include inputs for turntable, tuner, two decks and auxiliary, with dubbing support provided.  Reviews claim this was (and still is) one of the best sounding amps in its price range

In excellent cosmetic condition and working perfectly, this excellent KT-7300 stereo tuner was second in the lineup to the flagship Kenwood KT-8300 upon its release in 1976. The tuner is a bit larger than the amp so, because of that reason alone, it's not the original matching unit for the KA-3500 (that would have been the KT-3500).   However, the specs and build quality of the KT-7300 should be considered a major upgrade when compared to the KT-3500.

Basic specs:
Minimum power output: 40 WPC @ 8 ohms / 45 WPC @ 4 ohms
Frequency response: 20Hz to 20kHz
THD: 0.2%
Dimensions: 15"W x 5.5"H x 10"D
Weight: 22 lbs

About Kenwood...
Kenwood’s roots trace back to 1946, when it was originally founded in Komagane City, Japan as the Kasuga Radio Co. Ltd. The company initially focused on producing amateur radio and communication equipment, catering to a post-World War II market where radio was a primary means of communication. In the early years, Kenwood quickly gained a reputation for its technical expertise and high-quality components, establishing itself as a leading manufacturer in the Japanese electronics market.

In 1960, the company changed its name to Trio Corporation to reflect its broader ambitions. Around this time, the brand expanded its product line beyond radio communication equipment, venturing into consumer audio products, including amplifiers and receivers. The early '60s also marked the company’s entry into the international market, with its first overseas office established in the United States.

The name Kenwood came into existence in 1961 when Trio Corporation’s products began to be marketed under the Kenwood brand in the U.S. The name “Kenwood” was chosen to appeal to an international audience, as it combined the popularity of the name “Ken” with the term “wood,” evoking strength and reliability. The new brand name resonated well with consumers, and over the next decade, Kenwood would become a well-known name in both consumer and professional audio markets.

In the '70s, Kenwood expanded into high-fidelity audio equipment, releasing a range of products including amplifiers, tuners, and receivers that offered excellent sound quality at competitive prices. The brand quickly earned a reputation for delivering innovative, feature-rich products that appealed to audiophiles and casual listeners alike. Kenwood’s early success was driven by its commitment to quality and its pioneering approach to audio engineering.

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Integrated Amplifier  65 WPC Class A (2008)   $2400

First released in 2008, it is one of the "Holy Grail" Pentode/Triode Pure Class A stereo integrated tube amps.  This one has new Russian made  Genalex Gold Lion KT88 reissue vacuum tubes.  It also comes with the original factory remote control and a very sturdy, factory-built, triple-boxed shipping container and materials.  It should be noted that Ayon charges $180 for a replacement shipping box.

The Spirit uses the previously mentioned four KT88 and three 12AU7 tubes. It is a zero negative feedback design and runs in pure Class A. The preamp section has four line levels and there are speaker taps for both 4-ohm and 8-ohm impedance.

Though an integrated, the Spirit occupies a spot on the audiophile spectrum where convenience features give way to more purist priorities. The black brushed aluminum remote control was designed to match the amp’s finish.  It's a simple remote that controls volume and muting only. 
On the amp itself, there are no non-essential front panel buttons of any kind: no balance control, no tone controls, and no mono button. The amp not only has fully manual tube biasing, but has located this important feature on the back panel. The power switch is also located in the back.  Because of its "lack" of certain controls, some may say that the Spirit might not rate high in convenience, but with its performance being the main attraction...enough said!

Ultra-linear electronic circuits are those used to couple a tetrode/triode or pentoden vacuum-tube to a load (e.g. to a loudspeaker).  ‘Ultra-linear’ is also known as ‘distributed loading’; a circuit technique patented by  Alan Blumlein in 1937. Ultra-Linear “distributed loading” was intended  for guitar amps, etc.

• In pentode or triode, in which the screen-grid is connected to a stable DC voltage so there are no signal
variations on the screen-grid (i.e. the screen-grid has 0% of the  plate’soutput signal impressed on it)

• In triode, in which the screen-grid is connected to the plate (i.e. the screen-grid  has 100% of the plate’s output signal voltage impressed on it)

• a blend of triode and pentode, in which the screen-grid has a percentage (between 0% and 100%) of the plate’s output signal impressed on it. This is the basis of the Ultra-Linear “distributed load circuit” and is seen as a form of feedback,
which alters the behavior of the electron stream passing from cathode to anode.

Ultra-linear introduces negative feedback, which squashes and compresses the sonic performance.
So the Pentode/Triode operation will yield a vastly superior response and more of a “tactile” or SET sound, more of a three dimensional sonic signature. Quite Superior!

NOTE: All of Ayon Audio’s products are painstakingly designed and assembled in-house; the company even makes their own tubes. While they specialize in low-powered, single-ended designs, the Spirit integrated is the company’s ostensible attempt to craft a more mainstream offering: switchable between push-pull pentode and triode operation, the Spirit pumps out a robust 60-watts per channel in pentode and 40-watts in triode. With the original list price of $4500, the Spirit and the similar, triode-only Spark integrated, were Ayon’s twin entry-level offerings.   Entry-level it may be, but the Spirit is still a gorgeously built amp. Having it in your listening room will instantly identify you as someone who is quite serious indeed about their music playback. 

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amp (early 80's)  200 WPC   $750

In pristine cosmetic condition, fully serviced and tested, this Acoustat Twin 200 stereo amplifier underwent a thorough bench servicing that included the tricky bias adjustment.  Main cap values are well within original values; the interior of the unit is super clean as well.  The amp had previously been used very sparingly by the original owner.
This powerful amplifier delivers just over 200 watts per channel over the entire range of audio frequencies from 20 Hz to 20 kHz for its rated harmonic distortion level of 0.1%.  

(NOTE: the following technical description was provided by Gamma Electronics: 
https://www.gammaelectronics.xyz/audio_03-1983_acoustat.html

The front panel is totally devoid of any controls, with the exception of its rocker-type power on/off switch. A rather prominent nameplate identifies the maker and the product. As for the rear panel, most of it is taken up with a massive heat sink, but there is just enough room at either end to accommodate color-coded, five-way output binding posts and an input jack for each channel. This sort of channel isolation is carried on inside the chassis as well, with completely separate modules housing the parts for each channel. Six fuses are located internally (four d.c. supply-voltage line fuses and two a.c. line fuses). The TNT-200 uses four completely separated bilateral power supplies and a twin-core, quasi-toroidal power transformer with parallel primaries.

"Trans-Nova" is an acronym for "Trans-conductance Nodal Voltage Amplifier." Most power amplifier output stages are typically configured either as voltage followers or as transconductance stages (common in tube-type amplifiers). When Acoustat decided to design an amplifier employing MOS-FETs as power output devices, they found that neither of these basic configurations was well suited to such ICs.

Basic specs:
Power output: 200 watts per channel into 8Ω (stereo)
Frequency response: 20Hz to 20kHz
THD: 0.1%
Impedance: 4 ohms (minimum)
Power Consumption: 100 watts idling, 750 watts at rated power.
Weight: 40 lbs
Dimensions: 17.5"W x 14"D x 5.5"H

About Acoustat...
Acoustat was an American company known for its full range electrostatic speakers that began its research in the early 1970s and introduced its first commercial model, the Model X, in 1976-77. After pioneering advances in electrostatic technology and achieving critical acclaim, the company filed bankruptcy in 1984 and was subsequently bought by David Hafler.  The brand's history is marked by innovation in electrostatic panel design and amplifiers, leading to a loyal following among audiophiles and recording studios before its acquisition and subsequent market disappearance in the U.S. in the early '90s.

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