The 1978 Concept 16.5 Receiver, retailed for $950.00 and has the distinction of being the most powerful receiver ever fielded by a so-called "house brand", in this case, "Pacific Stereo", a subsidiary of CBS. In fact, many vintage receiver collectors regard the 16.5 as one of the best receivers ever made by anyone. The circuitry was designed by Dick Schram, who went on to greater glory as the founder of Parasound. Rumor has it that Dick still collects 16.5s. I know he autographed the case of a 16.5 for my friend SoCal Sam. According to my Tech, Tom Ishimoto, former Manager of Product Development for Marantz, the Concept Receivers were built in Japan by Tandy Electronics Corporation (TEC).

The standout feature of the 16.5 was "dual mono" design with huge twin power transformers. This design was originally pioneered by the H/K 930 about 5 years before the Concept. But the 16.5, rated at 165 wrms/ch had a damping factor of 450, much higher than any other contemporary receiver, which were usually rated less than 100. This was a "spec" you can really feel. In fact, the bass output on the 16.5 is simply stunning and it is difficult to believe that a Receiver is capable of such a powerful sounding output. While a damping factor of 450 is hard to believe, check the specifications for yourself in the thumbnails above!

I recently found a great new application for this old Monster. I plugged the output from my computer's Audigy LS audio card into the Tape 1 input on the 16.5 and now stream audio from the Internet into the 16.5, which powers some RBH Model 18 12" 3-Way Speakers. (RBH makes some great speakers and started off as an OEM cabinet maker for the likes of JBL.) The 16.5 gives the streamed music an AWESOME punch and clarity that it simply did not have being played over my "high-end computer speakers". I

My 16.5 is shown above, on the far left, with its trusty companion, an extremely rare Concept 2QD Quartz Direct Drive Turntable. The 2QD (link to manual and brochure) was supposedly manufactured by Toshiba and was the only turntable marketed as a Concept. It was sold along with the ELC Cassette Deck (.pdf of the Brochure) and the Concept CE-1 and CE-2 "Heil Air Motion Transformer" Speakers (thumbnail, far right).  I really like the way this combo makes one of my favorite LPs, Rosie Vela's Zazu, sound.

TECHNICAL INFORMATION:

The following technical information is quoted directly from the Concept 16.5 Owner's Manual:

FM SECTION:

"A dual-gate MOSFET and 5-gang tuning capacitor provides Concept with excellent sensitivity and immunity to overloading from very strong local signals. Concept also has an extremely steep quieting curve to achieve an outstanding signal-to-noise ratio on very weak signals.

The IF section utilizes three hand-picked, linear-phase ceramic filters to maximize selectivity while still keeping distortion extremely low.

Precise impedance matching of the limiter to the IF filters is also important in keeping distortion low. Concept accomplishes this by using three high-gain symmetrical limiters, which have over 90dB of gain. The detector package is also high-gain, with a wide-band, low distortion full quadrature detector. Overall gain for the IF system is better than 130dB, assuring you of noise-free, low-distortion reception even on the weakest signals.

A Phase-Locked Loop IC chip in the multiplex decoder keeps the tuner perfectly synchronized to the transmitter to achieve maximum stereo separation and the lowest possible distortion. Steep 19 and 38 kHz filters are built in; these eliminate spurious output signals without rolling off desired audio frequencies. This is especially important when making a Dolby-ized tape recording off the air, as such spurious signals can interfere with the Dolby process."

POWER AMPLIFIER SECTION:

"The Concept 16.5's power amplifier uses direct-coupled, fully complimentary driver and output stages, with four output transistors per channel to increase reliability. The transistors are mounted on extruded aluminum heatsinks for maximum heat dissipation, another measure promoting long transistor live. Two differential gain stages provide the lowest possible distortion at any power level.

A slew rate of approximately 38V/�S assures excellent square wave response, even at 10KHz. The slew rate exceeds the minimum required by over a 5 to 1 margin, indicating frequency response extended far beyond specification, and insures the clarity and transparency inherent only in a wide-bandwidth design, with no sacrifice in ruggedness.

An active protection circuit senses excessive current in the output stages and then disconnects the speakers until the fault has been removed. This circuit protects the output transistors, and also prevents DC from reaching the speakers and damaging them.

The Concept 16.5 is the only high powered receiver that features entirely independent dual power supplies. This ensures that each channel can deliver it full output power at all frequencies under all conceivable drive conditions. The benefits of independent power supplies extend beyond that: they insure musical clarity. In a conventional amplifier, heavy power demands in one channel induce cross-modulation into the other, and this crosstalk obscures fine inner musical detail. Independent dual power supplies insure that each channel will reproduce all the detail, with no crosstalk, no matter what the demands on the other channel. This enhances clarity and improves stereo imaging.

Each channel of the Concept 16.5 has its own oversized power transformer, heavy-duty bridge rectifier, and a pair of 10,000� high-voltage electrolytic capacitors. Low-level power supplies are obtained from separate transformer windings and are fully regulated for complete isolation from the power supply.

A separate relay is used to switch each pair of speakers, assuring that all the power is available to them."

The 1976 Pioneer SX-1250 set the audio world on its ears in 1976. I was a Junior at UC Irvine when I first heard about the SX-1250. And, I wanted one BAD! Thirty years later, that dream came true. I also got an SX-1280, but as you can see from the photos above, the SX-1250 is the better built of the two.

Pioneer's SX-1010 signaled the start of the legendary "Power Wars" in 1975, where most of the audio manufacturers of that time attempted to outdo each other with progressively more powerful receivers, reaching outlandish sizes. The 1010 was quickly topped by the Marantz 2325, then the Sansui 9090 and the Kenwood KR-9400. So, Pioneer, not to be outdone by its erstwhile rivals, struck back with the SX-1250. It was a big jump. The 1250's "all Silver" look quickly took hold and was shamelessly copied by all the other manufacturers. The "Blue Light" era of the SX-1010 and Marantz 2325 was officially over!

But, the SX-1250 was about much, much more than mere cosmetic ruffles. First, and foremost, IT WAS BUILT LIKE A TANK! It was, and still is, considered one of the best built Receivers of all time. The Toroidal Transformer power supply is still regarded as one of the best ever, with four massive 22,000 mfd Filter Capacitors. In fact, even though the subsequent SX-1280 was rated at 185 wpc, 20 wpc more than the SX-1250, the 4 Filter Caps in the SX-1280 were only 15,000 mfd. And the 270 watt per channel SX-1980 had essentially the same power supply as the SX-1250, making the 1250 considerably over-engineered relative to its rated power.

The construction quality of the SX-1250 was simply superlative with heavy shielding over every section. This attention to detail had not been seen in receivers before. This was surely the height of Japanese construction quality.

And, the specifications of the SX-1250 were competitive with some of the finest separates of the time. All in all, the 1250 was a "tour de force". That's why so many owners swear by it after having owned it almost 30 years! And, I have to agree. My SX-1250 is now over thirty years old, gets played just about every day and has never had to be repaired.

The styling for the 1250 is very stylishly conservative and, for that reason it has held up quite well. In the rightmost photo, a 1250 sits atop an SX-1010 and beneath and SX-1280, 880 and 1980. The second photo form the right shows and SX-1250 beneath a D-7000, Pioneer's first digital tuner Receiver. The styling of the D-7000 came and went quickly and no one else went there.

Soundwise, the SX-1250 is pleasant enough to listen to, but not memorable. The bass, like most Pioneers of this era is a bit muddy and brooding, lacking the punch and crispness of a Concept 16.5. However, the tuner section, even without Quartz Lock, pulls in weaker stations with exceptional clarity, where other receivers simple can't go there. Although the SX-1250 is relatively common on E-Bay for an admission price of around $400 to $700 mine will stay just where it is.

The 1978 Hitachi SR-2004 Class G Receiver, retailed for $1,195.00  and has the distinction of being the fifth most powerful "all in one" Monster Receiver made during the "Power Wars" of the late 1970's and one of the least well known.  In fact, with its dynamic headroom specification of +3db, it just might have been the most powerful of all. And, it WAS the most powerful Class "G" Receiver ever made.

Hitachi, which manufactured OEM electronics for most of the major audio manufacturers, was a relative late-comer to the Receiver "Power Wars" OF THE 1970's. However, when Hitachi joined the fray with the SR-2004, they put their best foot forward. Almost all the internal components in the SR-2004 were made by Hitachi, making this receiver a real rarity and somewhat of a "purebred". And, outside the box, it has a real presence.

The SR-2004 had most of the "bells and whistles" of the other Monster Receivers it was designed to compete against and a few unexpected extras like switchable IF Bandwidth (wide/narrow), "AutoLock" FM Tuning (triggered by changes in the capacitance when you touch the tuning knob) to prevent FM drift, and a SAW Filter. In fact the 5-gang front end on the SR-2004 was one of the best analog receiver tuners ever. Be sure to take a look at the spec. pages below.

The SR-2004's deluxe features also included two (2) different Audio Muting levels, a front panel Mic Input w/ level control and a very comprehensive Tone Control section with bass, mid-range and treble controls with switchable frequency settings for the bass and treble controls. The images below are from the Owner's Manual and the left most describes all the front panel controls. But, what really made the SR-2004 stand out was its "Class G" Amplifier, with a prodigious 200 watt RMS per channel power output, placing it among the most powerful receivers ever made. In fact, according to a review from the November 1978 issue of "High Fidelity" Magazine, it was capable of dynamic peaks of 400 watts/ch "that gives it a shot a first place in the receiver power race". When High Fidelity tested the SR-2004, it found that the power output was actually more like 240 watt/ch RMS. And, better yet, the Hitachi stayed relatively cool, a good indicator for long transistor life. That's why the SR-2004 was popular most among sound reinforcement professionals and DJs. Roger Russell, former loudspeaker Guru for McIntosh Labs was kind enough to provide me with a copy of this review (for a measly $5.00) from his collection of audio magazines:

So, now you know a few of the reasons why the HitachiSR-2004 is one of the greatest receivers ever made. The power supply was dominated by a huge Toroidal Power Transformer surrounded by four (4) huge capacitors, 2 per channel. All of the internal electronics were shielded by metal enclosures so that barely any wiring is visible.  And, of course, all eight (8) discrete output transistors on the massive heatsinks were proudly marked "Hitachi". There's nothing like being a purebred!

Unfortunately, Hitachi was never able to establish an audio brand identity in the American market, so the Hitachi audio line essentially disappeared after 1982 and the SR-2004 is now just a vague memory in the minds of many enthusiasts.

Functionally, the Hitachi gives up very little to the Pioneer SX-1250 performancewise. However, whereas most receivers sound "loud enough" with the volume set to 9:00, the Hitachi needs to go to 12:00 for adequate volume. However, whereas most receivers are maxed out at 2:00, the Hitachi just keeps going to 5:00.

For the technically inclined, what follows is a description of "Class G" amplification from a forum at audiokarma.org:

Class G, Class H Amplifiers Explained:

Soundcraftsmen made some EXCELLENT sounding Class H amps. The Hitachi Class G amplifier allowed them to make a 200 wpc unit that could double that output as required for short periods. These are popular where high-power and cool-running are needed, such as in pro applications and in mobile (cars) systems due to their efficiency. I have four of the big Soundcraftsmen amps, and let me say again, they are GREAT sounding amps (or they have no sound of their own, I guess is the point of my comment).

Class G
Class G improves efficiency in another way: an ordinary class AB amplifier is driven by a multi-rail power supply. A 500 watt amplifier might have three positive rails and three negative rails. The rail voltages might be 70 volts, 50 volts, and 25 volts. As the output of the amplifier moves close to 25 volts, the supply is switched the 50 volt rail. As the output moves close to the 50 volt rail, the supply is switched to the 70 volt rail. These designs are sometimes called "Rail Switchers". This design improves efficiency by reducing the "wasted" voltage on the output transistors. This voltage is the difference between the positive (red) supply and the audio output (blue). Class G can be as efficient as class D or T. While a class G design is more complex, it is based on a class AB amplifier and can have the same clean characteristics as well.

Class H
Class H is similar to class G, except the rail voltage is modulated by the input signal. The power supply rail is always just a bit higher than the output signal, keeping the voltage across the transistors small and the output transistors cool. The modulating power supply rail voltage is created by similar circuitry that you would find in a class D amplifier. In terms of complexity, this type of amplifier could be thought of as a class D amplifier driving a class AB amplifier and is therefore fairly complex.

Here's a different point of view from an audio technician, "Ron", who e-mailed me in response to this page:

"My other comment has to do with your definition of Class G, where you state: "an ordinary class AB amplifier is driven by a multi-rail power supply". This is incorrect. Classes A to D are defined by conduction angle of the output devices, regardless of number or level of supply rails. (In Class A, output devices conduct at all times, through 360 degrees). In Class AB, between 180 to 360 degrees, depending on input signal level. In Class B, 180 degrees. In Class C (never used for audio), less than 180 degrees. In Class D, alternating conduction through a small angle.) In contrast, Classes G and up (coined in Advertising, rather than Engineering) define the power supply and not the output device operation. IOW, a Class G supply can still feed a Class A, AB, B (or even C or D) output stage."

Thanks for the input, Ron!
 

The 1976 Rotel RX-1603 Receiver, retailed for $1,100.00 and had the distinction of being the most powerful "all in one" Monster Receiver when it was first introduced in 1976 (180w/ch RMS x 2). And, it was the most powerful Receiver ever made by Rotel, the British audio manufacturer. But, this should not come as a surprise since in 1976 Rotel also introduced the incredible RB-5000 Power Amplifier (shown at right, above) rated at an astounding 500 w/ch RMS x 2. I suspect that the RX-1603 has more in common with the RB-5000 than just the knobs!

The RX-1603 was of completely conventional design electronically, although the cabinet was designed to separate the front from the rear (tuner/pre-amp & amp.) because it was extraordinarily deep. This was similar in concept to the Sansui G22000/G33000, although not as well executed. Inside is a huge "Rotel" Toroidal power transformer with two filter caps the size of coffee cans. The front handles were not just for show, either. Given its bulk, weighing in at approximately 75 lbs., it was very difficult to move around without the handles.

I've listened to the RX-1603 a fairly regular basis and the sound is full and rich in detail. My speakers are not particularly sophisticated (yet) so the more esoteric elements of its performance I am not worthy to evaluate. It seems to be SIGNIFICANTLY more powerful that the Pioneer SX-1280, even though the rated power output is about the same. I read somewhere on the Net that the RX-1603 actually specs out a around 250w/ch RMS, but I have not confirmed this. Next time I take it in for service, I'll ask my Tech, Tom Ishimoto, to benchtest it so I can say for sure.

The RX-1603 gained a degree of immortality arter being featured on the cover of Stereo Review's issue covering the stunning rise of Monster Receivers in 1978. It's the second unit from the bottom in the rightmost photo. Personally, after the Marantz 2600, I think it's the most captivating looking Monster Receiver. The FM performance is a little weak, however, the amplifier section more than makes up for it delivering a powerful, punchy bottom end that doesn't overwhelm the crisp highs and detailed mids. It's a keeper.

Here's a German site with more about Rotel.

The 1979 Marantz SR9000G retailed for $950.00 and has the distinction of being Marantz's first Digital Tuner equipped receiver. It was sold only in Europe, however, was the design basis for the top of the line Marantz SR-8000 sold only in North America. Most audio collectors have considerable disdain for Marantz equipment from 1979 through the 1980's. Although not as big and powerful as the awesome Model 2500/2600 (shown in the second photo from the left) it replaced at the top of the Marantz lineup, the SR9000G was still a 1970's Monster Receiver in its own right at a benchtested 150w/ch. However, it marked a turning point in Marantz's fortunes, as the Company began a downhill slide after it was taken over (a .pdf of Marantz history) by Dutch electronics giant Philips.

Unfortunately, the SR9000G was a Monster with obvious signs of cost cutting. Although manufactured at the same Standard Radio of Japan factory that produced the Model 2600, the buttons were plastic, not metal. Gone were Toroidal power transformers and "dual secondary" power supplies of the previous generatoin. Also gone were double ganged tone controls and the brand-identifying "Gyro-Touch" tuning. And, the wood case was now covered with vinyl rather than real wood veneer. There was no metal case. Although the SR9000G was actually under development before Phillips took over, it sent all the wrong "mass market" signals to the loyal customers who had been devout followers of the Marantz brand during the 60's and 70's. And, the sales figures showed it.

The SR9000G is now an extremely rare Monster. Very few exist now. Many have no doubt been destroyed being shipped around the country in
E-Bay transactions. I have been able to find almost nothing about mine on the Internet, except on a German site, which did not translate very well. I took my SR9000G over to my friend Tom Ishimoto's shop and he benchtested it at 150w/ch, 20-20kHz at 0.022% THD,  a performance that puts it in the Monster Receiver league, albeit barely. Tom was once the Manager of Product Development for Marantz, and even he did not know about the SR9000G. That's how rare a bird it is.

But, issues of cost cutting aside, my SR9000G was redone with a real rosewood case by LBPete at AudioKarma.org. He did an awesome job. And, I hang onto it because I like the overall design a great deal. If the lens over the display had been aqua toned glass, the knobs solid metal and the case made from a real veneer, it would have looked and felt like a true top of the line Receiver for its era.

For now, it only performs like one. However, I do like the looks of the early 80's Marantz gear, some of which are shown above on the far right. If only the build quality had been up to par. Sad. Really.

The 1978 Toshiba SA-7150, retailed for $1,195.00 and has the distinction of being (according to Toshiba) the "world's first" receiver with a Quartz Digital Synthesizer Tuner. In that way it was the forefather of all that was to come. It was also an FM lover's delight, since it also had built-in Dolby FM, switchable IF Bandwidth (wide/narrow), Hi-Blend and even Air Check (a white noise generator) for setting recording levels. It also had a 150w/ch power amplifier with a "dual mono design" and a huge Toroidal power transformer. The Toshiba engineers were so fanatical about the power supply that the SA-7150 even had a separate power transformer for the tuner/pre-amp circuits.

To quote from the Owner's Manual:

"The all-important power supply for the SA-7150 is divided into separate supplies for the pre- and power amplifier stages. the power amplifier supply is then further divided into independent left and right power supplies, employing separate pairs of high grade heavy duty electrolytic capacitors (15,000�V x 2 per channel) and a massive Toroidal transformer for excellent regulation. The SA-7150 is thus able to deliver its huge reserves of power right down into the ultra-low frequency region with greatly reduced dynamic crosstalk distortion.

Big advances in audio circuit technology have given the SA-7150 Digital Synthesizer AM/FM Stereo Receiver an incredibly huge reserve of output power at practically non-existent distortion levels. Super-low-noise dual transistors (developed especially for Toshiba audio equipment) in the 1st-stage differential amplifier, and parallel push-pull connected power transistors (of particularly outstanding transient response) in the power stage, deliver 150 watts of power per channel (both channels driven) into 8 ohms from 20 to 20 kHz with no more than 0.05% THD."

Toshiba, which manufactured OEM electronics for most of the major audio companies, was a late-comer to the Receiver "Power Wars". However, when they joined the fray with the SA-7150, they put their best foot forward. Almost all the internal components in the SA-7150 were made by Toshiba, making this receiver, like the Hitachi SR-2004, a real rarity and somewhat of a "purebred". And, out side the box, it has a very distinctive look, with the bright digital display, multi-color LEDs and analog Power Meters rated up to 500 watts. As you can see, it makes quite an impression and, with its interesting combination of analog and digital design elements, not at all dated.

In 1978 Toshiba also released the ST-910 Digital Tuner (also marketed under the "Aurex" brand) which showed off its technical prowess. This review of the ST-910 from FM Tuner Info. Center gives you a taste of Toshiba's advance FM Tuner technology circa 1978, much of which is incorporated into the SA-7150.

The 1978 Setton RS-660 certainly qualifies as one of the rarest of the Monster Receivers. And, one of the nicest looking. In fact, the Setton line had only three (3) receivers, the RS-220, RS-440 and the "big one", the Setton RS-660. The RS-660 retailed for $900.00, making it one of 1977's more expensive receivers, although it was "only" rated at 100 w/ch RMS when introduced. The Setton line was allegedly designed by Allain Caire, an acolyte of Pierre Cardin (although it is mistakenly claimed that the master himself was involved) and was marketed to an "elite" audience. Setton was the French distributor for Pioneer and had decided to come to market with their own brand. In Europe, Setton distributed some really interesting equipment, like the outrageous (for the time) RCX-1000 modular receiver, which shares only it's knobs with the Settons shown here.

The RS-660's controls are amazingly smooth and the sound is "rich" and full. However, the wood sleeve that it comes in is covered with a really tacky walnut woodgrain vinyl, which get quite sticky with age, entirely out of step with the exquisite cosmetics of the faceplate. 

The Setton receivers have always been a source of some controversy since it is well known that they were not manufactured by Setton. However, that issue has now been resolved, since it appears that the Settons were manufactured in Japan by the same outfit ("Planet Research") that did the Lafayette Radio products, like the LR-9090. Other people claim it was made by Trio Electronics, parent of Kenwood. I recently acquired an LR-9090 and can attest that internally, they are about 90% the same, although the power transformer and the pre-amp board are different. So, they are not identical behind the faceplate but clearly made by the same manufacturer and while not identical twins, they are clearly brothers. (See middle comparison photo.)

All the Settons featured a unique "Security Panel" display, with indicators for "Heat", "Clipping" and "Protection". This included the fairly outrageous BS-5500 Power Amplifier (middle photos), a true "dual mono" design, complete with 2 power switches. This was basically the RS-660's power supply section multiplied by 2. The power supply filter caps in the RS-660 were fairly substantial at 15,000uF x 2. It also had switchable turnover frequencies for the Bass and Treble control and a Hi/Lo phono impedance setting on the rear panel. 

Attempting to add to the exclusive allure, each Setton Receiver was benchmarked at the factory and came with its own individualized spec sheet, signed off by a Tech. When the RS-660 first came on the market, it's published spec was 100 w/ch RMS. However, Setton had underrated it, and so it was re-spec'd at 120 w/ch RMS without any change in the circuitry. Even at that, it was still underrated. It's actually good for around 130 w/ch RMS.

However, a considerable amount of money was invested in the RS-660's "cosmetics". All the buttons are solid metal and the feel of the controls, with their nylon inserts, is almost silky. It is a real pleasure to use. But the vinyl on the case is another story entirely. How could they do this? I have had the vinyl case on mine redone with real walnut veneer by Merrylander at AudioKarma.org and I'm sure it's now the best looking RS-660 in existence.

I can't really say I listen to it very often because the Setton Receivers have a dreaded Achilles Heel: the power switch is built into the speaker selector and sometimes this can create an electrical arc which destroys the unobtainium selector. However, the much more common LR-9090 has the identical switch and those are much more common. In I bought one as a source of parts for the Setton.

When critics evaluated the performance of the Setton Receivers, they received fairly glowing reviews.

I haven't found any English reviews of the RS-660, although there is one in French. (Can anyone translate?) And, the LR-9090 was reveiwed by Stereo Review.

 

A detailed review of the smaller RS-440 from the November, 1978 Stereo Review had this to say:

"Although style is a very personal consideration, there can be no doubt that the Setton RS-440's front panel is both unconventional and unique - although unmistakably a stereo receiver it will never be confused with any other make. To us, the Setton RS-440 appears to be in impeccable visual taste, with sonic performance to match".