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Thread: RCVR: Harman Kardon 900+ Quadraphonic Receiver

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    Senior Member Quadrockasaurus's Avatar
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    Default RCVR: Harman Kardon 900+ Quadraphonic Receiver

    If you have any more photo's or comments to make on this Quadraphonic unit please feel free to post them in this thread....

    Harman Kardon 900+ Quadraphonic Receiver

    Rarity: RARE
    Average Sale Price: UNKNOWN


    Top of the line in the Harman Kardon Quad receiver range in the early to mid 70's just above the 800+. The 900+ looks mostly identical to the successor/predecessor unit (Model 150+) with a few visual differences...i.e. tuning dial went from a three color combo on the 900+ to just green. (...not sure which unit replaced which..??). The 900+ was also OEM-ed/rebadged as the "Williamsons Model 128" Quad Receiver.

    The 900+ has an onboard SQ decoder and CD4......don't have too much more info on this particular unit.

    The 150+ units appear to be much more common than the scarce 900+.
    Last edited by Quadrockasaurus; 04-24-2011 at 02:46 AM. Reason: ...added Williamsons info...

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Very nice!

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Does any QQ member prefer the "Joystick" approach to quad soundfield control? I do not - I can't ever get the setting to where it's "perfect" for every channel, and the ones I've seen seem to get dirty/noisy very easy, which leads to audio drop outs in some positions, etc... kinda like the cheap, unsealed front panel knobs in the Fosgate Tate II 101A: Television Tuner Cleaner spray is the 101A's best friend! I assume the earlier Fosgate Tate 101 Tetrasound has the same cheap controls too - it certainly looks like it does, the later 101A being a virtual clone of it.

    Thanks for posting the picture - I LOVE looking at pictures of quad gear.

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    I lusted for a 900+ back in the day (1974), did manage to later (2000) find a 150+ on eBay that I enjoyed very much until a channel went out. If memory serves, I believe I later sold that receiver to Lou Dorren!

    Next to the 150+ was the 44+ CD-4 demodulator and 8+ quad cartridge player. Coupled to some Advent speakers, Houses Of The Holy sounded like 1973 all over again.

    If I find pictures I will post.
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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Yup, a true beauty!

    Ah, Houses of the Holy. I will play it today on my system which, coincidently, has stacked Advents in each corner.

    EDIT: I think the 150+ was earlier because it seems they were around in the very early seventies and the 900+ was a little later. More towards the mid seventies.

    Doug

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    I can't tell from the picture if any of the buttons are labeled as such, but did the built-in SQ decoder have any form of Logic, either Full Wave-Matching w/Front-Back (or F/B alone) or Full Logic with F/B Vari-Blend? It seems that the date the HK 900+ was retailed would put it in the "logic available" category, either discrete circuits or the Motorola/Fairchild Full-Logic IC set. (The number of Logic sets and the combinations that CBS made available was so insane - a "make-it-up-as-you-go-along" approach, which SQ [and to a lesser extent, QS] really was!)

    As a side note regarding SQ Logic, it's too bad Sony never produced their own patented signal cancellation decoder - it was a true Parametric SQ decoder using Selective Cancellation like Vario-Matrix, Shadow Vector, Paramatrix and the Tate I/II DES; Sony had a QS version too - I've never been able to find out if either was sold in the Japanese market or not. Apparently, from what I've been told, Sony made high precision, and relatively low-cost, all-pass phase shifters for SQ and OEM'd them to other companies - Martin Willcocks told me they used Sony's 8-Pole phase shifters in the SQ decoder boards they sold to Audionics (the non-logic 'High Resolution' SQ unit) and in the first few designs of Willcocks prototype Tate DES decoders. The Fosgate Tate II 101A uses Sony's 6-Pole design (just the design and not an actual Sony-made board) and Audionics Space & Image Composer used the 8-Pole design.

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    I've never had a unit with a joystick but I always assumed the locator/stick was pretty handy if you had a large room and regularly listened in different locations in that room and just HAD to have the soundfield perfect no matter where you were...

    I wish I had more info on the 900...You'd think after so many years there would be some more info on this unit somewhere on the web....but there is very little, I got all the decoders info I have from the HK800+ ad Jon posted earlier in the Hardware section (..I'm assuming here that the top line 900+ would be equipped with the same decoders as the 800+)...I can barely make out the blurry details on the image I have...
    Last edited by Quadrockasaurus; 04-24-2011 at 12:11 PM.

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    This is a nice piece. I'm working from memory on this, so forgive me if I'm a bit off on spec's. I sold a lot of H/K in the day, owned two cassette decks and some Citation gear. I considered buying a 900+, but never did. Sold a few, though. First, here's what's great about this piece: Ultrawideband-an amplifier that is capable of producing a wider frequency response than we can hear. Why? It is smoother and more responsive in the audible range. It has a faster "switching time" than most Quad pieces, adding to realism. These are the biggest reasons H/K sounds so good. Great features like an early version of 2-Zone operation. Connect tape 1 out to tape 1 in, and you can run it as two systems (stereo only) with separate sources: any source on Z1 (front amps) and tape 2 on Z2 (rear amps.) Separate bass, mid and treble controls for front & rear.

    What leaves something to be desired:
    The joystick is the biggest drawback. It's almost impossible to balance with these things. They look cool, but tend to be "all or nothing" controls. The joystick was the deal breaker in why I never bought a 900+. Individual knobs or linear pots work way better. Power isn't very high. I don't recall the power ratings, but I recall perhaps 30-40x4? I know the 800+ was 22x4. Since power is logarithmic, 40W is slightly higher than 20W, 3db to be exact. Yet, there is double the headroom. I recall that it was less than full logic for SQ (front-back logic only?) In pushing the limits of performance, reliability is sometimes compromised. H/K gear of this era isn't as reliable as some of it's competitors with lesser performance. It's the reason I sold off my H/K Citation gear. I still own a CD-401 3-head H/K cassette. Like Marantz pieces of this era, tuner sensitivity is not great. With an outdoor FM antenna or proximity to FM transmitters, FM will sound better than most receivers. CD-4, stereo LP's and Q4's will likely sound better through this than most other Quad receivers. The added bandwith will add immediacy to full frequency sources.

    Sorry if I offended any H/K users. In light of everything I said, I believe that this is a terriffic sounding quad receiver, one of the best. Just be aware of it's strengths and weaknesses. It has simple lines and great styling.

    Linda

    Quote Originally Posted by Quadrockasaurus View Post
    I've never had a unit with a joystick but I always assumed the locator/stick was pretty handy if you had a large room and regularly listened in different locations in that room and just HAD to have the soundfield perfect no matter where you were...

    I wish I had more info on the 900...You'd think after so many years there would be some more info on this unit somewhere on the web....but there is very little, I got all the decoders info I have from the HK800+ ad Jon posted earlier in the Hardware section (..I'm assuming here that the top line 900+ would be equipped with the same decoders as the 800+)...I can barely make out the blurry details on the image I have...

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    I am a former customer service technician for H/K. I was with H/K from January 1974 to October 1988. I'm very familiar with the 900+ receiver. For about 12 years I was the only technician working on all multi-channel receivers at H/K's in-house customer service department first in Plainview, then Woodbury, NY. I know all of the weaknesses of all those "plus" models. I don't know exactly how many I worked on in total, but it had to be in the high hundreds, if not thousands. In other words, I probably had my hands on more 900+ units than any other individual technician in the world.

    The 900+ (and the 100+ & 150+) was designed by H/K in the USA but custom manufactured exclusively for H/K by a company named "Crown Radio Company" in Japan, not to be confused with a similarly named American company based in Indiana. I understand that the 900+ had appeared a few years later in some foreign countries (South America?) as a counterfeit after it was discontinued by H/K, perhaps relabeled. I'd be curious seeing one relabeled... could be a collectors item.

    The 900+ was basically an upgraded 150+ with slightly larger power transformers (TS-464 & TS-465 replacing the TS-436 & TS-436A transformers), a multi-color dial scale (replacing the green), and a CD-4 decoder built in replacing the phono preamp. On the 900+, the CD-4 board has the magnetic phono preamp stage. Also, the 900+ came standard with a wooden top (and side) cover. The 150+ had an optional wooden cabinet but came standard with a metal top cover.

    In quad mode, each channel in the 900+ could easily deliver 45 Watts per channel into 8 ohms. In stereo bridge mode, it was rated at 90 Watts a channel in 8 ohms but easily did more. Over 100 Watts per channel stereo into 8 ohms was typical. Power output ratings on H/K products were always at the time very conservative.

    Each of the 4 amplifier modules were the same circuit design (but not the same components, however) as the then top-of-the-line Citation 12 amplifier. However, the Citation 12 was produced in Plainview, NY with US-sourced components.

    The 900+ was plagued with noise (hiss) at minimum volume as the 2SC458 tone board transistors aged. In customer service, I later replaced all 2SC458s on the tone board with Motorola substitutes (with a 43025972 H/K in-house part number) to prevent recurrence of the noise. Also, the tone board was a double-sided board with feedthroughs from one side to the other. Those feedthroughs were notorious for failing, or becoming intermittent, requiring re-soldering. I used to re-solder all as a precautionary measure. Gaining access to anything, especially the tone board, was tricky if you were unfamiliar with it's dis-assembly. Repairing the output boards was mostly impossible without removal. I used to remove defective output boards and rebuild them outside the receiver. I had a stash of rebuilt boards to replace the defective ones and then devoted a couple days to rebuilding a bunch so I could just replace a defective board with a rebuilt board assembly. Brand new output board assemblies were never available. Each output board was identical but had different lead lengths and therefore were coded with numbers 1,2,3 & 4 to indicate installation location.

    As for the joystick, if everything is working correctly in the 900+, each channel will be equal in level and the joystick would be fine in dead-center. I thought the joystick idea to be quite ingenious. I don't know why anyone would have a problem with it.

    I'm not sure anyone would be interested in any of this information but it's been stored in my brain for many years and I'm happy to share rather than taking it to my grave, for anyone interested. I wonder how many 900+ receivers still exist on this side of a landfill.

    As for the 75+ and 800+, they were also designed by the H/K engineering team in the USA, but were custom manufactured by another company in Japan, not Crown.

    I currently own a 75+, an 800+, and a 900+, none are currently being used and not for sale. All were acquired by me long after leaving H/K.

    By the way, the 900+ pictured above has the incorrect tuning knob. The 900+ tuning knob was black. It looks like the one pictured came from a model 150+.

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    4morhktech, I'd be interested to know what the Motorola number was for the 43025972. I had a lot of noisy 2SC458s in an Akai quad 8track and replacing with a similar newer one (don't know the number offhand) helped, but not enough. Some day I plan to try all metal film to replace the carbon comp resistors (after replacing all caps for longevity) and see if that helps. If there was a known low-noise C458/ 123AP replacement I would get a bunch to keep on hand.
    Good information, thanks for sharing.

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Quote Originally Posted by quadsearcher View Post
    4morhktech, I'd be interested to know what the Motorola number was for the 43025972. I had a lot of noisy 2SC458s in an Akai quad 8track and replacing with a similar newer one (don't know the number offhand) helped, but not enough. Some day I plan to try all metal film to replace the carbon comp resistors (after replacing all caps for longevity) and see if that helps. If there was a known low-noise C458/ 123AP replacement I would get a bunch to keep on hand.
    Good information, thanks for sharing.
    It was a 2N3417, IIRC. They were general purpose devices used in a myriad of H/K products produced from the late 1960s into the late 1970s. They are not necessarily the lowest noise transistors available but they are magnitudes quieter than an aging 2SC458. And their reliability is high, they don't get worse with age. On the tone board of the 900+ they were fine. Be advised that the lead configuration is different than the 2SC458. The 2SC458 is ECB (when viewed from the beveled edge as the front, leads pointing down). The 2N3417 is EBC (when viewed from the flat part, leads pointing down). H/K bought the house-numbered 2N3417 in batches of at least 50,000. Not all were sourced from Motorola, however. Some came from National Semiconductor. They were fine too.

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Quote Originally Posted by Doug G. View Post
    Yup, a true beauty!

    Ah, Houses of the Holy. I will play it today on my system which, coincidently, has stacked Advents in each corner.

    EDIT: I think the 150+ was earlier because it seems they were around in the very early seventies and the 900+ was a little later. More towards the mid seventies.

    Doug
    Yup, the 150+ came out in 1972 and was discontinued in late 1974. The 900+ came out in 1973 and was discontinued in late 1975. There was an overlap when both models were being produced. The 900+ did not really replace the 150+. All remaining H/K quad models were discontinued due to lack of software support in late 1975... insufficient numbers of recordings were produced by the major record labels to support 4-channel hardware sales. As a matter of fact, H/K was supposed to come out with another quad receiver, the 700+. The 700+ was first destined to be built in Puerto Rico, then that changed to Plainview, NY. Production of the 700+ was canceled before it started (only a handful of pre-production prototypes were built). Some of the inventory of parts purchased for the 700+ was used to build the TA-600 stereo receiver in 1976 in Plainview. At the time, the TA-600 competed in a similar power/price range as the Japanese-produced model HK730. The TA-600 was conservatively rated 38W/chan while the 730 was 45W/chan. A great number of the US-made TA-600s were exported to European dealers because US-made products were hot ticket items there at the time. There are (or were) probably more TA-600s in Europe than the USA. Perhaps as many as 2000 TA-600s were actually produced. Not all of the 700+ parts were used up for production of the TA-600.

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    4morhktech - a HUGE thank you and QQ welcome to you! A big smile on my face reading your detailed first hand accounts about the HK quad receivers. It is holy grail stuff IMHO.

    As to the joystick for balancing, this was the most ingenius solution to control/adjust a quad soundfield IMHO. It simplified several decisions or adjustments into a single intuitive move. My first quad system was the 1972 Panasonic receiver and Q8 deck with the quad joystick balancer on a 20 ft cable. Using that was a lot of fun as you could solo out channels and concentrate on certain elements of the mix. That was an integral part to my quad listening fun and I missed it a lot with later gear. One day I may have one for my Marantz 4140 without taking a mortgage to get one.

    HK questions:
    1. Any idea why there was not an integrated quad amp issued? (if there was I'm not aware)
    2. Do you have any insights as to the HK 8+ quad cartridge deck? It was my favorite.

    Thanks again for joining our site.
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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Quote Originally Posted by 4morhktech View Post

    I'm not sure anyone would be interested in any of this information but it's been stored in my brain for many years and I'm happy to share rather than taking it to my grave, for anyone interested. I wonder how many 900+ receivers still exist on this side of a landfill.
    I am interested, and I am glad that you are sharing this information with us, although I don't really understand all the technical details, the H/K 900+ was the first piece of quadraphonic equipment I had ever seen, and is partly why I am into Quad...never saw a receiver with a joy stick before......that's when my journey began lol
    Last edited by 8trackman; 10-27-2011 at 04:29 PM. Reason: because I am stupid at times

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Quote Originally Posted by timbre4 View Post

    As to the joystick for balancing, this was the most ingenius solution to control/adjust a quad soundfield IMHO. It simplified several decisions or adjustments into a single intuitive move. My first quad system was the 1972 Panasonic receiver and Q8 deck with the quad joystick balancer on a 20 ft cable. Using that was a lot of fun as you could solo out channels and concentrate on certain elements of the mix. That was an integral part to my quad listening fun and I missed it a lot with later gear. One day I may have one for my Marantz 4140 without taking a mortgage to get one.
    I agree the remote is fun!.....sounds like I have the same system now that you did in 1972, I have all Technics/Panasonic gear.... haven't tried playing any quad vinyl yet buts its great for 8 tracks

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    You probably have REAL gear if Technics is involved! I had the very first (quite hissy) RE7750 receiver and RS 845US Q8 deck with the balancer. Nonetheless it brought me much joy when I was 14.
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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Quote Originally Posted by timbre4 View Post
    4morhktech - a HUGE thank you and QQ welcome to you! A big smile on my face reading your detailed first hand accounts about the HK quad receivers. It is holy grail stuff IMHO.

    As to the joystick for balancing, this was the most ingenius solution to control/adjust a quad soundfield IMHO. It simplified several decisions or adjustments into a single intuitive move. My first quad system was the 1972 Panasonic receiver and Q8 deck with the quad joystick balancer on a 20 ft cable. Using that was a lot of fun as you could solo out channels and concentrate on certain elements of the mix. That was an integral part to my quad listening fun and I missed it a lot with later gear. One day I may have one for my Marantz 4140 without taking a mortgage to get one.

    HK questions:
    1. Any idea why there was not an integrated quad amp issued? (if there was I'm not aware)
    2. Do you have any insights as to the HK 8+ quad cartridge deck? It was my favorite.

    Thanks again for joining our site.
    1. I had nothing to do with marketing so the answer is just a guess on my part. Bear in mind that a receiver is nothing more than an integrated amplifier with an AM/FM tuner built in. At that time most customers opted for a receiver than an integrated amplifier. Since they marketed a series of quad receivers, why build one minus the AM/FM tuner? It probably would have been a sales dud just like the few integrated 2 channel amplifiers from that time period. Remember that marketing wants to concentrate on products that the majority of people want to buy.

    2. I did not work on any tape equipment at H/K so my experience was limited to receivers, amplifiers, tuners, and preamps. There were other techs that specialized in tape products. I knew of the 8+ but never used one. I don't think the 8+ was a very popular product.

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    Senior Member Quadrockasaurus's Avatar
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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    4morhktech....another big thanks for taking the time to give us all this useful info on the 900+ (...and related) Quad units....

    I'm assuming then, by the info that you've given, that the "Williamsons Model 128" receiver I listed in my original post is one of those "after the fact" counterfeit 900+ units you mentioned...and not the real McCoy.

    FYI - found that info in an obscure post/thread in Audiokarma from a AK member in (..I think) Hong Kong.

    Cheers.

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Quote Originally Posted by Quadrockasaurus View Post
    4morhktech....another big thanks for taking the time to give us all this useful info on the 900+ (...and related) Quad units....

    I'm assuming then, by the info that you've given, that the "Williamsons Model 128" receiver I listed in my original post is one of those "after the fact" counterfeit 900+ units you mentioned...and not the real McCoy.

    FYI - found that info in an obscure post/thread in Audiokarma from a AK member in (..I think) Hong Kong.

    Cheers.
    I posted a followup to that topic on AK last evening. Those relabeled 900+ are most likely from that batch of overproduced units from Crown. I would love to see a photo of the front and back (and anything else) of any relabeled 900+. Crown had taken the liberty of producing more product than ordered assuming they would be ahead of schedule on the next batch. H/K canceled the order for more units and Crown was left with a sh*tload of unsold product. First, H/K labeled 900+ started showing up for servicing at warranty stations without US installed modifications (to the CD-4 board), then lots of orders came in for owners manuals (that were typically packaged with the 900+ in Plainview, NY). This raised a red flag about the unauthorized units. One of the warranty stations shipped a counterfeit to the National Service Manager for evaluation and a notice was sent to all warranty stations to disallow warranty claims on the counterfeit units. The National Service Manager advised me to bring any to his attention brought in to H/K that slipped through the cracks in the receiving department. I saw a few suspects over the years (with H/K labeling) but it was a non-issue because they were repaired out-of-warranty. H/K was primarily interested in not having to pay warranty stations for repair of non-authorized units. From what I heard at the time, Crown was in bankruptcy, and the trail from trading company to trading company in Asia made litigation over it very difficult and the issue was mostly forgotten. All of the H/K personnel knowledgeable about the situation gradually left H/K or passed away, so by now you won't find a single currently employed Harman employee even aware of it today, or even care this long afterward. It only lives on here in discussion forums. But I have always wondered what happened to the bulk of the counterfeits. Now the puzzle is coming together for me.

    Other than the fact that the counterfeits were not produced under H/K's authority or that H/K made a single dime from them, the counterfeits should be every bit the same as those sold legally under the H/K brand, with the exception that they don't have the small CD-4 modification board added to the CD-4 circuit. They were, after all, produced in the same Japanese factory as the legit units. However, the re-branded units may have additional changes that I'm not aware of.
    Last edited by 4morhktech; 10-27-2011 at 01:59 PM. Reason: 2nd paragraph added

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    Senior Member Quadrockasaurus's Avatar
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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Quote Originally Posted by 4morhktech View Post
    As a matter of fact, H/K was supposed to come out with another quad receiver, the 700+. The 700+ was first destined to be built in Puerto Rico, then that changed to Plainview, NY. Production of the 700+ was canceled before it started (only a handful of pre-production prototypes were built).
    Just curious....

    ....did any of the prototype 700+ units survive...?? Do any images exist..or brochures printed??. It sounds like that unit got pretty close to production, and I've noticed that with some other brands (..Astrocom, CM Labs, Marantz..etc) brochures were printed, or magazine images exist for stuff that ended up ultimately not being produced....
    Last edited by Quadrockasaurus; 11-03-2011 at 05:15 AM.

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Quote Originally Posted by Quadrockasaurus View Post
    Just curious....

    ....did any of the prototype 700+ units survive...?? Do any images exist..or brochures printed??. It sounds like that unit got pretty close to production, and I've noticed that with some other brands (..Astrocom, CM Labs, Marantz..etc) brochures were printed, or magazine images exist for stuff that ended up ultimately not being produced....
    It's very possible one or more prototypes could have ended up in the possession of former employees. They used to have sales to employees of obsolete models. But there weren't too many to begin with and there were functional problems that may not have been corrected, if the project was cancelled. It's very possible that they were just scrapped. I don't recall seeing any brochures but that doesn't mean they weren't printed.

    Externally, the 700+ looked very similar to the 800+ and was in approximately the same power output (per channel) class. Internally it was quite different than the 800+ and was to be produced in the USA.

    Had the consumer demand for quadraphonic products not sunk to a low in 1975, functional problems would have been corrected and the model would certainly have gone into production as planned. Instead, engineering reworked the whole design into the TA-600 (2 channel stereo) to use up as many of the production parts already in stock. But even the TA-600 was not produced in quantities sufficient to use up all 700+ parts. Many of the remaining unused 700+/TA-600 parts were sold off to surplus brokers when the 55 Ames Ct facility in Plainview was closed in 1980.

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Cheers....Thanks again for the info....

    P.S. An image below for anyone wondering what the (Stereo) HK TA-600 Receiver receiver looks like....

    Harman Kardon TA-600.jpg

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Quote Originally Posted by Quadrockasaurus View Post
    Cheers....Thanks again for the info....

    P.S. An image below for anyone wondering what the (Stereo) HK TA-600 Receiver receiver looks like....

    Harman Kardon TA-600.jpg
    Thanks, Quadrockasaurus, for posting that photo. It gives interested parties insight into the reason for the existence of the TA-600. It would never have been produced without the need to mitigate the financial losses of the canceled 700+.

    It should seem obvious that the front panel was initially intended to have the joystick in the right hand compartment where the function lights and tape monitor jacks now reside in the TA-600. The appearance of the 700+ prototypes was exactly like the TA-600, except the joystick took up the space on the right side just like on models 75+, 100+, 150+, 800+, and 900+.

    Another bit of trivia: There were a few incomplete prototypes built of another model, the A-600. The A-600 was a 2 channel integrated amplifier on the same 700+ chassis and similar front panel with 2 illuminated VU meters for each channel behind the blackout dial where the AM/FM dial scale exists on the 700+/TA-600. The A-600 was basically a TA-600 without the AM/FM tuner. I own one of the incomplete prototypes. The A-600 never went into production. Sorry I don't have a photo of it, and since it is incomplete, it lacks the final appearance most folks are interested in seeing anyway.

    You might have already guessed that in assigning model designations, the "TA" prefix for a receiver model stood for "Tuner-Amplifier", just as "A" stood for "Amplifier", and "T" stood for "Tuner". Those prefixes applied from time to time (but not always) throughout H/K's history from the beginning.

    By the way, the TA-600 had a very nice FM tuner section. It was far superior in performance to the tuner section in the 75+ & 800+ in terms of sensitivity and adjacent-channel selectivity.

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    This is a picture of my Harman Kardon 900+ receiver. This is what it looked like when I took the picture a while back and posted it on another internet forum.



    It looks like somebody photoshopped my image and posted it at the beginning of this thread. Whoever edited my original image did a nice job of making it bigger and eliminating the background.

    My Harman Kardon 900+ was the first quadraphonic receiver that I ever owned. I bought it used from a second hand Hi-Fi store in 1984 for $100. The store owner told me that it had a bad channel. As it turned out that was one of many problems. I learned a lot working on the 900+ because it had a whole host of problems, some strait-forward and some a bit more subtle. Trying to find lamps for it was not easy. Even back then Harman Kardon no longer stocked replacements.

    Thank you 4morhktech for your helpful comments. I sure wish I could have picked your brain back when I was working on my unit. As it so happened the tuner section just went out again. Besides the noisy 2SC458 transistors, were there any other common problems? How well did the CD-4 decoder work? I have never been able to get mine to work well. Was there any common failure mode for the amplifiers?
    Last edited by tcdriver; 06-04-2012 at 05:46 PM. Reason: removed comment about borrowing image

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    Default Re: RCVR: Harman Kardon 900+ Quadraphonic Receiver

    Quote Originally Posted by Disclord View Post
    I can't tell from the picture if any of the buttons are labeled as such, but did the built-in SQ decoder have any form of Logic, either Full Wave-Matching w/Front-Back (or F/B alone) or Full Logic with F/B Vari-Blend?
    It has no logic circuit. The SQ decoder was made using discrete transistors, resistors and capacitors.

    From a harman/kardon 800+ - 900+ product brochure:

    “The SQ matrix design of these receivers is of distinct professional quality. It employs the highest grade components with super-close tolerances unprecedented in a home music system. Indeed, it follows the close tolerances of the original CBS professional decoder, rather than the less stringent standards often used for receiver manufacture. The result is a superiority immediately discernible even to the untrained ear.

    The matrix system incorporates an eight pole filter rather than the less effective four pole type in most competitive systems. The eight pole filter ensures the “localization” of instruments and voices so that they appear precisely where they should through the appropriate speaker.

    Your choice of SQ MATRIX 1 or SQ MATRIX 2 enables you to treat a symphony orchestra, a rock group, a string quartet or a solo voice with the difference they each deserve.

    In addition, the separation coefficients of SQ MATRIX 2 are virtually those of the “universal matrix decoder”. Thus, these receivers are able to play back recordings made with all matrix systems (SQ, QS and EV) with accuracy, spaciousness and clarity.”


    From ad copy published in High Fidelity, January 1974:

    “IT’S AS FAR AS YOU CAN GO.

    If you’re up with what’s happening in the High-Fidelity industry you’ll know harman/kardon is currently producing the world’s most advanced receiver line.

    This 900+ is the cream of that line.

    It carries both discrete and matrix four-channel circuitry. So it will reproduce every type of quadraphonic music available. Most four-channel receivers carry only one.

    The 900+ puts out an astonishing 32 watts per channel, continuous, with all channels driven simultaneously. That’s a good deal more power per channel than many stereo receivers can muster.

    The 900+ does not weasel through the problem of stereo record reproduction by merely shutting off the two rear speakers. Instead, it uses a unique phase shift network to produce an enhanced stereo sound through all four speakers. Your stereo record library will sound better than ever.

    Built into this remarkable machine is an analog computer that distinguishes between music and noise on FM signals. No other receiver can pin down a station with such hair-splitting accuracy.

    And like other harman/kardon products, the 900+ carries ultra wideband circuitry. This ability to reproduce frequencies you cannot hear, significantly improves the characteristics of those frequencies you can hear. harman/kardon products are world famous for their fidelity. If you are in quest of the perfect sound, this could be what you’re looking for.”



    harman/kardon 900+ Specifications from a brochure:

    Power Output (stereo mode): 90 watts min. RMS per channel, both channels driven into 8Ω from 20Hz. to 20kHz., with less than 0.5% THD.

    Power Output (4 channel mode): 30 watts min. RMS per channel, both channels driven into 8Ω from 20Hz. to 20kHz., with no more than 0.5% THD.

    Power Bandwidth: From 10Hz. to 40kHz. at less than 0.5% THD into 8Ω, both channels driven simultaneously at 45 watts per channel.

    Frequency Response: From 4Hz. to 70kHz. at less than 0.5% THD into 8Ω, both channels driven simultaneously at 1 watt per channel.

    Square Wave Rise Time: Better than 3ÁS.

    Square Wave Tilt: Less than 10% at 20Hz.

    Total Harmonic Distortion: Less than 0.5% from 250 milliwatts to 45 watts RMS, both channels driven simultaneously into 8Ω from 20Hz. to 20kHz.

    Intermodulation Distortion: Less than 0.15% at rated output.

    Hum and Noise: Better than 75dB below rated output.

    Damping Factor: 30:1 at 8Ω

    Tone Control Action: +/-12dB bass boost and cut at 50Hz. +/-12dB mid-range boost and cut at 1kHz.. +/-12dB treble boost and cut at 10kHz.

    Dimensions: 20 1/8 W x 17 D (including knobs) x 6 ╝ H (including feet)

    Weight: 45 pounds [20.4kg]
    Last edited by tcdriver; 06-04-2012 at 06:39 PM. Reason: correct spelling, logic question answer

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