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Hifi Review Harman Kardon Signature Series Harman Kardon is a name long associated with high fidel­ity sound reproduction and they’re still going strong with the release of their Signature Series – a 200 watt per channel power amplifier and a Dolby Surround Processor/ Tuner. We recently had a chance to have a close look at both of these products. Actually there are three products in the Signature Series range, the two already mentioned and a 5-channel Surround Sound amplifier. While the two power amplifiers are fairly con­ vention­ al, the Signature Series 2.0 Dolby Digital Surround Processor/ Tuner is quite different in that it packs all sorts of features into a case which has few external controls. In fact, it has just nine pushbuttons and a large knob as its control comple­ment. The real control complexity is “hidden” and only becomes evident as you use the remote control and the menu system on the front panel display. The remote control has quite a good layout of buttons, 61 in all, which are easy to read – an important point. The labell­ ing on some remotes is 4  Silicon Chip very difficult to read, especially in subdued light and you wonder if the designers have ever used them in a typical home situation. One feature that we particularly liked was the “sending” LED which flashes whenever you push a button. It is amazing how often a TV set or other appliance will not respond to a remote command and you immediately wonder whether the set is at fault or the remote. With this Harman Kardon remote, at least you know that it is “sending” the command. Since this Processor/Tuner is designed to be the heart of a Surround Sound system, its remote handset should ideally control the TV set or video projector and the VCR or DVD player, as well as any other sources such as CD player and tape decks. For this reason, the remote control is a “learning” type and so it can learn all the other remote control functions. This is good be­cause if you do have a full Surround Sound system, you don’t want to be juggling three or four remote controls. While the front panel of the Processor/Tuner is sparse, the rear panel is crammed with lots of input and output sockets to handle audio and video signals from a wide range of sources. Six pairs of audio analog (line level) sources, such as CD players and tape decks, can be selected and these can be paired with three composite video inputs or two S-video inputs. This means that sources such as hifi VCRs, DVD and laserdisc players can be fully con­trolled. Up to six separate digital program sources may be connect­ed, via four coax and two optical data inputs. As well, you can connect the six Surround Sound decoded outputs from another source (should you be so well-heeled) so that you have centra­ lised control of everything via the remote handset. There are also two pairs of outputs for connection to tape decks and six outputs for surround The apparent simplicity of the Harman Kardon Signature Series 2.0 Processor/ Tuner belies the complexity of its features. This is reinforced by the array of input and output sockets on its rear panel. sound; ie, left & right front, centre, rear left & right and subwoofer. Mind you, there is one input omission which may or may not be a drawback, depending on the program sources you normally use. If you like listening to vinyl records, you will need an external preamplifier for the magnetic cartridge signals. As well as all the audio inputs and outputs, there are antenna connections for AM and FM stereo tuners, an RS-232 socket and sockets for IR remote and trigger control signals. As you can imagine, when the majority of these inputs and outputs are in use, the result is a mass of cabling but the real complexity lies in the circuitry inside the Processor/Tuner. Not only does it provide Dolby Digital (AC-3) and Dolby Pro Logic processing and digital to analog decoding of purely digital sources, it also makes use of the RDS data system in use in Europe although this is of no use in Australia. Naturally, in line with other Dolby Pro Logic decoders, the Harman Kardon provides a full range of theatre sound modes (four), music modes (also four), plus stereo, mono and mono plus. The latter is a mono mode for Dolby Digital. We don’t know why you’d want it, but there it is. When using a Dolby Digital source, there is even a “late night” mode which while maintaining full signal bandwidth, reduces the peak audio levels to one quarter or one third of normal. We interpret this as a reduction in peak levels of 10 to 12dB, a significant decrease. Harman Kardon refer to this as the “good neighbour” since it mutes loud audio transients such as explosions or musical crescendos. Just to show how complex the Processor/Tuner is, the ow­ner’s instruction manual has no less than 65 pages (all English). This impression of complexity is reinforced when the top cover of the case is removed, revealing a myriad of integrated circuits and LSIs dotted over a number of large PC boards. Even the power supply is quite complex, employing two The remote control has lots of buttons but is fairly self-explanatory in use. The Harman Kardon Signature Series 1.5 stereo amplifier is well finished, with an absolute minimum of ornamentation. December 1998  5 TOP: inside the Harman Kardon amplifier, showing the large toroidal power transformer and the heatsink fabricated from sheet alumini­um. The rear panel view is shown above. E-I transformers with copper straps around them to reduce hum radiation. Stereo power amplifier By contrast with the Processor/ Tuner unit, the Signature Series 1.5 power amplifier is simplicity itself. But it is large, and heavy. It measures 438 x 191 x 387mm and weighs 21.4kg. Apart from the on/off switch and a power indicator, the front panel is devoid of any ornamentation. The back panel is pretty sparse too, with just two pairs of loudspeaker terminals, two RCA input sockets and a 6  Silicon Chip socket for a trigger control, referred to earlier. There is also a small slide switch to provide bridged operation of both channels. Sparse it may be, but this is an impressive unit, especial­ly when you remove the top cover. This reveals a large toroidal transformer mounted vertically against the front panel. This may seem unconventional but as we found with our own 100W/channel amplifier published in February 1988, this arrangement gives minimum hum pickup in the two audio channels. As far as we can tell, the pow- er transformer has separate centre-tapped secondary windings to effectively provide two completely separate power supplies to feed the two power amplifi­ers. This arrangement maximises channel separation although it does mean that more components are required; ie, an additional bridge rectifier and filter capacitors. The power amplifier circuitry itself is largely hidden from view by the very large heatsink which occupies most of the chas­sis. The heatsink is interesting because it is not the usual large aluminium extrusion but has been fabricated from sheet aluminium. The chassis and top cover have been well and truly perforated to provide plenty of ventilation for the heatsink, so that no fan is necessary. As far as we can tell, the Harman Kardon power amplifier employs bipolar transistors throughout and has separate relay muting for each channel. As well as the main power transformer, there is a separate smaller transformer and power supply board and this evidently provides the standby function, so that the power amplifier itself can be switched on and off by a trigger signal of between 6V and 12V from the Processor/Tuner unit. The Harman Kardon amplifier is rated at 200 watts per chan­nel into 8Ω loads and 325 watts per channel into 4Ω, for a rated harmonic distortion of less than .03%. In bridged mode, it will deliver 650 watts into an 8Ω load, again for a rated distortion of less than .03%. While being delightfully vague about circuit configurations (ie, they tell you nothing), Harman Kardon emphasise that they only use a minimum of negative feedback to achieve their amplifi­er performance. The implication is that lots of negative feedback is somehow “bad” and the less feedback, the more merit in the design. They state that the negative feedback in the amplifier is less than 25dB. Naturally, we don’t agree with this approach. If using lots of negative feedback achieves high performance, then it is all to the good, as far as we are concerned. Harman Kardon’s figure of 25dB probably applies to the overall negative feedback from output to input but in our experience, any amplifier design which performs well and uses little overall negative feedback actually uses lots of SILICON CHIP This advertisment is out of date and has been removed to prevent confusion. The interior of the Processor/Tuner is complex indeed, with lots of ICs, LSI chips and surface mount devices. local negative feedback around each stage. Often this feedback may take the form of emitter degeneration or lag compensation but it is feedback nonetheless. So while we would not criticise an amplifier with low over­all negative feedback just because the designer took that ap­proach, we do think it is doing it the hard way. The other notable feature of the Harman Kardon amplifier is its very high output current capability and this amplifier is rated at ±130A. Again, while we don’t think high current capability is bad, we cannot see why any amplifier of this power rating could ever need to deliver a peak current in excess of 125 amps. To explain further, a power ampli- AUDIO PRECISION SCTHD-W THD+N(%) vs measured 10 LEVEL(W) 21 AUG 98 10:54:28 ELECTRONIC COMPONENTS & ACCESSORIES •  RESELLER FOR MAJOR KIT RETAILERS •  PROTOTYPING EQUIPMENT •  CB RADIO SALES AND ACCESSORIES 1 •  FULL ON-SITE SERVICE AND REPAIR FACILITIES •  LARGE RANGE OF ELECTRONIC DISPOSALS (COME IN AND BROWSE) 0.1 0.010 M W OR A EL D IL C ER O M E Croydon Ph (03) 9723 3860 Fax (03) 9725 9443 Mildura Ph (03) 5023 8138 Fax (03) 5023 8511 Truscott’s 0.001 0.5 1 10 100 300 Fig.1: harmonic distortion versus power into 8Ω loads, with both channels driven. Distortion is well below the rating of .03%. ELECTRONIC WORLD Pty Ltd ACN 069 935 397 30 Lacey St Croydon Vic 3136 24 Langtree Ave Mildura Vic 3500 December 1998  7 AUDIO PRECISION SCTHD-W THD+N(%) vs measured 10 LEVEL(W) 21 AUG 98 13:56:00 1 0.1 0.010 0.001 .0005 0.5 1 10 100 500 Fig.2: harmonic distortion versus power into 4Ω loads, with both channels driven. Distortion is still well below the rating of .03% while maximum power is more than 360W. AUDIO PRECISION SCTHD-W THD+N(%) vs measured 10 LEVEL(W) 21 AUG 98 12:12:52 1 0.1 0.010 0.001 .0005 0.5 1 10 100 1k Fig.3: harmonic distortion versus power into an 8Ω load in bridge configuration. Maximum power before clipping is over 700W. fier rated to deliver 200 watts into an 8Ω load will have a peak output voltage of ±56.6V. In order for it to deliver 125 amps, the load im­pedance would have to drop to below 0.45Ω or 450 milliohms. Now we know that some loudspeakers have very nasty dips in their impedance curves but we have never 8  Silicon Chip come across one that dipped below 1Ω. And any loudspeaker with such a dip in impedance would have to be regarded as a bad design anyway, not worthy of being connected to high quality equipment such as this. Test results Testing this elaborate equipment was neither simple nor quick as there were so many functions to look at. In the end, we had to be realistic and be content to test only a few functions of the Processor/Tuner while being much more comprehensive in testing the stereo power amplifier. In short, we were able to confirm all the specifications of the Processor/ Tuner that we actually tested and can state that it is fairly conservative in its ratings. Total harmonic distortion is quoted as less than .03% from 20Hz to 20kHz and it easily meets that as it does for its frequency response rating of 20Hz to 50kHz within ±0.5dB. For the Harman Kardon power amplifier, we easily confirmed the power ratings, as the accompanying power/distortion curves demonstrate. Harmonic distortion was typically below .01% which is considerably below the rated figure of .03%. The power amplifier is very quiet as well, delivering a figure of -116dB (unweighted) with respect to 200W and -120dB A-weighted. Its frequency response is very wide and is only 2dB down at 200kHz. Listening tests confirm that this is fine equipment indeed but where it really performs is on music that “begs to have the wick turned up” such as full symphony orchestral performances and on pipe organ. This reviewer is a fan of Wurlitzer theatre organs and when playing this material, the Harman Kardon amplifier is simply awesome. Mind you, you do need speakers to handle the power and a large listening room to really enjoy it. Overall, we were very impressed with the Harman Kardon Signature Series equipment. The stereo power amplifier is beauti­ fully engineered and has bags of output power while the Proces­ sor/Tuner is a technical tour-de-force, with more than enough facilities to satisfy the requirements of the most comprehensive home theatre sound system. Recommended retail prices are as follows: Signature Series 2.0 Processor/Tuner $4395; S/Series 1.5 stereo amplifier $2895 and S/Series 2.1 5-channel power amplifier $2995. For further information on the Harman Kardon Signature Series products, contact the Australian distributors: Convoy International Pty Ltd, Unit 7, Discovery Cove, 1801 Botany Road, Botany NSW 2019. SC Phone (02) 9700 0111. MAILBAG Technology disposal to cry about I’d like to make some observations and comments regarding your editorial in the September 1998 issue. First, as an amateur constructor, designer and would be trainee electronics tech, your notes hit the mark perfectly. I regularly scour the tips in this area looking for items of “junque” that may be either recycled, repaired or experimented upon. You would be flabbergasted at the treasures that surface at more than regular intervals. However, nothing can be got for free these days so a token payment to the salvager who owns the rights to the tips I scour sees me get away with some awesome bargains. For example, the desk at which I’m sitting ($20) is fully electronically height adjustable, weighs 160kg and cost me less than 5 cents to repair (a roll pin). It cost $2000 new! The 15inch SVGA monitor ($3) I’m looking at cost the price of 25mm of 0.8mm solder to refix the data input plug to the main board, courtesy of the Queens­ land Education Department. The 586/100 ($6) that’s doing the number crunching cost $100 for a used 210Mb HDD, courtesy of an unnamed national company. I’ve since added a 32X CD-ROM, 1.2Mb 5.25-inch floppy, sound card, more RAM (from 12Mb to 16Mb), PCI video card and a BJC255SP printer, all new at retail prices. Oh! I almost forgot the gas strut office chair ($5) re­ p aired with a 20-second burst of the MIG welder. How’s that? What I’ve just described has taken me some two years to complete and doesn’t happen every day. Every other day sees 386, 286 and XT computers, monitors from mono to SVGA, washing ma­ chines, stereo components (wow, that’s another story!), lawn mowers, whipper snippers, lashings of various parts, reusable timber, glass panes, light fittings, heavy timber doors, tele­phones, hand and electric tools and small stationary engines (some brand new!) added to the list. I’m not kidding! Now for the frightening part. How about computers that have become superfluous to company needs for whatever reason(s) that still have (working) hard drives installed, from financial insti­ tutions, accountants, hospitals, homeowners, etc. I’m not kidding! How do I know? The hard drives are still full! I wipe ’em and sell ’em but the information on some of them would make your eyes pop! What can one do with such “ancient technology”? This is not my idea but I thought it was a beauty. I discovered a book by R. A. Penfold (Babani Electronics Books BP272) entitled “Interfacing PCs and Compatibles” that describes in detail the use of 74LS138 decoders and 82 (C)55 PPI (Programmable Peripheral Interface) to interface computers with external I/O for use with relays and data-logging circuits using BASIC programming. My specific use for this is a watering system for my yard, presently switching 24 taps at programmed intervals to water my 6-acre yard. Another good point is the use of my 586 to do the program­ming and compiling to an EXE file This is then copied to a boot disk and fired up using the autoexec.bat file right after the computer boots. Once the bugs are ironed out, the 286 I use for the inter­ facing can use a floppy to boot up – no hard drive or monitor is needed, just a keyboard and video card. S. Clavan, Black River, Qld 4818. Old PCs needed for schools I write with regard to your editorial in the September 1998 issue of SILICON CHIP. Yes, there is a need and use for 386/486 vintage computers. I am an electronics, systems technology, robotics teacher (secondary) who could use such machines. My primary use would be to run the many programs that work quite happily with Windows 3.1 – pro­grams such as LEGO Control Lab, PC Logo, Intellecta and the Softmark interface project from the last issue of SILICON CHIP, to mention but a few. My secondary uses would be to teach computer repair and upgrade skills to students. I believe some local schools are already into this activity. To emphasise the need, this year my school received a dona­tion of 4 x 486 computers, without monitors, mice or keyboards from Alcoa. Setting up the computers with monitors, etc, broke our budget and we may be able to find enough money with P & C help next year to provide software and site licences. I am at a reasonably well-off secondary school in Perth but there are many other schools not so well off, especially the smaller primary schools (and country schools) who could also put such computers into productive classroom activities. To your readers, if you have such computers to give away, please contact your local schools. M. Callaghan, Maddington, WA. Old computers are not useless I found your editorial on old PCs very thought provoking, to the point that I am tempted to put pen to paper – electronically speaking, that is. In my semi-retirement I have made up many inexpensive com­puters from leftover parts for friends and those who cannot afford the latest technology (ie, $50 286s) with which they can accomplish almost anything apart from playing fast RAM-hungry games and perhaps running some of the high-end business graphics. I am amazed that the Educa­ tion Departments have seen fit to issue Pentiums to our schools when those in the USA are quite content to utilise other depart­ments’ outdated models, which in this country are virtually given away to stunned bidders at local auctions! Is Australia really so afflu­ent; can we actually afford it? Thus, in answer to your editorial, I do not find those unloved machines useless – they are indeed a most useful tool and teaching aid. Dare I suggest that the educa­ tors of this country think again before squandering huge sums on machines that really are not necessary in the circum­stances? J. Harding, Lauderdale, Tas. December 1998  9 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au