On The Right Frequency
Article was published in Hi Fi World June 2012 edition
Japanese giant Hitachi has developed some cutting edge audio technology over the years and are famous for the power MOSFET transistor. Here Haden Boardman looks at their skills in FM synthesised radio, with the FT-5500 tuners.
Hitachi is one of those mega corporations it is difficult to completely understand from a Western point of view. Actually pronounced "sta'chi" in Japanese, the company is simply massive, one of the biggest in Japan. Set up back in 1910, as a coil winder and motor maker, they are more famous outside of audio for Bullet trains, boats, and power stations! Even today, the company is simply huge. Like Sony, the company's first foray into audio electronics was a simple six transistor radio back in 1958. But Hitachi became a major player throughout the late nineteen seventies and early nineteen eighties. The company developed a 'core' of
large scale integrated circuits (LSI) which became very applicable across the entire audio industry, used by virtually every other Japanese maker, and a many UK companies as well. Early synthesiser tuners have a very bad reputation for strange 'whistles' and back ground noises. But really they should not. FM radio is quite simple: you have an 'RF' stage to amplify the small radio frequency signal, an 'oscillator' stage, which is the bit usually varied when we tune in an FM radio, this is 'mixed' with the incoming 'RF' signal.Vary the oscillator, and you vary the 'mix' output.This is fed in to an 'IF' or'intermediate frequency' stage. The 'IF' stage has a very narrow bandwidth, traditionally tuned to 10.7MHz, which filters out
all the rest of the stations outside of its bandwidth, allowing just the frequency 'tuned in' to pass through. Say you want to tune in to 107 MHz, setting the oscillator to 10 MHz (107/10 = 10.7) would allow that frequency to pass through the 'IF' strip. The final radio stage is the demodulator, where the frequency modulated signal is demodulated and the audio signal appears, in mono plus stereo difference information. The Stereo Decoder finally outputs a stereo audio signal! On synthesiser tuners the oscillator is rock-like stable (usually Quartz crystal locked); on earlier tuners, the oscillator can (and will) drift causing tuning to fluctuate. Complex circuits control the
synthesiser circuits and they make auto tuning and presets possible. Where a lot of early tuners made a mess was in cramming in the direct read out fluorescent tube displays (FTD), and it is the necessary drive electronics here which caused all the noise, commotion and audio interference. The two Hitachi FT-5500VHF/ FM tuners covered here represent the main stay of the nineteen eighties Hitachi designs (there was also a later FT-5500MD, part of a 'high end' 360mm wide system with wooden end cheeks - technically this is a shrunk MKII). Both have a strong reputation, but which is the best sounding? A recent investment in a Blake Eight Element FM antenna has allowed enough signal to be split between two radio sets, making comparisons a mere flick of the input switch! Technically there is not a great deal between these tuners. They both feature Hitachi's 'FCCS'
"The strong reputation these two models have earned does seem justified"
Field Condition Computer System, which automatically sets the RF gain and, if necessary, narrows the IF strip (this is not a great thing for the sound, but handy on weak stations). With the MKI you can do this manually.The MKII does it when you store in the preset memory bank. The MKII boasts a direct decibel readout of RF signal strength and this was pretty accurate, the MKI has a more crude moving coil meter. Other than that the MKII is black anodised, where the MKI is finished in a nice copper bronze, which I quite like. You are always at the mercy of the broadcasters with radio, but I was lucky to catch a couple of live performances, and was quite pleased with the results... Most listening was conducted with the BBC nationals, with the odd sojourn to Classic FM and Smooth Radio. Sound wise, there was a certain 'house sound' to both tuners.They are slightly soft in the treble, clean, noise free, but easy on the ear. Bass on both units had a slightly warm edge, a mild 'woolly' quality. Midrange was clean and defined, stereo image slightly restricted compared to references (a surprise seeing one of Hitachi's own chips, the HA I 156 is one of the most popular FM decoders ever). RF performanc
was similar on both, the MKII seemed to sulk a bit more on strong signals (other people have reported the reverse), the MKI exhibiting no problems. Neither set had any background noises or whistles, even on quite hard-to-reach stations. Hiss was similar on both. Sound wise, the MKI was much more open and organic sounding than the later tuner. This may seem a bit of a surprise, but is not considering differences between the two units.The MKII was slightly more 'tailored' in its sound than the
MKI.There are several 'mods' about which would remove and replace the post stereo decoder audio filtering and output stage responsible for this 'house sound'. Frankly, I do not feel it worth the effort or expense. Lifting the lid, on the inside, the reason for the differences between the two became more obvious.The MKI is based around a cornucopia of Hitachi chips, the MKII shares the same chassis and lid, but the main printed circuit board is populated with devices from another Japanese giant Sanyo... presuming Hitachi had licensed them to make their technology would be speculation on my part, and the board does look like it was engineered by the same designer chaps... but other than the engineered 'house sound' these are two totally different tuners. In fairness, both tuners are very good sounding.A comparison to a still in production RDS tuner at the £300 mark saw both units winning by a comfortable amount, it was actually embarrassing. So for those seeking a really inexpensive, modern preset tuner really should consider one of the FT5S00 models. Repair and service wise there is nothing much to worry about. Set up and alignment is pretty bullet proof, I have never seen or heard of
a faulty one. Both use a small 'back up battery' for station memory (just about visible in our pictures - on both of these tuners, the little thing was still working). If you do find a faulty one, it is simply not worth dealing with. Supply of these units is very plentiful, they sold lots, and they sell second-hand anywhere from less than a fiver, to fifty quid tops, more on cosmetic condition than anything else. The strong reputation these two models have earned does seem justified in comparison to the 'new' tuner test. The MKI is the better sounding unit of the two by a length, but it is far from night and day, more down to condition and price... and the best thing about the pair of them is the low price and performance offered for the cost of a gourmet coffee and cake!