Cassette Decks: Marantz SD-460

September 4, 2008

I purchased this autoreverse cassette deck at a secondhand shop in London’s Notting Hill District for something like 40 quid. It looked hardly used but someone had removed the cassette load door. Happily my local HiFi shop managed to order one for me, and it fitted nicely.

The autoreverse feature of these decks are typically scorned at by some cassette users for having a detrimental effect to the sound. There are two possible choices for tape head configuration – either use a 4-track head and switch pairs in-use depending on the direction of the tape, or use a 2-track head and spin it around on a little platform to again match the tape direction. There is also the complication of driving the correct reels, providing twin capstan rollers, sensing tape type and overwrite protection, adding an erase head (or two!) and ultimately maintaining good speed stability and audio fidelity

I’m happy to say my SD-460 performs well in this respect, and is reliable to this day. This is even more remarkable given that the great Dutch Royal firm of Philips was in ownership of Marantz when this deck was built – and their traditional cost cutting which fails other Phillips products hasn’t taken it’s toll with this one 🙂


Cassette Decks: Yamaha KX-300

May 13, 2008

This is my preferred deck for recording cassettes – and was used mostly with TDK Chrome soundalike “SA90” series of tapes for best results recording either from vinyl, radio or CD. I never got into using ‘Metal’ formulation tapes – their price put me off!

IMG_1743

The single directional tape transport of the KX-300 is soft touch controlled by switches and also an optional infra-red RS-K3 remote control (top right!) allowing easy use of the track search and phrase repeat features found more commonly on CD players. The motor drive is stable and mostly forgiving of slightly warped cassette bodies 🙂

Yamaha KX-300 Specs

Motor

Capstan – DC servo motor

Reel – Flat torque DC motor

Heads

Recording / Playback – Amorphous

Erase – Double Gap Ferrite

Wow and Flutter

WRMS – less than 0.05%

W.Peak – less than +/- 0.08%

Signal-to-Noise Ratio

(Dolby NR off) – better than 60 dB

(Dolby B NR on) – better than 68 dB

(Dolby C NR on) – better than 76 dB

Frequency Response

Normal tape (-20dB) – 30 to 17,000 Hz +/- 3dB

Chrome tape (-20dB) – 30 to 19,000 Hz +/- 3dB

Metal tape (-20dB) – 30 to 20,000 Hz +/- 3dB

Harmonic Distortion

(315 Hz, 3rd) – no more than 1%

Channel Separation

(3150 Hz) – 40 dB

Crosstalk

(125 Hz) – 55 dB

As well as Dolby B and C Noise Reduction, this deck features a headroom extension system called ‘Dolby HX Pro’. This is a worthwhile improvement that increases the upper limit of frequencies that can be recorded on most type of tape. The Dolby HX Pro circuit does this by dynamically reducing the level of bias signal added when recording high frequencies that are known to have a self-biasing effect.

So what is this bias stuff about then? Well, in analogue tape recording a bias signal (a single frequency of roughly 100 kHz) is added to ‘help’ the magnetic particles on the tape into behaving linearly to the audio signal excitation coming off the recording head.

For good recordings the level of bias applied is important.

With too little bias, or none – as it was before this high frequency recording technique was discovered by the Germans during WWII – the tape formulation’s magnetic particles don’t properly align to represent the original signal level resulting in playback distortion. With too much bias signal, the high frequency information in the original signal is slightly erased from the recording.

Tape manufacturers generally make tapes to match different industry standardised bias presets (Type I, III, IV), and these are normally automatically selected from the identification holes present on the top of the cassette shell.

Though above these industry standards most Hi-Fi manufacturers tended to align their cassette decks to a particular cassette brand and model – and make the matching tape purchasing recommendations in their manuals, though this also could be seen as a useful marketing strategy, particularly for deck/tape products from Sony.

The Yamaha KX-300 deck was one of the few sold in the low-to-mid price range to have a variable bias control for the user to adjust the bias signal further from industry presets to match his/her preferred tape use, and a play trim control (+/- 3 dB at 10 kHz) to slightly boost or cut treble on playback of poorly recorded tapes.

A MPX (for Multiplex) filter is normally found in-use with Dolby B (or C) recording circuitry to avoid the stereo pilot tone (19 kHz) of an FM broadcast from confusing the noise reduction circuit. This deck usefully allows that low pass filter to be switched out when recording from non-radio sources.

Overall, I am pleased with this deck – I’ve thrown loads of tapes at it over the years from when I bought it in 1989. It still works fine today.