This Koetsu Rosewood Signature cartridge (serial no. 065) was manufactured around 1992…
(The white label is a distributor’s label, not from Koetsu.)
Below… this Koetsu Rosewood (serial no. 11756) was manufactured in the mid-1980s – I purchased this cartridge on the second-hand market in 1987.
The previous owner had a Garrott Brothers ‘Microscanner’ stylus installed onto it.
In 2002, I commissioned Melvin Ang (Koetsu S E Asia) to deliver the cartridge to Koetsu in Japan to have it re-built and upgraded to Rosewood Signature specification. The original Rosewood body, much valued for its age, was re-used but everything else was replaced.
(The Signatures are samples selected with closer-tolerance, matched coil characteristics.)
The re-built cartridge is shown here, mounted onto a Wand tonearm…
And below, mounted onto a TransFi Terminator linear tracking tonearm…
Yoshiaki Sugano began actively making Koetsu moving coil cartridges during the late 1960s, after retirement from a career mostly at Toyota Motor Co. Sugano also pursued an interest in painting.
Following publicity from enthusiastic overseas reviewers such as The Absolute Sound magazine, demand grew rapidly, especially from the USA. Sugano was assisted by his wife and daughter.
No doubt informed by Sugano’s knowledge of traditional sword-making, the Koetsu moving coil cartridges place emphasis on careful material selection, ‘aging’ and fine adjustment.
For example, I understand that the magnets are Samarium-Cobalt or Platinum-alloy, the magnet-yokes high Cobalt content steel alloy, the tension wire is Berylium. Coil wire gauge, 6N copper and silver-clad copper, are carefully specified. The cantilevers are solid Boron, slotted to receive a highly polished diamond stylus (around the shank of the diamond, there is a rectangular reinforcement plate, similar to a ‘tsuba’ hand-guard of a Japanese sword). A one-piece Diamond cantilever-stylus is also available.
Every Koetsu cartridge was tested and listened to on Garrard 401 turntables (except for the Blacks which are only sample-tested)… so it would not be surprising if Koetsu cartridges sound very good on idler or rim-drive turntables.
Sugano’s own music system consisted of a Garrard 401, with his own tonearm and a step-up transformer. Loudspeakers were 3-way horns, together with an infinite baffle, wall-mounted bass driver, all actively driven by multiple low-wattage amplifiers (made a friend). He regarded his system as only a ‘modest’ system.
Sugano would enjoy western classical music whilst painting, in a living room-studio with parquet-wood floor.
Koetsu cartridges continue to be manufactured by his sons, Fumihiko Sugano and his brother.
There continues to be a range of Koetsu cartridges available… beginning from the lowest cost, metal-bodied Koetsu Black. Then there are the wood-bodied models… the Rosewood, Rosewood Signature and several Urushi lacquered models. There are also lower-output, Platinum-alloy magnet versions of the wood Koetsus. The very best Koetsus are the stone-bodied models, all of which employ the Platinum magnets.
My own humble experience with Koetsu cartridges began with the Rosewood in 1987. I was using an Audio Research SP8 ‘Mk I’ preamplifier (phono input impedance 49.9k Ohms).
Like many Koetsu users, for many years I thought that the Koetsu did not have very good tracking ability… high level, high frequency passages (eg. female voice) would occasionally distort.
It was only after much experimentation that I learned how to optimally ‘load’ a moving coil cartridge. With proper loading on the preamp input, the ‘mis-tracking’ disappeared. Many owners use 100 Ohms loading. This is a good starting point. I have found that loadings between 50 – 130 Ohms can work well, depending on your system and preferences.
On reflection, this is not surprising, as Sugano used a step-up transformer…. and assuming say 26 – 28dB transformer Gain, connected to a 47k Ohms preamp input, then the load impedance presented to the cartridge would be 117 – 75 Ohms.
I currently use a vintage Fidelity Research FRT-4 Step-Up Transformer, which has switchable Gain – 31dB – 26.3dB – 25.2db – 20dB. (Shown here with loading resistors changed to Caddock TF020 – these now removed completely.)
Another option, these above are modern Stevens and Billington Step-Up Transformers, 20dB Gain (installed into metal boxes).
The sound of the Koetsu Rosewood or Rosewood Signature is warm-toned, with plentiful low level, harmonic information and ‘decay’. High frequencies, when optimally loaded, are not ‘forward’ and record surface noise is not emphasised (like many high-end cartridges tend to do). Sound presentation is ‘big’ and ‘spacious’. On a belt-drive turntable, the Rosewood can sound very ‘resonant’.
(More recent Rosewoods seem to have slightly more high frequency presence, a slightly more ‘neutral’ tonal balance.)
On a rim-drive turntable, the Rosewood gains some ‘leading edge’ definition to everything. Bass is stronger but not unnaturally ‘tight’. There is increased energy & scale, more ’empty space’ within the ‘soundstage’ and more clarity, more ‘solid’ ‘images’.
- I prefer to use my Koetsu Rosewood/Signature cartridge with the alloy bottom plate removed. This may be sacrilegious but the sound has more dynamic freedom and ‘openness’, greatly improved ‘separation’ and retrieval of information. (There seems to be some effect on magnetic fields and/or eddy currents.) The bottom plate seems to soft-glued in place and can be removed with (great) care, without damage.
- Brass mounting screws – compared to stainless steel, brass screws and nuts provide weightier bass, smoother treble extension, more ‘solid’ tone and overall more ‘sustain’. Stainless steel sounds more ‘clean’ and ‘tight’, with a smaller, less expansive presentation.
- Tracking Force 1.95gm (to 1.97gm). Melvin’s advice is spot-on here.
- Vertical Tracking Angle (VTA) – set by ear, together with Tracking Force, usually cartridge top-plate is near-parallel to record.
- Koetsu – Warwick Mickell, Australian Hi-Fi.
- Koetsunami – Alvin Gold, Hi-Fi News & Record Review, Sept 1984.
- Remembering Yoshiaki Sugano – Stig I. Bjorge, Stereophile, 27 Jan 2002.
All comments welcome!…