Dear Jerome,
some experiences with Koetsu....maybe helpful....
If we look at the Koetsu Range than:
1. We have the Koetsu Black and the Rosewood Standard.
Both share exactly the same Generator - 6n copper wire, Smarium Cobalt magnets, Ogura Boron needle with the spezial sugano design at the tip.
Both have 5 Ohm internal resistance and share the same output of around 0,4mV - not 0,6mV as we can read sometimes....
The difference is the body material - the Black ist the only Koetsu cartridge with an aluminium body the weight is a bit higher than with all wood body carts and helps the medium mass tonearms often paired with this cart, we will see later, why this could be important.
Both carts share a slightly different body-form - they miss the scoop on the bottom plate behind the needle and have a slight angled underside - so that you can easily see the needle during the adjustment process.
With the Roseewood Signature things geht a little more different...
The Rosewood Sig ist the first Koetsu, that shares the traditional body with the bigger wood cartridges - means - no angle anymore at the front underside and the traditional bottom Plate with the scoop.
Also the tolerances with this cart are higher, than with the Black and Rosewood Standard, the Rosewood Body uses older material and the precision and QC ist higher with this model.
The generator with this 3 models is the same - just higher tolerances and purer material on the Rosewood Signature.
And all three share the monting system with screws an nuts....which is not the easiest way to mount a cart!
That brings us to the Urushi range....
With the Urushi we get different coil wire....it is still 6n copper - but here Koetsu uses the silver cladding process - a very thin silver plating which will be put on the copper wire with a special technique.
The body material is again rosewood, but in this case there is the artful Urushi laquer used to harden the wood!
Also these models have 0,4mV output and 5 Ohm internal resistance, the same needle and the same Sugano design with the sahpe of the diamond.
The one and only difference is the Vermillion....
Here Koetsu uses different wire and half of the turns on the coil.
That means - you have still the 5 Ohm internal resistance, but the Output drops to 0,2mV!
This is the one and only Urushi, wich uses this different generator!
From the Urushi Range on, wie have threaded holes to mount the cart!
Next in the lineup ist the Rosewood Platinum Signature...an as the name implies - we now have not anymore a smarium cobalt magnet system - now Koetsu is using the very rare platinum magnets for building the generator!
Coils are the same, as with the Urushi models (not the Vernillion).
But as a result of the platinum magnets, wie have a slightly drop in output - from 0,4mV to 0,3mV.
The wood, which is used with the Rosewood Platinum Signature is much older as with the smaller Rosewood models. It is also much darker.
This ist the "smallest" Platinum model available in the Koetsu range.
Which brings us to the Stone bodies....they all use today the platinum magnets - so they have 0,3mV output.
With the stone bodies wie have now a very, very hard and heavy material - so they all sound different to all wood body carts.
General view:
Koetsu carts are low compliance carts and need a heavy arm - all starts at 14g - but more is better....19 - 22g is the best range.
With the black it is a little bit different - because this cart is a little more heavy because of its aluminium body - and the stone cartridges are also heavier as the wood bodies....but around 19g is a fine starting point.
When we think of the equipment Sugano San used to voice his carts, than the tings get clearer and we get some good advice for our installation.
Sugano used a Garrard 401 and a Fidelity Research FR 64S.
The FR64S is a very, very heavy tonearm with an amazing performance - the energy transfer with this arm is amazing.
The Garrard 401 is an idler wheel table with a lot of torque.
The combination of an idler wheel and FR64S tonearm is a completely different experience than lets say a Rega Arm with a Oracle Delphi - with the Delphi we get, what we can read nearly in every Koetsu thread on the internet - flabby bass, rolled off treble, great midtone, but coloured and slow.
The Oracle with the Rega is just an example - most of the tables and arms used with a Koetsu produce such a sound - some more, some less....
If the bass is flabby and reaches not deep, also slow and mediocre - that the arm is too light, and can´t handle the energy the cart send to the armtube.
The sae is also the case with the rolled off treble.....
If we use a idler drive or a heavy mass drive, a very good direct drive and something near the performance of an FR 64S - we get a completely different experience....dynamic is good, resolution is also good, bass is tight and deep, and we get this amazing midtone, a great space is also in the mix.
Do not get me wrong - it will never be a Lyra cart - but we have a very nice resolution at the top end, with some silky smooth hights and a lot of space and air - a Koetsu is more analytic and colder on top.
We get not the speedy bass performance of a Lyra, also not the fleshed out low midband - the Koetsu is fuller, and, yes it is a little bit slower - bot it is not rolled off in the bass region, and it is not flabby!
That brings us to some adjustment points....:
VTA:
Should be level - use therefor the top plate of the cart - or the headshell!
VTA is than perfect, if high frequency events (S, T, SCH) with the human voice are a little bit in front of the vocals....if they are in your face - the VTA is too high....
If you cannot reach a good centerfill, VTA is too low.
And do not lough - a Koetsu is very, very sensitive with VTA.....
VTF:
Black and Rosewood Standard need a bit unter 2g
Rosewood Signature needs something around 1.95g maybe a tad less!
Urushi around 1,9g
The Stone Body carts can handle less than 1,9g!
And forget the tracing test record....a Koetsu will fall short with a tracking test on a test record - BUT it will handle the strongest soprano voice near the last groove!
Means in the real world it is a fantastic tracker!
Electrical Things:
If you use the cart with an active RIAA stage - than a good starting point will be 100 Ohm.
Yes - you get more sparcle with 300 Ohm - but listen to the S and, SCH and T in the vocal performance on your favourite record - is it natural - or is it synthetic....
My experience is - 100 Ohm is almost perfect.
If a Koetsu sounds nice with an active stage - that it can bring all the bells and whistles on the table, if you use a SUT!
One of the most legendary SUT´s out there, which can be used with a Koetsu - and which also Sugano used is the Cotter MK II L or P!
With the Urushi Vermillion and the Stone Bodies, as also the Rosewood Sig Platinum the Cotter MK II L is the one to use....with the 0,4mV Koetsu the Model P is amazing!
I read here in the context of the Koetsu used with a SUT some advices using a 40:1 SUT - that is much tooo much......
To get the idea:
40:1 32db Gain 29 Ohm
30:1 29db Gain 53 Ohm
20:1 27db Gain 117 Ohm
With a 0,4mV Koetsu a 20:1 SUT will be fantastic, and with the Vermillion and the Platinum Koetsu it could be something between 20:1 and 30:1 - 30:1 will work - depends on the MM stage an the gain you will have!
With 30db of MM gain, I would choose 30:1 - with 40db or more MM gain 20:1 is enough!
And yes - a Sut needs some hours to sound like it should do....but be careful with running a CD Signal through it...because - remember - the Sut is made to get on its primary a Signal of 0,XmV!!!!! - A CD Player has 2V and more - that is not a good thing for running in a SUT.
Use your laptop with volume set on minimum and use a white noise signal from the web - listen if you can deztect distortion - if the SUT distorts, it is still tooo much gain on the input side!s
Hope that helps....
Greetings
Ekki from Berlin....
PS: I use a Koetsu Urushi Wajima, A Koetsu vermillion Mono and a Koetsu Rosewood Signature with Frank Schröder Reference and CB Tonearms (19 - 22g eff mass) and a Cotter MK II P as also a Cotter MK II L.
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