Post by Owen Y on Aug 18, 2019 11:52:45 GMT 12
The first easily accessible mechanical part inside the SP-10 is the Mechanical Brake. Immediately under the main platter, after removing the 3 hold-down screws, is a thin alloy cover plate (with a grey rubbery spacer piece under to prevent any vibration) covering the mechanical brake. 
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Post by Owen Y on Aug 18, 2019 11:56:50 GMT 12
How the Mechanical Brake works: A solenoid working from the On/Off switch pulls a felt strap 'brake shoe" onto the sub-platter & also maintains half-braking force on the platter to assist record cueing.
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Post by Owen Y on Aug 18, 2019 12:52:10 GMT 12
The motor is held down onto the SP-10 top plate inner flange, by 4 small M4 JIS screws. Also, there is a black plastic guide plate (see below) for the brake strap that is held under the same screws - which introduces 3mm of plastic interface under the motor screw fixings. With the DD motor's high torque & with the feedback motor control, you'd expect the rigidity of motor fixing to be a critical factor.    (Plastic guide plate & Mechanical Brake strap removed.)
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Post by Owen Y on Aug 20, 2019 22:06:43 GMT 12
Of course, with the Mechanical Brake removed, the platter takes a few secs to come to a stop (as below). (But I have to admit that I was really liking the stock SP-10 stopping & starting instantly  )
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Post by michaelw on Aug 21, 2019 11:21:31 GMT 12
that's why i've kept mine in place also handy during setup, turn on power supply, brake stops platter from accidentally moving 
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Post by Owen Y on Aug 21, 2019 13:14:44 GMT 12
Me too, I liked using the brake-lock during setup but, having suffered a near accident by inadvertantly touching the start switch, I've gone back to the ol' blutak for now 
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Post by Owen Y on Aug 21, 2019 19:17:18 GMT 12
However, the main reason for removing the Mechanical Brake is in order to remove the plastic interface under the fixing screws - which IMHO prevent the (surprisingly small sized) M4 screws from holding the DD motor absolutely firmly. With the plastic brake guide also removed, I replaced the JIS head screws with hex socket screws - a hex wrench permits a more positive, torquing up. Together with spring washers & flat washers, I was able to get a tighter fixing, without stressing the alloy thread too much. (pic below.) (More screws than the measly 4, would be ideal, but that would mean drilling/tapping the frame flange (not difficult) & removal of all the PCBs under (quite a bit more work) to avoid metal swarf.) With all this done, this little tweak seems to 'change' the performance of the SP-10 significantly. There is initially a noticeable increase in HF extension, more treble sparkle, finer detailing, finer resolution, more 'radiant' harmonics. Overall more precise sounds, sharper 'outlines', clarity of image separation & some real sense of 'depth' location in the soundsage. I've had only a couple of sessions, so take the following with a grain of salt for now ....but it seems not a case of incremental improvement, but rather, this SP-10 now seems to be a much better turntable - reproducing in a manner that I don't think I've heard from a TT. I am surprised that this DD TT can reproduce sense of stereo imaging & 'space' in this manner. And we haven't touched the motor-rotor yet - which I was thinking also has potential to be improved mechanically. 
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Post by michaelw on Aug 21, 2019 19:57:18 GMT 12
krebs mod for the motor ?
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Post by colinf on Aug 21, 2019 20:08:05 GMT 12
krebs mod for the motor ?
What’s that? ☁️
AMR-iFi R&D
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Post by Owen Y on Aug 21, 2019 21:52:25 GMT 12
From your Gennedy pics - an 'organic oil' has been applied to the motor (stator) base, the stator itself, the speed servo sensors & the rotor-magnet support frame (pressed steel). colinf - the Krebs Upgrade webpage is here.
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Post by colinf on Aug 21, 2019 23:47:45 GMT 12
Just been reading the Krebs Upgrade page, thanks for the link. It was interesting to read that they have seen a distorted version of music on the direct drive power supply to the motor due to stylus drag. “In an effort to improve this TT, we built a heavy duty power supply. Listening tests definitely showed a positive change and out of curiosity we placed an oscilloscope on the power supply's output. To our amazement we saw a distorted picture of the music that was playing at the time. Even high frequencies in the music were present in the power supplies output. This meant two things. 1) The power supply was not nearly stiff enough 2) The platters speed was being modulated by the music due to stylus drag and the servo was attempting to correct these errors, drawing current from the power supply in the process. The platters inertia was not enough even at high frequencies, so speed correction became necessary. The servo was acting to correct these errors.” I didn’t realise it was such a significant problem! Turntables like the Garrard 301 etc don’t have any servo mechanism, perhaps why they have their own general family sound. Ditto belt drive TTs.
AMR-iFi R&D
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Post by Owen Y on Aug 25, 2019 14:18:25 GMT 12
I've been wary of the feedback comparator speed control system (PLL?) used on the SP-10, thinking that it would be audible (or become audible at some stage) & detrimental to sound. However, so far, I have not been aware of anything odd. With the more solid motor fixing, the TT is more 'precise', the ear is drawn to the 'mix' of recorded tracks, which seems to be more clearly laid bare. The stereo effect from more precise image 'specificity' is much more obvious (even on some run-of-the-mill recordings). With the new re-issue of Abbey Road, I dug out my (English stereo) copy & was struck by the complex mix (over complex?) of this late-period Beatles album. eg. George's 'Here Comes The Sun' is splendid - the acoustic guitar opening is sparkling & George & Paul's vocal harmonies much more clear than I remember. I dug out also Joni's Hejira, which I knew contained really atmospheric, complex instrumental mixes - eg. Amelia is wonderful, the swirling vibraphone incredibly now so much more 'in the room'. Although any TT is capable of generating stereo 'soundstage' from a 2-ch stereo recording, Belt-drives can enhance the sense of 3D space or 'ambience' by retrieving or generating low-level info & harmonic decay (ie. the time dimension).... this D-drive TT seems able to precisely reproduce stereo information by reproducing 'leading edges' more clearly than Belt-drives (IME) - something that a Rim-drive TT too, do better than Belt-drives (generally speaking).  
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Post by Owen Y on Sept 6, 2019 9:21:07 GMT 12
A top-view of the current setup: 
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Post by Owen Y on Sept 19, 2019 10:33:41 GMT 12
Minor update:For the record, I've ditched the Mag-lev footers (4) under this TT. This TT sounds better (to my ear) when supported on solid plywood blocks (3) 85x85x65H, distributed 2 at the rear, 1 at the front. Support blocks are best not placed under the SS baseplate - treble becomes a touch edgy, uncomfortable. Supported under the ply plinth perimeter - the sound is sharper, clearer, dynamic, rhythmic, with a light, agile touch. Image height & scale is good. Nice treble extension, nice 'sustain'. My feeling now is that the rotational forces of the DD TT require strategies that focus on rotational rigidity - and the Mag-levs are not great in this regard (although great for isolation under gravity forces). Another example of why you can't just assume that what works on one device (eg my previous TT), will work similarly on another one. Possibly it's the different mechanics of a DD TT vs a rim drive? Or the plinth type/design - solid slate vs semi-solid plywood? Always use your ears, I say  (The Mag-lev footers - now removed from the laminated plywood blocks.) 
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Post by colinf on Sept 19, 2019 19:25:54 GMT 12
Interesting concept, Owen. I’ve just removed the maglev footers under my Garrard but wasn’t happy with the coupling of the TT to the stand and floor on wooden feet as it resulted in an unfocused image and coloured low midrange. I decided to try rolling 2 beach towels tightly under it, one on each side. That seems to work surprisingly well...nicely dynamic while still sounding more natural than the maglevs.
AMR-iFi R&D
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Post by Owen Y on Sept 19, 2019 22:13:37 GMT 12
Hi colinf - I sometimes utilised 2 soft + one hard support - the idea of a single 'grounding' path, as it were. But this TT (in this wood plinth) seems to work well with 'hard' (wood) supports. (Currently however, I am not using a dedicated TT stand, but have the TT placed on a wood table/rack.) As said, you just have to keep using your ears
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Post by Owen Y on Nov 22, 2019 14:58:59 GMT 12
It's time to remove the Kenwood L-07D tonearm & install another tonearm - a Fidelity Research FR-64S (the only other decent tonearm that I have to hand).  Tonearms - FR-64S (centre), FR-12 (top), Kenwood L-07D (bottom). We need to make up a new arm plate to fit the Kenwood hole (plus maybe a spare blank arm plate). 
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Post by Owen Y on Nov 27, 2019 17:01:34 GMT 12
While I await machine time, the Transfiguration Temper is installed back onto the Terminator-SP-10. It is a fairly small/shallow cartridge, (& for various reasons relating to the VTA adjuster), I decided to make a small (3mm thick) spacer for under the headshell. 
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Post by Owen Y on Nov 28, 2019 8:54:28 GMT 12
The Transfiguration jumps into life on the Terminator-SP-10. The SL-1210 begins to show what this cartridge can do, but on the SP-10, there's more of everything - scale, transparency, control, punch, tempo, urgency, drama, micro & macro-dynamics (particularly revealing on the subtle & nimble Mozart Concertoes), spatial separation & resolution. Everything seems to have exceptional urgency, pace & subtlety of timing with this cartridge. Bass balance is good, very good, but not extraordinary. The SL-1210 revealed to me what this 'ring-magnet' MC could do, but on the SP-10, it's almost exhilarating I feel that there's more to come yet from the SP-10... 1) Jury is still out in my mind on our plinth build, so far so good & as confirmed on the SL-1210, rotationally rigid support is essential for a DD TT, no soft feet. 2) Fixing down the SP-10 motor (as we have done) is a must, rotational rigdity as above.
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Post by michaelw on Nov 28, 2019 10:13:39 GMT 12
could all those who say the cartridge is the most important part of the record playback system be right ? nooooooooooooooooooooooooo
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Post by Owen Y on Dec 12, 2019 9:59:46 GMT 12
Playing the Transfiguration Temper W MC cartridge on the SP-10MKII, on the Terminator linear tracker. (Bass seems a bit heavy replaying on my desktop spkrs + sub.)
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Post by michaelw on Dec 12, 2019 10:10:25 GMT 12
Video unavailable This video is private.
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Post by Owen Y on Dec 12, 2019 10:23:55 GMT 12
Sorry, accidently 'Scheduled' it for later. Try now.
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Post by michaelw on Dec 12, 2019 12:17:12 GMT 12
works now wobbly record ! you have almost as many turntables as m.citroen
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Post by Owen Y on Dec 12, 2019 12:39:07 GMT 12
Monsieur Citroen is well ahead of me by quite a few, IIRC
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Post by Citroen on Dec 19, 2019 16:26:51 GMT 12
I think your quality per turntable ratio is much higher than mine though!
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Post by Owen Y on Apr 24, 2020 17:02:00 GMT 12
The Kenwood tonearm experiment on the SP-10 was, on balance, not entirely successful. Mainly because the headshell connection was not totally rigid (I need to look into this a bit). So, the Fidelity Research FR-64 tonearm is next up. This is an iconic tonearm, one that has a 'characterful' sound & has a degree of 'cult' status. Not entirely neutral, was my thoughts in the past, but properly matched, you could maybe hit its 'sweet spot' - the high performance motorcar analogy comes to mind perhaps. Some say that this tonearm works well with a Koetsu - not a combo that I've spent time listening to, but I still have a Rosewood Signature here to hand. Of course, the Koetsus themselves need careful matching, as I've spent many years (not) discovering. I don't have an Garrard 401 (like Sugano used), but the Koetsu seemed to come to life on my TransFi Salvation rim-drive TT. So, we need to hear the FR-Koetsu combo on this Technics DD. Finally got some machine-time, to get an FR-64 arm-board cut for the SP-10:  
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Post by Citroen on Apr 24, 2020 18:40:41 GMT 12
It really is paying off for you now, isn't it, after all of those nappy changes etc!
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Post by Owen Y on Apr 24, 2020 20:51:20 GMT 12
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Post by Owen Y on Apr 27, 2020 13:49:09 GMT 12
Unscrewing the Kenwood tonearm (will re-visit this arm another day):  Test-fitting the new FR-64 arm-plate - spindle-pivot distance looks pretty good: (This is a 6mm alumin plate, but because the platter height on the SP-10 is quite low, we have trimmed arm-plate rim thickness down a couple of mm.) 
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