Post by Graham on May 11, 2017 13:31:36 GMT 12
Suspicions confirmed,the Excel cartridge is picking up EM radiation from those big bad transformers on the amp.
If I lift the turntable vertically the hum fades away.
I could reconfigure the positioning of the amp and turntable to reduce or eliminate the hum, but the low output issue would still remain.
I wasn't planning on buying another preamp or step up device so must accept the fact that this otherwise excellent LOMC cartridge is not compatible with my system. Sure glad I didn't pay 700 Euros for it !!
Thanks for your help with the diagnosis.
Cheers
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Post by Citroen on May 11, 2017 13:51:36 GMT 12
Send it my way Graham... 
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Post by michaelw on May 11, 2017 13:54:22 GMT 12
the vultures are out ...  psst ... i'll give it a try 
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Post by Owen Y on May 11, 2017 14:13:29 GMT 12
I'm sorry, it goes in the order of first contributors to this thread
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Post by Graham on May 11, 2017 14:17:41 GMT 12
Show me the money !! ie make me an offer I can't refuse. I'm OK with a try before you buy arrangement.
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Post by michaelw on May 18, 2017 23:19:25 GMT 12
thanks to graham for sending the excel down. unfortunately not a great fit in my system. the highs were definitely clear and high but also clearly elevated. bass was tight but didn't have the impact i like. spatial detail was good, firmly locked within the boundaries of the speakers. more dimensional and immediacy would have been nice. no problems with the low output as the cartridge did not exaggerate background noise. overall very much a product of the 80s. all yours monsieur citroen !  
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Post by Citroen on May 19, 2017 8:23:29 GMT 12
I get my 80's fix with a Supex SD1000
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Post by Graham on May 19, 2017 15:35:06 GMT 12
Well the wandering Excel has returned home being as it didn't suit Michaels system or taste.
That's OK and understood as it didn't really suit mine either.
Michael noticed something that had escaped my attention and that was the cantilever was slightly bent or angled to one side.
I have just performed some micro surgery using 2 toothpicks and a very steady hand and have tweaked it back into line. There were a few tense moments as the cantilever is hollow sapphire so will not bend as readily as alloy.
I've convinced myself that the hum has been reduced slightly by twisting the pairs of cartridge leads together, and it's not audible a metre away from the speakers anyway.
It's back on the Oracle/MMT at this stage with a bit more weight added to the headshell and being evaluated again.
It might just be a keeper after all.
Cheers
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Post by michaelw on May 19, 2017 16:22:57 GMT 12
well done on the micro surgery. not for the faint hearted !
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Post by Owen Y on May 19, 2017 16:51:15 GMT 12
On your Phonobox SE II, I'd experiment with 22 ohms & 100 ohms, Graham. The Excel has only 3 ohms coil imped & those settings connect only 1 resistor in circuit. Let us know how it works out.
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Post by Graham on May 20, 2017 14:38:43 GMT 12
I understand the 'rule of thumb' for impedance loading is 10 to 20 times the cartridge impedance,so that's 30 to 60 ohms.
On the ProJect in this range with 120pF I have either 22 or 69 with nothing in between.
I have tried both, and also 100, but can't really hear any difference.
Maybe my ears are stuffed as I know I can't hear above 13k anyway.
A legacy of advancing years, loud music and even louder racing engines.
Did you experiment with this Michael and have any recommendation ?
I think the valve amp tends to soften the top end anyway to give that warm valve sound.
Cheers
Graham
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Post by michaelw on May 20, 2017 17:08:56 GMT 12
hi graham,
i tried 47 - 100 - 47k
47 i felt was a bit too tight, 100 was better, 47k best - the most open sounding but noticeably bright
if you can't hear any difference between the lower impedances and 100, stick to 100, it will also help optimise the output going into the project.
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Post by Owen Y on May 21, 2017 17:28:12 GMT 12
I understand the 'rule of thumb' for impedance loading is 10 to 20 times the cartridge impedance,so that's 30 to 60 ohms. Yes that's a good rule of thumb. That's why most low-med output MCs (which typically have coil impedances of 5-6 ohms) are often recommended to be loaded with 100 ohms. - Capacitance is unimportant for MCs (important for MMs). - The loading ohms value is often not that precise or sensitive, eg the difference between 60 & 69 ohms is likely inaudible. The values i suggested were the ones that engaged only one resistor in the Phono Box switch settings - the others, you will see, engage 2 or 3 Rs in parallel to arrive at the specified value. MC cartr loading is not just a tonal balance question.... MM & MC carts are magnetic 'circuits', which tend to resonate (in the ultrasonic region), due to inductance-capacitance. MMs can be damped with capacitance loading (pF). MCs are damped with resistive loading (ohms). You may have seen Jim Hagerman's real nice explanation: www.hagtech.com/loading.htmlThis explains why michaelw perceived brightness with 47k loading. Other observations such as dynamics, openness...etc, I think are system and/or cartridge dependent. From a technical, power-delivery standpoint, the higher ohms loading will usually deliver more output (volts). (Except in the case of Step Up Transformers - but that's another story  )
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Post by michaelw on May 21, 2017 18:42:14 GMT 12
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Post by Graham on May 21, 2017 20:10:43 GMT 12
Thanks Michael and Owen for your advice. I'm on a steep learning curve with LOMC cartridges.
I'm listening to some Vivaldi concertos at present with the loading on 100 ohms and the Excel does sound quite lovely.
Maybe it is better suited to classical music anyway.
I don't think I'm imagining it but the volume output seems to be slightly higher on this setting and the hum is almost non-existent.
I also may look into fitting a slightly heavier headshell as I think this would suit the 8cu low compliance.
Cheers
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Post by michaelw on May 21, 2017 20:48:03 GMT 12
yes, loading is resistive, when you load down a cartridge (small impedance number) some output gets shunted to ground. another reason to try 47k/unloaded
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Post by Graham on May 21, 2017 21:09:41 GMT 12
OK, last silly question. Well for tonight anyway.
The ProJect SE II doesn't specifically have instructions for achieving 47K loading for MC ( just for MM), so do I presume that with no jumpers installed in MC mode the default setting is 47K ?
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Post by michaelw on May 22, 2017 0:03:40 GMT 12
good question.
will it even work in mc mode with no jumper ?
the manual states a range of values from 17 ohm to 220 ohm if you fiddle around with the jumpers but there's no mention of omitting all jumpers.
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Post by Graham on May 22, 2017 9:09:52 GMT 12
Yep, its works fine in MC mode with no jumpers !!!!
Maybe I need to check the input impedance with a meter.
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Post by Owen Y on May 22, 2017 10:33:10 GMT 12
Yes, can check the phono inputs with ohm meter. But I wouldn't put a meter on a cartridge.
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Post by Graham on May 22, 2017 10:46:27 GMT 12
Sure enough, the default setting on MM and MC with no jumpers is 47K ohms.
So I guess that means there are a pair of 47k resistor hard wired internally and all we are doing by adding the jumpers is adding resistors in parallel to lower the total resistance. Slowly getting my head around how this all works.
To me it sounds the same on 100 or 47k so which do you think is preferable in theory ?
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Post by Owen Y on May 22, 2017 11:32:43 GMT 12
PS. Unplug power, meter probe inside RCA & other probe on RCA outer.
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Post by michaelw on May 22, 2017 11:46:30 GMT 12
that's a good bonus !
i'm sure the old projects i reviewed couldn't do 47k mc ...
if you can't hear any difference and the rest of your amplifier chain doesn't protest ...
go 47k so you can get every bit of the excel's 0.2mv output.
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Post by Graham on May 23, 2017 15:11:30 GMT 12
Final report on the Excel for those who are not sick of hearing about it ! After much faffing about with alignment, tracking weight, and preamp loading it now sounds very very nice so it has had a reprieve. I have fitted it to the Sumiko headshell which weighs in at 12 grams which suits the 8cu compliance and is tracking at 2 grams. The preamp is being used with no jumpers to provide 47K impedance which provides a slight lift in volume compared to other settings. This results in the normal listening level being around 1/2 volume with no audible hum. I think any brightness that may result from this 47K impedance is countered by the warmness imparted by the valve amp resulting in a very nice balanced sound from my system. It sound particularly good with classical music, violins sound clear and natural. Good wide sound stage and placement of instruments etc. Mark Knopflers Privateering has some very strong deep bass which can get a bit boomy and muffled, the Excel does a good job of taming this. My test for sibilance is Peter Gabriels So album, and unfortunately the Excel does no better than any of my other cartridges there. But I suspect none will. I an now a happy chappy and although I'm not a great believer in burning in I have to say the cartridge is sounding better and better the more hours it has played. Jees, maybe the worlds not flat after all. Cheers
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Post by michaelw on May 23, 2017 15:49:34 GMT 12
congrats !
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Post by Graham on Jun 26, 2017 20:47:16 GMT 12
The very faint 50hz hum finally got to me so I solved it by the most obvious method.
I swapped the two turntables over so that the MC cartridge on the Oracle is further away from the amp transformer!! The SUT is fed into the Graham Slee MM preamp now instead of the ProJect.
Simple huh, should have got off my chuff and tried this sooner. 
Although I had convinced myself I couldn't hear the hum from the usual listening position it was clearly impacting on the sound. The sound is now clearer/cleaner and the low frequency has lost some of the slight booming that occurred with some records. I suspect moving the turntable further from the LH speaker also wouldn't hurt.
Maybe the 50hz was being superimposed subtly onto the LF to exaggerate it. Who knows. It just sound better now.
The TD125 will only be used with MM cartridges which never seemed to pick up this hum anyway.
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Post by michaelw on Jun 26, 2017 23:25:18 GMT 12
winning
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Post by Graham on Apr 27, 2018 12:57:35 GMT 12
I've been faffing about with the Excel again and have now got to a stage where I think it is sounding very very nice.
What I have done is add some weight to the headshell and installed the additional counterweight to the MMT arm as being a low compliance cartridge I felt it would benefit from more effective mass.
I have also installed silicone in the damping system and set it to maximum by winding the adjusting knob down.
The result in my opinion is that this unique and rare Shibata cartridge is now having to work a bit harder against this mass and is starting to perform as intended.
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Post by Owen Y on Apr 27, 2018 13:21:57 GMT 12
I believe that I may have mentioned this previously? A 6gm, 8cu cartridge needs a tot Eff Mass of over 30gms. ie it was probably made for a tonearm (of that era) like the Fidelity Research FR64. Fluid damping does the same job (increasing Eff Mass). With too low Eff Mass, the res freq is way too high & bass will likely be weak, undynamic. Good work!
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Post by Owen Y on Apr 27, 2018 13:32:35 GMT 12
Generally all the earlier style MCs work best on heavy tonearms. Ortofon's Resonance Freq graph is a useful tool (on their webpage).
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