Some cartridge recommendations

The old cartridge is more than likely past it's prime and also I would worry about stylus wear. It would be a good idea to have it examined and possibly rebuilt. HOWEVER, the MC 10 has a stupidly low output and you are certain to have a poor signal to noise ratio with it. You will be much better off with a modern cartridge with a higher output. I would suggest a Soundsmith Zephyr. It will match your tonearm nicely, It has 4 times the output of the MC 10 and company support is second to none.

The Ortofon MC Super Cart's come in at 9 Grammes in weight have 0.25-0.3mv output, but more importantly have the Wide Range Damper in use, the WRD, has an impact on Sound, that is extremely impressive.

The Super series are Cart's in need of a MC Input or alternatively a SUT - Head Amp used in conjunction with a MM Input. 

The Soundsmith Zephyr is a MI design, weighs 11 Grammes and will only need a MM Input. 

I have 'no one must have preference', in my Cart' collection I own LOMC's,  HOMC's and MM's and Ceramics. At present the preference is for the use of LOMC's, which has been such for quite some time, especially when learning about the designs that can be put in place for a Cart' to be rebuilt.

As I age further, I don't quite see the need for the expense of LOMC's, as my overall hearing range will most likely not be getting the best from investments made, when that day appears is yet to be encountered.

The Ego and Forum Talk to be had, might be the area that is most beneficial from owning very expensive LOMC Cart's, when a certain period of being alive leaves one with age related hearing deficiencies. I don't need to be asked at present numerous times if a I would like a Tea or Coffee, but I do have a wife who swears I am hard of hearing. I prefer to call it hard of listening 😏. 

In general many systems can't reproduce the frequency range that a Source Material can generate, either via a Cart', CD Player or Streaming Service. Most systems will have a cap to the frequency range and Roll Off some where before the extremes.

If one has invested in a system that can reproduce such a wide range of frequency, measuring frequencies that are present in an environment between 17hz - 20Khz is not hearing 17Hz to 20Khz frequencies, as ones hearing will need to be without impairment to get to hear such frequencies.   

Fortunately for myself, replaying recorded music is viewed as merely being one method of listening to music, where listening to music in conjunction with my interest in audio, is viewed merely as a form means to create a form of entertainment.

Even though equipment can impact on the sound being produced, and this is an area of the interest I have made much time to increase experiences through encountering different equipment, the end product for myself is strictly viewed as a means to be entertained only.

For the OP, suggestions of uber expensive Tools to enable music to be replayed are best of taken as a reference to a product, but not necessarily the required purchase route, to what is going to create, what is most suitable to your learning, which is most suitable to attain what is perceived by yourself, as your own unique listening preferences.

'Experiencing Equipment' and learning through these 'in front of experiences' is the key, listening to equipment owned by others is a very prudent way to strike items  of the 'interested in list', placing them on the 'unwanted list'. 

If the SP10 was purchased new by your grandfather and if it’s never been serviced and/or was in storage for many years, you might want to consider having it evaluated for speed constancy and etc. Check speed with any inexpensive strobe device. If it appears to work fine, you might get away with doing nothing. Electrolytic capacitors die with age and especially when left uncharged for long periods of time. Replacement is cheap because lytics are cheap. I’d go with a low or mid price MM or MI cartridge. Contrary to what was written above, you don’t need to buy an expensive LOMC in order to enjoy flat response out to and beyond 20kHz.

Dear @backwash : You own an integrated unit that seems a good one.

For the posts I can see that no one owned the original Ortofon MC10. I owned and after the Denonn 103 the MC10 was my true " first " LOMC cartridge with really high quality level performance, so you don’t need to change it due that you said that your uncle almost not used.

Your manufacturer says that the phono stage can handled MM and HO MC cartridges and your Ortofon MC10 is a LOMC cartridge so you will need an external SUT as the Denon AU-340 that you can buy through ebay. This step up transformer is of very high quality even that the model is a vintage one, I still own this Denon 340 and comes with the needed rigth gain for the MC10.

Regards and enjoy the MUSIC NOT DISTORTIONS,

R.

My Integrated can handle MM or MC carts it is full adjustable by dip switches inside on the phono card. It is however fixed at 50 db of gain.  This is the newest Modwright integrated, KWH 225i.

After looking at the Soundsmith website it appears all their carts like more gain than I have available.  They say 58-64 bd for gain. 

I have had the TT checked by a competent local tech and it is in perfect spec and near perfect cosmetic condition. I have it setting on its own steel table with a 1.75" maple top. (made from a piece of industrial equipment extremely heavy on a concrete floor) It is level and not moving short of an earthquake. 

Thanks again for all your comments.