Just Snagged a Micro Seiki DD-35 - Need Help With Affordable Cartridge Options for SM-505

Your DJ cartridge will work, but if you want a significant upgrade in sound quality you need a Hi-Fi cartridge, for this tonearm look only for MM or MI type. Your turntable looks nice.

I’ll give you a few options ...

1) If you want all in one: Grado designed a DJ series of cartridges based on their popular hi-fi models, if you want to combine a nice sounding DJ cartridge with the ability to swap the stylus for much better souding and more delicate Hi-Fi stylus then you can buy any stylus from Prestige series ... they are compatible with DJ100 or DJ200 cartridge body, i even asked Grado to make sure).

2) If you need just a separate Hi-Fi cartridge look for SoundSmith MI cartridges, probably used (you can find them for a good price). Make sure to check new Garrott Brothers cartridges from Australia. Other members will definitely add all those Nagaoka, AT and ususl suspects as always.

3) BUT If you want something very special and MUCH better than relatively cheap modern MM/MI you can look for some amazing vintage cartridges at $300-400 range from Audio-Technica (AT-ML150 OCC with Beryllium cantilever and MicroLine stylus), Grace (F-9), Pickering XSV-3000 (with Stereohedron stylus), Victor (X1-IIe with Titanium cantilever and elliptical stylus) for example. In this case you have to buy only from reputable source to make sure they are perfect.

PM me if you have specific questions 

A great match with that particular arm! This is the best sub-$500 cartridge available!

This is funny statement.

In my opinion even Grado Signature XTZ ($750 in the 80s and probably twice as much today) is not the best cartridge compared to some others in sub $500 category, but the cheapest Grado MI can't compete even with vintage $350 Pickering XSV3000 or $450 AT-ML150 OCC. 

What is good about Grado Prestige series is a range of different styli avaibale today from Grado, including top of the line 8MZ, TLZ, XTZ, so the upgrade of the stylus (and oversall sound) is always possible. 

Grado DJ100 and DJ200 has the same MI generator as the Grado Black.
Those Grado DJ carts belong to the Prestige 2 series and they are the best sounding DJ carts designed today (with extended frequency response up to 50k Hz and does not require high tracking force as most of the other inferior dj carts).     

@mycoscot Maybe you just have to replace your dj carts with a pair of Grado DJ100 or DJ200 ? Technics headshell will work fine on your Micro Seiki tonearm. 

For some reason, I couldn’t get a Numark cartridge to fit on the SM-505. It fit in well, but not fully set into the tone arm and there was no locking mechanism.

Do you mean something like Numark CC-1 or this one ?
Both are better in recycle bin than on a turntable, those are very bad quality cartridges, don’t waste your time with it even for djing.

Buy yourself a pair of Grado DJ-100 to mount on any lighweight headshell and use them for DJing or for home listening. When you are ready fo upgrade just buy a better stylus for this Grado.

If your Micro Seiki has some problem with headshell lock just send it for repair to anyone who can fix Micro Seiki. Your Micro Seiki tonearm designed for use conventional headshell, they are universal, nothing special.

Push and lock, this is how it works. 
This is standard headshell and standard tonearm for this type of headshell. You can't damage it, maybe it's just too tight, but it's great for connection of the headshell pins and tonearm pins. Push and move the ring to lock it.  

If you sample music from the records you need the best possible cartridge to get exactly what's on the record in the best possible quality. You can't extract music from the vinyl groove with your cheap cartridge. The key factor is stylus profile, check it.  Look at the contact area in white. This is natural "nude" FineLine diamond under my macro lens. 

This is from the vintage Ortofon Hi-Fi catalog: "The 'FINE-LINE' shaped DIAMOND (on the right) distributes the stylus pressure over a much wider contact area within the groove (look at the white marks) than is possible with conventionally shaped diamonds such as Conical (on the left) and Elliptical (in the middle). This provides greatly reduced wear on both record and stylus at the recommended tracking force. In addition, the 'FINE-LINE' STYLUS also provides better tracking ability and lower distortion at high frequencies in the critical inner turns of the groove.
Diamonds used in Ortofon styli have several different shapes, each designed for a specific purpose. We look upon diamonds as our best friends. We use them exclusively. Compared with other stylus materials they do cost more, but the extra expense is fully justified by the resulting superior performance and extended life."

For the sampling for music production your current cartridge is the worst ever. You also need a decent hi-fi phono stage (not necessary expensive), but definitely not a dj mixer. I think you already have a high quality Analog to Digital converter. 

I think your new turntable and toneam is nice, but cartridge is much more inportant. Those DJ carts does not have "nude" diamonds and normally they are all conical (worst profile ever) or elliptical, but very low quality. Grado made a better cartridges for DJs, but for sampling you need a Hi-Fi cartridge if you want the best. I think it worth $300-400 investment and you will be blown away by the difference between your cheap cartridge and a decent hi-fi cartridge.