Rega Planar 3 : Heavily upgraded yet produces a sound that I don't like


I have the Rega Planar 3 turntable for 30 years now. It had an original everything including a 100$ nottingham analogue cartridge/stylus.
Sound was not bad but pretty basic....
A few years ago I started upgrading it. I did all the upgrades together and the result is... not good. The sound is very accurate but it is too bright, there is almost no Bass and drums have no attack whatsoever.
I can't eliminate where the problem is because all upgrades are irreversible.
I know that the Ortofon Rondo Red has a very bright sound but still...

 

Here is a list of the upgrades :

1. ISOkinetik ISOvert Rega Tonearm VTA Adjustment Kit

https://www.analogueseduction.net/isokinetik-upgrades-and-parts/isokinetik-isovert-rega-tonearm-vta-adjustment-kit.html

 

2. Cardas Litz purple phono cable

 

3. ISOkinetik Tonearm Low CG weight

https://www.analogueseduction.net/isokinetik-upgrades-and-parts/isokinetik-isoweight.html

 

4. Ortofon Rondo Red Cartridge/stylus

 

5 Linn Linto phono pre amp (an old but outstanding piece which has a cult following).


6. I use Rega Elicit Apmplifer


triskadecaphobic
I tried a Ortofon Red on my Planar 3 based on all of the bang for the buck reviews. I added a spacer to help with the VTA etc.
Hated the sound it was basically as you described.

Sold the cartridge for $50 and moved on. So I am not saying this is a bad phono cartridge, I just think on the Rega TT these aren’t the right combination. Luckily a friend sold me a newish Rega Elys for only a few more $ and the sound improved 100%. 
If you have a lot of vinyl and plan to play records do yourself a favor and move up to a better cartridge. 
Or a Dynavector 10x5, or to check with a different phono stage.
Rega 3 is basic but still produces fast bass and attack.
G
Cardas cables are anything but bright, so you can let that bit off the hook.  One thing: Weren't especially the early Rega turntables notorious for running too fast? Have you changed the turntable belt along your upgrade path?  Anyway, check turntable speed.  If it's too fast, that could account for most of your symptoms.  Wouldn't hurt to upgrade the whole shebang, either.  (Better turntable, better cartridge, but that's an easy out.) For speed check, I recommend don't use a cell phone app.  Do use a good strobe-based device.  Best is the KAB strobe kit.  Buy it once and use it forever for any future turntable.