Newbie Question: VTA and Rega P25/RB600

Hi all ... recently I've returned to vinyl (and diggin' it!) with the loan of a good friend's vintage Thorens, and while I'm awaiting delivery of my Rega P25 I am wonderin' about setup of the Rega, specifically, about the lack of VTA on the RB600.

My questions would be (and feel free to throw more in, not sure I really know what to ask at this stage)

1) What are the sonic affects of VTA out of whack/not optimized?
2) How do aftermarket mods work in regards to the RB600?
3) Will I need to worry about VTA if I use a none-felt mat?
(Dyna vector 10x4 cart)
you can buy spacers at made for Rega 2mm and 4mm. it's truly a pain to adjust rega arms but that is the only option now for your turntable. in reality you cannot optimize VTA in Rega for the performance you can only optimize it for the cartridge profile i.e. not realy precisely.
you can also experience with different mats and felt mat is not the best for the records in particular. there will be always small particle left from felt when you flip over your record. rubber mats tend to accumulate too much statics.
you can also try to play with no mat.
Origin Live and Expressimo Audio both make variable VTA adjusters for the Rega arms. They are around $40. They are threaded adjusters, and not the easiest to use, but they do work. You can dial it in exactly, with a little patience and a good ear.
Generally, to adjust VTA, you start with the tonearm level while it is playing. Then, you put the arm back on the clip, and perform an adjustment, either up or down. Listen to the result, and determine if you went the right way or not. Make only small adjustments, and play around like this until you get the best sound. Different cartridges like different VTA, and you can only get it right by listening, and adjusting.
As per Mara & Twl. I'll add: patience is rewarding & keep the arm level, if not, SLIGHTLY off (hi or low) until yr cartridge settles. Then go back & re-adjust. Don't worry, it's easy!
I believe the 10x4 dyno is pretty on for the rega, and you may not need to adjust vta for it. You should look into the specs on it as they compare to the rega cartridges. Better yet, contact a rega dealer, or the importer and ask.

enjoy the vinyl!
Very helpful responses, much appreciated folks.
Also check out Clearaudio Aurum Beta - it is short and very nearly perfect without any VTA adjustment. It is a great Cartridge regardless.
I agree w/ marakanetz go w/ a spacer for the rega 600 arm, pending on cartridge you use will tell your thickness you need. My last turntable was a p-25/ rb-600 /benz ace as I did not opt for a spacer and fought it the whole time, my solution was to play one side at a time and not lift your needle. So learn from my procrastination PUT THE SPACER IN.
I also put a ringmat 330mkII on it, sonicly I felt it did not change it dramaticly what it did do is reduce the static from the felt mat. As I dont wash every record each play .
The P25 arrived, mounted up the Dynavector 10x4. Nice overall sound, plenty of details in the mix (love that about vinyl), however it's noticeably light in the bass and maybe a tad bright on top -- but the lack of bass is pretty aparent. Spin up the CDP as a reference (Linn Ikemi) and the comparison is obvious.

I believe I've got the cartridge aligned properly and the tracking is set to the recommended 1.7g. I experimented with tracking from 1.5 to 2.5 and went back to 1.7, none of which really did much for the lack of low end.

I'm running it through my MC setion of my Linn Karin preamp not the MM section. Tried the MM section for grins and no affect.

Is this sounding like a VTA issue?

If so which direction do I go to correct this type of symptom?

Thanks again for all the help, much appreciated!
It sounds like a VTA issue to me. Lower the pivot end of the arm, slightly. If it is already as low as it can go, then cut a piece of cardboard(non-corrugated) that is about the thickness of a matchbook cover, in the shape of your platter. Put it under your mat. If this improves things, then try using two layers of cardboard. Once you figure out how high to go, then you know what thickness of the new mat will be, that you need to buy. I know cardboard may not be the ideal material to do this with, but we're not looking for a permanent solution with this, just trying to determine how much spacing you need for your VTA adjustment. You can then get the right thickness mat, that will be made of the right material. If you would rather use another material than cardboard, that's fine, just so long as you get the spacing result that you want.

The other option would be to buy pre-made spacers to put between your cartridge and the headshell. This is alot more difficult, but will achieve the same end.

Also, the 10x4 is designed to work into your MM input on your phono section. It is possible that the loading on the MC section may be set at something other than 47k, which is what the 10x4 is designed to work into.
The Dynavector 10X4 will need a 2mm spacer when using the stock Rega felt mat.
The ExtremePhono mat, being thicker yet will require quite a bit more compensation from the looks of it.
The Dyna is a high output MC and is intended to be used at the 47K ohm MM input/load.
Expect it to take at least 30+ hours of play just to limber the suspension and another 20 or more hours before the cartridge is fully broken in.You'll want to double check your VTF at the 30 hr mark.
I, umm, err, ahhh ... wired the cartridge outta phase.
Oops. Sounds a wee bit better now.

Tossed on the new mat and its sounding pretty darn good! (as opposed to just plain bad prior) Thanks all.
Oh well! And not one of us even suspected that. Glad you got it working.