Some general info for better understanding
Decca SXL made the very best recordings (from the Team, Hardware and from general understanding...Mercury is a different chapter) from the music repertoire we can listen today.
Decca was extremely careful not to get bad customer feedback (distortion, overdrive, don’t forget, those were different times from cartridge design- round diamond tip - ...) and SXL was a sale on commission!! Unsold records came back to Decca and were melted.
That is the reason why they are so expensive today. Simply limited Quantity.
Sound is - or was - first rate. I think, a Benchmark which was never surpassed for their Titles.
Those Stereo SXL were very expensive in the early 50’s and it was pure luxury to get those after the war, the Economy was still down.
In USA there was a similar economic situation but fixed pricing was cancelled around 1960.
London CS was created from Decca because Decca couldn’t use their own name in USA.
(There was a small private label which was named Decca). To avoid any problems, Decca decided right from the Start to create for USA a new Name, London.
Now for the "Sound"
For both Labels they used the same Mastertape.
But the main difference was - or is - the Peak of the cutting process. Decca thought, the US listener expects a different kind of sound, the result was a ~ +2dB Peak in the cutting.
This means, a distortion in the headroom was accepted.
But this is rare, those Decca Cutters were real artists, unsurpassed. But they can sound a bit different based on that (depends on your ears and quality of playback chain).
Next difference, Decca thought that USA wants something "Physical", means, thicker LP’s.
For Londons they used 20gr to 40gr. more vinyl. This varied a lot 1958/1959 and became Standard from 1962 (∼ 205gr). When you compare such records (SXL / London) you should use a Arm with VTA adjustment. This is mandatory.
It is a very interesting chapter for a curious audiophile, because we have different diamond cuts in our carts and that will make a huge difference when we talk or rate such records.
Also, not every SKL was available as a London CS and reverse. And of course, completely different Prints onto the Box.
Decca was also very open for information transfer, they had a good Management and later a Partnership with RCA (Living Stereo) to do their European recordings. RCA was happy because those sessions were way cheaper than in USA (affiliated unions).
A class on its own again...but this is also a different chapter.
