So, my thoughts on the 1988 "standard" TDA1541A chip vis the S1 single crown:
Back to back in my system, I found that the standard chip has a sightly more forward presentation in the vocal/presence region and seems to give voices a bit of an extra "pop" in the sound stage. It's quite addictive really!
The single crown puts voices a bit further back in the sound stage relative to the standard chip (not too far back overall - just compared to the standard chip) and provides a slightly cleaner and more polished overall presentation. There's a little more clarity and space/separation around elements of the music.
To be clear, we're talking about relatively small differences here - tweaks to the sound of what is a simply magnificent DAC.
The beauty of these two chips is that I can swap between them to tweak the sound and presentation of my system. For the time being the single crown will remain in there.
I think it's a credit to Clay's design that it can show the differences between these chips. Nothing is being obscured or hidden. That's part of the beauty of this DAC in my opinion - it lets the chip shine in all its glory.
To throw a spanner in the works... on the topic of different chips and "crowns" it is worth reading up on what this all actually means. There are some good websites and forum discussions on the topic and as I understand it, a single crown is not a guarantee of superior measured performance. Not all chips were graded during any given production run, so there's a chance that ungraded chips could have performance specs that meet the single or double crown specs! It's a bit of a lucky-dip regarding what you get. I can only speak for my personal experience which has been positive - it may not be the same for everyone.