I had the chance to do this comparison lately with a person i met who owns a cs300X with my own CS300, both equiped with RTC E84L(military grade made by Siemens) and 5751 Jan GE. It happened that we had both equiped our beloved amps with almost the same tubes.(his 5751 Jan Ge are triple mica, black plates wheras mine are standard nos 5751 Jan Ge)
We did the listening at his place on Tannoy Turnberry speakers. Well, there is a difference we could notice, and quite a big to our tastes. I still love my amp, but i really liked what i heard with the CS300x.
To sum up this listening afternoon, we listened on several CDs only 4 or 5, classic, jazz(old and new recordings), the sames for both amps and before any listening, we let them sit for ten minutes for warming up.
We started with mine(CS300), on the other amp owner room and equipement. We were having fun, drinking coffee and small cakes, one guy that never listened to that little leben before that was there with us was thrilled and awed, and while listening to my amp, we did get to hear a nice sounding amp with the tannoy. I have to say that on one recording, a violin was very sour and wrinkled my hear, it never happened on my on rig at home, i was quite surprised.
When we changed for the CS300x, its owner was choked by the sounds of its amp, like it had less mater in sound, shallower in a sense but was way sharper in stereo imaging. I prefered it myself to mine for the sharper stereo. The third person with us prefered mine to the cs300X, for its warmer and eftier sound. When we got to listen to the same violin, it was nice this time and the arshness had disapeared. So in the end, there is a difference, but i cant tell whether one will prefer one or the other. Everybody that is going to spend as much money in an amp IMHO should consider listening to the amp before buying it. Mine is just fine at home, and i dont feel i'll change for a newer one like a cs300xs, even i was quite impressed by the cs300X that was much more on the analytic side.
Last note to consider here : I bought my CS300 in 2014 while it was bought for the first time in 2004, and i liked the sound of the amp i was going to buy on this second hand market.
I got it checked after by a professional for potential worn out components. Nothing was changed on it and every thing was good according to specs. I just replaced all the tubes that where worn out, just after i bought it and it even sound way better. But i can't tell what wat its life before, how it was used(often or not), and from what i was told(by the 3rd or 4th owner) (and from what its worth) it has not been modified in anyway. I have seen in this gigantic thread a chart with the component differences. And on the specs, the cs300x is a pound more heavy that the CS300. I could not find the Schematics of the CS300, to compare with the schematics of the CS300X thats all over the web.
Oh and btw, i use a an AKG K701 and the guy, who owns the CS300X we made the comparison with, uses the same headphones
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