Anyone listen to Zu Audio's Definition Mk3?

Spirit,
You make some very good points,there`re different pathways to upgrading a system. The cost of the Duelund CAST is based on the capacitor size/value in uf. Mine are 5.6uF(speaker) and cost me 850 USD.The 1 pair I placed in my DAC(output capacitors, 1uF) cost 440 USD. The improvement is 'very' substantial. Spirit, depending on the size of your speaker caps(what size are they?),the cost may be equal or even less than many high end cables(power or interconnect).Just something to think about as tweeter cap quality is a big contributor to the overall sound.

Charles, I had a little bit of a mindstorm, and thought you were suggesting I replace the caps in my Hov pre! That would have cost me a tidy sum, in effect the cost of totally new amplification!
I'll check with Sean on the cap value on the tweeters in the 4s and give this some serious consideration. Luckily here this is a rel. simple install job, no soldering needed, just temp. dismantling of tweeter.

Spirit, If I were you I would not do any mods to anything without having first run the system that you set up.

Simon did mention to me something about that cap mod, but it was in the context of dealing with cables and poor digital front ends. IOW when there is vinyl there is no hint of a problem.

Digital has always sounded brighter to me so this is no surprise at all. I have to say I am not used to anyone describing our amps as bright or lean. Just Google 'Atma-Sphere' and you will see what I mean. The Druids we had here did not have even a hint of it.

Spirit,
I would agree that first get comfortable with your new speakers and their fit into your system. Once this is done and you have a good sense of your sound ,then further changes 'if needed' can be chosen.
Speaker capacitor changes can be a relatively simple step that can yield marked improvement quite often.You have plenty of time,so no rush.
Regards,

Unless an owner asked for something different, Def4s have a Mundorf cap on the Radian super tweeter. I know Zu continually evaluates new capacitors for in-line upgrades and as options for customers before or after delivery. I wouldn't go so far as to say that the Mundorf "holds back" the Radian in Def4 and Druid5, but you can certainly alter the perceptual output contour of the very top end by changing the tweeter network cap to voice your system. I will have more to say on this in January, as I will be doing a few cap comparisons on my Def4s and Druid5s in a few weeks.

I agree that Atmasphere OTL amps are "clean & lean" on Definitions; less so on Druid, which tends to help any amp deliver more tonal body in the midrange. And for some reason, Superfly conveys Atmasphere sound more like Def than does Druid. I get more natural presentation from specifically Audion SET than from any push-pull tube amps, OTL or otherwise, but I also have to say that the amplifiers under discussion by Spirit lately in this thread are all in the family of highly credible amplification for Zu, and that includes his Hovland. Yeah, sure you're getting some silicon sound from the Hovland power amp but compared to what normal music aficionados are dealing with, we here are talking about spending silly money to correct a relatively narrow deficiency. Not that I wouldn't spend it or haven't! Once the right power amp is lashed to a Zu speaker it becomes very straightforward to sort sources, cables and even to dial in setup.

Phil