Anyone listen to Zu Audio's Definition Mk3?

213Cobra, you come to the rescue of us poor, non-technical souls out here! I do love the sound of my Def2s thru the Hovland combination, and if this is continued into the Def4s I won't be in a hurry to switch amps. Handy really, since giving my cash to Zu won't allow me to for the time being anyway!
So I gather from your answer, if I'm not mistaken, is that I don't have to chase possibility of using full range of preamp's volume control to acquire more dynamic control over sound if I'm happy with sound with preamp never beyond half way up as it is anyway.
Reading between the lines, the Berning amp combination, to your ears, is leaner tonally and faster dynamically than the Audion 845 SET, and the latter is where your musical happiness lies. That is warmth and tonality win over detail and speed, given the choice between highlights in these amps' signature attributes.
Luckily in the UK I'll be able to get a home demo of Audion Black Shadow and matching pre, and Berning pre/pow combination to make a clearer decision (if ever get to that stage).
Just getting back to the Def4s, since this thread is about them, can you go into any discussion re their stiffer structure: I gather quite a bit more metalwork has been applied esp. in the plinth for the sub bass and also the front panel for the FRD's/supertweeter which has increased weight 50% and contributes a lot to controlling cabinet resonances.

Wow, after reading this entire thread I am ridiculously tempted to get the MKIVs.

I currently have the MKIIs + Tom Evans Linear A + PS Audio Perfectwave DAC (all my music is digital flac). Very happy with the combo but would love to hear the MKIVs. Probably will have to wait until they hit the used market before I can afford them though.

To all those who got their pair, enjoy!

It's always helpful to have more of your volume control's range be useful and accessible than less, if all other things are equal. But would you be happy with a preamp you like less just to get more useful range from your preamp's volume control? Unless the useful rotational range is very small, probably the answer is no. You have two feasible choices if you like your power amp:

1/ Get a lower-gain preamp if you can find one you like as much;

2/ or more feasibly, get a pair of Rothwell RCA inline attenuators (review: http://www.enjoythemusic.com/magazine/equipment/0803/rothwell.htm) These can be placed in-line between your preamp and power amp, to scrub off 10db of gain before the audio signal hits the power amp inputs. If you look around, you can also find similar attenuators at 12db and 15db reduction. Simple, effective, cheap and you get more useable twist in your volume control. Don't obsess about having another resistor in your signal chain.

You could also get a TVC from Music First (expensive) or DIYhifisupply.com (affordable), for attenuation without gain.

I do hear the Berning as tonally leaner (a little too lean) than the Audion Black Shadow 845 SET. Audion electronics are uniquely fast among tube gear but fully fleshed tonally, so I don't agree that the Berning has more apparent speed than the Audion. The Berning sounds "faster" than the majority of SET amps outside of Audion particularly, and some Sophia. I have to extrapolate that Melody qualifies too. Others might. Audion's 2a3 and 300B amps are also impressive like the two top line amps that have silver content, for their quickness, so it's not just a top-line exlusive for them.

You can tune the Audion 845 SET nicely to preferences for warmth and tone or objectivity, via the 845 tube selection. The 845A, B, C, T, KR Audio, and NOS RCA/United/GE tubes lend the amp different voicings. With the Berning, your locked.

As for the Def4 cab structure vs. Def2: I haven't yet seen a drawing of the interior of 4, to see the actual strucure improvements beyond the obvious, but the obvious things are very significant. First, the speaker no longer has 4 ten inch holes cut out of its rear panel, where Def2 had 4 sub drivers. That by itself strengthens the tower box. Internal damping has been upgraded and I believe there is more corner and junction bracing. But the other obvious change is the speaker tower's foundation. The stronger box no longer compromised by cut-outs in the back panel is now firmly bolted to a 1-1/2" thick machined aluminum plinth that is vented for sound to escape and serves as mounting for the 12" downfiring sub. It's a robust, very stiff physical foundation for the more rigid box to rest upon.

I surmise the front panel is now marginally stiffer in addition to being damped by the considerable mass mounted to it. The baffle should be a little stronger in the upper half of the cabinet because the size of the Radian supertweeter forces the FRDs to be mounted further apart than on prior Definitions, reducing how much structural mass is lost in a concentrated area on Def 1 & 2 where the FRDs slightly overlap the supertweeter cut. But the big progress on reducing cabinet talk was between Def 1.5 >> Def2, with the upgrade to 15 ply voidless birch from MDF. That difference for intrusive cabinet resonances was dramatic.

Phil

I've been a Zu owner for the past 6 years going from Presence to Def2 with the new Nano drivers.

With all due respect for Zu as a speaker builder I have found AC/IC/SC from other brands have brought my speakers to their max.

SET amps are good for what they do but there are other amps that from top to bottom will out run them.

Having SOTA gear from power/source/amp/wire to speaker will unleash the Def speakers to their full potential. I see some Zu owners just plop down their speaker on the stock points. I have found a huge upgrade in Footers by Equarack/Stillpoint Ultra under the Def2 that transforms the sound of the speaker.

You can kick my butt, but the 845 amp with some OK wire and OK power on the Def4 will not keep up with Def2 with the new drivers and SOTA gear.

There is no other speaker in my sights than the Def4 for the future but if you have the Def2 with the new Nano drivers and SOTA gear you just might have better tunes than the Def4 owners with lesser gear.

213Cobra, will definitely try those attenuators. Now can I offer a little advice to you: please try the SpatialComputer Black Hole anti-standing wave device. All I'll say it has totally transformed the way my Def2s sound, by removing bass humps in the room (I have a node of 27.1Hz in my room), so much so that I often pop around to the back of the 2s to see if the bass is still pumping out (of course, it is). Sorting out the lowest octave has allowed bass definition (eg kick drum/plucked bass strings), midrange intelligibility and treble extension to improve, causing a real increase in transparency and soundstage. My guess is I'm experiencing a lot of what the improved bass in the Def4s is going to give me.
When I get the 4s, I'm going to investigate the possibility of more units to help at least a further 3dB (unless bass loading of the 4s really presents no issue).
My listening space is 22' wide x 27' deep x 13' high, to one half of the 22' width, a v.live industrial loft type space.
Re the Def4s, how are you getting on with the 5 way user controls on the back of the speakers? I know someone with open baffle spkrs whose active bass module has similar adjustments and he has relied on Behringer dsp shaping to maximise sound. Are Def4 owners likely to need dsp for the bass adjustments? My question is that do you settle on one setting at a time (from default), each setting independent of the next? If each setting DOES affect the next, surely there will be just too many combinations to try.