What amp are you using with your Zu Essences?

Just a scored a pair of these and I was just wondering what people were pairing up with them. I've heard they work best with tubes. Has anyone tried solid state or Class D and then moved to tubes? How many or how few watts have worked for you? Thanks in advance for any stories.
I have a pair of Essence and have just transitioned to tubes from solid state-- actually, I'm still in transition as I won't have my pre until the third week of February.

Current setup:

Zu Essence

Manley 300B SE/PP monoblocks (11 wpc SET; 24wpc PP); SET at 0-2dB negative feedback; PP at 1-3 dB negative feedback.

Sony ES receiver serving as a temporary pre-- being replaced with a Manley 300B pre.

Sony HAR-D1000 cd

Zu Libtech speaker cable
Zu Gede interconnects to the amps
Zebra Cables custom interconnects from CD to pre
Zu Mother power cords

11 wpc in SET mode plays LOUD in my room 12*16*8. The sound is exceptionally liquid, dynamic, and three-dimensional. This should improve dramatically when I use a better pre, but it's pretty fantastic now.

I have also paired the Essence with the Sony ES Receiver, a Cambridge 340A integrated, and a Rega Elicit integrated. Best sound was obviously the Elicit, but the 340A put in a strong showing.

Some points about the Essence with tubes: the top-end is very balanced and well integrated with the FRD. The impedance of the ribbon tweeter seems to interact with the tube amp to shelve the response down slightly to better intergrate with the rest of the frequency spectrum. Bass is full and weighty. In-room response is in the high 20's in my room.

Some points about the Essence with solid-state: the 340A (roughly 40wpc) has more than enough power to be speedy and exceptionally dynamic. The Elicit has a little more headroom, but the difference in power and drive is not noticeable. The 340A is slightly more punchy at the expense of smoothness, lack of grain, and the flow of the Elcit. Overall, an amp with the characteristics of the Elicit is a better match in the solid-state world. Placement can be tricky with solid-state as I found the treble response to be a little "hot". I don't want to overstate this as it was easy to deal with, but others (in the Zu camp) have different opinions on the magnitude of this issue. I found it easy to compensate for this by using different interconnects and speaker cables (annealed copper) from Zebra cables. This smoothed the response nicely. In addition, experimenting with toe-in so that the tweeter outputs cross behind the listening position on the midpoint of the rear wall smoothed this.

Overall, 11 SET wpc really lights up the Essence in my room. A small but noticeable difference from 24 PP wpc-- better grip in the bass, slightly more dynamic, slightly less liquid.

Having owned every Zu speaker (except Superfly), most on multiple occasions, I'd opine that virtually any amp will work ok.

That being said there are better matches than others. My recommendation after thousands of hours would be to stay away from Class D amps with every Zu speaker. In general they seem to suck the warmth and polish out of Definition, Essence, Druid, Tone,Presence, and my newly arrived Omen Defs.

Most other topologies work quite well and sound terrific; pay particular attention to the speaker's impedance. For example, OTL amps are not ideal with the Omen Defs (6 ohm) whereas Class A solid state is magnificent. The best amp with the Omen Defs so far, to my ears, is the Pass XA30.5.

Alternatively, Presence and Druid with their 16 and 12 ohm impedances, work extremely well with OTL.

Class D amps can be wonderful with the proper speaker but to my liking, Zu is not high on that list.

However, at the end of the day, if you like what you hear go for it. Afterall, your money.

Dealer disclaimer
FirstWatt J2, M2 and F5 are terrific as are my 25wpc EL84 class A push/pull monos. My 8wpc Yamamoto A-09S or Woo Model 5 work very well too (both 300B) but I personally prefer the 25-watt transistor amps for their better low-level resolution, grippiness in the bass and lower noise.
I had the Essence and they were paired with a Melody I2A3. I bought it based on Zu's recommendations and found it to be a nice pairing, and there was never a question of not enough power.
Audiofeil's comment about OTLs and ZUs is incorrect. There don't seem to be any OTLs that will not drive the 6 ohm ZUs quite well.
In fact my previous statement is correct.

Having had 3 pairs of Definition (6 ohm) here with an Atma-Sphere S-30 for over 2,000 hours of critical listening I'm quite sure of my conclusion.

The only instance in which the S-30 worked properly was on 1 pair of Definitions that had a 30 ohm load option. The bottom end performance was extremely poor using the 6 ohm taps. I suspect the Omen Defs (6 ohm) would perform similiarly.

I did not use the M-60 or MA-1 models so no opinion with them is offered.

Thank you.
Additionally, if you go to the Zu website and view the speaker comparison chart you'll see amplifier recommendations for various amplifier topologies.

Please note that Zu's comment for Omen Def (6 ohm) and OTL is a tenuous "maybe".

Thank you
02-11-11: Atmasphere wrote:
Audiofeil's comment about OTLs and ZUs is incorrect. There don't seem to be any OTLs that will not drive the 6 ohm ZUs quite well.

No good deed goes unpunished.
I am driving the Definitions with Decware's new Torii 26 watt EL34 based amp and it is absolutely a stellar combination. I have found that Zu speakers are very amp friendly so enjoy them!
Apparently Ralph doesn't like dealers who don't toe the company line as I've just been removed from the list of Atma-Sphere dealers.

That's certainly his prerogative and I make no apologies for expressing what I believe to be honest opinions based on actual listening experiences.

I wish Ralph and his company all the best.

Thank you.
Is Ralph really that petty and sensitive?
"02-11-11: Audiofeil
Apparently Ralph doesn't like dealers who don't toe the company line as I've just been removed from the list of Atma-Sphere dealers.
That's certainly his prerogative and I make no apologies for expressing what I believe to be honest opinions based on actual listening experiences.
I wish Ralph and his company all the best.
Thank you."

Did you check with Atma-Sphere before making this statement, as it is always best to speak with the manufacturer before making possible invalid claims/statements?
>>making invalid claims/statements<<

I don't really need to check with anybody, manufacturer or otherwise, to report what I hear. That's not my style.

Anyway, I've been offered my job back; no decision as of this moment on my part.

This is my last post regardless of what follows; readers please feel free to email or call should you wish to discuss
Charles1dad, to answer that, if you can, take a look at the posts I have made here on audiogon and see if you come to that conclusion.

I don't like being called 'petty' but it may well be that that is the case. But there is more going on here than just this thread. In email conversation Bill expressed pretty much the same as he did in his last post just above, and I agree with him that he is not beholden to anyone regarding his own opinion.

However, you have to think that something is amiss with this statement:

For example, OTL amps are not ideal with the Omen Defs (6 ohm)

-not having heard any of our larger amplifiers with the ZUs, larger amps that handle 6 ohms easily, the statement is simply incorrect. Now if he had said 'smaller OTL's,' I would have cut him some slack, but even then with a set of ZEROs *any* smaller OTL can manage a set of ZUs just fine.

Now I have steered people away from our amps when they have had incompatible speakers, since it would do no good to sell someone on something that does not work- you only make them angry and there is no point in that. What Bill is not telling you though is he has not sold anything of ours nor have we heard from him in well over a year. He used to be one of our more active dealers. Its been my experience that when a dealer goes from active to inactive that its not out of chance.

We have a good working relationship with ZU and have had their speakers in house. Their speakers have always been an effortless load for most of our amps, but given that they are so easy to drive, the question most people have is how our smallest amp, the S-30, will do on the speaker. With the 6 ohm models you use a set of ZEROs and it works fine. With the higher impedance speakers you hook it up directly.
Zu has also built the speakers with higher impedances- it might be that it is just for the S-30 but I think they are targeting other amplifiers as well.
Historically Audiofeil has frequenty praised your products and seems to hold you in high regard personally. He was very specific in stating that in the case of the Zu Definition(6 ohm load) the S-30 was`nt a ideal match, but the 30 ohm version was fine. You even suggested the need for the Zero for the 6 ohm load if using the S-30 amplifier, which supports Bill`s experience.
I've bitten off all my nails. Time to go for the ritz crackers and cheese whiz.

I had the Essence paired with a VAC Avatar and they got real loud with awesome bass at 27 watts. I'd avoid class D like the plague because no matter how many thousand dollar systems I've heard with class D, two to my own dismay, I've always been disappointed with the lack of dimensionality, and lack of bite in the mids.

I feel like this is another thread that will self destruct.
Sounds like there is definately something in the air this week. We have dealers whining and manufacturers spitting their dummies (pacifiers) out over here in the UK at the moment.

It sounds like Audiofiel and Atma-Sphere need to meet on common ground, kiss and make up.
Sorry for creating a bit of a storm in a teapot, but thanks for the suggestions. Currently I'm using a Sharp SM-SX1 digital integrated. And I'm kinda stunned how good it is. It puts out 52 watts per side which is plenty. And they're good watts, crystal clear without sibilance, nice tight bass. I can only imagine how much better tubes are going to be. I'm definitely going to check out the Decware and First Watt suggestions--any more?
Cayin A-50T. EL34 based amp. It sounds great, and is very reasonable on the used market, usually under 1K. I have upgraded the tubes in my to the Genelex Gold Lion KT-77, and it really performs.
Charles1dad, What you say is true but about a different post- so in that we regard we are writing about two differnt things, but perhaps I take things much more literally than you.

What should be pointed out here is that a speaker that is 6 ohms is not going to match a transformer-coupled amp *ideally* either, unless that amplifier has a 6 ohm tap.

In the case of a small OTL, you only have to use a set of ZEROs. In the case of the ZERO, if you look that the website-


-you will see that the autoformer is treated more as a set of ratios than a specific impedance like 4 or 8 ohms. What this means is that if you have something like an S-30, and using the 2:1 ratio, that the amplifier will be driving a 36 ohm load. As far as the S-30 is concerned, this is ideal. The speaker does not need a *lot* of power, and the 45 watts that the S-30 will make in this example will really wake the speaker right up, better than most transformer-coupled amps.

Now you may not realize this but we used to make a product like the ZERO about 20 years ago, we stopped when the ZERO came out because it was a lot easier to explain the ZERO than it was our own product!

People were always asking 'Don't you obviate the OTL thing when you do that?' and the answer is no. Its funny how people had this story that an OTL had to be a certain way, and were equating the ZERO and its predecessor with regular output transformers, and there is a huge gulf between the two. The bottom line though is that it is just a way to make music, and I've never seen it as anything else.

That is why I always recommend to our dealers that they have a set of ZEROs on hand.
Bill is somewhat of a jerk. If you don't agree with him, well, you're just wrong. No room for any possibility that he might be the one who's wrong. Oh, and if you don't agree with him, you're almost certainly mis-informed.

Talked to Bill about a First Watt amplifier more than a year ago now. I said I would be happy to buy from him if I could have an in-home audition with return privileges, same as what Reno was offering. He suggested I should take Reno up on an in-home audition, return the amplifier, and purchase from him instead. I declined the offer.

Bill will likely say there's more to this story than that, but I'm happy to share the complete email exchange with anyone who wants to see it.
I am currently using a Rotel RA820 integrated to good effect.
Although I am looking at alternatives in the near future such a First Watt F5, Pass Labs INT30.5, Luxman L590A MkII.
Have a read through some of the 6 Moons reviews of the above amps and also the Yamamoto amps to get a flavour of what is out there as the reviewers have Zu Essence speakers.
Has anybody paired (or heard) a Viva (Solista or Solista LT) or one of the Mastersound amps with the Zu Essence?? I'm leaning towards one of these, and want to be in the 18-20 wpc SET family of amps.

My Art Audio PX-25, a superb amp in it's own right, sounded amazing on the Essence, but alas, it runs outta steam for my rather large room.

Phil, the Zu guru highly recommends the Quad II's, Quad II-40's, and Quad II-80's. If I recall correctly, the all-out winner is supposed to be SET using 845 tubes.

I have also heard that EL-84 based amps do well.

I like my Manley's, but it would be nice to have the funds to compare.

I've heard Viva and Mastersound big SET on Zu speakers other than Essence. Have listened to Essence on Audion 845 monoblocks and Audion Golden Dream PSET monoblocks. Both of those amps are 25w. The Viva is euphonically old school. Not as illuminating as you should get at their price. The Mastersound 845 I've heard was more credible for being musically convincing. Audion handily elbows both aside.

A PX25 SET amp will generally sound quite clear but will run out of steam in a larger room, especially with the 4db less efficient Essence. 20w of SET is a clear dynamic improvement, all other things being equal. But just as my 300B PSET amps are not quite as dynamic as my 845s, despite the same power rating, remember it's the "drive" more than the steady state power that matters. Put a first class 845 SET on any Zu speaker and you're done. But that's not cheap, "first class" being the determinant. I do find the Quad II to be an excellent p-p step back from SET, for the 12+ ohms Zu speakers, with the more complex Quad II-80 and II-40 being highly credible at more power. Use the Shuguang Treasure power tubes. In this pool of amps there's bliss to be found.

Thanks Phil... I should have mentioned that the amp I amp looking for needs to be an integrated amp, or at least a pseudo-integrated, which has an attenuator.

I do like 845s! Before the Art Audio PX-25, I had a pair Art Audio Quartet monoblocks, which were also fantastic (though not SET, but PP). Maybe a Carissa with an attenuator would work well?
The Quad's sound amazing on a pair of Superfly's that I recently got a chance to audition. I really loved the combination. I have a pair of Omen Defs and I used to have the Essence.....I did not get a chance to hear any of those with the Essence, and the Essence is so different than all other Zu products. BTW I have a Carissa coming this week, so I can let you know about the combination.

Phil do you have a favorite 845 Tube for the Carissa? It is coming with the KR 845 (that's what I remember anyway).

I would also recommend that if you have not heard the other speakers in the line-up, do yourself a favor and go check them out. If you are near SF I would be happy to have you over.
>>Phil do you have a favorite 845 Tube for the Carissa? It is coming with the KR 845<<

The KR 845 is built and sounds different than a vintage RCA or Amperex 845, or the Shuguang tubes patterned after them. Earlier in the KR's production there were some serious reliability problems deriving from the KR's ribbon filament. Like all KR tubes, that example is otherwise beautifully constructed. The ribbon filament problems were a design and execution issue. I don't know whether the high incidence of problems with that tube have been resolved more recently. However, that tube has a robust, transparent sound that in some systems can be icy but always very clean toned.

Once you get into tube rolling, preferences get very personal and it surprises me to hear the wide range of variances in how two people who have generally the same sense of audio fidelity can land on the question of which 845 power tube to use. For the tonally sophisticated 845 amps, in which I'd include the Carissa, I generally prefer the Shuguang 845B graphite plate tube among current available production. It has authoritative shove, deep bass with very good definition, beautiful midrange and the top end has very fine transient body but never sounds strident. The metal plate 845C has an initially exciting spray of focused detail. In a high end 845 with wideband output transformers and a fast circuit, that tube will sound strident. But on a vintage-voiced 845 SET like the Japanese Triode 845 or some of the inexpensive Chinese 845s, it can wake up the amp and give it speed and detail that its warm voicing otherwise obscures.

Similarly, you wouldn't want the 845C in a system with Essence and it's cold ribbon super tweeter, but it can be just the thing with, say, a pre-v4-08 Druid. So KR 845 may be too strident on Essence depending on the rest of your gear and how reinforcing of treble your room is. It's a borderline call. On Superfly more of a matter of taste. I think with both speakers the affordable and widely available 845B is the best choice. Also true with Definition. I haven't yet taken the time to find out whether the Shuguang Psvane 845 is worth its price relative to the 845B. I'll also add that the graphite plate 845B has proven both reliable and long lasting in my Audion Black Shadow monoblocks.

The wealth of knowledge and experience in Phils posts never ceases to amaze me. The man knows his stuff, especially pertaining to driving Zu speakers.

I spoke with him at length about amplification choices for my Superflys and, though I resisted at first, looking for a lower voltage/less intimidating option than 845 set for a home with an infant, his enthusiasm for the set was always present and when the opportunity to try one in my price range came about, I bit and it has been one of my best moves in this hobby.

I have about 26 hours on a pair of the Psvane (Pavanes) he mentions above. Had an 845b crap out prematurely and used the opportunity/excuse to give it a whirl. It needs more time to settle, but I'm starting to see a lot of potential here.
Thanks a Million Fred and Phil! I certainly look forward to getting the 845's in place, though honestly I am absolutely loving the Modwright Pre with a Pass Labs XA 30.5. Awesome dynamics, bass, transparent....loving it:-)

I do appreciate the feedback immensely on the 845's and I will await Fred's feedback on the Pavanes. I think the three of us have a similar tastes, and I absolutely agree that what one man loves, the one next to him may hate!

Truth be told, its pretty hard, IMO to make Zus sound bad... I've only had one amplifier combo I actually 'hated' Ironically it was one that Zu actually had on their recommendation list (my dad had a Panasonic XR-25 gathering dust--figured I'd give it a shot).

I'm no stranger to Pass designs driving Zus and they can be pretty darn good--I liked the Alephs in particular over the Firstwatts. The Alephs were recently de-throned by a Redgum RGi120 as my favorite solid state option for my Superflys.
VERY musical combination.
Been reading, and have a pair of Omen Def's on the way, and
wonder why no mention of Peachtree as a recommended amp for Zu's as they were what was used at the shows mainly??
Peachtree integrateds sound fine on Zu speakers, though better on the 12+ ohms speakers than the 6 ohms Definition configurations. "Fine" being the operative word. That is, for their cost Peachtree integrateds are beyond reproach. If you can afford more, by all means put more money into your amplification for more engagement, presence, musical intimacy and more convincing recreation of the recorded event. It will be quite worthwhile. You will get no-apologies, serviceable fidelity out of Peachtree + Zu, but you'll be leaving quite a lot of the speaker's musicality, involvement and sonic potential untapped. Peachtree is far less than optimal, and far more than objectionable, the classic mid-fi dilemma as to where you put your cash.

As I've written many times before: going lighter on the Zu speaker (lower in the line) and pushing more of your cash into exceptional amplification is generally the better route with Zu if funds are constrained and you have a set total spend allowed.

The Peachtree is a fine choice and you will likely be happy with it. The truth is, the Omen Defs and the Superflys are so transparent that every amplifier change will produce dramatic changes, all of which are of course just a matter of taste and personal preference I have heard the Omen Defs with many amps and a very good solid state integrated is the Virtue amps with the tube buffer (also recommended by Zu). There are many good options, and what I have found is it is just best to try several amps to get a different taste so to speak so that you can determine what you like best.
Thanks Phil & Morgan! I do have a XPA-2 that I was running with my standard Omens and thought it sounded way better
than (using Peachtree as a pre/dac) just the Peachtree by
itself. I guess thats the way I will run the Omen Defs.
Also, I was thinking (hoping) the Peachtree would be a better
match for the 6 ohm Omen than the 12 ohm...no??
Your own ears will tell you, but no, reducing speaker impedance will not make the Peachtree's amp section sound better tonally. 6ohms may allow it to sound a little more energetic, however.

Morganc... very interested in your thoughts about how the 845-based Carissa plays with your Omen Defs! Please keep us posted!
Hey Phil,

That's exactly what I was talking about, thanks! I knew it would not change the tonality but was thinking it may have a little more energy & punch perhaps. I will more than likely
run the XPA-2 anyway, but was thinking if I did not need it, I could turn the amp (XPA) into a sub.

I will follow this thread as I would like to try tubes maybe.

Any thoughts on how these may work with something like a Jolida 302BRC?? I have never come across anyone mentioning
Zu/Jolida combo's but would think it would be a very sweet

Thanks again!
Well, I just sent away for a new tube compliment for my LA-Audio 100r. KT-94s produce plenty of grunt (90 wpc into 8ohm) and a good deal of image saturation, which is something that is missing with the Sharp. Less pristine and sweet than the Sharp, I'm betting that Essence tweeter gives a more artful presentation with the LA Audio.

I'm curious to know, why are the Essences considered different from the more typical Zu sound/models. I know they are less sensitive, but how does that actually play out in the listening arena?

After reading up on some suggestions I'd really like to hear the Pass XA30.5; thanks again all--fascinating discussion.
I will start with the disclaimer that I am no audiophile or expert, and I have to say that I enjoyed the Essence until I upgraded to the Omen Defs. However, the Omen Defs are not that far away from the Def mk ii (especially with a few mods)and maybe even better in all categories except the bass (direct quote from Sean Casey). Both the Omen Defs and the Superfly excel with dynamics, sound staging, and are both very musical. The Superfly produces a bit more of an intimate feeling for me, though they both sound like you are at a live show....with great presence and tonality. I never got that from the Essence. The Essence excelled with vocals and jazz, but when things "got busy" so to speak, especially on the high end, my ears fatigued at even low volumes. This only happens with the Defs for me at higher volumes for longer periods of time, and with better amplification, it keeps getting louder and longer before I fatigue!

I am loving the Pass XA 30.5 at the moment, though I do have a Carissa 845 on the way. If the Pass is displaced, let me know and I will give you a great price on it.
"1markr Morganc... very interested in your thoughts about how the 845-based Carissa plays with your Omen Defs! Please keep us posted!"

I will for sure! It arrives Wednesday and I am off Thursday afternoon.....so I will gladly give you an update:-).......

For anyone else, especially you Phil, have you tried the Art Audio PX-25 with Zu? If so I would love to hear your thoughts, especially if you can compare it to the Carissa or a similar 845.

FWIW, the Essence ribbon tweeter output is "aggressive" with solid state gear, but nothing that can't be accommodated/resolved through careful (small) changes in positioning. I found that toe-in so that the tweeter output intersected on the rear wall behind the listening position minimized this in my room. Listening height plays into this as well.

That said, all of this went away with tubes. The impedance curve of the tweeter shelves down the output just a little on my Manleys. My Manleys are a very good match for the Essence albeit a pricey one at the new list price.

Telescope: are you still running the XPA-2? How is it treating you?

Yes, I am using it with a Peachtree Nova as a pre/Dac
and the combo is wonderful! I want to maybe try tubes
sometime, but feel no need at the moment.
Nice Telescope.....I talked to Sean and Adam at Zu and they both prefer Solid State with the Defs. Their favorites are the Pass Labs from the F3 to the M2 to the XA 30.5. What types of music do you listen to? What soumds the best on your system?

To digress a little, I am using an Almarro 318B with Zu Druids and the amplifier is wonderful. However, the sound from the Almarro is heavily dependent on the pre tubes. I settled with a Mullard brown base CV569 (6SL7) and a Sylvania 6SN7GTA for wonderful warmth and detail. The SED 6C33C power tubes bettered the Sovteks with a little more detail and extension.

This tube combination (by my ears and preference of course) gives the best midrange that I have ever heard out of any amp and still had delicate and revealing highs without harshness. With the wrong pre tubes, the Almarro sounded dull and blurred. Perhaps the Zu people did not have the Almarro on their list because they did not tube roll it or perhaps did not review it, as it bested the Melody I2A3 which they said is "awesome".

I owned a Cary 300SEI with Western Electric 300B tubes and the Melody I2A3 recommended by Zu, but found the Almarro 318B to sound superior overall, especially for midrange warmth and engagement. The Almarro also has delicate and revealing highs and can even rock when called upon with its measured 20 Watts of SET output. The Melody I2A3 had a tad more finese and silkyness in the highs and a little more forward soundstage. The Cary, 300SEI although very nice, suffered from a little bit of the dryness that I almost singularly seem to hear in some of the Cary equipment.

However, the Almarro won handily in overall midrange presence, giving out an immediate front row center sound with full tube 3D realism and depth. It was wonderful with vocals, instrumentals and jazz, yet still possesed engaging sweet yet detailed silky highs - and as mentioned, can play rock when called upon without being embarrassed. The Almarro should have no trouble powering Zu Essence, Sous or Omens (or Omen Definition speakers for that matter as it powered both my Druids and Tones simulataneously in an effortless fashion).
Got hold of Primaluna Prologue 2 integrated with KT88 output valves for use with my Essence, it was certainly interesting, having never used valve amps before it did open my ears to the philosophy behind the Zu speakers designs, so much so I got some Svetlana EL34 output valves and Philips control valves for it, now it is sounding sweet.
Next step is to try out the Zu cables in place of the Mogami I currently use.
I got my Essence speakers about 6 months ago replacing a pair of Druids. I drove the Druids with an Almarro 300B which is a really nice match. Once I got the Essences, I decided to try some new amps. I started with a Red Wine 30.2 after reading about them for years ... I found it dry and lacking clarity even after a factory tune-up. I moved on to First Watts F1. The sound had the sparkle and clarity I was used to from the Almarro but not quite as much depth. It had more firmness on the lower end and pop on drum sticks. But the F1 did not have enough power - I use a MAC with no preamp. I go from itunes through Pure Music software into my Exemplar DAC and to the amp. I replaced the F1 with an F3 using the same set-up. That is an ideal pairing to me. I kept the Almarro and switch them out ... different sounds but I consider them equal.

BTW - I listen nearfield (6' between speakers and 6' from me) throughout the day as I work at home. So I was going through tubes every few months.

For grins and because I have the bug, I just bought an F5 to see how it compares. I'll post my thoughts in a few weeks once it arrive and is up to speed.
I'm Having fantastic results with Art Audio's High Current Jota amp. It's a 20-24 wpc SET amp, and this thing has the power and finesse to drive my Zu Essence effortlessly. Great, musical combination!
I'm using an Art Audio Carissa and a PX-25 and loving them both. I have decided that for me the PX-25 is a better fit as I listen at what I believe are too low volumes for the Carissa with such high sensitivity speakers ( I have 101dB Sensitive Omen Defs). The Carissa is better with jazz and vocalists, but I prefer the PX-25 for electronica, rock, etc as it is a bit more dynamic, but a little less life like compared to the Carissa. Either one though is a great pairing with Zu's.