ARC VSi75SE v. MF Nu-Vista 800

THe operant word re: HT was "double duty". My legacy components, those I use for "serious" 2-channel listening, will be routed directly to the new integrated, bypassing all HT electronics & cables.

Context: The home theater uses relatively inexpensive $2K Class D amps to power the surround & center speakers; but its FL & FR signals will be sent to a single dedicated input of the integrated. Not yet sure if I’ll route analog FL/FR receiver output directly to an analog input or first pass the receiver’s unprocessed digital output through an external DAC. But there’ll be time to make that decision after I settle on an amp.

Either way, I’ll always drive the front-channel Harbeths with the same higher-quality power amp (and possibly preamp), regardless of whether the source is the existing A/V receiver playing a multi-channel disc or streaming 5.1 movie; or a stereo SACD, LP, or outboard DAC.

Oh, and re: headphones, the MF has a line-level output that would drive my Class A HP amp nicely.  I'm not sure how I'd extract headphone output from the ARC but that's not a dealbreaker for me.

I hope that clarifies things.

But I’m a little confused myself. After recommending the ARC, you cite the MF as the better choice. Was that a typo?

One other thing: I hope you’re not conflating popular MF’s M-series amps with its more esoteric Nu-Vista line. Completely different animals; e.g., the Nu-Vista integrated that just replaced the 800 I’m considering lists for $22,000; with Nu-Vista separates running twice that.

The Nu-Vista line is based on a modern version of 1950s nuvistor technology -- essentially tiny solid-state metal-and-ceramic vacuum-tube-like devices. I’d suggest browsing Michael Fremer’s Stereophile review of the 800 for a quick heads-up if you’re not familiar.

Btw, Mikey’s review contained some of the highest praise I’ve ever heard him give to an amp. In fact, some of his characterizations of the 800’s sound quality seem a lot like those I’ve heard about ARC tube gear. Hence, my original question.

See: https://www.stereophile.com/content/musical-fidelity-nu-vista-800-integrated-amplifier

Anyway, thanks for the reply; I think we were discussing a similar issue earlier this week, and I consider it a real opportunity to be able to discuss ARC gear with someone as knowledgable as you.

But given these clarifications, do you still recommend the MF? Remember that I’m trying to consider only differences in sonics at this point.

Wow, I didn’t expect that.

Here’s why: Without the ability to audition, my expectations were based on: comments from knowledgeable people like you; trusted reviews; manufacturer reputations; and pricing. One key element was Fremer’s Nu-Vista review -- "the best product that this company has ever produced” — as well as lots of owner comments about the unique sonics produced by nuvistor technology.

The Nu-Vista 800.2, which replaced the 800 model I’m considering, differs primarily in its power-supply design & aesthetics (minimal if any change to the audio signal path). Sure, I know that PSs are critically important in any amplifier, but in my application, the 800’s 330wpc means that my Harbeths -- nominally requiring 25wpc -- will rarely suffer from lack of overhead. And my system includes $10K of power-conditioning. So I suspect that the 800.2’s improvements, wouldn’t be as dramatic in my system as they would in one built around, say, power-hungry Wilsons, or even Maggies.

OK, given all that: The 800.2 is a $22,000 box that probably sounds more like than unlike the 800. The VSi75 is ARC’s mid-performance integrated, normally selling for about $8K; and you & others have said here that, despite sounding more like than unlike ARC’s Reference amps, it’s not in a class sonically with the Ref 75.

So I wouldn’t have been surprised if you’d told me that the Reference 75 boasts clearly superior sonics than one of MF’s $5-10K MX-Series amps. But the VSi vs. the Nu-Vista? I’m not contesting what you say, because your opinion is far better informed than mine. I’m just saying that such an unequivocal statement was a surprise. Your initial comments about not being too familiar with MF products suggest that you might not be taking into account the Nu-Vistas’ reputation for sounding very different than MF’s more popular MX amps. Nonetheless, your comment pushed me far in the direction of going ARC.

But then you brought up another important point that I hadn’t considered. My listening is split pretty much 50-50 between "critical" SACD/phono/hirez streaming stereo and HT multi-channel. Do I really want to "waste" that much tube life watching TV? Maybe tubes are just a poor match for this application. And maybe the VSi is simply not configured to work in a HT Bypass application – no sub out & no bypass input. So am I back to Square One?

I’d originally hoped to find a way to share the Harbeths between two distinct sources: That is, drive them from the AV/receiver when watching TV, but switch them to better-quality electronics for critical listening. I finally gave up. Maybe some speakers have multiple, auto-switching inputs (like my MartinLogan sub), but not the Harbeths.

So since the solution I really need is out of reach, I’ve spent a lot of time trying to shoehorn products like ARC & Pass Labs integrateds into an application they weren’t really designed for.

None of this should imply that this conversation is not very, very helpful. I’ve always wanted ARC in the house, but maybe it’s just not in the cards. So that’s why I’ve been trying to get a fix on what the Nu-Vistas sound like *directly compared to* other products I’m considering. Your above comments are the most helpful I’ve found so far, so thank you again.

ghdprentice, I have a related question.

I see that the recent Stereophile review of the entry-level I/50 integrated notes that "When power tubes or the tube set are replaced, the I/50 must be biased by a trained technician to ensure proper operating values."  Holy cow, does this sound right to you?

Given that the likelihood of finding an appropriately trained technician is pretty low out here, does that mean that I'd have to ship my ARC integrated to the factory every time I need to replace a tube?

FWIW, I have a degree in Physics and decades of experience working with electronics, so it's hard to believe that something as simple as biasing vacuum tubes can't be done by an experienced user with a voltmeter.

I contacted ARC directly and, as usual, it shot back an immediate response: The company does not recommend users biasing their own tubes but does so for general safety reasons.  The rep emailed me a 16-page illustration of the procedure.   It looks way more complicated than it needs to be -- even the Dynaco ST-70 was mroe user-friendly in this regard -- but it's nothng I can't handle.

The advice I've gotten here is, as usual, excellent.  But TBH, I really am losing my mind.  “Overthinking”?  Well, yeah, maybe.

Priority #1 is giving my Harbeths whatever they need to shine, spending up to $10-12,000.  There are constraints, but are dealbreakers if the sonics are there.  The perfect choice would be an amp that:

i) my 70-year-old back can lift

ii) has an HT bypass

iii) will also work halfway decently powering the front speakers of a home theater (e.g., minimal warm-up time)

iv) has either a line- or speaker-level output for a sub

v) can be programmed to work automatically with a Logitech Harmony

I’ve considered several ARC & MF Nu-Vista models, as well as integrateds by Hegel, Levinson, HiFi Rose, and Ayre.  Bottom line is that the best-fit ARC model is its entry-level I/50, which lacks most of the functionality I want, but at least is light & has a HT bypass.  The Nu-Vista 800.2, which has just begun to ship, has an equally impressive reputation, but at 300/500 wpc and 90 pounds, it’s not perfect.  A better fit would be the lower-powered, lighter 600.2, reportedly due Q1 2024, but so far that’s just a rumor.

So maybe I need to rethink this from Square One.  I just started looking at a Pass Labs solution: the 20lb XP-12 preamp and 48lb XA25.  Just not sure if a 25wpc class A has enough oomph for the Harbeths, but I think Stereophile gave the Pass a rave review based on listening through a larger Harbeth model than mine.

Still, the I/50 is tempting.  It’s just hard to say whether I’d prefer the ARC or Pass “house sound”.  It’s not even personal preference, since there’s no way for me to audition either one first-hand.

I guess this is all part of the fun of this hobby!  Was it J. Gordon who defined “audiophile” as a person thinks more about stereo equipment than he does listening to it?

Key typo in my last message: That list of "constraints" are NOT dealbreakers.  They're nice-to-haves, significant, but I'd work around them if I had to.

arafoq: The H590 is definitely on my short list, but some of the comments here suggest that even the entry-level ARC I/50 -- as well as MF’s limited-edition Nu-Vista products -- are in a whole different class. Again, w/o the ability to actually demo any of these amps, all I can do is ask and listen to responses.

The little Pass Labs amps, I believe, are quite robust when it comes to current sourcing. Wattage doubles, in fact, from 25 to 50wpc when going from 4- to 8-ohm (presumably resistive) loads.

One reason I’m considering the Pass now, at this late date (aside from reading so much praise from Audiogon users), is Herb Reichart’s rave Stereophile review, in which he pairs Pass’s integrated INT-25 with larger Harbeths than mine.

https://www.stereophile.com/content/pass-labs-int-25-integrated-amplifier

Btw, that review includes comments from Joe Pass himself about why his low-powered Class A amps "drive so many loudspeakers with so much dynamic authority and unmatched transparency".  Worth a quick read.

erik: My understanding (and anyone with more currrent knowledge, please correct me) is that MF came up with a new variation on the old RCA nuvistors.  Supposedly, it discontinued the Nu-Vista 600 & 800 because of parts-availability issues -- but they were talking about front panels!

My SWAG is that MF is still working off its existing inventory, but has the means to manufacture more nuvistors as needed.  They actually sell nuvistor kits online.  And don't forget that tne Nu-Vista models are characterized as "limited edition."  I don't think they produce too many of these exotic beasts.

arafiq: I’ve spoken to others who found the 25wpc Pass gear more than adequate for mid-sized Harbeths, but again, the devil is in the details. Can you give us an idea of the size of your room, listening levels, etc. when you found the INT-25 to be underpowered?

E.g., Was your experience closer to playing string quartets at moderate volume in an 8x10 room or blasting Black Sabbath at realistic volume levels in a 30x25x8 room?

Just trying to put things into perspective, since I’m about to purchase a simiilar amp for my Harbeth C7s without the ability to audition the gear before buying.

classicalreflections:  So you're saying that the biasing procedure is much simpler on the VSi  than on the i/50?  You don't have to open up the chassis, clamp probes onto a resistor, etc.?

arafiq: Great feedback, exactly what I was looking for. Thank you.

Re: the C7 v. the 30.1, those two models are very similar, identical drivers & ports (admittedly arranged differently), similar cabinets, impedance curves, etc. The 30.1 is nominally 1 dB less efficient, so when I hear that a particular amp can drive the 30.1 well, I assume that I can extrapolate that recommendation to the C7.

FWIW, Alan Shaw claims that the C7 is his personal favorite model when driven with at least 80wpc. However, the XA25 is a high-current device (10A in the specs), and I suspect that its 30-ish wpc (into 6 ohms) is more powerful than you’d expect. And then there’s Herb Reichart’s high praise for the Harbeth+XA25 combination in his Stereophile 30.2 review. But still...

Your comments comparing the Lux & Pass are interesting. But I’d be even more interested in context. What size room, the type of content you played, volume levels, mounting, powered sub crossover freq, that sort of thing. I’m sure you’d agree that in this type of comparison, those details can make all the difference. In fact, your personal C7 experience seems to confirm Shaw’s (and Reichert’s) comments about these easy-to-drive yet finicky thin-walled boxes. Reichert found that even eliminating the blu-tak attaching his 30.2’s to Sound Anchor stands degraded their sound. And Shaw claims that, despite being designed to be insensitive to differences in cabling & ampflification technology, simply removing the grill cloths compromises his design. So again, devil in the details.

At this point, after digging through offerings from Levinson, PrimaLuna, ARC, Hegel, HiFi Rose, and Ayre, it looks like the XA25 & the Nu-Vista integrateds offer the best compromise among sonics, cost, connectivity/functionality, and form factor -- at least for my particular application. Even the INT-60, great as it must be, would not fit my system & room.

Unfortunately, there’s no way for me to hear these components before buying. All I can do is have long conversations with people who have had first-hand experience. And so far, there’s been no consensus about whether the XA25 is a good match with small-to-medium sized Harbeths like the C7 & 30.2. Many people, including trusted reviewers in Stereophile & TAS, describe in detail how beautifully they work together. But others, like you and Pass Labs’s & Harbeth’s own customer service reps, recommend more power.  Sigh.

One final question: Thinking of presentation, the things that the XA25 is noted for: holographic, three-dimensional soundstage, reproduction of room ambiance ("the players are in your room" v. "you are with the players in their own room"), realistic image size, Quad-ESL-like coherence, etc. -- did you lose any of that with the Luxman?