Jeff Rowlands Amp and Dac vs. VAC amp and DAC


Hello, I am new to this forum but I have a question. I am trying to pair an amp + DAC with my Wilson Sabrinas. I have listened to Jeff Rowlands integrated with the Aeris DAC. And the VAC Sigma integrated with the Aeris DAC. Price is a factor and so is space. Does the 625 need a pre-amp? Any suggestions or thoughts? 
rinpoche
I am using a biwire set of Elrod Gold Statement speaker cables between my VAC Phi 200 and a pair of TAD CR-1's.  I will admit they are stupid expensive, but they improved my system sound in ways that I appreciate enough.  Before that I was using a true biwire of Clear Day Double Shotgun cables, which I think are fantastic cables, in general, and crazy good for the money, IME.

Hi again rinpoche? Are you in Canada? And is your dealer Angie Lisi from American Sound? If this were the case, please say hi to Angie from me... He was singly responsible for making me discover the magic of the Rowland sound in 1998.


Concerning Einstein, I heard their products a few times at some length, but never managed to like them much. Regretably, the word "rough" seemed to apply more often than not... With my test tracks, Einstein never reached terribly close to the top of the musical heap, and tended to blow tubes on sharp . Treble intermodulation was too easily present... On the other hand, the brand might have improved since a couple of years ago.

   



 

Guido, wow, that is amazing. Okay. I have a list now. I see you like the Jeff Rowland equipment. So do I.

Mapman asked if there was one if there were any systems I would not be happy with from among the ones I have heard. To be honest, this is a great question too. I don't think I want to live with the PS Audio (I would always be thinking I could do better), or the ARC (though can't say why exactly — maybe it tries to do too many things all at once: amp, preamp, DAC, headphone amp). The Air Tight the shop had would not be sufficient to drive the Wilsons and they only bring in amps on order so that ruled that out. So that brings me back to the JR and VAC, where all of this started. If the JR and VAC Sigma were the only amps to choose from, I think I would go with the JR for ease of use and the 'weight' behind the sound (if that makes sense). The Sigma is really lovely, and though I haven't heard it with the (controversial) Wilson's, it lacks something by comparison. That is why I want to wait and hear the 200 IQ. And see if this is better. But JR for many reasons, some practical, is winning so far. 

I did come across an amp that looks lovely though there is no dealer where I live. It is called Einstein. I have no idea about price or anything else, but it has a nice look to it. And since I don't have a 'woman-cave' -- the equipment is right in the main living space, aesthetics are also important. JR wins hands down over VAC on this one -- though those little orange glowy tubes are nice to look at!!!

I will listen to the Dvorak pieces. Very exciting. 

Hi Rinpoche, SS vs tubes is not the best way to look at the problem of amps... Rather, the thing to look at is the actual sound of individual amps, or at least the house sound of particular brands. Hence, you are doing well in your current path to final choice... One Rowland SS, and one VAC tubed... Yes, definitely you will find marked differences between the two amps... Yet their audible personalities have much more to do with the sonic phylosophies of the two designers, then about one amp using SS and the other one tubes.


Good idea to evaluate amps or any other component always with the same set of recordings... I have been using the same 6 audio tracks for the last 15 years... THis has helped me to create a stable frame of reference.


I use mostly the following pieces...


Antonin Dvorak -- In the Old Castle (from a 4-CD set of all Dvorak piano works on Brilliant Classics CD) with Anna Poroscina playing a a Bosendorfer grand... I look there for harmonic exposure and stability of the piano tone across the 7 octaves, naturality of attacks, persistance of decay, and extent of low level information (sounds emitted by the performer, felt noises, piano bench).


Antonin Dvorak -- introduction to string sextet with double bass. The introduction has some passages with the higher string parts bunching together in the mid treble during the cusp of cadenzas.... Many amplifiers cannot handle such closely scored sostenuto in the treble region and break apart: The sound becomes shrill, strident, and unlistenable because of intermodulative artifacts.


One more Dvorak... 2nd movement of the Symphony from the New World Op. 95 with the Israel Phil under Leonard Bernstein... My favorite performance of this work.... Look at the following:


* How does the amp handle the opening fanfare for lower brass...

Can you hear the individual horns and trombones, or does the image become homogeneous and an indistinct musical pudding?

Gradually the brass section shows some cuivre.... Does it remain coherent and musical... Or does it exibit signs of intermodulative strain?

Are the timpani pitched or tubby?

How well can you hear the hall in the low level information?

How clear is the double bass line.... deep and well pitch, or surfacy and tubby?

What happens in the ff at the end of each section? Does the amp sail through without effort with all instruments still clear and sweet.... Or Does the image seem to saturate with a front-to-back collapse of stage and images, and the appearance of hardness?

Can you hear Bernstein stomping his feet to encourage the players some 12 minutes into the movement?

Can you hear him subvocalizing during the final brass fanfare in the movement?


Few amps can do these things correctly even if they are fully broken in. The M625 original version (except for the very first few serial numbers) negotiated all the scenarios above without any issues... The S2 version is much improved over the original.

  

I do not have sufficient experience with the VAC amps to make a meaning ful comparison.


Regards, Guido

I have eclectic musical tastes that include jazz, classical, rock, world music, and even ... broadway!
One of my favorite Broadway albums, featuring many of the all-time classic songs, performed by a great operatic singer:

www.amazon.com/Love-Julia-Migenes-Johnson/dp/B0001XGP28?ie=UTF8

It appears to also be available on vinyl, which is what I have.

Best,
-- Al
 
Question for Rinpoche.

If you had just heard any of the systems you have heard, and not others to compare to, are there any that you think you would not be happy with long term?

My point is these are all great sounding systems in their own way. Each with strengths and weaknesses like always. In the end all that mattters for a music lover is ability to enjoy the music to the max.

Personally, having heard a lot over the years, I think there are many systems both expensive and less so that I could live happily with if I had to. Yet no two sound exactly the same. The only way I can assert which sounds "best" overall is to compare to live music I have also heard over the years.

Just wondering.   It's different things that justify any purchase to different people but in the end its ability to enjoy music that matters most to a music lover, not the gear.
I hear you (no pun intended, LOL). At first I will probably be a bit nervous about tubes, but I am sure I will get the hang of it, if I go that route. I wonder, what cables do you use with the Phi 200? 

Also, I will listen to the musical suggestions. I am not familiar with them. I have eclectic musical tastes that include jazz, classical, rock, world music, and even ...
broadway!

One of my go to songs this time around for auditioning has been Peter, Paul and Mary's All My Trials. Just pulled it from the vaults and it is a lovely acoustic song. I have other tests as well including Bach's double violin concerto, Prokofiev violin concerto #2 Andante, Diana Krall's version of A Case of You, Maria Callas singing 'La Mamma Morta', Keith Jarrett (who by the way walked out of a concert I attended last year in Paris because too many people were coughing), and many, many more. So much great music. Now all I need is an AMP!!
Rinpoche,
I had to smile when you mentioned seeking inspiration from music to fuel/assist your writing process for your book.  I find music essential for both writing and mathematical calculations - - I just find it helps bring my mind to better focus (I'm a bit ADHD, so it is nice to have music exciting and activating some itchy brain circuit to steady me down).  And I find I can do both with great simultaneous involvement, truly having some ecstatic experiences in just such times.

I am a VAC Phi 200 owner that wrote about them a bit earlier.  I have heard that the iQ is a very nice step up in sound quality, so I think you are wise to wait for that audition before making a decision.  I will bet that it tips the scales!

I have changed from the stock VAC Shuguang tubes for sound that I find better:  Gold Lion KT88's for the power tubes and Shuguang Treasure CV181-Z tubes for the input and signal tubes.  And actually I have lately mixed the original Shuguang 6SN7 tubes back into the driver station for my favorite overall affect in my system and to my tastes.  My basic point is that there are better (different?) current production tubes to try, and mixing and matching can dial in the "flavor" a bit to suit.  And they don't break the bank, by any means.

Keep enjoying the journey, and I am sure you will end up with a musically satisfying system.  (And, yes, cables make a difference, too, but let's defer that topic for now...)
I mentioned Purist Audio cables. They have a cult following, not that it is the only great brand. Cables can really make or break the system because signal transmission is just or almost just as important as signal processing. If you decide to buy them new, I suggest you contact albertporter here on audiogon. He is a very experienced audiophile with incredible system, he will help you choose the right cables, he sells them too. I talked to him in the past. Purist cables need at least 200 hours of burn-in time to sound best, I can confirm it.
I think, VAC has good Chinese tubes in it, but of course one can do better with New Old Stock tubes. Most people here replace those factory installed tubes, I guess. I would for sure.
Most agree that at their best tubes sound better than transistors but this level of performance costs a fortune. At more modest levels there is no clear answer, it depends on many things including personal preferences. You could even try " poor man's LAMM " Rogue Audio Pharaoh hybrid integrated. It's $3500 new, many like it a lot. Both VAC and Rowland integrateds are what, about $11000 each new?
First thing I play when testing a system is album entitled 'Cielo e Terra' by Al Di Meola. It is atmospheric mesmerising acoustic guitar music.
Next I play vocal by Dead Can Dance. Then Bitches Brew by Miles Davis, then Inner Mounting Flame by Mahavishnu Orchestra, then the rest if I need to, usually not because by that point things are almost always clear to me. But if you listen to opera and big orchestra, it may make sense to start with that. Just don't expect too much - no system can adequately reproduce the power scale and instrument separation of a full orchestra. They can't record it adequately either, by the way.
Rinpoche,
I'd play recordings that you both enjoy and are pretty familiar with. You're use to how they sound in your system and thus will easily detect any differences in presentation provided by a new component. This approach has been very effective for me through the years. We all here are interested to read your listening experiences with the select group of amplifiers.  This is an enjoyable thread. 
Charles, 
What will be the first thing I play on it? Now that is a thread we should work on. What is the first song you play on your new stereo?
If classical music is of interest, try Dvorak's "New World Symphony," Jascha Horenstein conducting the Royal Philharmonic Orchestra, Chesky CD31.  Out of print, but available from various sellers at Amazon:

http://www.amazon.com/gp/product/B000003GCZ/ref=olp_product_details?ie=UTF8&me=

And if classical music is not presently of interest, it very well may be after you hear this recording, which you will not believe was recorded in 1962!

Best,
-- Al
 
What are break-in test tones? 
Are you saying after the first 1500 hours if its the JR? Cuz I can't wait that long!!!!!

I am so fortunate to hear from all of you. Really. I mean that seriously. Not only are you all so knowledgeable, you are also giving and helpful....and funny (see jon2020). Okay, so maybe I am in denial. But I hear that cables are important! No? 

And, inna, you are so right. I am torn. Solid state is easier and I am anticipating that tubes might be more fiddly (also I need it for TV and film). But maybe worth it! So, good idea to suggest a hybrid. In fact, that is why I went to hear the (demo) PS Audio amp. The LAMM/Kharma/Purist Audio could be my stereo goal — for my retirement (or with my retirement fund?). 

I am happy though that you all seem to like JR and VAC. Really. I don't want to make a mistake at these prices. It certainly won't be top of the line VAC — they are out of reach, or JR top of the line. But the 200 IQ is affordable. And who knows the Rowland might just win out in the end — we will see. Let me first hear the VAC (an early suggestion on this thread).

I am also really getting very excited to see how this turns out. What will be the first thing I play on it? Now that is a thread we should work on. What is the first song you play on your new stereo? You folks are fabulous. I mean that. 
Hi.
I suggested Kharma/LAMM/Purist Audio because this combination could be your reference point even if you cannot afford it new but maybe you can used. Besides, you appear to fluctuate between solid state and tube electronics of similar level, and I can understand that. I suggested the path that I myself would take. I like both Rowland and VAC. Few amps play midrange as well as top of the line VAC yet some choose LAMM. And better Rowlands are up there in the top solid state league. Personally, if I wanted to keep Wilsons I would probably choose Rowland over VAC for better dynamics bass and scale. In any case, whatever you decide - you are to have an excellent sound.
Rinpoche,
As you let on more and more about yourself in this hobby - Mark Levinson gear with B&W 802's for 15 years, and your consideration of cables, you have exposed yourself - audiophilia nervosa is already lurking inside you.  You are just at the denial stage! 😅
What gave you away?  - when you think about cables, you are done for. ☺

Good luck with your hunt! 😂
Hello, 
I just contacted a LAMM dealer and the M1.2 monoblocks sell for $27,190 USD. So, given that — as much as I am sure they sound gorgeous, it is out of my budget. I appreciate the help, but I really can't afford that right now. But, as you can see, I am open to suggestions within reason. I mean, who wouldn't love a $30,000 amp!!!!!
Your sober advice resonates! I was started to see who carries Lamm and Kharma! Not the same dealer. Not even in the same province. Okay. Stay the course. One step at a time. I am on the right track. Trust my heart and my ears. And when possible ask, listen, and learn from others. Got it!!
Rinpoche 6-8-2016 12:10pm EDT
But, from some of the advice I am getting here, it sounds like ’starting over’ from scratch is perhaps preferable.
Not at all, IMO. And I strongly second both of the very well said posts Charles has provided today.
Onhwy61 6-8-2016 12:07pm EDT
From reading these forums it’s my observation that new audiophiles don’t have long-term success in building truly high end systems in one shot. To Inna’s point, it’s too complex. I’m not sure if this also applies to music lovers and I’m most interested to find the outcome for the OP.
My perception has been that in many such situations the audiophiles in question are the type that is probably incapable of ever being satisfied, and who are embarking on a never-ending merry-go-round. And in other cases are persons asking for help only after making outright mistakes in their purchase decisions, due to poor system matching or other factors. Neither of which appears to be the case here as far as I and at least most of the others are concerned.

Best regards,
-- Al

Rinpoche,
You are on the right pathway,  you do not need to change or in any way alter your approach.  You motive is clear and direct,  you simply want your music to sound enjoyable in your home. This is the best reason one could offer in my opinion. I personally don't see the need to become bogged down and obsessed with audiophile concerns to the point where one can become neurotic.  It's possible to take what should be "fun" and replace it with angst and frustration.  Keep doing what you are doing,  enhancing the joy of listening to music.  You love the Wilson sound,  who cares what someone else may think about them. 
Charles, 
Thank you all again and again for your honesty and your sage advice.

Sorry for the lengthy response, but maybe this will help. First, I don't really see myself as an audiophile or view this adventure as a hobby. Believe it or not, I just want to buy a great 'stereo' so I can really engage with the music. My goal (and maybe this is true for all of you as well) is to get it right and live with it until I need to go to take it to next level — should that time arise. I don't know how to tweak. And in a way that is why I was a bit leary of tubes but willing to learn 'for the music'. 

Now, you can judge me if you like, but for 15 years I was quite happy with my Mark Levinson amps and CD transport and B&W 802's speakers in my home. Then, I sold my home and needed to scale down. I heard the Wilson's and really liked them. I thought a good amp would be the next move. But, from some of the advice I am getting here, it sounds like 'starting over' from scratch is perhaps preferable.

But I have a full time job (as I am sure most of you do too). I am in the middle of writing a book and want to listen to music to inspire me. Create a kind of transcendental experience as it were. So, while going to hear various combinations of amps and speakers is exciting and makes a lot of sense, it is also very time consuming. And where would I go? Dealers where I live seem to specialize in certain amps with certain speakers. If I want to mix and match how does one do that? Also, I already have the Wilsons (as polarizing as they might be — obviously I see that some people LOVE them, and some people don't). 

Therefore, to recap, so far I have heard:
1. JR, VAC, and ARC with Focal
2. PS Audio with Audio Physic
3. Hegel integrated with Wilson Benesch
4. Luxmann with Wilson Benesch
5. Air Tight with Harbeth

I eliminated #3 and #4 very quickly. Also, ARC didn't really match JR or VAC. And #5 was very very sweet for an introductory level set up. The two that have been most engaging to my ears so far are still the JR and VAC (but I think I should hear the 200 iq with self biasing).

However, I have not yet to hear any of the amps with the Wilsons. Who knows, maybe when I do I will be disappointed and see that they are a weak link? I could try to find dealers as products are suggested? THANKS  — oh, and then there will be cables!!!!!
The OP loves her Wilson's, but I do believe she mentioned earlier that she had not listened to any competing loudspeakers when she acquired them.  Her frame of reference is limited.

From reading these forums it's my observation that new audiophiles don't have long-term success in building truly high end systems in one shot.  To Inna's point, it's too complex.  I'm not sure if this also applies to music lovers and I'm most interested to find the outcome for the OP.

Hi rinpoche, if budget precludes the new M725 S2, I warmly recommend the M625 S2 over the original M725.


As for VAC vs Rowland, I personally prefer the organic sound of Rowland electronic.


 

rinpoche, I'm with Charles, maintain the course you have set and I'm sure you will make a choice that you will find very musically satisfying with your Wilsons. In the end it is what sounds right to you.
Inna,
The inescapable aspect about this hobby is it inevitably boils down to subjectivity. You make the valid point of expending the field of other competing speakers and components and the benefits of this exposure. I don’t know the extent of Rinpoche's  awareness of other speakers however it’s quite clear she loves what she’s heard from the Wilson Sabrinas. She could hear a dozen different speaker brands and still prefer the Sabrinas or as you suggest, find ànother that impresses more.

No one can audition every possible choice available so in reality there’s a limit to the level of exposure one can achieve. Wilson as is Magico are the epitome of polarizing High End brands and they generate very passionate defenders and critics. Rinpoche has heard the Wilson and really likes their sound, that’s important and significant. Identifying the sound you prefer is the key step towards assembling an audio system that will keep you happy and content for the long term.
Charles,
Call me names if you wish, but I suggest you get rid of Wilsons and start listening to various speakers/amp combinations. In a few months you might end up with something truly great. 
Your wallet appears to be pretty good if not exactly perfect..
In your place I would probably start with Kharma/LAMM/Purist Audio and then move from there.
Of course, both Rowland and VAC would give you excellent sound with your speakers, but that's not my point. If you want great sound - you must make a great effort to achieve it. So far you are not making it. Sorry, man.
I hear you. Thanks for the support. I agree. But, my wallet is not deep. So, hopefully I will get it right the first time. I will let you know as soon as I make the plunge, 

".....I am finding the wait a bit brutal, but patience is going to pay off down the line."

+1, Rinpoche.

The wait is killing me more. :)

You remind me of myself when I first started in this crazy hobby more than 2 decades ago.
It was the same then - too many choices and too many decisions to make but only 1 final decision can be made. You will learn that you have to pay to gain experience in this hobby - to get the best overall sound, from all the different components, that suits you and your room.
Opening your wallet often is the only one inescapable fact in this hobby..

Happy hunting!

J.


Hi rinpoche, unless the M725 monos on sale are the S2 version, the M625 S2 that you are considering will deliver a much purer, more musical sound.


The original M725 of course will be more powerful than M625 S2, because each monoblock is equipped with its own 1200W SMPS and PFC unit.


Thus, unless sheer power / authority is a factor, I recommend you go for the M625 S2.


For the best of both worlds, there is now an M725 S2 in full production.


Saluti, Guido


You are adorable. And I can hardly wait to get something. BUT I am still waiting for the VAC 200 iq to come in so I can listen to it. I am finding the wait a bit brutal, but patience is going to pay off down the line. I have decided not to go with the PS Audio. It is still between the JR and VAC -- unless some of you have other suggestions. I rejected the ARC GSi75 -- it was good but I thought the JR and the VAC were better. There is a pair of JR 725 monoblocks for sale???? but I feel badly for the store if I go that route. Am I crazy?
Rinpoche,

I know everyone is dying to ask but is not asking.
So, I will ask the obvious - have you decided what to get?

J. :)
Very solid choice on paper for your speakers and would appear to mate well with tube preamp if desired.  

Rinpoche,
I must agree with ricred1. It's all up you once you've listened to a component. You'll get opinions that run the spectrum,  unavoidable due to the subjective nature of it all. The new PS Audio BHK  has received excellent reviews Thus far. You're correct, there are many really fine products available. As has been said here before trust your ears and pick what moves you the most emotionally. 
Charles, 
rinpoche,

I feel your pain. Unfortunately no one can tell you what to buy. Only your ears and wallet can decide what's best for you based on your sonic priorities. It's a pretty easy decision, what sounds best based on how much you want to spend. 
Hello everyone. I would love your input on this. Today I went to hear a PS Audio amp (BHK 250) along with either a PS Audio DAC, a Sim Audio 750D DAC/cd transport and at one point we added in a VTL pre-amp. It sounded very good. My question(s) are: what do you think of the PS Audio BHK250. It is a hybrid (though you all probably know that). And what do you think of the SimAudio 750D instead of the Jeff Rowlands Aeris DAC? Any insights you could provide would be great. There are so many great pieces out there, it is now hard to figure it all out!!! Input is welcome. And the VAC 200 is not in yet so no news to report on that front. 
Ugh sorry to hear that Rin sounds like a lousy dealer and I'm assuming a different dealer than the one offering JRDG and VAC? Hopefully so and don't look back, no reason to return to a dealer that would treat you like that!  And good for you keeping an open mind and auditioning other amps, but sounds like your heart is pretty set on either JRDG or VAC so I hope you are ultimately able to arrange an in-home audition on those two.
Hello. Just to update you all -- I went to listen to two new amps this morning: a Hegel integrated (they didn't have the H-30) and a Luxman. As nice as they were, in my mind (and heart) they were not as engaging as the JR and/or VAC integrated. When I asked the salesman/owner if he would recommend or if he had anything else to listen to he did mention something in the $35,0000 range and then he bascially said 'go and buy those if you want something commercial'. Also, her was aghast at digital music (which I do use for many reasons) and said something about a "Stradivarius"? Well, on to the next!!!!

rin, that is good advice from Charles.

You are well prepared.  The only thing else I can think of is go in with a good sampling of the kinds of music you will be listening to planned out ahead.. Some good recordings, some lesser, various genres of interest, etc.


Hi Rinpoche,
You are correct in that as good as home auditions are your time with the amplifiers is understandably limited. However it’s still a very worthwhile and valuable exercise. You reference using your ears and heart, absolutely the right approach. Choose what musically touches you the most deeply and you’ll be fine. That's what music lovers do and you're a self confessed music lover. 
Charles,
I wish it was easier to audition the amps with the speakers. It is an expensive journey and I won't have a lot of time with the pairings. So, let's all hope my ears (and my heart) are open to the music. Thank you again and again. 
I have had very low NF SS amps designed to sound more like tube amps and they had their unique charms.

The best products are always designed by the best engineers capable of making the right design decisions and backed by a manufacturing process capable of realizing it reliably. Well designed and made products + system synergy is everything when it comes to performance and results. These are all top notch product lines being discussed so the key is to get the synergy right and each amp line is significantly different in that regard..
Mapman,
Yes I see your point, expanding the potential field of speakers that could be used successfully.
Zero NFB amplifiers would require more specific /careful speaker matching.  But oh so good when that match is right  😊.
Charles, 

Charles I simply meant they get it right for their products as designed not that they do it any better or worse than others who do it differently for different reasons. Practically their tube amp market share probably does help confirm the relative effectiveness of their approach for many using many different speaker designs.


I would love to own a VAC but would probably only do it if I were willing to build my system around it, mainly the speakers. Atmasphere (OTL) is another example of a higher output impedance tube amp that dictates certain speakers more for best results. SET tube amps are of course another.  


ARC tube amps would seem to fit better for more that build around certain speakers that may be a harder load to drive but still prefer a tube amp.

Different strokes......

Mapman,
I don’t believe that ARC gets the use of NFB anymore (or less ) right than does VAC. I say this because it strictly depends on the speaker in question. For example Al’s speaker sounds better with his amplifier’s zero NFB setting . In fact the scenario is true in my case as well. My particular speakers sound their very best with my zero NFB amplifier compared to those with NFB.

So again depending on the speaker characteristics either the ARC or the VAC could be the "ideal" choice. ARC’s 14 db of NFB may or may not be the preferred amount. Amplifiers which offer selectable NFB levels are  a very good approach as it provides flexibility. Perhaps the Sabrinas are more compatible with amplifiers that rely on increased NFB.
Charles,

ARC seems to know how to do NF with tube amps right and on paper would seem to be called for with the Wilson speakers.


I lost track. Is ARC versus VAC versus JR in home with the Wilsons the shootout? Or just JR versus VAC?

Its a great shootout by the way. Three of my absolute favorite brands each with unique pros and cons. Any tickets available? :^)

  Can't wait to hear the results.
So far, it sounds like JR is still winning for combining great sound and ease of use. And perhaps the VAC 200iq is next given its new self-biasing feature, though I have still to hear it. The exciting listening adventure continues!! 
Charles1dad 5-25-2016
Based on what Al has written it seems that the ARC tube amplifiers may utilize a larger degree of negative feedback (NFB) than the VAC amplifiers. I say this due to the lower output impedance (higher damping factor ) of the ARCs. Depending on the particular speakers this can be advantageous. It truly is dependent on the speaker design and intent of the builder. The Sabrinas could require amplifiers with more NFB with the resultant lower output impedance. Again, nothing substitutes for actual listening experiences.
Yes, that’s all true and well said, Charles. The VAC 200iq is specified as using 6 db of feedback, while the ARC Ref 150SE, for example, is specified as using 14 db, a considerable difference. I’ve never seen the corresponding number for the MC-275, but its unusually high damping factor (for a tube amp), its somewhat low gain (feedback reduces gain, everything else being equal), and numbers I’ve seen for other classic MC tube amps, suggest to me that it could be in the vicinity of 20 db or so.

My older VAC Renaissance 70/70 MkIII amplifier, btw, has a six-position switch that allows the user to select the amount of feedback. The settings range from zero to 7.5 db. I use the zero feedback position, which works well with my particular speakers (which have a particularly flat impedance curve and no dips to low values at any frequency).

As you indicated, judicious use of feedback in a design can be either advantageous or disadvantageous depending on the characteristics of the speaker that is being driven. And also on how well the design of the particular amp avoids the sonic downsides that feedback can potentially introduce.

Best regards,
-- Al