Audio Research REF 80S Reviews/Comparisons

I truly enjoyed reading & learning about the REF 80S, but that's it, no more to this story/ experience?

 

 

@fsonicsmith

But I love the sound of well-recorded electric bass guitar and on the new John Doe album I am smiling from ear to ear at how totally natural the timbre and tone of the bass sounds-something I did not get with the 150 SE. The sound of the drum toms sounds more timbrally (not really a word) correct too with the 80S.

 

Finding the ARC Reference 80S is more natural in reproducing tone and timbre would be enough for me to declare it superior to the REF 150 SE. This capability is so crucial (to me anyway) and many components fall short in this area.

I know that there is more to come with regard to listening impressions as playing time hours accumulate. However knowing it excels with "natural" presentation/tone/timbre makes it a keeper already.🙂

Charles

@fsonicsmith excellent writeup, thank you. 

A provisional update :-), the Ref 80S is sounding fine. Very fine. I am at 65 hours so I have a ways to go and the route was fairly choppy along the way. Never terrible but often just so-so and primarily lacking in bass snap. Today, Steely Dan's "Everything Must Go" and John Doe's new (and excellent) album "Fables in a Foreign Land" are deeply satisfying. 

Based upon my impressions so far the 80S has a bit softer but no less detailed sound than the Ref 150 SE. The 150 SE strikes me based upon memory as having a more "scientifically precise" sound with just a touch of dryness compared to the 80S. The 150 SE is a powerhouse and when called for it will push out bass that hits you in the gut with satisfying decay and tautness that I am still not quite getting with the 80S. But I love the sound of well-recorded electric bass guitar and on the new John Doe album I am smiling from ear to ear at how totally natural the timbre and tone of the bass sounds-something I did not get with the 150 SE. The sound of the drum toms sounds more timbrally (not really a word) correct too with the 80S. But best of all, I felt a slight nit-pick was in order with my Devore 0/93's in the upper midrange where things could sound a bit course and unnatural that I attributed to the design of the Devores. Now I question that conclusion-that perception is gone with the 80S!

How about it compared with Ref 75 SE? 

 

@fsonicsmith - thanks for the update.  My 80S has several hundred hours on it.  The sound will get even more refined.  I think the lower bass registers even tightened up too. 

ARC made numerous circuit changes in the 80S.  Perhaps a very important one is the auto-biasing function.  Maybe the KT-150s operate in closer sync because the bias of each push-pull tube is more tightly aligned.  That is just a guess.  

Please report back after you rack up more hours.

BIF

 

 

   

@fsonicsmith 

 

Valuable input. Thanks.

Here is what I wrote in the "Devore" thread (Speakers) that I think also, even if partly, answers your question;

I don't want to give things away before the final vote tally is in, but the O/93's simply sing holistically, organically, and full of joie de vivre with my ARC Ref 6 and 80S fed to them with Cardas Clear SC's. Previously with my Ref 150 SE in the same system I heard a slight discontinuity between the woofer and tweet, a minimal but nagging dry spot and woodiness with male vocals, alto sax, and similar frequencies in the midrange band. That small niggling misgiving has completely vaporized with the ever-so-sweet Ref 80S. I have only 100 hours on the new amp and it reportedly needs 300-500. Dynamic synth drum attacks along the likes of "Get Innocuous" from LCD Soundsystem's second album "Sound of Silver" are still sounding soft and not as sledge hammer on iron spike precise as with my former Ref 150 SE (which fwiw I am holding onto for the heck of it) but I am confident that with more time that precision will arrive too. 

The point of this post is simple; don't underestimate how utterly great the O/93's can be in a small room with the right synergy. Pat Martino's guitar work in "East!" is thrilling with this combo. 

I only have about 100 hours on the 80S so far. I am hearing great things already. The sound is simply more coherent than the 150 SE. The 150 SE kept a better grip on synth drums and lower bass in general. The 150 SE always struck me as presenting a soundstage with placement of instruments/sounds and images that did not seem quite natural and instead a bit exaggerated (and I believe the Ref 6 preamp does this a bit as well). An artificial spaciness if you will. The 80 S does not have this characteristic and seems to be a better match with the Ref 6. 

@fsonicsmith - can you share some updated impressions on the Ref 80S.  How does it compare to the Ref 150SE?

 

Thanks

 

BIF 

@fsonicsmith - agree with ghdprentice re change in sound refinement.  The 80S will open up.  In my experience, ... just like ghdprentice said.  I look forward to your comments on the 80S in general after 200+ hours and also how the 80S compares to the 150SE.

 

Enjoy the amp.  I think you will be pleased.

 

BIF    

@fsonicsmith

 

Thanks for your comments. You are in for a treat. If I haven’t mentioned this, you can expect mediocre performance for for about 100 hours… pretty good til around 120… then flipping back and forth between good and bad… then after 150 hours good performance… getting better through 600… and while the slope of improvement decreases, the amp continues to improve through 1,000 hours.

 

I can’t imagine anyone leaving the cage on the amp. It is great seeing the tubes. I must admit to really liking the meters… I know it is just for show… love the show.

@charles1dad  

Thank you. As to writing, right back at you. I promise further listening impressions.  

@fsonicsmith 

Congratulations on getting your new ARC REF amplifier.  You write and express yourself well. I'm looking forward to further listening impressions as you see fit..

Charles 

Well, my new amp is set up and has about five hours of break-in so far. I am sure no one wants to read about such mundane things as shipping woes but I feel compelled anyway to talk about the condition of the outer ARC shipping box. UPS managed to beat it to within an inch of it's useful life. Multiple gouges that penetrated and pierced the box, destroyed corners, collapsing seams, simply destroyed. UPS had covered several sides with black and yellow tape warning it's employees that the box weighed over 70 lbs. I can only guess this tape motivates the employees to heave the box around even more rather than handling it with care. I have been in this hobby for a long time and have a wall of shipping boxes along one side of my basement, some of which were used for there-and-back return shipping of heavy amps for service or mods, several for very heavy loudspeakers, etc. and nothing approaches the condition of this box. I know the debate never ends but in my world living in Ohio UPS sucks the worst. 

Luckily despite the above I found no sign of damage to the amp itself and the box ARC packs at the top containing the manual, tools, and tubes was also fine. 

So now onto the little I can tell you. Kudos to ARC for finally realizing that no one likes removing 18 screws to take a flimsy top cover off an amp (the Ref 150 SE) and now they have implemented a clever slide-back and lift design secured by just three hex screws. The top cover is built of thicker pot-metal (that might be harsh) and with sturdier design and reinforcement. That said I could not help but notice that once re-installed with tubes in place the rear flange does not sit parallel to the top plate of the base. Not off by much and no one sits and stares at the back of the amp but at this price little things count. My manual included the usual ARC QC card indicating my amp was built in June of 2021. Warren Gehl's initials are on the final sound check line. The box containing the tubes also includes a screwdriver marked as being meant for adjusting the sensitivity of the ghost meters and yet the manual does not say a word on the subject. 

It is obvious that this iteration of the Ref series amps borrows from the Galileo Series in terms of the outer case construction. Beyond a doubt it results in a stiffer less resonant outer-shell though whether that does or does not affect ultimate SQ is unknown. I always felt the construction of the Ref 150 SE was curious with such a seemingly flimsy base supporting such heavy transformers despite any sign of actual flex. 

The first time I saw photos of the Ref 160M's I thought the amps were fuggly (Midwest term) and garish. The looks grew on me though unboxing this amp was my first opportunity to see one in person. I still can't say I love the look-though I love the look of the Ref 6 pre-but even after taking into account the pride-of-ownership bias inherent in life, in silver this is a handsome amp. And when powered up the ghost meters add not just flair but some elegance. 

Sound? Well, yes, I have sound. Streaming the Shins "The Worm's Heart" on Qobuz though my Aurender W20 into my SW1X DAC III Balanced via a combination of Analysis Plus Silver Apex (DAC to Ref 6) and Cardas Clear Beyond (Ref 6 to Ref 80S) powering Devore O/93's via Cardas Clear and hooked up the 8 ohm taps I heard sound but not music. Wooly bass and a jumbled mess of very familiar music. Ten minutes in I heard a glimpse of a broad soundstage that almost sounded like music but within five minutes more it lapsed back into the jumbled mess. I am being purposefully harsh. The amp is clearly fine and just needs to wake up. Over the rest of the first five hours (until my wife screamed that she had enough since I was outside entertaining friends despite only moderate volume) I heard signs of promise with the bass already firming up. 

As should be obvious, I can not yet compare the Ref 80S to the Ref 150 SE in terms of music reproduction. That will follow, likely in two to three weeks. 

@bifwynne -No there is no epilogue. ARC told me that there are no authorized techs in my area though for some reason they thought I live in Florida. Just the same, I know that there are no authorized techs in Ohio. I am still in a holding pattern with the amp. I will likely take it to the tech I have referred to above-he works on pro audio gear mostly and knows his way around tube amps. If ARC were to give me an RMA anytime soon I would ship it off to them. I don't mind knowing that it will be five months before I get it back if I could just ship it off to them. Weird, illogical, but that is just where I am at. The Ref 80S is sitting in my downtown office where it was shipped to and I am in France on vacation. This weekend I will be home and setting it up. 

@fsonicsmith - is there an epilogue to the 150SE situation?  Did ARC suggest next steps?  How about a local ARC authorized service tech. 

Even if the repair is properly done, I would expect that the tech would thoroughly bench test the 150SE to make sure it was operating at factory spec.

 

  

@bifwynne Greg looked at the pics and said "that is strange". But when I read your first reference to the slow start circuit fuse I thought "yeah, that's what I think happened to mine".

I expect anything that goes wrong other than a power tube resistor to be an expensive repair. 

@fsonicsmith - unless I am mistaken, which may be the case since I am not a tech, you have the same problem I had. The plastic cover of the slow start circuit fuse is burned. If so, the solenoid start switch and thermister need to be replaced. This is not a cheap repair. An ARC service center tech quoted me $1K. Did Evan or Greg share their impressions of the pics you posted? If my guess is correct, I was told that the whole circuit board needs to be lifted and the underside inspected. For a couple of parts costing less than $50, that could be a lot of labor. Please advise.

I owe ARC and Evan an apology. They are the best. 

https://www.dropbox.com/s/bxihgvsdvjdt2lg/IMG_1689%202.JPG?dl=0

https://www.dropbox.com/s/rjx5gh3oz4ma19f/IMG_1690%202.JPG?dl=0

@fsonicsmith - I agree that phase angle is important.  If the speaker's phase angle is highly capacitive at low frequencies and the impedance is also low, most techs would say that the amp should be able to produce a lot of current to get the speakers to hum.  I am not sure I agree with your comment that speaker sensitivity means little.  I surmise that my Ref 80S can drive my S8s with little trouble because the S8s are very sensitive (92db).

Let me challenge point you about finding an authorized ARC service center.  Greg made a few suggestions to me last year.  I have no reason to believe that the situation has changed.  Best to call Greg.

Last, .... if you don't mind, what specifically is ailing your amp?  Do you know?  What is the problem? 

Most of the passives (resisters, caps, etc) are low tech items.  If something in the power supply regulation circuit went bad, ... that could be a different story because the Ref 150SE has a solid state power supply.  It may be that a qualified tech could do the fix if the problem is not that technical.  Again, ... best to call Greg.

 

BIF  

   

       

BIF, thanks. I could be mistaken but I don't believe ARC has authorized repair facilities any more. And I don't mean to argue unnecessarily but I have the personal view that phase angle means far more than nominal impedance. "Nominal" has a meaning-"of name". It along with claimed sensitivity means little. 

@ghdprentice Thanks!

FYI… on power cords for your new Ref 80’s. My REF 160s (same design) is very sensitive to changes in power cords. I have been tried all versions of Cardas Clear… in my system they are all warm… but attenuate the details a bit too much… although has more detailed upper bass. I tried Transparent (not the ones specifically made for an amp) this was great on details but the bass lost heft. So, I tried a Audio Quest Monsoon and seems just right. I bought one… I may try a Dragon sometime, a member here recommended it.

 

The difference between the Cardas and Audio Quest was not subtle at all. Actually a bigger difference than between the REF160s and the REF160m monoblocks.

@fsonicsmith 

 

See my responses below:

• Although every loudspeaker is (duh) different, what is the nominal impedance of your Paradigm Sig S8 V3’s and what tap did you find best?

Response:  The S8 (v3) nominal impedance is 8 ohms, but that is misleading.  The impedance and phase angle curves are all over the place, ... like most modern speakers that are voiced to be driven by a solid state/low output impedance amp.  More important I think, .... the S8s are rated at 92db sensitivity.  The 8 ohm taps seem to work best, ... on both the 150SE and the 80S.  The high sensitivity makes the S8s a good fit for the 80S.    

 

• Did you play around at all with power cords? And related to that, are you going to through a power conditioner or straight to the wall?

Response:  No playing around with power cords.  I use stock cords.  No power conditioner. 

****

@fsonicsmith .... did you consider using an ARC authorized service center?  Greg should be able to give you some names.  I am still not clear about what ails your amp, but the 150SE circuitry is not rocket science and there are probably only a few key parts that go bad. The real cost is labor.

My main problem was that the 150SE amp is heavy and bulky.  The ARC tech guy I wanted to use would not lift the amp, so I had to schlepp it to his location.  That was a nonstarter for me, ... but maybe not an issue for you.  Also, if you need fresh KT-150s, consider Upscale Audio and be sure to let them know you are matching pairs for a 150SE.  The matches should be pretty tight.

 

Let me know how you make out.

 

BIF            

 

 

 

 

So I called and had a very pleasant conversation with Evan. I explained my situation. I asked for a schematic. He asked someone else while I held and said "yes, we can send you the schematic". I gave him my email. Hours passed. Nothing. So I wrote three times asking for the schematic I had been told would be forthcoming and Greg Christensen ghosted my question and instead circumvented to how long it would be (6-9 months!) before I could return it. This over a course of three days when I brought up the schematic each and every time.

I am very happy ARC owns ARC again. I am very happy they are answering their phone again. I am not so happy about the backlog (though understandable) and the lack of a direct clear answer (avoidable and inexcusable).

Now all that said, a tech with tons of experience (Vern Leckrone of CT) told me that the best way to get my amp repaired the right way was with ARC and as I said above, between the lack of a schematic and the lack of reliable tubes I am willing to wait and pay the huge premium. The Ref 150 SE is a great amp so why not get it done right?

@bifwynne

1) What did you end up doing with your 150 SE? Once repaired I need to decide if it worth selling them or just hanging on to them for a while. Between being discontinued and repaired I suspect they won’t sell for much.

2) Although every loudspeaker is (duh) different, what is the nominal impedance of your Paradigm Sig S8 V3’s and what tap did you find best?

3) Did you play around at all with power cords? And related to that, are you going to through a power conditioner or straight to the wall?

I will never know for sure, but I suspect my 150 SE failure had something to do with plugging it into an Isotek Aquarius that in turn was being fed by an Isotek EVO3 Syncro. When my startup fuse and nearby resistor blew, the fuse blew in the Aquarius and I suspect the failure was due to inadequate current supply in the face of heavy current draw though I have basically no understanding of EE. Granted, I had been using my amp this way for over three years with no problem. But this time with the new amp I am going right to the wall which has a dedicated circuit.

 

@bifwynne 

My 80S is due to arrive today. My Ref 150 SE remains all boxed up and taking up space in our foyer waiting for word from ARC as to an RMA. I am constantly tempted to simply take it to my local tech. ARC not willing to provide a schematic is one hurdle and the high cost of KT150's is another. 

@fsonicsmith - sorry if I blinked and missed something, .... but what happened to your Ref 150SE?  Did you get the Ref 80S yet?  If so, did you get a chance to compare the 150SE to the 80S?

 

I took the same journey.  My Ref 150SE needed an expensive repair (start-up circuit needed a thermister and solenoid switch).  I decided to go the Ref 80S route as noted above.  My 80S is pretty much broken in now and sounds terrific.  I don't have a good sonic memory, but I think it sounds incrementally better than the 150SE.  As noted by me and others, I like the circuit enhancements, especially the fuses on the KT-150s.  I suffered through blown bias resisters in the past and it is no fun to soldier in new ones.

I look forward to hearing your reactions.

 

BIF

        

@fsonicsmith I agree. If you are talking the same pre, I will choose XLR output too.

But if the pre has only RCA output, and I love that sound,then there is no choice.

We must ask the power amplifier with RCA input.

Conrad Johnson , VTSP 360 and Rega pre ,and Luxman Cl38uc ,they are all very good,but go down with RCA only.

I listen to many pres and till now,I  stay with the pre with RCA only.

At end of day, What kind of house sound let you make the decision.

 

 

I am a true believer in true balanced. The Ref 6 was optimized for running balanced and even though some may disagree, running true balanced is not only about hum rejection. Since my Ref 150 SE blew, I have been using my Ampsandsound Nautilus which offers both fake-balanced (transformer coupled since on SET amp can not by definition be balanced) and SE inputs. I have tried both. Even with the transformer coupled "balanced" inputs, running XLR's rather than RCA's sounds much better. My XLR's are Cardas Clear Beyond. My RCA'S are Analysis Plus Silver Apex. No doubt "it all depends" but with the Ref 6 the scary-real soundstage depth, height, and width collapses with RCA's. Bass tonality suffers too. 

As another example, I have a Luxman 750u headphone amp. It needed a minor repair (internal fuse). The tech who repaired if for me, Steven Leckrone, emphasized to me that the Luxman circuitry on his test bench made it clear to him that running balanced from input to output (the headphones) was essential for best sound. 

The best things for me is that 80s have RCA input besides with XLR. They finally realize that both kinds of input will be more welcomed than that before with XLR only.

 

Thanks dhite71 OP

My 150SE is not operable. When it does come back repaired I will  have a tough choice to make. Between the cost of repairs and a new tubeset that I am sure ARC will insist upon I am not likely to recoup a lot of money-relative to costs-on the used market so I may keep it. 

I don't expect the 80S to make a huge difference. I hope there is an incremental change for the better. Even if there is not, I will admit that the idea of less tubes to maintain, the new feature set, and the drastically better looks (the 150SE is pretty plain jane!) will be sufficient for me. But I will be frank-with the new four layer circuit board and what is claimed to be a better circuit design I am optimistic I will like the sound better. 

I would love to know who at ARC is at the helm of recent circuit design. ARC touts Warren Gehl as "design engineer" but I don't buy it. Ever since the tragic early passing of this guy, ARC (imho) has not been clear as to who the brains behind the operation is. 

Well, congrats Mr. Smith!

That is a bit of a frustrating situation with the long service delay to push you there but with the other ARC gear I suspect the REF 80S was in your future no matter what : )

Is the 150SE operable for you to compare or will you only be going off memory?  I truly do hope you have zero doubts and it is a slam dunk upgrade.  

The features and aesthetics are fantastic so looking at that amp alone will bring much joy.

I am happier than I have ever been with the 75SE/5SE/2SE and feel quite fortunate to be here.  For the first time in my life there is nothing about my system that shows fault.  I of course want to upgrade other things for the fun of it but am trying to tame that beast.

Looking forward to hearing your impressions right out of the box and as times goes on.  Enjoy!!!!

Wow, thank you ghdprentice

charles1dad (always love your posts) and

tomic601

As I said above I will report back. My AD who has been an ARC dealer for many years pitched the new ARC trade-in program for the Ref 6. Instead of paying $3K to have one’s existing Ref 6 upgraded to an SE the offer is to send back the Ref 6 and get a brand new SE for $4.5K. My reply was "why would anyone want to pay an extra $1,500 for basically the same thing". He laughed and said, "yeah, well, the program was a response to the fact that they are badly backed up doing repairs and don’t have the time to do upgrades to existing units". ARC’s service department told me it would be 4-5 months before they will even provide me with a return authorization to send in my Ref 150SE for repairs! So while I appreciate the congratulations my decision to buy the Ref 80S was somewhat under "distress" (that being a reference to the definition of a true arms length sale as one in which the seller is under no particular compulsion to sell and the buyer is under no particular compulsion or need to buy). For two thirds of the price I could have purchased a pair of Manley Snapper monoblocs which are also true balanced and in light of my love for my Steelhead and love for how responsive Manley Labs is to any question or request for help I was very close to buying the Snappers instead. What I love about Manley is that their products are not only tried and true but then stay constant. The Snapper remains virtually unchanged for almost 20 years! Obviously the Manley approach is in stark contrast to the ARC approach, the latter of which reminds me of Apple phones.

 

Wonderful !,,,, enjoy the music

@fsonicsmith

Congratulations! I have no doubt that the Audio Research REF 80S is going to please you greatly and provide splendid music listening joy for many years. Glad to know that ARC has replaced the protective resistors with fuses in their current generation amplifiers. Smart move and long overdue in my opinion. +1 for the auto bias implementation as well.

Charles

@fsonicsmith

 

Congratulations. I will be interested in hearing your impressions… after the 1,000 hours mark.

I auditioned in home, a brand new ARC REF160s… then bought one… breaking it in… then because of a weak meter, I got another new one… which I broke in. I was really surprised that sound really continued to improve through 1,000 hours… although most was by 600. Then my dealer lent me a borrow a pair of REF 160m mono-blocks for the last couple months. It has been fun. Same power and design.. exactly… but separated in two chassis. I run them in triode mode (70wpc)… the power difference makes a tiny difference. But the sound is a bit more natural in triode mode. After lots of time. The soundstage is wider and deeper with the mono blocks. My conclusion is that if I had a choice of what to buy right now… I would pay the extra $12K for the mono blocks… but would not now pay to upgrade (perhaps because of the house remodel last year). I will wait for maybe the Ref 160SE (mono blocks)… or the next higher redesign… ? Ref320?.

Well, I am joining this club, meaning I am going from a Ref 150 SE to a Ref 80S. Mine was ordered today and will be here in five days or so and then I will of course need to let it settle in before I can comment. My pre is a Ref 6. I am the original owner of the Ref 6 and Ref 150 SE. My dealer informs me that I should hear a significant improvement. We shall see but the truth is that I don't need the 160 watts @ 8 ohms and 70 is more than sufficient. I have an eight watt SET amp (Ampsandsound Nautilus) that provides all the power I need. So for starters that means four less very expensive KT150's to worry about ($275/each from ARC to meet ARC's stringent testing and performance criteria for these very irregular tubes!). 

Something else that was not mentioned above but that is very important to me-this is the first modern ARC circuit design to fuse the output tubes. In all of my previous ARC amps dating back to a VS110 the output tubes were not only prone to arc-ing/blowing but when they did they would take out a paired resistor meant to protect the remainder of the circuit. You either had to be handy with a soldering iron or be prepared to take it in for service. 

So between the hopefully better sound and all these new features paired with the sexy looks.....I had to go for it. My Ref 150 SE needs some minor service and then it is going up for sale. 

dhite71 ... If your >1000 spec relates to the Parasound HCA 2200ii's damping factor, I surmise that the Parasound was a transistor amp, possibly with lots of negative feedback, thereby resulting in a near zero output impedance.

The output impedance of the Ref 75SE and Ref 80S is about 1 ohm in the low frequency space off the 8ohm tap, thereby resulting in a damping factor (DF) of 8 if the corresponding speaker input impedance is 8 ohms in the same low frequency space.  By contrast, the Ref 150 had a DF of 14 off the 8 ohm tap.  

My layperson understanding is that a "high'ish" DF helps to control the woofer and is a factor in yielding tight bass.  I recall reading posts from some of our A'gon tech members that a DF over 20 does not incrementally add all that much by way of woofer control. 

That said, I am sure that DF is not the only spec that drives quality bass.  If Ralph Karsten (Atmasphere) catches this post, maybe he will explain (again) the various tech factors that contribute to quality bass.  Such factor include, for example, in large the quality and input impedance of the speaker itself.  For example, if a speaker has an input impedance of 16 ohms in the low frequency space, the DF would be approximately 12 if, for example, the amp's 16 ohm tap's output impedance is say 1.3 ohms.  

In any case, enjoy your 75SE.  It is a great amp!!      

Thanks for your feedback, BIF.  Your experience is about what I would expect.  The new features were long overdue!  Biasing the REF150 was a pain having to remove the cage.  At least my 75SE has the pots accessible from the faceplate.  

I love the aesthetics of the new models.  

Damping factor makes no sense to me.  I have read that is about controlling the speaker to make the bass more impactful.  The spec on my old Parasound HCA 2200ii is '>1000'.  Well I can tell you the bass on my Classic 120s, the REF 150 and now REF 75SE are all superior.

Glad you are enjoying.  Let me know when you get the SE ;)

Dana

dhite71 .... I just picked up a Ref 80S about 2 months ago.  My old amp was an early build Ref 150SE, which was getting long-in-the-tooth.  The 80S is basically one-half of a Ref 160S, but has all the other bells and whistles.  I have racked up about 200 hours on the 80S so far.  Although ARC says the amp requires up to 500 or 600 hours to fully break-in, I surmise that any incremental improvements in SQ will be more nuanced.      
I bet your Ref 75SE sounds almost the same as the 150SE, ... just half the power.  If you run highly sensitive speakers, the 75SE likely drives them with little effort.  My speakers are rated at 92db sensitivity and the 80S does a fine job of driving them. 

And incidentally, my 150SE was originally an early build 150.  ARC did the SE upgrade about 6 years ago.  The SE upgrade made a huge difference.  So it would not surprise me if your 75SE sounds even better than your old 150.

By way of comparison, IMO, my 80S has a somewhat more refined presentation than the 150SE, but we're talking about maybe 10% to 15% or so better.  The mids and highs are slightly more detailed, ... sharper. Maybe even sweeter, but not rounded or "tubey" by any means.

The bass is surprisingly tight for an amp that has one-half the power of the 150SE and a lower damping factor (8 versus 14).  Not sure I understand why that is so.  

Oh, ... and I really like the 80S' auto-bias and the push-button tube check features.  The KT-150s drift and I didn't love manually checking and adjusting bias on the 150SE.  The 80S does bias adjustment automatically.  The 80S can play in triode mode too, but I kinda' like the old-fashioned ultra-linear mode. 

One other nice feature is that the amp has a restart delay protect feature.  The feature delays restarts for 2 mins after shut-down, which protects the circuits from an overload until the PS caps discharge. 

In summary, IMO, based on my experience with the 150SE, I bet the 75SE is no slacker by any stretch. So I get you point about waiting for the 80S SE to come out. ;) That said, I think for those who are in the market for a tube amp, the ARC Ref 80S and 160S are amps to really check out. They are truly wonderful amps.

BIF  

Your 75 remains a superb amplifier especially considering the relative RRP..... You are running KT150’s ? If not also look out for a pair of genuine pre 1980 6H30 DR’s (beware the many later production claiming to be genuine DR’s)