Audio Research REF 80S Reviews/Comparisons

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  

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 ... 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!!      

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. 

@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?.