For efficient speakers, how much difference does an amp really make?

You are on the right track. The Binford 2000 LE at 113 dB is so efficient it doesn’t even need an amp. The voice coils pick up RFI, you don’t even need a source!

Sorry, but its been a long day of silly questions- and even worse replies. Look, you want music, or you want watts? You want music then you forget watts, get something like a Raven integrated (or Prima Luna, if you’re okay with the whole CCP export virus thing) and sit back and laugh at how you ever thought anyone actually ever had a need for hundreds of watts.

Because yes of course there are huge- not subtle, huge- differences between amps. Especially when you get into good tube integrateds and discover what solid state has been trying (and failing) to be all these years.  https://systems.audiogon.com/systems/8367 A 50 wpc tube amp. All the power you will ever need.

But if on the other hand you want watts then okay, its your system, be my guest. You’re off to a good start. Carry on.

(or Prima Luna, if you’re okay with the whole CCP export virus thing) and sit back and laugh at how you ever thought anyone actually ever had a need for hundreds of watts.

Because yes of course there are huge- not subtle, huge- differences between amps. Especially when you get into good tube integrateds and discover what solid state has been trying (and failing) to be all these years. https://systems.audiogon.com/systems/8367 A 50 wpc tube amp. All the power you will ever need.

Isn’t your Melody and Dayton Audio Amp are came from the virus exporting CCP?

My speakers are fairly efficient as well.
 I have 650W mono’s on them.
i like the headroom, and the ease of the audio.
 I will never look back at less than 300+W rms.

 That’s just me.

you will need the headroom for finale, the crash from a sudden ending song, or a crescendo, with absolutely no chance of clipping., and the effortless capability of having more high quality watts.

been through quite a few amps/receivers since about 1985/86

 lived with 150w receivers amps for years, until I bought a amp which failed, and they gave me a sunfire 300 on loan, I’ve never looked back.

my .02¢

I had a pair of outlaws on trial..... they were ok but their ATI built amps sound much better.  Those speakers deserve better !!    The ATI 2002 is a bargain on the used market.  McCormack DNA 225 also great value used. 

I have had both in my system and although I have gone to the dark side, those are two amps I could live with again if I ever went back to SS.  I had the 225 on loan and actually bought a DNA 125 new, great amp that I regret selling.

Personally I would avoid something as old as the Adcom ...  those are pretty old at this point .   

Watts do matter if you want top notch dynamic peaks. That is basic physics.

A 50 watt tube or Class D amp may seem to deliver more per watt but that is mainly due to the fact that these amps soft clip which makes clipping more digestible to the ear by rounding off the peaks smoothly.

For best performance always best to be sure to avoid clipping, especially hard clipping like most amps but also soft.

How much exactly is needed is very speaker dependent.

My personal experience has been most any speaker benefits from more watts where the amp does not have to ever break a sweat to drive them.

I use 500. W/ch Bel Canto Class D. This will drive almost any speaker to lifelike volume effortlessly without ever getting warm.

I also have 60 watt Bel Canto Class D amp. This is lovely within its SPL limits with most speakers like a good tube amp but more limited in regards to ultimate dynamics and SPL.

If an amp does not clip, chances are it will sound good. What sounds best from there is much more subjective and harder to predict.

Years ago I worked in a TechHifi where we live demoed and sold most every line of receiver and amp from 15 w/ch to 200 or so.

The bigger model in every line always sounded best. Nobody ever chose fewer watts after listening because it sounded better.

Amps do sound different. The difference can be subtle or huge. Sometimes subtle differences can be worth the upgrade too.

I would not recommend an older Adcom. I just don’t think they’re a very good amp.

I don’t know your amps or speakers, but I wouldn’t solely focus on more watts as the solution for greater clarity and bass. What is your price range?

You can delete the duplicate topic by going into My Profile > Discussions Started > the Settings icon on the right > Delete discussion

Horses for courses

@millercarbon   

Sorry, but its been a long day of silly questions- and even worse replies.

This is supposed to be a forum to pose question and exchange ideas about audio.  Why do you prefer to turn it into a platform for you to critique both the questions and responses from forum members? Obviously playing this role gives you some sense of self validation but it really isn't in a positive spirit.  You're like trying to be some martyr who suffers fools all day, and despite the agony you endure listening to the substandard drivel, you still offer nuggets of wisdom to the undeserving masses.  You just give and give don't you?...(gag)

Wow, some of you guys are wound up tighter than Dick's hat band. There is nothing wrong with a little comic relief in the form of sarcasm from time to time. If we all stuck to the script, toed the line, behaved "normally", how dull would this place be?

To quote Sgt. Hulka, "Lighten up, Francis"..........

Oz

@three_easy_payments....+1

amps make a huge difference.  don't obsess about power ratings.  I use 45w to drive speakers with an SPL of 84dB at trade shows (in 13 x 20 rooms) and at the end of the day my ears ring.  

Quality over quantity assuming you meet the minimum needs for the listening environment you are in. 

Going lower power and/or tube amp is no assurance of superior sound quality. It is often an assurance of lesser macrodynamics and headroom, as arctikdeth pointed out.  

I have reviewed lower powered tube/SS amps, but for my personal systems I prefer more robust tube/SS amps, regardless of the efficiency of the speakers.   :) 

Mapman.....TechHiFi....boy that brings me back....

Just to be clear, 90-93dB is a moderate efficiency.


The problem you run into with moderate to lower efficiency speakers (less than 89dB) is something called 'thermal compression'. This is the tendency for the voice coil to heat up dynamically on peaks, which limits power with many amplifiers. The more power you throw at it, the worse it gets. This is why efficiency speakers (+96dB) have greater dynamic punch.

It’s true that listening at too high an SPL continuously beyond ~ the mid 80s causes hearing loss, so if one is armed and dangerous with an amp/speaker combo truly capable of delivering clean, dynamic peaks in the 90s or greater like one might hear at a live concert, be careful. There is only so much of that really good stuff the human ears can handle.

Soft clipping lower power tube amps are a good compromise from that perspective. Your ears are safe and as teh soft clipping kicks in rolling of the dynamic peaks, you will probably hear more of all the rest that is in the recording. That’s still a lot of good music.

Hate to make soft clipping amps sound similar to modern loudness wars recordings but the end result can be very similar.

Disclaimer: I like a lot of modern loudness wars CDs with good material done well otherwise, but only on a  good suitable powered setup capable of delivering the goods.

+1 @atmasphere 

To add to Ralph's (Atmasphere's) comment, based on the specs shown at the end of this document the 93 db figure is based on 3 db of anticipated "room gain." The anechoic figure is 90 db, which IMO is probably what should be relied on when comparing the specs of this speaker to those of others. Also, the impedance curve shown near the end of that document indicates an impedance of about 5 ohms for most of the region below 1 kHz, where the majority of amplifier power is typically required. Sensitivity of 90 db/2.83 volts/1 meter corresponds to about 88 db/1 watt/1 meter for a 5 ohm load, which is definitely not high efficiency.

That said, the relatively flat impedance curve and the relatively small impedance phase angles at most frequencies suggest that this speaker should be fairly versatile in terms of amplifier selection. I wouldn't want to speculate, though, on how much of a difference you are likely to hear in your particular system going from the Outlaw to another amp you may consider. I would just say that the difference is likely to be less than it would be if your speakers had particularly challenging impedance characteristics.

In any event, kudos to Ascend for providing the detailed information they have provided in the paper I linked to.

Good luck. Regards,
-- Al

i am absorbing all of this...it’s a lot to process.

My system is very happy at low to medium volume levels. The sound is open and clear and produced seemingly without effort. It ramps up nicely until you get to a place where things start to change. The open sound starts to close up a bit and there is a strident tone that creeps in as the volume gets to what i would call “loud”. We’re not talking Wembley Stadium loud, or vibrate the windows loud, but the kind of volume you’d want for a favorite song when you really want to enjoy it.

Maybe the speakers are just tapping out, but i doubt it. i suspect that the slim, cool running M2200’s are simply running out of puff. Whether that means amps or watts...I have no idea, but I suspect these speakers have more to give.

I think it’s pretty clear that more watts are not always better watts...but i’m curious...what is the secret sauce that makes an amp with less wattage capable of driving a system with more authority and gusto than one with higher wattage?

And the big question....short of buying a dozen different amps and auditioning them on your own system at home, how can one even begin to make intelligent guesses about what to try next?

I agree from reading the specs that these things are 90db efficient with a 4ohm minimum stated. Absolutely typical of pretty much every modern tower speaker around these days. If you owned actually efficient speakers the world of lower powered amps would become available to you, including small single ended tube amps that many feel sound more like music should. 

dtrandall, well, most peoples' systems are "happy" at lower volume. Doesn't take extreme sound for that comfortable sound. 

It's not assured from your descriptions that the issue is not the speakers. If you are hankering for a more voluminous sound than those speakers can provide, it won't matter what amp you put on them, they'll be quite limited in comparison to some other designs. Something to chew on. 

See, you thought it was a simple, "Pick the right amp," question. Nope; it's much more complex than that. However, accept the challenge of finding your dream system and have fun with it.  I recommend you first familiarize yourself with the expected performance outcomes of different speakers and genres of speakers. In the end you could pick even an entirely different genre of speaker. It's a wide open field of discovery. 

Get thee to shops (when open again!) to hear some stuff, and for sure try to attend a show - eventually. Until then, keep reading, keep exploring, keep asking... LOT's to learn and consider. You won't have an easy time picking, and when you do you'll be tempted to second guess your decision. Perhaps you should, perhaps you shouldn't. There is no magical template. Building your dream system IS a lot of trial and error over time, and no one can magically make it appear for you, unless you simply accept their recommendation, and in that case you still have no assurance you did the best.  :) 

The more serious you are about this, the more gear you have to handle, if your goal is to gain assurance you are moving upward toward a highly developed rig. You pick how hard you want to push on that.  :) 

I'm going to be candid, blunt in one respect, in regards to assessment of your system/speakers. I mean NO disrespect, this is for analysis of your desires. The cabinets are small and light, the volume on cabinet and driver size is quite limited. I had a set of Kirksaeter Silverline speakers similar; nice, but lots of upscale characteristics to gain if I wanted to move up. Imo, some of the messier sound you hear is due to the cabinet when volume elevated, and I suspect the bass gets messy as a result. 

I suspect your speakers are the better upgrade. That is not to suggest you could not see some improvement with a different amp; of course you could. However, if you want to vastly change the experience, you should seek different speakers. That would be a sea change in performance. 

You mentioned "low end grunt"; I wonder if you are wanting more impact, more presence. Those speakers cannot give it to you in spades. the bass performance on those is closer to a bookshelf than a big tower speaker. Imo, begin looking for different speakers, not a different amp. A move to an Adcom or similar will be more lateral than upward. Different speakers can blow this performance out of the water. If you don't have enough money, save for it. It will be most worthwhile. That's not to say the Outlaw amp should not be upgraded eventually, but imo speakers are the direction to go.  :) 

I have zero interest in debating my recommendations.  

"I have zero interest in debating my recommendations". Doug, you just blew the wind out of a few sails here!! Kudos

Not all amps of a similar power rating are created equal in terms of ability to drive any speaker well.

Usually amps with ability to deliver more current will perform better with more challenging speaker loads regardless of efficiency rating, which are common these days.

The indicators of an amp like that is ability to double current delivery into 4 then maybe even 2 ohms and usually have higher associated Damping factor, more like 50 or higher rather than lower.  Some amps, the ones I tend to like most,  may include explicit current delivery capability specs.


Used to be these amps were also big heavy and expensive if Class A or even A/b but these days not necessarily the case. Some very efficient Class D amps with better power supply circuitry can deliver a lot of watts and current when needed out of a smaller lighter box. The efficiency of the amp essentially helps compensate for the inefficiency of most speakers out there these days.

Both BEl Canto Class D amps I use are good examples. Look up teh specifications of teh Bel Canto ref1000m amp for example.

Another significant factor has to do with output impedance of pre-amp used. Not an issue with most SS pre-amps however tube-preamps have higher output impedance which means a SS amp it mates to should also. 60-100kohm or so input impedance is what to look for. Some amps are designed this way to work well with tube pre-amps, some are not. Good impedance matching from pre-amp to amp minimizes distortion and general results in better clarity and definition top to bottom.

Regarding Ascend Sierra speakers specifically, I am not familiar with those but the specs I see on the company website for these models in general seem to suggest moderately more efficient than many at best and that they tend to go for somewhat extended bass for their size which almost always means a few extra good quality high current watts could only help since they have to work harder to deliver flat extended bass from a smaller package. A 300 watt continuous power rating is a good indicator that the speakers should be able to handle pretty much as much power as you could ever practically throw at them.

Current is king. An amp that is comfortable at 4 ohms and stable to 2 ohms will be able to drive those with authority. An amp that is stable at 4 ohms and nothing below will likely sound thin as volume increase. I had this problem in the past with an integrated that was 4 ohm stable but not really happy there and with a power amp.  
At the time I upgrade to a Rogue Hydra (100w class D and doubles output down to 2 ohms) and my speakers came to life.

Because I import Art Audio, I brought in a pair of $17K mono-blocks and not shockingly, they have plenty of current to handle my lower impedance speaker.  

many manufacturers put in a power supply that delivers a big number into 8 ohms but won’t be up to the task as impedance drops. 
At times you can find that Hydra in the $1500 to $1800 range.  A stereo 100 which will have 50w in triode, 100w in ultra-Linear would be another great choice for hybrid and tube gear.  
For Solid State, Musical Fidelity is a strong value and does well at 4 ohms.  If you can find a used M6 PRX, they are amazing.  A new one is $2300 I think.  The older ones were $3K.

My take - the more efficient the speaker, the more the balance shifts toward quality from quantity when it comes to amplifiers. 

For a given budget, any amp designer is going to have trade-offs between power and finesse. There are obviously going to be some designers/companies that are more creative/efficient, etc. but building a more powerful amp means higher voltage parts, bigger transformers and caps, bigger heatsinks, larger chassis, etc. which take budget away from higher quality components. 

In other words, high efficiency speakers do not, in the least, diminish the benefits of a high quality amplifier, but they do reduce the need for tons of power. If anything, a high efficiency speaker will expose the limits (noise floor, linearity, etc.) of your electronics much more readily than a low efficiency speaker. 

If you've got high efficiency speakers, take advantage of your lower power demands to get an amplifier with more refinement for the same budget.

High efficiency speakers done well is a good thing but good quality full range ones are big bulky and thereby relatively expensive and generally require a lot of room to breathe.  Not for everyone. 
No single approach can do it all best.  Hence the variety. 
Also, these days, high efficiency Class D amps are a game changer delivering more often for less and in a smaller easy to handle package that is practical for many.  

Yes a good powered sub or two set up well is a very effective way to address power needs. Power needs for flat extended bass increases exponentially as  frequency decreases which is why most good subs these days deliver 100s of watts often using Class D amplification. Plus use of a crossover that relieves the bass load on the mains usually results in better performance from those as well because now your main amp has to not work as hard as before trying to do it all. Best thing since Swiss cheese......

Try an integrated tube amplifier or preamp + power amp set. With those speakers, anything over 100 WPC RMS should work fine, and give you a lot better sound than your current Outlaw mono blocks. 

In your shoes, I’d audition the ACEYYK 160 watt Bluetooth integrated tube amp. Amazon has it priced at $1,010.99 delivered. If you don’t like it, just return within 30 days full refund. If it’s somehow defective return is free. If it’s a case of “well, I just don’t like”, then shipping back I’d in you. But you get the benefit of Amazon’s enormous discounts with UPS and FEDEX; or you can use a USPS flat-rate box if it fits. 

Mapman- I used to love those tech Hi-Fi catalogs and recently found a few scanned online - great memories of reading those as a teenager and lusting after the top systems with the multi track recording features.

Ok

Use a good tube amp, something similar to the Acin class AB stereo hybrid integrated amplifier 

I like overpowering my speakers always because headroom is a good thing to have when it comes to the sound on the bottom which is extremely difficult to do when you are trying to make the bass notes sound correct I myself am a bass player so I am very critical about that there’s lots of choices
if you have a good dealer that will let you take things home like I do at gig Harbor audio in Gig Harbor Washington they let you try out anything they have on the floor you can bring home I’ve tried lots of amplifiers and I’ve probably owned at least 200 different systems in my life so far I have about six different places where I live and my business it’s a never ending hobby and it is the hobby that will keep me Engaged for the rest of my life

" My system is very happy at low to medium volume levels. The sound is open and clear and produced seemingly without effort. It ramps up nicely until you get to a place where things start to change. The open sound starts to close up a bit and there is a strident tone that creeps in as the volume gets to what i would call “loud”. We’re not talking Wembley Stadium loud, or vibrate the windows loud, but the kind of volume you’d want for a favorite song when you really want to enjoy it.

Maybe the speakers are just tapping out, but i doubt it. i suspect that the slim, cool running M2200’s are simply running out of puff. Whether that means amps or watts...I have no idea, but I suspect these speakers have more to give.

I think it’s pretty clear that more watts are not always better watts...but i’m curious...what is the secret sauce that makes an amp with less wattage capable of driving a system with more authority and gusto than one with higher wattage?

And the big question....short of buying a dozen different amps and auditioning them on your own system at home, how can one even begin to make intelligent guesses about what to try next? "
   I run speakers that are normally at least 104db efficient. The excursion of the woofer for instance is minimal. Efficient speakers mean more DB with FAR less cone movement which results in less distortion. I also use bigger than normal cabinets and horns because the best effortless sound does not come from small speakers. Things that sound good at low to moderate levels will sound bad at higher levels often because you have pushed beyond capable working limits of those small boxes and drivers. Yes you got more volume but the quality of it goes down.
  I run per channel a single 15" woofer inside a big horn and have a large horn for mid to HF using a two inch horn driver and yes it is a two way system. With Crown amps like an XLI800 at 200 watts per channel 8 ohms I can turn the volume up half way on the amps and then about a half of the way up on my PC which I use as a music server and can easily measure about 95db sustained and peaks up to 105db depending on the music from 10' away. I have no doubt I could sail right past 113db with no problem but I am not interested in doing so.
  If your cables and connects (and no I don't mean fancy ones but ones that make good solid connections and normally 12g which is overkill) are up to snuff, as I try to keep mine, a system like this is dead silent on idle and then goes to live performance levels and does not strain to do either. There is headroom to spare and even at low volumes 0f 75 to 80 db it sounds better than speakers that are not as efficient or too small for the job.
  You can also drive speakers hard enough that even if they were really good sounding in your room at low levels above a certain sound level your sound begins to break up and then that becomes audible.

  Bad music files can sound OK at lower levels but when you push your speakers hard those bad files sound even worse. Over time I have given up on some songs I really like because of the poor mastering which ruined it.
  I suspect from your description of your system and problems you have a number of things going on.
  Last but not least is this. Why guess when you can download a free program called "REW" and load it on your laptop, buy a calibrated mike such as a "UMike" and a mike boom and measure what effect each thing has including the system response to your room itself. Finding out where the worst frequency problems occur can often be tamed with a simple stand alone EQ but you could spend eternity trying to just fiddle and get the best results. Yeah it is a pain to learn to use on your own so find someone to help you nearby who can stop in to help you. Then you no longer have to throw more money and gear at an ever growing pile of stuff that still never satisfies you. You analyze what is going on and eliminate your problems one by one.  

I have a 30 year old pair of Klipsch Forte speakers.  They are 98 db sensitive so never thought I needed more than a couple of watts.  Then I bought an old Altec Lansing Pro amp and modded and refurbished it.  200 watts per channel.  Wow what a difference watts make.  Now I don't just hear it, I can feel it.  

Hey dtrandal

The amp can make a huge difference. At 90-93db efficiency your speakers are very efficient and will work with a lot of amps. If you prefer solid state (I don’t know your budget) I would listen to the Pass Labs little 30 wpc pure class A model XA30.8 which is balanced. If you’re ok with single ended his pure class A model XA25, both sound great. I own the XA30.8 and my speakers are 83 dB! It drives them effortlessly all day long and always remained so musical. There’s also a lot of great tube amps out there as well. Any good quality 50 watt tube amp would be all you would ever need. Good luck.

Scot

@scothurwitz, what do you mean “Pass Labs little xa30.8”?  That sucker weighs 93 lbs!  But I do agree, it’s a great amp.

Sadly, I’m an audiophile on a budget.

In fact, my entire system...preamp, monoblock power amps, CD transport, turntable and speakers didn’t cost as much as the Pass XA30.8 amp does all by itself. Maybe one day....

I have many speakers, but currently using Zu Dirty Weekends, which are like 97dB/w with a 12ohm impedance.  I've tried 3 different amps on it.  My 120wpc Rotel sounded terrible on them, but my Bryson 4B-ST (reCapped) sounds great.  And...  with really dynamic material, I will blink the clip lights on this 250 wpc amp!  Now....into 12 ohms, it's really only about 165 watts, but the Zu's will utilize the full voltage swing of this big amp.  The Zu's are clearly an easy load, yet i clearly hear differences with each of my amps.  I have a newer Byston that I'm looking forward to trying on them that might sound even better....... or not?  

Hey doni,

My comment on the Pass Labs "little" 30 wpc xa30.8 was just referring to the watts per channel. The watts per channel on a spec sheet really doesn't mean much and certainly doesn't tell you what the amp sounds like.

Yes, you are correct, there is a reason it weighs 93 (88 net) lbs, Nelson Pass understands the importance of and knows how to build a well made power supply. That "little" amp is ALL power supply. His newer xa25 is also supposed to be great amp (if you don't want or need balanced). There's a reviewer for "The Audio Beatnick" online magazine that owns both of those amps and he feels the xa25 sounds even better (in certain area) than the xa30.8.  

I had that xa30.8 amp connected to a pair of Magnepan 3.7i's WITH a pair of their DWM woofers wired in parallel (talk about a difficult load) which presents a constant 2 ohm load to the amp and that amp handled it without even breaking a sweat! I ran that system like that for 3 years and never once had a problem with it. It was one of the most musical sounding setups I have ever owned.

Scot 

Efficiency and easy load are not the same.  
Efficiency means things get louder faster. 
An easy load means all frequencies get handled similarly and lesser difference to be expected  from amp to amp other than how loud things go. 

Dtrandal, I concur with those that suggest that those speakers are the limiting factor. You are only going to get so much bass out of such small drivers. That said, I’ve owned a few Adcom amps, and they really do have great bass with decent detail.

They still make amps, by the way, and instead of buying a decades old used one, you might consider something from their current offering. I’ve had both the 555MS and the 555SE at 200 wpc.

I would suggest the 565SE, at 250 wpc. But, it needs around 2 volts at the input stage to achieve full power. Can your preamp put out 2 volts? By way of comparison, your Outlaw amps achieve full power with only .85 volts, or 850milivolts. So if you are getting really loud before your volume knob is at 10 o’clock, then you probably have close to 2 volts potential anyway. Depending on the volume pot scheme, that is.

Or, if your preamp has XLR outputs, you could buy a couple of Schiit Vidar amps and employ them as monoblocks(they operate as mono's when connected with XLR) for 400 watts per channel. I also have that amp btw, another great option.

I've compared my little Dennis Had Firebottle amp to other tube and SS stuff and have concluded that there's something about a well made single ended tube amp that just sounds musically right, and no push pull amp I've used over the years even comes close, including tube amps. I'm fine being tied to efficient speakers as they also seem to sound better than otherwise, and a lower powered SET or SEP matched with the right efficient speakers will work to make music play loud and clear with no transistor glare or artifice...I do use a few hundred SS watts for my subs though...matches perfectly.

my audiolab 6000A preamp can output a maximum of 2.3V. I will take a look at the Adcom 565SE. Sadly, it does not have a true balanced XLR output, but that is certainly a feature i’m considering for down the road.

93db speakers are not that efficient. They will take some power to drive. I use Altec speakers that are around 99db and drive them with Mac MC40 monoblock tube amps. At normal listening levels (loud) I'm not using even a watt of power. If I crank them up till I start to hear some distortion (clipping) they are way to loud.
When I got into this hobby I was always chasing bigger amps, more power, had in-efficient speakers and thought that was the only answer. After a buddy showed me what a few watts on some Klipsch horn speakers could do I had to re-evaluate my thinking.
I also wonder on an amp that is designed for say 300watts, just how good is that first watt of power. Are the solid state devices really that linear at levels just a tiny fraction of their rated power? At 1 watt it would be running at 1/300 of it's rating and on softer passages less that 1/3000 of it's rating. Tubes seem pretty immune to that sort of thing, at least my Mac's are.

Billwojo

For high efficiency speakers, amps ar a big deal. IMO, an amps output "gain" is key. Or should I say, the combination of your pre and amp's output gain. If really high (especially with tubes), you will be more prone to hear hiss, noise, etc with high efficient speakers. 

The gain structure of the current model Adcom amps are all below 30 db, I believe.  The 565SE's gain is 27 db.  When I was checking out the input sensitivity of this amp, I noticed what appeared to be an error as the Adcom spec page lists it at 12.1 volts input for unity power.  I emailed Adcom and they responded within a few hours, saying the spec is actually 2.1 volts.  By way of comparison, the 555SE is 1.7 volts.

I’ve owned both the Ascend Acoustics Sierra 1 and Sierra 2 with the Raal Ribbon Tweeter. The brand is meticulously designed and tested. The components employed are anything but off the shelf, and it shows. When I put the Sierra 2 up against my Paradigm Monitor 7 V3(a tower), I was almost shocked.

Shocked at the mediocre sound I had been putting up with for about a decade. But the Monitor 7 was merely designed to be a slightly better option to the big box options back in 2003, and the industry was turned on its head since then. Still, it demonstrated to be that the Ascend Sierra 2 was a serious speaker.

Anyway, I’ve never heard the Sierra Tower, which is a different animal from David Fabrikant’s various bookshelf designs. Typically they were all easy loads, benign phase angles, and relatively inefficient. I haven’t owned my Sierras for about 3 years now, so haven’t kept up with what they’ve been up to.