Al, On relatively rare occasions when I crank up the volume it did remain controlled, clear and unstrained in character(95-103 peaks) but I just want to maintain good hearing as long as I can . I'm not getting any younger that's for sure, but my hearing is still quite good. Charles, |
Al, Wow, you really listen at very high SPLs.A few days ago a friend and I visited a local jazz club and his phone has an application for SPL measurements. Average volume was roughly 87-92 with drum kit peaks 100-105 (we were very close to the stage) but it was loud (unamplified that night, thakfully).I'd fear for my hearing with those levels at home on a regular basis. Most of my jazz CDs have a range of 25-35 db, but my average listening level is likely noticeably less than yours. I'm very familiar with your VAC REN 70/70 amplifier and it is a classic in my opinion (so is the 30/30 version).There's just something unique and special musically with DHT output tubes, in both SET and push pull mode. Regards, |
"Does your system belt it out pretty loud and non fatiguing? OR does it seem to be very detailed and airy, but when you turn it up loud, can you listen for long periods? Matt, I havent heard Als Ulysses but Ive heard the model just under them - the Argos; so Im very confident that Als system would knock your socks off. But additionally, if you ever have the chance to hear a pair of Volti Vittora speakers, I would highly recommend that you take the opportunity; just to finally put to rest, any reservations you might have left, of what a few tube Watts can accomplish with the right speaker. |
Hi Matt, I have no experience with Dynaudio speakers, but my instinct would be to proceed with caution before going to tube amplification with them. In addition to the comments by Ralph and Mapman just above, I would emphasize that high quality high powered tube amplification tends to be quite expensive. And you clearly need lots of watts. Based on the impedance curve of your speakers, shown in Stereophile's review here, I would consider their 86 db/2.83V/1m sensitivity to be roughly equivalent to 84 db/1Watt/1m. At typical listening distances (say 10 to 12 feet or so) that would mean that 70 watts into both speakers would produce a maximum SPL of around 96 db or so. While that is adequate for most listeners when listening to highly compressed rock music, I suspect it would be very disappointing with a lot of material having wide dynamic range (i.e., a wide difference in volume between the loudest and the softest notes). My listening is about 90% classical (including a lot of wide dynamic range symphonic material), 5% rock, and 5% miscellaneous. I've measured some of the classical material I listen to as reaching 105 db at my listening position, which my 98 db/1W/1m speakers and 70W amp handle comfortably. Although I haven't heard them, if you do want to consider tube amplification you may want to look into the higher powered models from Rogue Audio. Some of them provide close to 200 watts, at relatively reasonable prices, and seem to receive generally favorable user comments. Best regards, -- Al |
Dammit! Al, I would love to spend an evening with you listening and drinking. Here's my question Al. I have never tried tube amps and I am fearful that I would miss some SLAM and Impact of the presentation. Does your system belt it out pretty loud and non fatiguing? OR does it seem to be very detailed and airy, but when you turn it up loud, can you listen for long periods? (I guess loud would be above the 35w range)I would love to hear some good tube amps with a different speaker that works well with tubes. There are no stores I can visit nearby. My Dynaudio Contour 3.0s are really great.But they are 86-87db and require a lot of power to open up. My MC352 can drive them over 350w easily and the speakers are rated at 200w. I was thinking of switching to a pair of 70w monoblock tube amps. but I really dont think my dynaudios would like that. of course I have nothing to support this really.what do you think AL. Am I missing out on goosebump city,or is my hybrid system the best I can hope for with these speakers. |
Csontos, I think that I might understand where some of the tube skepticism among the solid state crowd comes from. Quite often, tubes are used in applications that are less than ideal. I hear them all the time. Thats not to say that a mistake was made. A person has the right to consider only the elements of music that are important to him, and choose a tube amplifier/speaker combination accordingly. But while this person is satisfied with his tube application, others of us might listen to his system and hear musical compromises that we wouldnt make for ourselves. What Atmasphere, Almarg and others are trying to tell you, is that many of the shortcomings that you perceive to be inherent to tubes, are more likely to be common application flaws. |
I understand that speed and other sonic parameters are subjective and individually just personal perceptions. I've found good tube power amplifiers to present a wonderful realistic sense of timimg, pace and musical flow.The presentation is very fluid with well preserved continuity. The two Spectral based systems I heard (if they're considered typical of a"fast" SS amplifier) were not even close as far as retaining the believable and natural musical flow and timing.The sound was mechanical and artificial in character But again, this is just my own observation. Regards, |
05-20-13: Csontos I would venture to guess that Al, but especially Ralph believe it's not possible to arrive at life-like sound without tubes given some of their prior posts. To that end I would like very much for either/both to cite some tube amps that are as fast as any ss amps they've heard so far. Imo, you can't get there without serious speed in an amp. Hi Peter, No, I for one would certainly not make any such claim. In part because my listening experience with solid state amps during the past decade or two has been minimal. Prior experience led me in the direction of tubes, with which I've been very happy, and in recent times I've simply had no interest in high end solid state. And my speaker preferences have always tended to be in the direction of those having impedance characteristics that are benign and tube-friendly. For examples of tube amps that are "fast," for starters consider Ralph's OTL amps. Although I haven't had the pleasure of hearing any of them, by all accounts I've ever seen they have that characteristic in spades. And among tube amps having transformer coupled outputs, my VAC Renaissance 70/70 Mk III certainly doesn't disappoint. While I realize that you "don't care about published specs," I'll mention that they are rated as being down only 0.5 db at 90 kHz on a small signal basis, and at 58 kHz at full power. At -3 db those ratings are 103 kHz and 85 kHz, respectively. Not very different than the very highly regarded Pass XA.5 series solid state amps, which are rated to 100 kHz (with no specification of power level or how many db down that is based on). Yes, I know, a few solid state amps, such as those made by Spectral, go out to 1 or 2 MHz or more, but whether or not that is overkill, and whether or not it may even be sonically counter-productive, are certainly debatable. As a point of reference, I'll add that I frequently compare listening results between my amp + speakers and my Stax electrostatic headphones + Stax solid state headphone amp. I doubt that anyone would ever accuse the Stax components of being "slow," yet I am not disappointed with the "speed" of the amp + speaker combination. Tubegroover, thank you most kindly for your expression of appreciation. Best regards, -- Al |
Csontos I would venture that the Atma-sphere amps, which I have heard in several unfamiliar systems over the years and in my experience the Berning zh series amps are as fast and transparent as any ss amps I am familiar with. Check out Berning's website for the numerous reviews of these amps to get an idea of their performance characteristics.
I have owned and been listening to the Berning zh270 for 11 years and the comments you have made above regarding tube amps in general are true in many instances but certainly not all. This amplifier rivals any ss amp I've listened to with reference to transient attack, pitch definition and bass control. |
I would venture to guess that Al, but especially Ralph believe it's not possible to arrive at life-like sound without tubes given some of their prior posts. To that end I would like very much for either/both to cite some tube amps that are as fast as any ss amps they've heard so far. Imo, you can't get there without serious speed in an amp. For me it's 'the' most important factor. I really don't care what else it does well or poorly (within reason). And I don't care about published specs. |
I do not consider Dynaudio speakers and tube amps to be a natural match by design in general, and would not do that without hearing first but that's not to say you might not find something to like there if you heard it. Agreed- in spades! |
"My questions is: is there anything to be gained by switching to these higher power tube amps over ss amps?"
Maybe or not. It would all depend on what you specifically are shooting for and how well what you have meets your needs or not.
I do not consider Dynaudio speakers and tube amps to be a natural match by design in general, and would not do that without hearing first but that's not to say you might not find something to like there if you heard it. |
Me too regarding Nelson Pass designs. One of the few SS designs that to my ears really get closer to making music sound real other than , to my ears, a tube solution (preferably of the OTL variety) ideally matched with the speaker. It always comes down to synergy when making choices and this is not so easy. There are many speakers with difficult load characteristics that are superb that will not electrically match with tube amplification. There is no simple answer to this complex paradigm. Melding components together in a manner that makes recorded music sound real is not easily achieved by Tube vs. SS discussion, too many factors involved in the equation that is evidenced by the same questions continually being asked, IMHO.
I really appreciate the contributions of Almarg and Atmasphere (Ralph) to my better understanding of these issues. |
I'm a big fan of Nelson Pass, Ayre and Ridley Audio. That's my short list... I think there are a few other candidates out there but I've not been able to hear them. |
Hi Bruce,
I suspect that the specified damping factor of 40 for the MC-352 (actually, it is specified as "greater than 40," but I'll assume 40 for present purposes) represents the output impedance of the amp for a given output tap divided into the speaker impedance that tap is nominally intended to be used with.
If so:
The output impedance of the 8 ohm tap would be 8/40 = 0.2 ohms.
The output impedance of the 4 ohm tap would be 4/40 = 0.1 ohms.
The output impedance of the 2 ohm tap would be 2/40 = 0.05 ohms.
The output transistors would presumably see the same load when an 8 ohm speaker (that is truly 8 ohms) is connected to the 8 ohm tap, compared to when a 4 ohm speaker (that is truly 4 ohms) is connected to the 4 ohm tap, compared to when a 2 ohm speaker (that is truly 2 ohms) is connected to the 2 ohm tap.
BTW, thanks for your kind comment earlier in the thread.
Best,
-- Al |
Al, does the autoformer lower the output impedance of the amp, or increase the perceived impedance load of the speakers. I appreciate the DF math works the same way, but just wasn't sure what changes.
In other the DF of amp is 20:1 if speaker impedance at the test frequency is 20 ohms and the amp's output impedance is 1 ohm. DF is still 20:1 if speaker impedance is 10 ohms at the test frequency and the amp's output impedance is .5 ohms.
Cheers,
Bruce |
Atmasphere, are you comfortable telling us which in your opinion are the 5 ss amps that come close? Just curious. |
I will add this to what Al said: It is generally thought to be a good sign when a typical solid-state amp doubles in power as the impedance of the speaker is halved. A sign of a good power supply, IIRC.
And yes, generalizing about amps based solely on the amp being solid-state or tube is certainly problematic. But this doubling-down into lower impedance is something that applies for the majority of solid-state amps. Your amps happen to be an exception to that rule of thumb. |
Thanks very much, Matt. Yes, the Daedalus Ulysses, in the configuration I have that was introduced about 3 years ago which includes "all poly" crossover capacitors, is 98 db/1W/1m. It also has a very flat impedance curve, as well as high power handling capability, all of which makes it unusually versatile with respect to amplifier selection.
Regarding your question, what I said was "the power capability of a solid state amp into 4 ohms MAY [emphasis added] be as much as twice its capability into 8 ohms."
As you probably realize, the power capability of MOST solid state amps will be substantially greater into 4 ohms than into 8 ohms, in many cases approaching twice as much, and in some cases equaling twice as much. Two ohms may be a different story, of course, as a lot of amplifiers will not do well dealing with such a heavy load.
As you indicated, though, your McIntosh MC-352 amplifier has the same output rating into 8, 4 and 2 ohm loads. That is essentially a consequence of the unusual autoformer-based design of its output circuits. I am not aware of any non-McIntosh amplifiers that use a similar approach.
As opposed to a tube amplifier utilizing an output transformer, however, the solid state + autoformer approach provides considerably lower output impedance/higher damping factor (damping factor being spec'd at 40). As a consequence of that it WILL, like most solid state amplifiers, to a very close approximation double actual power DELIVERY (as opposed to CAPABILITY) as load impedance is halved, AS LONG AS it is operated within its 350W or so capability, and as long as the impedance of the speaker is a reasonable match for the output tap on the amplifier that the speaker is connected to.
In contrast to most tube amps, that essentially places the MC-352 in what Atmasphere refers to as the voltage paradigm camp, i.e., its output voltage for a given input will be essentially constant regardless of load impedance, as long as the amplifier is operated within its capabilities.
Regards, -- Al |
Jallen I just put in a pair of MAZDA CIFTIES-12AU7's and I really like the top end end on these. Awesome sounding tube made in 1962 for the French Military. |
Almarg.....I am not sure what solid state amps you are speaking of. Not all ss amps DOUBLE IN POWER OUTPUT when the load changes. My McIntosh MC352,350w per channel Amp does not change in power output for 8,4 or 2 ohm loads. So I am perplexed by your statement. It also seems to me that you are lumping all SS amps together and thats not fair. Nice system and I bet those speakers are 95db sensitivity or better so they work well with the Tube amp. I wish I could hear it. |
I've owned a LOT of tube guitar amps and a couple of SS and hybrids...tube amps are simply snappier and make people happier. I do use SS bass amps though, as you need extreme power for that. Same with tube hifi amps...60 watts per side with 90db speakers and a SS sub (so sue me) shake my walls if need be, so I bet this sort of thing would shake yours. Also regarding heat...with only 4 KT120s there is not too much more heat than a recent partly class A SS amp I was using, but the tube heat is expected...a Twin Reverb will make the beer on top of it sweat all over the place...just a warning. |
Ralph, I tried your experiment of ramping up the gain. I was playing an EMI CD of Tchaikovsky (sp?) Nutcracker. The dynamic range is between 20 and 30 db. I never made it beyond 95db. At that point, external distortion made me turn the gain down. I'm referring to wifey. She threatened to throw a bucket of water on my gear. She introduced at least 90db of negative feedback and the odd ordered harmonics from her screaming really hurt my ears. Any suggestions? |
GE / SYLVANIA? Last I checked they were pretty similar, if not identical. Unreliability of this tube vintage keeps me looking to new stuff. I do like my 12 AX7 Amperex Bugle Boys and Sylvania and Tung Sol 6 SN 7 tubes, but they are more plentiful. Jallen |
If I could make transistors do what I can do with ease with tubes I would make transistor amps. But I can't and no-one else seems to be able to do so either, although a very few (less than 5) come close. That thing that tubes do is they don't make odd ordered harmonic distortion the way that transistors do. Most solid state devices have a non-linear capacitive aspect that is inherent in the junctions of the device. This capacitance is multiplied by the amount of current through the device. This is one reason transistors make more odd ordered harmonic distortion than tubes. The discussion about guitar amps does have relevance here. Guitar players prefer the smoother (lower odd ordered harmonic distortion) sound of tubes, especially when overdriving (clipping) the amplifier. Because tubes (triodes in particular) are the most linear form of amplification known, it is possible and practical to built a tube amp with no negative feedback that has fairly low distortion. This is really hard to do with transistors, and it is notable that the best transistor amps made (in my book) are all zero-feedback designs. However, 99% or so of transistor amps use feedback, and feedback actually *increases* the odd-ordered harmonic distortion in any circuit. Since the ear uses odd ordered harmonics to figure out how loud a sound is, by adding trace amounts to the signal the result will be brighter and harsher. The bottom line is if you want it to sound real instead of just a really good hifi, you have to find a way to get rid of that negative feedback. Usually that means going to tubes, and then finding a speaker that works. BTW: High efficiency speakers would make life a lot easier, but I thought those type of speakers sounded shrill and thin. It may be because I have only heard them with ss amps. The last sentence here is the important bit. My speakers are 98 db 1 watt/1 meter, and go to 20Hz. I can shake the building with a 60 watt amp, without concern of clipping the amp. Most 'high power' systems I hear cannot play with the volume, the impact or the clarity I hear at home. Even at +100 db sound pressures, it still sounds smooth and relaxed. IME most audiophiles won't listen at levels over 90db because their system is too harsh. Real music plays at +100 db levels, if you can't do that at home without discomfort, something is wrong with the system. |
HEY. you 6550 guys, you need SYLVANIA 6550's not those shrill GE's. I use Winged C's myself as the last quad I saw of unused Sylvania's was going for $600 and that was a few years back. |
I'd first get your speaker selection worked out, then worry about amplification. Speaker-amp matching is so key. And speakers are the most important component in the chain. Settle on them, then start figuring out a good amp to match them. |
It was an experiment. Thankfully(I guess). I love consensus though. I also love being a pain in the ass. I have nothing else:) Tubes or ss, it's all the same to me. It only has to sound good. Less maintenance with ss. |
Now you did it!! I want another one :) |
Onhwy61, That amplifier can be tweaked very easily, most don't know. Removal of the top allows access to (I'm going by memory) five white nylon setting screws. Two of which, will adjust the Gain amount. CAUTION: Turning up the wrong ones can result in possibly frying the board or such. I would imagine the information is easily found online.I had adjusted mine at least a few times. Great Crunch!! |
It is currently in my "archive". I had considered getting an additional Super cab, minus amp, to use as an additional extension speaker cabinet... ala' Super Full Stack! |
Isochornism, I don't use it very often, but I still have a GK250. It's a wonderful amp!
Csontos, nobody does that unless there is no other choice. Impedance and gain mismatches are usually the problem. |
Onhwy61 & French_fries Also, in regard to your mention of two channels, I have an old beat-up black face Super Reverb. When I got it my amp tech made it "healthy" and since it's condition, I didn't mind adding a toggle switch in the back. You would play through the clean channel, the reverb and tremolo would work with that channel. Throwing the toggle would overdrive into the second channel. ALL controls worked together!!! Many tonal combinations and MUCH power!! It was a real sleeper. People always wondered how that amp could crank so much!! HA And the original speakers always stayed intact :) |
Okay, let me try this again. I was referring to a home stereo ss amp, preferably a mono one. I tried a Denon with my guitar years ago. It sounded pretty good. |
Onhwy61, I did have a SS guitar once for a few months A GK 250ML. The cabinet was metal and built like a tank!! Very interesting little amp. It screamed! Csontos, And yes, this GK amp was stereo, 50 watts, I believe. I am unaware of any other stereo guitar amps, but I would not doubt that others do exist. |
Wow,, what great responses!!! Sorry I havent gotten back to this thread sooner but was gone for a couple of days.
The speakers I use now are Dynaudio T2.5, they are rated at 6 ohms, but I don't know the sensitivity, probably less than 90db. I am looking at Tyler MM5 speakers at this time. Ty has a new version of the MM5 coming out but I don't know it's sensitivity either. The AR9's are down at my shop and I use a PA amp for those. I had been an AR fan from the early 70's.
High efficiency speakers would make life a lot easier, but I thought those type of speakers sounded shrill and thin. It may be because I have only heard them with ss amps. Over the last couple of years Ive attended some of the audio shows and have listened to high efficiency speakers that sounded great. Most if not all powered by tube amps.
If I go with the MM5 that will have a lot to do with what I end up with for amps. What some of you have said about the advantages of smaller power tube amps compared to higher power tube amps makes sense to me. The cost of tubes, the heat generated and the time it takes to warm up are all things I need to consider, but I do love the sound of some tube amp systems Ive heard.
If this was an easy decision I would not have ask for all your wise and esteemed opinions. |
While many guitarist swear by tubes there is a sizable group of solid state amplifiers. The Roland Jazz Chorus is a widely used solid state amp. The Line 6 DSP based amps also have a following. The blues giant Albert King used a solid state Acoutic brand amp with his Flying V guitar. Additionally, most bass guitar amps are solid state. Guitar amps can have one or two channels. Typically the channels are not used together for stereo, but as two mono channels, one "clean" and the other "dirty". In live performances some guitarist use multiple amps in conjunction with stereo effects processors to achieve a stereo guitar sound. There are a very limited number amps that do this within a single chassis, the before mentioned Roland being one and I believe Gallien & Krueger made a few models. I agree that music production is different in concept than music reproduction, but at one time Allan Holdsworth used VTL Tiny Triode for amplification. I'm actually a little surprised that tube high end manufacturers haven't branched out into instrument amp production in large numbers. |
Yes, I'm aware of that. Hence my reference to a mono amp, specifically one intended for music playback. I was responding to his prior comparison. I'm thinking not a lot of effort is put into ss guitar amp design. |
Csontos, as to your question toward French_fries, I will expound on guitar amplification for your edification. Guitar amplifiers have always been in mono form since inception. French_fries, Twins are high power, but what a glorious tone!! My 58' tweed champ @ 5 watts is loud for my apartment. It does one tone only, one I agree with, and the volume goes up to 12! |
Jallen, When I was using a push pull 6550 amp the Winged-C served me well.Your suggestions for the OP are on the mark. |
In response to Mattmiller I agree there is something magical about a well executed 75wpc tube amp. Contrary to another post, I find many modern tubes quite good. In comparing NOS 6550 GE tubes, the Winged C had much better bass and none of the shrillness I find in the GE. The KT 120 is another fine tube. The Gold Lion Tubes have many fans. In response to the original post, connect with a local audio group and see who is willing to allow you to audition their gear or a dealer with a generous return policy. Jallen |
My goodness! What's it gonna take to convince you guys?:( |
Al . . . you're the best! Would you adopt me?? ;-') |
05-10-13: Mattmiller Efficiency and Sensitivity are words that get confused when talking about speakers. That is true. But I don't think that the references to efficiency in several of the earlier posts represent unreasonable uses of the term. Strictly speaking, speaker efficiency would be defined as acoustic power out vs. electrical power in. It would be expressed as a percentage, and would be a very small number for nearly all speakers. It would also be a number that is rarely specified, and that is not particularly helpful. It is common, though (and reasonable, IMO), for the term "efficiency" to be used to refer to sound pressure level at a distance of 1 meter in response to an input of 1 watt. And for "sensitivity" to be used to refer to SPL at 1 meter in response to an input of 2.83 volts. 2.83 volts corresponds to 1 watt into 8 ohms. So for an 8 ohm speaker "efficiency," per that loose definition, and "sensitivity" would be numerically identical. For a 4 ohm speaker, efficiency per that definition would be 3 db less than sensitivity, since 2.83 volts into 4 ohms corresponds to 2 watts. That difference will have greater significance in the case of a tube amp than a solid state amp, because the power capability of a tube amp into 4 ohms will generally be similar to its capability into 8 ohms, while the power capability of a solid state amp into 4 ohms may be as much as twice its capability into 8 ohms. On another note, in my previous post when I said: Another point I would make is that IME a forte of tube amplification tends to be imaging and dimensionality. Although I have no basis upon which to be certain, my suspicion is that that is not a strong point of these speakers, and that potential benefit of tube amplification would likely be wasted on them. it occurs to me that my wording could be taken more negatively than it was intended, due to my use of the word "wasted." To clarify, my intention was just to say that I suspect that the potential benefit that IMO tube amplification can often provide with respect to imaging and dimensionality would probably not be realized with AR9 speakers. One reason for that suspicion, in addition to its general configuration, is the comment in the review I linked to that the AR9 is designed to be placed close to the wall, which usually results in imaging being compromised to some degree. Regards, -- Al |
Jond, Your point was clear.Some NOS tubes are wonderful and justify the premium cost they demand. But you can certainly do very well without them depending on the tube type in question as you have demonstrated. Regards, |
Woah guys, I think my last post was somewhat misinterpreted. First of all by ignorant I just meant ignorant of NOS tubes which I basically am, so I was not being defensive nor did I take offense at anyone's comments. I am sure I could easily be spoiled by NOS tubes but as Charles1dad points out I am happy with my system as it is now. Very happy in fact. Unless anyone feels like donating a quad of super fantastic NOS EL34's to me of course! ;-) |
Jond, it was not my intent to imply you are ignorant, clearly, you are anything but. |
Jond, NOS tubes is a vast arena with different tiers, some are excellent others not so, there're numerous variables to consider. Here's the big picture, you're very happy with your system's sound and that's truly the bottom line. There're people with chronic frustration, indecision, and confusion who aren't really enjoying their systems. Be glad you're not one of them. If you always look forward to hearing music with your system, you're doing fine. Regards, |
Schubert point taken and the reverse holds true as well. Maybe I am satisfied because I have really not delved into NOS tubes and so don't know enough not to be satisfied. I concede that is entirely possible but I am happy, and less broke, in my ignorance. Cheers. |
I second the comments that have been made by several people to the effect that the answer to the original question is speaker dependent. Winggo, I see that in a thread you started about a year and a half ago you mentioned having a pair of AR9 speakers. If those are the ones in question, given their vintage (1970s), their modest 87 db efficiency, their nominally 4 ohm impedance, and their high power handling capability, it is safe to assume that they were designed with solid state amplification in mind. As some of the others have said, the suitability of using high powered tube amplification will be significantly dependent on how the impedance magnitude and impedance phase angle of the speaker vary as a function of frequency. I couldn't find any indication of the speaker's phase angle characteristics, but according to this review their impedance magnitude is generally between 3 and 5 ohms, with peaks of 10 ohms at 750 Hz and 8 ohms at 27 Hz. In comparison with a solid state amp, a tube amp will tend to give slightly more emphasis to frequencies in those vicinities. Another point I would make is that IME a forte of tube amplification tends to be imaging and dimensionality. Although I have no basis upon which to be certain, my suspicion is that that is not a strong point of these speakers, and that potential benefit of tube amplification would likely be wasted on them. My bottom line guess is that these speakers would do reasonably well with something like one of the higher powered Rogue Audio tube amplifiers, but you would be likely to do just as well if not better with a somewhat lower priced solid state model. Regards, -- Al |