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Optimum amplifier wattage for 3a


dick

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My AR-3a's are very nice with an old Onkyo receiver TX8210 (rated at 48WPC @ 8 ohms "RMS" (??) both channels). Dynamic = 80WPC@4 ohms; Continuous = 60WPC@4 ohms. It is possible that I might shift the Onkyo to another setup and thus would like, in time, to consider a new amplifier (no tuner) for the AR-3a's. I'm a bit focused on one (Cambridge Audio 540C) that's rated at 75WPC (@, I suppose, 8 ohms). Is this too much? What's the optimum? One doesn't crank up the volume here. Mostly we listen with the Onkyo volume =/- 1/4 up from null. What's the advantage /disadvantage of more watts at this civilized volume level? What do you recommend?

The AR speaker brochure (http://www.mbzponton.org/n2awa/AR_loudspeaker_manual_11_1973.pdf) says that no fusing needed, the "AR can handle amps rated at 100WPC with conventional music...input material." The brochure also recommends 25W "RMS"/channel for the 3a. I don't know what RMS is....

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The more clean power available, the better. I had original AR3As and 2AXs back when they were new. At the time that I sold them, the best sounding amp with the 3As was a Phase Linear 400, at 200WPC RMS. Lesser power amps were not as capable. Note that this was NOT because I played them at extremely high volume...a 200WPC amp will only produce 3db more volume that an equally well made 100WPC amp. 3db is generally considered a noticeable increase in volume under normal conditions. SO essentially, it takes 2x the power to make a noticeable volume change.

What happens with lower power amps is that they go into clipping rather easily, remember...classic ARs are very inefficient speakers. So as you raise the volume on a low power amp you can get into clipping long before the speakers are "loud" which WILL destroy tweeters. A high powered amp, therefore, is actually much safer and sounds better.

I powered my current set of restored 3As for many months with 270WPC from a McIntosh Power Amp. That amp is now powering my LSTs. I'd suggest that 100WPC is the minimum amp I would use with the 3As and the more power, the better. Dynamic power spec is useless, it's designed for marketing, not reality. RMS power is the only meaningful spec as far as an amp's output is concerned. The output statement of a good amp might read something like, "20hz to 20khz plus or minus .x db at xyz watts RMS per channel with both channels driven."

Obviously, folks will use whatever they want to use for power but personally, I would not recommend an amp under 100 watts RMS for these speakers and I personally haven't used less than 200 WPC since the early 70's.

Note...I blew out tweeters in my 2axs and 3as (all replaced free by AR) with three different previous amps, including the AR Amp which, at 60WPC was the most powerful amp I had up till I bought the PL amp. After that, never lost another tweeter..

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"At the time that I sold them, the best sounding amp with the 3As was a Phase Linear 400, "

I need to clarify... my sentence above sounds like a statement that the PL 400 was the best of all amps available for 3As. That is NOT what I meant to say. I meant to say it was the best sounding amp that I PERSONALLY had ever used with them. I had several amps in the 40 - 60 watt range, Fischer, McIntosh integrated, and the AR amp. The PL was the first "HIGH power" amp that I owned and it made the AR3As sound much better than the previous amps (and it didn't blow tweeters). The PL was followed by several Carvers, then by a New York Audio Labs Moscode 600 (300WPC) and the McIntosh 7270. The Mc and the Moscode are my two primary amps now. My Moscode was "upgraded" a few years ago by George Kay, the original designer. The Moscode sounds a bit more "musical" than the Mc but both are excellent.

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My AR-3a's are very nice with an old Onkyo receiver TX8210 (rated at 48WPC @ 8 ohms "RMS" (??) both channels). Dynamic = 80WPC@4 ohms; Continuous = 60WPC@4 ohms. It is possible that I might shift the Onkyo to another setup and thus would like, in time, to consider a new amplifier (no tuner) for the AR-3a's. I'm a bit focused on one (Cambridge Audio 540C) that's rated at 75WPC (@, I suppose, 8 ohms). Is this too much? What's the optimum? One doesn't crank up the volume here. Mostly we listen with the Onkyo volume =/- 1/4 up from null. What's the advantage /disadvantage of more watts at this civilized volume level? What do you recommend?

The AR speaker brochure (http://www.mbzponton.org/n2awa/AR_loudspeaker_manual_11_1973.pdf) says that no fusing needed, the "AR can handle amps rated at 100WPC with conventional music...input material." The brochure also recommends 25W "RMS"/channel for the 3a. I don't know what RMS is....

One can not have "too much" for the 3a. Damage comes from clipping which would come from lower wattage amp being pushed beyong it's limits into the AR's 4 OHMs.

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My question is, there must be an upper limit of power fed to loudspeakers ?.....I would think a huge amount of power, say a thousand...two thousand watts would shred a smaller speaker like a 3a. It just seems that most of the speakers of aprox. 1.5 cu. ft. just would not be up to large amounts of power. That being said, back in the 70's a friend of mine had four AR-1W's as speakers for his cabinet set-up for playing bass in a rock band (don't ask me where he got the idea !) He had a Marshall amp and I don't recall the power, but it was a very healthy amount and produced some pretty serious bass.

It just seems that if one had a high powered amplifier, it would make sense to get some high end speakers or an array that are designed to handle the output.

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My question is, there must be an upper limit of power fed to loudspeakers ?.....I would think a huge amount of power, say a thousand...two thousand watts would shred a smaller speaker like a 3a. It just seems that most of the speakers of aprox. 1.5 cu. ft. just would not be up to large amounts of power. That being said, back in the 70's a friend of mine had four AR-1W's as speakers for his cabinet set-up for playing bass in a rock band (don't ask me where he got the idea !) He had a Marshall amp and I don't recall the power, but it was a very healthy amount and produced some pretty serious bass.

It just seems that if one had a high powered amplifier, it would make sense to get some high end speakers or an array that are designed to handle the output.

Naturally, all speakers have a limit to the amount of power they can handle. Manufacturers will often quote the max their units can safely handle. My sense, is distortion sets in, however, way before those levels are reached. Pushing to the max is never recommended and I can't imagine why anyone would want to do that.

If you have a high powered amp, you have more flexibility in that you can more easily drive some "tough loads", like AR-9's, LST's etc. All amps, however, have volume controls so you can just as easily power very efficient speakers. I think the speakers you acquire have more to do with your taste in music, the size of the room, appearance, and certainly WAF. Last thing I'd worry about is whether my speakers can handle my amp turned on full.

Regards,

Jerry

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It just seems that if one had a high powered amplifier, it would make sense to get some high end speakers or an array that are designed to handle the output.

The idea of high power in high fidelity sound (as opposed to the kind of sound that comes out of guitar amplifiers) is not to pump massively high amounts of power into your speakers, but to have massively higher amounts of headroom available between the output needed to play the material you want to at the sound levels you want and the output at which the amp goes into clipping and starts sending nasty sounding and/or speaker-damaging distortion into your drivers.

My 3a's are currently hooked to an old HK750 integrated amp. 45 vintage-era WPC @ 8 ohms, approx 60 WPC @ 4 ohms, very similar to the old AR amp. In my 10x10 home office with my normal listening material (solo pianos, jazz and chamber music quartets, etc.) at normal listening levels, they probably never see more than a couple of watts and I'd probably be able to use this setup here forever with no risk of ever blowing anything. If I replaced the HK with one of Mexicomike's 200WPC powerhouses, they'd still never see more than a couple of watts, but they'd be much better set up for a try at the 1812 Overture. Someday I'll finally get around to moving them out to the living room where they're supposed to be, and they'll need a more powerful amp (the HK will be staying behind and going back to running my AR-6's, which are really better suited to the office).

Pick your amp to suit your listening needs and the needs of the rest of your system, not the other way around. For the listening conditions you describe, the Cambridge will most likely be perfectly fine.

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The idea of high power in high fidelity sound (as opposed to the kind of sound that comes out of guitar amplifiers) is not to pump massively high amounts of power into your speakers, but to have massively higher amounts of headroom available between the output needed to play the material you want to at the sound levels you want and the output at which the amp goes into clipping and starts sending nasty sounding and/or speaker-damaging distortion into your drivers.

Absolutely right! The power meters on my 270WPC McIntosh amp have a peak-hold switch which makes it easy to see what the max power the amp put out at any moment. W/ the LSTs TYPICALLY the power doesn't exceed 3 WPC when listening to pop music from most digital sources at normal levels in my rather small room - which is way too small for the LSTs but it's set up in my office so I can do whatever and have good sounds. That 1812 overture, on CD, will hit almost 25WPC at that same volume setting. Raise the volume to more like the serious listening level and those 25WPC peaks are suddenly around 100WPC. Now here's the really interesting part...put the VINYL LP of the SAME recording of the 1812 on the TT, set the volume level at the beginning of the piece to be the same as the CD and sit down. The finale of that piece NOW requires the amp to hit 250WPC! The volume at that level is not, as you might think, excessively loud. But I have found virtually any classical music LP to have a much greater dynamic range than the same classical music performance on CD, which explains the difference in the power required. I find this rather curious because CDs, at least in theory, should have a much better dynamic range than LPs But that's a different discussion.

Anyway, I agree that with normal casual listening there is not much of an issue with amp power at all. But I think it's good to realize that turning the volume up may result in a lot more power being needed than one might think.

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Anyway, I agree that with normal casual listening there is not much of an issue with amp power at all. But I think it's good to realize that turning the volume up may result in a lot more power being needed than one might think.

Trying out what I think is Kent's script, hmmmm, cannot see it reformatted as I type. But to the issue initially brought up, its seems that Mike's comments above settle the power issue for me. Thanks to all for various reports and comments, both on and off CSP.

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But I have found virtually any classical music LP to have a much greater dynamic range than the same classical music performance on CD, which explains the difference in the power required. I find this rather curious because CDs, at least in theory, should have a much better dynamic range than LPs But that's a different discussion.

The media does, but any recording can only output as much dynamic range as the recording engineer puts in, and newer recordings on CD seem to employ more compression than older ones on LP. I have an old dbx "dynamic range expander," and probably apply as much or more expansion to digital sources as I do to LPs. Let's just hope recording engineers are not applying this "digital age" habit to new LPs, now that they seem to be making a comeback.

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Thought I'd add a bit more "data" re the power thing.

About an hour ago I decided to check the actual volume vs the power so I again put on the LP of the 1812 overture. I pulled out my Radio Shack DB meter and set it on C weighting which corresponds to the way we hear things. At the beginning of the piece the speaker volume at my listening position was at 70db and the amp was putting out around .027 WPC. You read that right, POINT OH TWO SEVEN watts per channel. In the middle of the piece the volume was up to around 80db at the louder portions and the amp was hitting peaks around 30WPC. At the finale, with the bass drum and cannons going, the amp hit 250WPC and the db meter showed 88db. It never was louder than 88DB!!!

So it was never "loud" yet a lot of power was needed. Admittedly, because of the bass drum and cannons, it was all bottom end which takes a lot of power. But again, it highlights that depending on the material, it CAN take a LOT of power and still not be all that loud. My 270WPC McIntosh amp could not even come close to reproducing this piece of music at concert hall levels which would probably in the 93db range. To see what would happen if I raised the volume to a point where I could JUST tell it was louder, the amp activated it's "powerguard" clipping circuit at 90db which automatically restricts power to prevent clipping.

ALSO keep in mind that due to limited space my seat is only about 6-7 feet from the speakers so in a room more suited to my LSTs, the perceived volume at the listening position with the same setting would be considerably less, to the point where I would be saying, it's not loud enough!

To add STILL more data, I then listened to a CD of Madonna's "Rain" at an 88DB peak. I used this piece because it is well recorded and has a nice bass drone that I figured would take some amp power. The amp peaked at around 28WPC. Yet rain SOUNDED a lot louder to my ears than did the 1812. OK, THEN I played ABBA (yes, I have an eclectic taste in music), again trying to match the 88db. I figured it would take less power than it took for Madonna but not so! Mamma Mia took around 50WPC! How about the Beatles? Taxman took around 40WPC. Wow, takes less power to play the Beatles then Abba? Doesn't seem right. Elvis' Moody Blue needed around the same as John, Paul, George, and Ringo so at least that makes sense. I then almost got caught up in a marathon of "what about this CD or that record" but I figured I had done enough measuring...

But wait! One last measure. Instead of matching DB, what if we match power and see what the db level is? So I put ABBA back on for another crack at Mama Mia and started raising the volume. I was at 98db when the Powerguard circuit activated at 270+WPC. I realize that a real rock concert will produce levels FAR higher than this but frankly, ABBA at 98db was way too loud for me. No, it wasn't ABBA-related, 98db was just too loud for me! As a final point, my listening level as I'm sitting here at the computer, NOT seriously listening to music, is around 75 db with the amp purring along at around 1 WPC!

So there you are, more than you ever wanted to know! Again, it all depends on the material. IMHO, pop material probably won't tax an amp much, even if played at fairly loud levels.

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But wait! One last measure. Instead of matching DB, what if we match power and see what the db level is? So I put ABBA back on for another crack at Mama Mia and started raising the volume. I was at 98db when the Powerguard circuit activated at 270+WPC. I realize that a real rock concert will produce levels FAR higher than this but frankly, ABBA at 98db was way too loud for me. No, it wasn't ABBA-related, 98db was just too loud for me! As a final point, my listening level as I'm sitting here at the computer, NOT seriously listening to music, is around 75 db with the amp purring along at around 1 WPC!

So there you are, more than you ever wanted to know! Again, it all depends on the material. IMHO, pop material probably won't tax an amp much, even if played at fairly loud levels.

I don't have any measuring equipment, but I'll guess that if you were to do frequency checks of these different sources you would find that the extreme highs and lows of the pop stuff don't go nearly as high or low as the 1812.

Now, do you happen to have 1812 on CD for a comparison...?

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I don't have any measuring equipment, but I'll guess that if you were to do frequency checks of these different sources you would find that the extreme highs and lows of the pop stuff don't go nearly as high or low as the 1812.

Now, do you happen to have 1812 on CD for a comparison...?

I thought that maybe I did have the same performance on CD (Telarc, Cincinnati Symphony but I don't. This record was THE test for low freq tracking in the mid 80's and it would bounce the tonearm/stylus right out of the groove on some allegedly good TT/tonearm/cartridge combos. Frankly I'm surprised that my AR XA TT and Ortofon cartridge can track it without the slightest problem; my Oracle TT and Signet TK10 cartridge - about $2500 more expensive - couldn't do any better.

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I thought that maybe I did have the same performance on CD (Telarc, Cincinnati Symphony but I don't. This record was THE test for low freq tracking in the mid 80's and it would bounce the tonearm/stylus right out of the groove on some allegedly good TT/tonearm/cartridge combos. Frankly I'm surprised that my AR XA TT and Ortofon cartridge can track it without the slightest problem; my Oracle TT and Signet TK10 cartridge - about $2500 more expensive - couldn't do any better.

I have a copy of this LP as well (I used to have two, one I never let out of my hands and another I let people borrow). Used it to drive a lot of my friends who owned "more modern" turntables than my AR TT and ADC XLM combo crazy when they took it home and tried to play it on their tables after listening to it on mine. :)

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  • 2 weeks later...

OK, I'll stick my two cents in about amplifier power. When AR3 and AR3a were on the market, a stereo amplifier which could deliver 25 wpc RMS of clean power was a very expensive purchase given the technology of the day and the value of money. Those that could deliver it at low frequences were rarer still. AR3/3a is additionally a difficult electrical load because it is not only nominally only 4 ohms but is lower at some frequencies. Some otherwise capable amplifiers could not handle it, especially early solid state amplifiers. Ironically this is not a good match for nominally powerful low cost 100 wpc modern HT receivers rated to power speakers of 8 ohms. You can put a 4 ohm 100 watt resistor in series with the speaker which will waste power but it will work and keep the amplifier from blowing up. 50 watts will still be available to the speaker. The effective amplifier damping factor will drop below one which is not necessarily a bad thing since AR3a is designed for critical mechanical damping anyway.

Amplifier power is far more complicated that just having a simple single number. Amplifiers of identical power rating can perform differently. Even the FTC's efforts to end the ludicrous horsepower race in the 60s and early 70s was inadequate.

How much power do you neeed? That depends on the efficiency (sensitivity) of your speaker (AR3a is low but there are much worse in this regard), how live and large the acoustics of your room are, and how loud the loudest undistorted sound you have to produce is. Also how far away from the speakers you will be.

How much power can the speakers take? The woofer is variously rated at from 100 to 150 watts continuously. But impluse power testing by Hirsch Houck Laboratories showed it could handle over 1000 watts of impluse power. The midrange and tweeter handle far less. The tweeter was guaranteed to handle 11 watts of power at any frequency within its range. However, as you reduce the level setting, the combination of the potentiometer and tweeter will handle more. I don't have any figures for the midrange driver.

Most high quality solid state amplifiers with a power bandwidth of from 20 hz to 20 khz in the range of 100 to 150 watts per channel at their rated distortion and stable with loads of 2 ohms or more are good choices. Amplifiers of 60 to 90 watts per channel will work well if not driven too terribly hard playing loud music with lots of very low frequencies in large dead rooms. I think Julian Hirsch once used a 150 wpc amplifier many years after his original tests on AR3a and found they would play very loudly and cleanly.

I'm going to have to disagree somewhat with Ken Kantor's statement that all solid state amplifiers sound alike if they are working properly and operated within their power ratings. I think there are often small and rather subtle differences which don't show up on bench tests with load resistors. These are due IMO to minor differences in FR under real world loads. That can be compensated for with a equalizer so that one amplifier can be made to sound like another without terrible difficulty of one is patient. I am no longer of the opinion as I once was and that many audiophiles still believe that you can't have too much power. I don't think that under normal use, all other things being equal, you'd hear a difference between a 200 wpc amplifier and a 500 wpc amplifier driving AR3as.

Once upon a time, pop music might have loud but not very low frequency sounds. That changed with the use of electric basses and electronic keyboards and other elecronic instruments. Usually it does not have a very wide dynamic range especially when compared to classical music. This is not the same as saying that it can't be very loud, even played at literally ear shattering levels. What it means is that the differences between the loudest and softest parts of the music are not very great. Often, it's kept in the range of 10 db for various reasons. Some classical music can have a dynamic range of around 70 db, too great for vinyl without compression but within the capabilities of compact discs.

Sound systems with very wide bandwith where very low frequency gain is high compared to that of run of the mill sound systems even with subwoofers have their own special problems and limitations. They are subject to acoustic feedback for one. (This is why the AR turntable fares so well, it has been designed to be relatively immune to external vibrations where many more espensive turntables weren't. Even some CD players can have their lasers knocked off the track with very loud low frequencies if they are not reasonably isolated from vibrations. Also turntable rumble that might be inaudible on lesser systems can be a problem with very wide range systems. And a surprisingly high number of recordings both vinyl and cd have low frequency disturbances including hall rumble recorded on them. All of these problems are non-existant or existant to a much lesser degree with more modest performing systems. And then there is glass breakage. There are 28 panes of glass in my main system listening room and I accidentally nearly shattered every one of them simultaneously with a loud low frequency organ pedal note one day. My AR9s are connected to a 60 wpc amplifier so you have to be careful.

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There's lots for me to learn about the 3a in regard to amplifiers. I thank all for their contribution to this thread. To end my search (but certainly not necessarily this thread) I visited a local hifi shop where the owner is as old and as knowledgeable as many on this forum with regards to the 3a. I sought a new amplifier, but I wanted to make a selection in a way that mattered here: subjectivity out-trumps objective data when it comes to listening in our household.

The shop owner sent me home with 2 integrated amplifiers for testing--each beyond, of course!, my buying plan: a Cambridge Audio 640A and a NAD C372. Our speakers, on tiny felt pads, rest on the floor in a rather large space - the ceiling slopes up from 9' to 16' and the listening portion of the room is about 24'x40' -- we can be anywhere in this area and expect to hear and enjoy music. The ceiling and floor are, to my way of thinking, pretty good for acoustics: they're pine boards--hat there are of walls are gypsum wallboard & windows. Morevoer, my wife is a weaver and there are many rugs and fabrics about the place. Lively yet absorbent with lots of air molecules to push around.

We don't sit and listen; we're up and about, reading or cooking or whatever. We do have ageing ears (I'm off on the tweeter side, wife is off on the woofer side), but we don't crank the volume up to anything but "pleasant" levels although there are mini-discussions about what's too loud, too inaudible...if you've been there you know what I'm talking about.

In this amplifier shoot-out the NAD was simply superb and the CA noticeably lagged behind it. We took the NAD. Differences between the amplifiers were entirely subjective, but the subjectivity of the entire house population was in entire agreement: the NAD was satisfying and enjoyable re: articulation, resonance, highs & lows (we listen to mostly classical music--from Betthoven symphonies to cello&piano duos to Callas--but go also for gamelan, Mexican folk music, tabla -- eclectic, huh?). We heard things never before heard...a common comment here as we fine-tuned the 3a's (Hi-Vi Q1 R tweeters, L-pads), and now upgraded the amplifier.

Here's some of the specs for those who might care to review them, give a critique. You'll notice not only 4 ohms capability, but 2 ohms as well.

Continuous average power output into 8ohms 2 x 150W (21.76dBW)

Rated distortion (THD 20Hz-20kHz) 0.02%

Clipping power (max cont. power/channel) 180W (22.55dbW)

IHF dynamic headroom at 8ohms 3dB

IHF dynamic power 8 ohms 220W (23.42dBW)

4 ohms 340W (25.31dBW)

2 ohms 460W (26.62dBW)

Damping factor >150

Frequency response 20Hz-20kHz ±0.3dB

3Hz/70kHz -3dB

Input impedance R and C 20kohms / 470pF

Input sensitivity (for rated output into 8 ohms) 770mV

Signal to noise ratio, A-weighted ref. 1W >-100dB

ref. rated power >-120dB

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Hi there;

Just my 2 1/2 cents worth of commentary about the AR-3A speaker system.

First of all, the 4 ohm rating is at 1,000 hertz, the midrange driver, not over the entire speaker range.

The woofer does go up to about 25 ohms, which is really what requires power amplifier reserve.

The lowest of 1 3/4 ohms is also a consideration for the stability of the amplifier.

Overall, an amplifier with a bandwidth of 20-20,000 Hertz, 1.5 ohms - 35 ohms impedance, 25 - 500 watts sine wave, and a damping factor of perhaps greater than 100.

Only a personnal audition in a large, stable soundroom with suggested sound equipment will give a decent showing of the AR-3A speaker system's capabilities.

Same can be said for the LST's and other speaker systems.

In a very intimate setting an AR amplifier will supply adequate sound output.

Increasing the room size and or volume level will place more demands on the amp of course.

Using a jump from the AR amp to a Crown DC-300A/IC-150A, a reference that I do own, will bring shivers up your spine.

The bass is felt more, much more, more gut wrenching than with the AR amp.

The Crown has more power output and with a much higher damping factor.

The amp and pre-amp will also have their own sonic signature or sound differences with also using different discrete components.

If I had never heard a Crown amp/pre-amp with my AR-3A's I could only read other listeners comments and would very likely still be initally happy.

I was completely happy when I only had the AR amp and AR-3A's, so I thought.

Hearing the AR-LST's with the AR amp was another major step-up.

Adding the Crown amp/pre-amp to the LST's was the next step-up.

This can be an addiction, for sure.

I feel that listening to other equipment, after the fact, can only, most often, lead to disappointment and additional expenditure and loss in used values.

If you are certain as to what equipment you want, set that as your initial purchase, and last one.

As I write this I am smiling and thinking about how many relationships and marriages have been ruined, mine included, because of this hifi addiction.

How many members here have a great sound system and no groceries or furniture? LOL

There was and is better equipment to drive the AR-3A's, only you can be the judge as to which is.

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