Pro Amps for AR speakers

[Sonnar]

I read some interesting posts by Tom Tyson about using pro amps to drive AR 3a, and I' m very curious because until my recent conversion to tubes amps, I 've ever used old pro amps with my AR set, a Crown PSA-2 , a Soundcraftsmen LA2502 and an Altec 9440A. Despite their age, these amps sounds very well , real Hi-Fi amps, and easily drives the difficult loads of AR 3 and 3a. They were very heavy and expensive, while modern pro amps like Crown XLS1000 are lightweight and very cheap, and I have some doubt about their sound quality , in particular for digital amps. I' ve seen also analog pro amps like QSC ISA280, it seems well built, powerful, reliable and affordable, but the question is still about their sound. Are these amps really better than old pro amps?

[owlsplace]

For our age group, 60+, that started with analog equipment, I think there will always be reservations about the sound quality of modern sources.

The generation that grew up listening to synthesized music with bass that slaps you in face however would perceive something different.

I'm adjusting but I may have to buy a turntable and revisit the past for a full appraisal of the situation. I have lots of vinyl around ...

Roger

[Sonnar]

Well, Roger, I admit to have some reservations about digital sources, and in fact I still have a good ol' Thorens TD 125 and my vinyl collection is larger than my CD's . But I 've learnt to appreciate the bright side of a good digital source . In the same way , I 'm asking myself about the opportunity to have lightweight, non expensive powerful amplification, but my question is about their quality. However , many modern pro amps are still analogic , just like the QSC ISA280 , and probably more oriented toward a good hifi sound . What is their real quality level ?

[tysontom]

Well, Roger, I admit to have some reservations about digital sources, and in fact I still have a good ol' Thorens TD 125 and my vinyl collection is larger than my CD's . But I 've learnt to appreciate the bright side of a good digital source . In the same way , I 'm asking myself about the opportunity to have lightweight, non expensive powerful amplification, but my question is about their quality. However , many modern pro amps are still analogic , just like the QSC ISA280 , and probably more oriented toward a good hifi sound . What is their real quality level ?

Well, I sort of started this conversation quite some time ago, but I have lived with Pro-type power amps for several years now, and I have been very happy with them. One disadvantage, most have fans that run all or most of the time.

As for sound quality, the simple expedient is this: if a power amplifier has very low distortion, clean and ample output from 20-20 kHz, low noise and good stability into any load, it makes no difference what circuit topology is used, or whether or not it is analog or digital. If two amplifiers measure identically into a load, those two amps will sound the same. I've got two QSC and two Crown Pro amps, including the tiny, lightweight XLS1000. I use this amp to drive a pair of AR-303As with an Allison ESW to equalize the bass flat down to 20 Hz. The sound is smooth, effortless and clean, and I don't hear any noises, buzzes or distortion.

With this amp, the fan only runs on high-current demand, so it can be used like a normal consumer amplifier. Therefore, it sounds every bit as good as the big Adcom GFA-555 II that I had before it, and it is probably ten-times more durable and reliable over the long run. Both the Crown and QSC amps have 5 and 6-year factory warranties. Pro equipment has to stand up to day-in and day-out abuse that consumer equipment rarely faces, so you can't go wrong with it. Also, class D digital amplification is much quieter now than in the early days of its development. There is no humming or buzzing as with the old-school class-D designs from the 1970s and 1980s.

[Sonnar]

Thank You, Tom, I have to feed my old ladies shown here, AR 3 are very power hungry speakers. The lovely Eico ST 40 is ideal for late night listening, but these speakers needs a lot of clean power to give their best. AR 3 brings easily the Soundcraftsmen to its limits, so I' ve found an used, very beautiful Crown Macro Tech 600 in excellent conditions for a budget price. It' s an A/B class old ( 2005 ? ) iron gear , designed for low impedance speakers. Someone says these old analogic amps are good sounding also in hi-fi use, but I have some doubts about its matching with my Marantz model 33 preamp, because I' ve heard that pro power amps needs high sensitivity preamp inputs.

[owlsplace]

165.JPG166.JPG167.JPG Thank You, Tom, I have to feed my old ladies shown here, AR 3 are very power hungry speakers. The lovely Eico ST 40 is ideal for late night listening, but these speakers needs a lot of clean power to give their best. AR 3 brings easily the Soundcraftsmen to its limits, so I' ve found an used, very beautiful Crown Macro Tech 600 in excellent conditions for a budget price. It' s an A/B class old ( 2005 ? ) iron gear , designed for low impedance speakers. Someone says these old analogic amps are good sounding also in hi-fi use, but I have some doubts about its matching with my Marantz model 33 preamp, because I' ve heard that pro power amps needs high sensitivity preamp inputs.

I don't think you will have a problem there as the Marantz has a 3V output and it looks like the Crown has switchable input sensitivity and can be driven to full power with less than 1V input.

Here is the spec sheet on the amp: http://www.parts-express.com/pedocs/specs/245-400-crown-specifications-44573.pdf

Roger

[tysontom]

165.JPG166.JPG167.JPG Thank You, Tom, I have to feed my old ladies shown here, AR 3 are very power hungry speakers. The lovely Eico ST 40 is ideal for late night listening, but these speakers needs a lot of clean power to give their best. AR 3 brings easily the Soundcraftsmen to its limits, so I' ve found an used, very beautiful Crown Macro Tech 600 in excellent conditions for a budget price. It' s an A/B class old ( 2005 ? ) iron gear , designed for low impedance speakers. Someone says these old analogic amps are good sounding also in hi-fi use, but I have some doubts about its matching with my Marantz model 33 preamp, because I' ve heard that pro power amps needs high sensitivity preamp inputs.

I don't think the Marantz preamp will have any trouble driving any power amplifier, especially the high-power, "grounded-bridge" Crown Macro Tech 600. Any preamp capable of 1+ volt output can easily drive a power amp through the high-level output. Crown's Macro Tech amplifiers are excellent performers, and the 600 can easily power a pair of AR-3s without any issues whatsoever, and this should be a fine combination. The Crown is a low-distortion, low-noise amplifier and will work well.

One issue you will likely have is fan noise, and you might want to figure out a way to dampen that noise by putting the amp in a cabinet with doors on the front, in a closet or find some other means to tackle that problem without blocking the air flow to the amplifier. Another thing you will have to do is to either fabricate or purchase a set of XLR-to-RCA type cables, changing the output from balanced to unbalanced, but this is quite easy to do (or simply buy the cable from Parts Express). As you know, the Marantz has unbalanced RCA-type consumer connections, and it probably doesn't have XLR outputs. The Crown MacroTech amps do not have unbalanced outputs, but this is pretty standard in the industry since 99% of all professional equipment is pro-level balanced-line XLR or 3-pin phone jack connections. Again, all you need to do is purchase or fabricate a cable that converts a balanced-line to unbalanced line.

The chart below shows the prodigious power available from this smallest of Micro Tech amplifiers, and you can see (and probably already know) that this amp is a fine performer. It is a class AB amplifier, I believe, which uses more of a brute-force power supply than the newer digital-switching versions, but all of these amps performs extremely well, either in a professional or consumer application.

--Tom Tyson

[Sonnar]

Thank You All for Your suggestions, very useful because in fact the old Marantz preamp has only commercial RCA outputs. I have a second pair of AR 3, shown here over Altecs, probably Teak finish or Cherry ,I don' t know. I have an idea : the Marantz preamp has two outputs , so I could use two power amps ( I have to find another Macro Tech or buying two XLS1000 ) to drive a " quartet " of AR 3 speakers, removing Altec Valencias and postioning two AR 3 per channel close to the rear wall and at one feet by the floor. Probably bizarre, but fascinating : four 12" AR 3's woofers playing together !

[ar_pro]

Here's a good discussion of the double AR-3a setup, Sonnar:

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7059

[Sonnar]

Very interesting! The better solution is to use a power amp for every pair of AR set , and the inexpensive class D pro amps offers a lot of power at the same cost of an integrated consumer hifi amp. I'm not interested in having deeper bass than I have , but in having a punchier sound . The D'Appolito configuration probably it 's not ideal with AR 3 , because of their 1 Khz frequency transition to midrange . I have also one pair of AR 3a , and I could place them between two AR 3 slightly positioned toward external and internal in front of the listener , for an AR LST look-alike radiation, but with the punch of six 12" woofers.

[JeffS]

Sonnar,

I drive my pair of 3's with an original NAD 3020 (which gives adequate levels in my rather live room) mainly because I don't want to damage the suspensions on the mid and hi drivers. I had to replace a 'popped' tweeter last year (which was the original unit), so I'm being cautious. Have you had any problems driving your 3's with the high powered amps?

Tom,

Does the Crown XLS1000 have a full time fan or does it switch on when needed. I have a QSC 1450 which had a continuously running fan (until I disconnected it) but this isn't the best way to run it.

[tysontom]

Sonnar,

I drive my pair of 3's with an original NAD 3020 (which gives adequate levels in my rather live room) mainly because I don't want to damage the suspensions on the mid and hi drivers. I had to replace a 'popped' tweeter last year (which was the original unit), so I'm being cautious. Have you had any problems driving your 3's with the high powered amps?

Tom,

Does the Crown XLS1000 have a full time fan or does it switch on when needed. I have a QSC 1450 which had a continuously running fan (until I disconnected it) but this isn't the best way to run it.

All of the QSC amps I own (3) have full-time fans (variable-speed in most instances), but the Crown XLS1000 runs only on demand. I use my Crown to drive a pair of equalized AR-303A speakers, which works fine and doesn't present an impedance load even close to the AR-3, but I think the Crown XLS1000 would drive the AR-3 fine. The efficiency of each of those speakers is just about the same, but the load presented to an amplifier by the AR-3 is tougher. An AR-3 dips below 4 ohms at certain frequencies (probably down to 2.5-3.0 ohms at certain points), but I did drive four-ohm AR-10Pi speakers with the XLS1000, and it had no issue whatsoever with them either. The fan in the XLS1000 has only turned on a couple of times, and that only occurred when I was pushing the system very hard. It's amazing how much output power is available from that little Crown amplifier, and the sound is very clean and undistorted with low noise. I have found virtually no difference in sound quality in comparing Crown and QSC amps; they are identical for all intents and purposes, and both amps are completely stable under any possible load condition.

I had an Adcom 555 II power amp (which I liked a great deal) in my system previously, and I replaced it with the tiny little Crown, which does the same thing with greater reliability and durability as far as I can tell. I was getting some noise issues with the Adcom (likely power-supply capacitors), and I didn't want to rebuild it or take a chance on a failure down the road, so I sold it. The sound quality of the Crown was every bit as good as the Adcom in a package one-fourth the size and weight, and the Crown has a longer warranty.

--Tom

[Sonnar]

JeffS, I use amplifiers from 10 watts to 400 to drive AR 3 and 3a , and in 40 years I haven' t any troubles with tweeters om my AR, KLH, Advent, Allison. I remember in the '70s many people burned AR tweeters using early SS amps: these amps had a lot of problems with low-impedance , capacitive loads, and was easy to reach the clipping and destroy loudspeakers. The NAD 3020 shows about 40 watts per channel on 3.2 ohms, but this is a peak limit; the dynamic range of orchestral music in modern digital sources can easily needs 200 watts of undistorted power driving a pair of AR 3 or 3a. And it' s safer to use an amplifier with a large reserve of power instead of a little amp , because 200 undistorted watts ( peak ) can' t destroy a loudspeaker, but a little amp in clipping easily reaches 100% of distortion. I 've used without any problem the powerful Crown PSA-2 , 600 watts on 2 ohms, stable on every load, but I' ve seen a lot of AR tweeters destroyed by Marantz 1030 or 1060 in clipping. And never use tone controls or loudness, it' very dangerous for tweeters. Sometimes I use the little Knight KA-25 , 10 watts per channel, to drive AR 3, but only in late night listening, at 70 / 80 db max. pressure level and with an analogic source, but it' s a tubes amp, with a progressive and soft clipping, while trasistors have a vertical increase in distortion at the clipping. Another very Dangerous thing for tweeters is the back cueing if you use Reel-to-Reel tape deck: only professional drivers are designed to survive it. So , if You want to drive Your AR 3 with NAD 3020 ( I have done it for many years with my 3120 ) You have only to be sure not to exceed its limits.

[JeffS]

Tom,

I'm glad to hear that the Crown amp has an on demand fan. My QSC amp has served me well for a few years now and the only feature about it that I dislike is the full time fan. Without the fan connected I've driven AR-9's at near peak levels for around 30 mins before the amps' thermal protection shuts it down. Still, I made upgrade to the Crown just to have a fan that kicks in when needed.

Sonnar,

My primary reason for using the 3020 is to keep any further damage from happening to the foam dots that hold the tweeter dome in place. When I acquired my AR-3's in 2012, one of them had been exposed to direct sunlight much more than the other. While this gave the cabinet a beautifully 'lightened' appearance, it also caused two of the foam dots to fail, letting the voice coil out of the gap. Surprisingly the tweeter still worked but had some distortion, so I replaced it. Last year, the suspension on the tweeter in the other speaker failed and I had to replace that one also. For the replacement tweeters, I've coated the foam dots and dome perimeter with Permatex Form-A-Gasket sealant and I'm hoping that these units will stay in place. So, given your experience I may ease them into something with 100 or more watts / channel and see how they hold up.

Jeff

[Sonnar]

JeffS, very beautiful AR 3's pair ! What kind of wood finish they are? Sun and dust are the reason because I keep my loudspeaker under covers when not in use, a big packaging box for Altec Valencias and blue velvet coats for AR speakers. I understand the reason why You use a low power amp, but having power doesn' t necessarily means to use it. It' s just to have a power reserve when the speakers needs it , far away from clipping . In addition, in my experience the big 12" AR 3's woofer ( and 3a , of course ) shows better and full bass only with high current, high power amps, also at normal listening levels, so I think it' s very interesting to have the opportunity of a cheap , quiet , lightweight power amp like Crown XLS 1000 or equivalent .

[JeffS]

Sonnar,

Thanks. I purchased these speakers at an estate sale from the original owner. They were sitting on a carpeted floor in a room with a cathedral ceiling and end wall that was all glass. They were next to the window and got plenty of sunlight, so much so that the top of one of them had a section that was very dry with open grain. Of course the first thing I did was give them a couple of coats of BLO. When I first brought them home I thought that they may be something other than walnut (the warranty cards were gone) but the bottoms are much darker than the sides and tops so I believe they are 'bleached' walnut. I love the look!

I also use 303's in another system and drive them with ~ 150w/ch so I understand the need for reserves but I've been babying the 3's because of their age and condition. I think it may be time to ease up on the power diet I've given them.

[ar_pro]

I think you're correct, Jeff - that looks like sun-bleaching; but what a great color.

For some reason, sun exposure on the later-model AR speakers seems to produce a sort of orange tint, which is not nearly so nice.

[Sonnar]

AR 3 were imported in Italy since early '60s, but the bigger part of them are in dark oiled walnut, as the first pair I bought in 2009, early production I presume from their serial numbers ( 24....I don' t remember ) Also my AR 3a are finished in classic oiled walnut. The second AR 3's pair , late production ( serial number begins with 64.....) came in with a lighter wood finish, but warranty cards are gone so I' m not able to identify the finish. Perhaps I' m a lucky man, but every loudspeaker ( wf, mid, tw ) works correctly except for one midrange with a broken wire, that I restored with an aluminum solder. Surprisingly, tweeters shows sparkling and transparent highs, however I 've heard that those tweeters suffers of suspension deterioration after many years.

[der]

I too have been lucky Sonnar. My AR3a tweeters still sound good as well. I'm sure my hearing has deteriorated over the years but I still hear good output from them.

der

[tysontom]

AR 3 were imported in Italy since early '60s, but the bigger part of them are in dark oiled walnut, as the first pair I bought in 2009, early production I presume from their serial numbers ( 24....I don' t remember ) Also my AR 3a are finished in classic oiled walnut. The second AR 3's pair , late production ( serial number begins with 64.....) came in with a lighter wood finish, but warranty cards are gone so I' m not able to identify the finish. Perhaps I' m a lucky man, but every loudspeaker ( wf, mid, tw ) works correctly except for one midrange with a broken wire, that I restored with an aluminum solder. Surprisingly, tweeters shows sparkling and transparent highs, however I 've heard that those tweeters suffers of suspension deterioration after many years.

Sonnar,

If you can, post a few more pictures of your AR-3s (the second pair) with a bit more light on the speakers' side panels. The wood looks much like quarter-cut walnut veneer, but it's really hard to tell. That dull grill molding (which is always solid stock on the AR-3 cabinet) is hard to identify, and resembles dark-stained birch. AR cabinets -- the many thousands of them -- came in a variety of walnut shades and grain configuration. Some were "half-round" cut with very wavy cathedral figuring of the black walnut; others have very little figuring; some were dark and some were lighter. The cabinets might be cherry, or they could be birch that someone sanded and stained a walnut color.

Throughout the late 1950s and into the 1960s, AR speakers were exported from the US to Europe and elsewhere by a company known as Delrama. My AR-3a "Cut-A-Way" speaker (see images below) belonged to that outfit and was used at shows in Europe and elsewhere. Later on, AR had facilities in Europe to handle overseas' distribution, and the exporter service was slowly discontinued.

--Tom Tyson

[Sonnar]

TomTyson: here are some pictures of my second AR 3 pair, taken in natural light and with flash . My father bought his AR 3 in early '60, they had a different grille cloth , very similar but with tiny golden filament , but maybe I' m wrong, at the time I was five years old. At present I' m relaxin' in late afternoon, listening my AR 3, Vivaldi, The Four Seasons: to me it's still the best speaker I' ve ever heard in my life.

[ra.ra]

Those are all gorgeous, Sonnar.

The pair shown in post 21 appear to be pine plywood cabinets with perhaps a solid nosing of birch, all stained to match. It also looks like this pair might have grilles that are lighter in color than the first pair?

Two pairs of AR-3's makes you a lucky man! Very nice.

[Sonnar]

Yes, probably correct, it could be pine plywood. Thank You , my two daughters call my AR speakers " The real daughters " ! In fact, at the time of my birth date in 1960 my father had a pair of AR 2 and we 've ever had AR speakers in our family , so these speakers are real part of our family life. First pair's grilles are original, slightly yellowish by the age , second pair aren' t original but very similar, JKent brings me from USA when he came to visit Rome ( Thank You Kent! ). A few minutes ago I opened another thread about restoring another AR 3's pair . Many audiophiles friends with excellent speakers ( Quad ESL, Maggies, B&W, Kef, ProAc and many others top-ranking speakers ) came to my home to listen my fully restored AR 3 and suddenly fell in love , and they all wants a pair for their home. However, while AR 3a were sold in Italy in large quantities, very few AR 3 were sold in early sixties , so we have to search some pair with difficulty and restore it accurately.

[oldguide]

Just a quick note re the fans on pro amps. There is an easy fix for this if you are a bit handy: remove the stock fan and replace it with a quiet computer fan with the same specs. An added bonus is the a computer fan moves more air with less noise.

[tysontom]

001.JPG002.JPG003.JPG004.JPG005.JPG006.JPG007.JPG008.JPG TomTyson: here are some pictures of my second AR 3 pair, taken in natural light and with flash . My father bought his AR 3 in early '60, they had a different grille cloth , very similar but with tiny golden filament , but maybe I' m wrong, at the time I was five years old. At present I' m relaxin' in late afternoon, listening my AR 3, Vivaldi, The Four Seasons: to me it's still the best speaker I' ve ever heard in my life.

Perfect! Thanks. Those are 100% plywood with birch molding,and someone has stained them (did a good job) mahogany or walnut color. Another way you can tell is the plywood "plies" showing on the back panel. The veneer-finished speakers used a compressed board known as Nova Ply (and others), and the plywood cabinets were used only for the utility-finish versions. The gold thread in the grill material was used up through AR-3 Serial Number 19000 or so (I have it written down somewhere). After that, AR stopped using the seran grill material with the gold thread and used only the ivory-colored material. Note, too, that by 1967 or 1968, AR-3s came from the factory with AR-3a-type cabinets instead of the original AR-3 cabinets, and the grill panel was attached to the inner molding rather than being tucked under the grill-panel molding.

Those are very nice AR-3s. Congratulations!

--Tom Tyson