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AR Stereo Amplifier/Universal


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#1 gary_wong5

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Posted 26 January 2009 - 03:43 AM

I came across this vintage AR integrated amplifier at friend's place. How does it sound? Worth buying? :rolleyes:

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#2 JKent

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Posted 26 January 2009 - 04:10 AM

I came across this vintage AR integrated amplifier at friend's place. How does it sound? Worth buying? :rolleyes:


I use the AR amp pictured to drive my vintage system. 60 "big" watts per channel and well built. Looks like you have the 220 volt overseas version of this. Good find.
Kent

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#3 Mexicomike

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Posted 26 January 2009 - 04:11 AM

If it works, absolutely! Of course the price would be the deciding factor. There were overheating issues caused by poor Bias Pots with the early versions of those amps that was corrected on later versions. I picked this one up about a year ago and made the mods to bypass the old pots but still allow bias adjustment. There was a long thread on the site about it where I asked a lot of questions, posted pics of the internals, and explained what I did. Do a search on "AR Amp" and it should show up.

Note that the amp is NOT a great match for the bigger AR speakers. It's OK but it will NOT bring out the best in a 3A, for example, being a bit light on power for that. HOWEVER, I ran it with my 3As for several months and it did just fine. But the comparison between it at 60WPC and an amp in the 300WPC range is quite apparent. One thing it does do really well is tone controls. I realize that may sound stupid but it remains the only amp/preamp I have ever used that actually has useful built-in tone controls

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#4 genek

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Posted 26 January 2009 - 05:22 PM

I came across this vintage AR integrated amplifier at friend's place. How does it sound? Worth buying? :rolleyes:


Condition is everything, and this one looks pretty rough from the picture.

If an AR amp is in good shape, the primary areas of concern are old caps failing and the fact that amps of that period tended not to be very well shielded against RF because they were made in a different era when the atmosphere wasn't loaded with MW transmissions, cell traffic and home WiFi. I auditioned one last year that was in excellent condition, but suffered from an extremely high background noise level that I eventually concluded was the result of RFI.

#5 tysontom

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Posted 26 January 2009 - 05:35 PM

I came across this vintage AR integrated amplifier at friend's place. How does it sound? Worth buying? :rolleyes:


Gary,

I hope the amp looks better overall than it does in the picture (of the output terminals) you attached in your message . There appears to be a lot of rust and corrosion on the back panel -- not a good sign. The first thing to do with any AR Amp is to "turn it on" with a DVM, VTVM or any good voltmeter connected across the output terminals of each channel, separately. From this you can determine the DC offset voltage -- a very important thing. Ideally, the offset voltage should be in the millivolt category. If you have more than 1 volt DC voltage present across the positive and negative terminals, with the amp idling, then you need to further investigate before connecting to a speaker. Do not connect the amp to speakers unless you know for sure that it is running in the "safe" offset category. Bias problems used to plague the AR Amplifier, and if there is a serious problem the output fuses (these are not "speaker" fuses as such) will usually blow before damage is done, but sometimes damage can occur to the woofer voice coil. Often, too, people would substitute wrong-value fuses (e.g. and oversize fuse) in the output section, and damage to a speaker could easily occur in that case. If everything checks okay, however, then the amp is an extremely fine-sounding piece of electronics. It produces over 90 watts-per-channel into four ohms, so it is much more powerful than it would seem, but by the same token it needs to have a good supply of cool air to circulate across the output heatsinks.

--Tom Tyson

#6 JKent

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Posted 26 January 2009 - 05:56 PM

Gary,
Gene and Tom know what they're talking about. When I bought mine, I actually bought TWO on ebay, took them to Bristol Electronics here in NJ and told Tim to do what he could with them. The verdict: One was "dangerous" and not worth repairing. It had the wrong fuses and was unstable. Tim repaired the other one nicely--replaced some caps, power cord, cleaned it all up. I used the best cosmetic parts from each, then sold the junker on eBay (with full disclosure of its problems, for parts or repair). After using the AR for about 2 years, driving AR2ax speakers and, through a speaker selector box, big KLH Twelves, I notice some noise upon turn-on and a little hum (transformer going?). Probably time to take it back to the shop.

If you do buy one, you will have to remember it is about 40 years old and will need to be thoroughly checked out and, probably, repaired before using. I agree with Gene that condition is everything and that one does not look great. See if you can look under the hood. The junker I bought is shown in the photo--pretty bad.

If you don't want headaches you're better off with a brand-new amp. Something like this gives a lot of bang for the buck:
http://www.parts-exp...amp;ctab=5#Tabs
But if you love these old American-made classics and are willing to put some work and money into them, it's pretty neat driving vintage speakers with a vintage amp.

Good luck!
Kent

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#7 Mexicomike

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Posted 26 January 2009 - 05:57 PM

Here's the thread where I addressed some of the bias stuff re the amp...

http://www.classicsp...mp;hl=Amplifier

#8 soundminded

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Posted 26 January 2009 - 06:05 PM

I came across this vintage AR integrated amplifier at friend's place. How does it sound? Worth buying? :rolleyes:


In 1967 about the time I bought mine for $166 this amplifier was an outstanding value. It provided lots of clean power, was relatively reliable, its tone controls worked exceptionally well, and there was nothing like it anywhere near the price. Even a Dyanco Stereo 120/Pat 4 combination I later built from kits cost more. It was a fine choice for anyone needing to drive AR3, AR3a, AR LST on a budget. But time marches on. That was over 40 years ago. Things have changed drastically. If you have a nostalgia for such things, it will cost you time and effort or money to clean it up and get it back to where it once was. This one looks like it's seen better days. Even mine is retired sitting on a shelf waiting for me to get to it. The pots have been replaced but it still has a 0.5volt DC offset on one channel and a 2 volt DC offset on the other. Evidently, even the resistors drifted. If you are looking for a fine amplifier to drive your vintage speakers, I think there are better choices. Many here like Adcom amplifiers and they are an excellent choice. There are also many fine used pieces on the market often at rock bottom prices because nobody wants them anymore. Most people don't even know what they are. Lucky us. Many have been restored or kept in first rate condition. Choose from some fine names like Hafler or a high powered vintage receiver from Marantz, Pioneer, or Sansui, or even Kenwood and you won't go wrong. That's my opinion for what it's worth. I'd pass on this one.

#9 genek

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Posted 26 January 2009 - 06:14 PM

Choose from some fine names like Hafler or a high powered vintage receiver from Marantz, Pioneer, or Sansui, or even Kenwood and you won't go wrong. That's my opinion for what it's worth. I'd pass on this one.


I ended up passing on the AR I auditioned in favor of an HK750. It's "only" 15-20 years newer than the AR, but even that amount of time seemed to make a big difference in RF shielding and heat generation (I could have used the AR as a space heater in my small home office). It also has more inputs and tape loops, and to my ear the sound and the tone controls even seem to behave similarly to the way the AR did in the same system.

#10 soundminded

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Posted 26 January 2009 - 07:08 PM

I ended up passing on the AR I auditioned in favor of an HK750. It's "only" 15-20 years newer than the AR, but even that amount of time seemed to make a big difference in RF shielding and heat generation (I could have used the AR as a space heater in my small home office). It also has more inputs and tape loops, and to my ear the sound and the tone controls even seem to behave similarly to the way the AR did in the same system.


I don't know why anyone would question the AR amplifier's RF shielding. The unit is completely enclosed in sheet metal which is more than you can say for many newer receivers I've seen, especially some built in the 1970s and 1980s. The AR tone controls were unique having a sliding inflection point as well as increasing amplitude with further rotation away from their neutral position. All other designs I'm familiar had a hinged response at a fixed point. (All you audio history buffs, is this what was meant by baxandall tone control circuits?) But far more useful and effective are graphic equalizers that are also quite cheap. These were not available to consumers when the AR amplifier appeared on the market.

#11 genek

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Posted 26 January 2009 - 07:27 PM

I don't know why anyone would question the AR amplifier's RF shielding.


An audible reduction in background noise when I unplugged my wireless router was my first clue. Further reductions by terminating unused RCA jacks was the next. Unfortunately, I ran out of things I could try to reduce RF intrusion and still had noise. The HK amp had none of these symptoms.

I haven't had a chance to try another AR unit since, so it's possible that there were failing or failed components in that one, but I didn't notice any of the other usual signs of that.

#12 Mexicomike

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Posted 26 January 2009 - 08:52 PM

As far as heat - "space heater" - My AR amp does not get more than slightly warm since I replaced the pots and adjusted the bias and offset. I've run it all day with the 3As at fairly substantial volume levels and it takes it in stride. As I noted, you CAN get the offset voltage down into the 10mv or less range if you replace the original pots OR the resistors with new, quality pots. Doing that, it's no longer the potential firestarter!

Certainly there are better (newer) and more powerful amps for the money but it is a pretty good little amp IF you deal with the bias/offset weakness. If you're into vintage AR, it's a really neat addition. An AR TT, Amp, and (in my case at the time) a pair of 2AX's and it's 1969 all over again! I remember bringing home Abbey Road and having a houseful of people just sitting and listening...well, drinking too.

Of course, as I noted in another thread, my original AR amp actually DID catch fire! and was replaced by AR. The replacement also oveheated and they replaced that one. I had three different ones from 69-71. The last one was fine but I sold it anyway because I didn't trust it and I wanted more power for my new 3As. I used the 3As in front and the 2AXs as "rear channels" wired in a way that I can't exactly recall at the moment. Seems like it was some sort of out of phase thing but dang if I can remember. Sounded good to me at the time though. :rolleyes:

#13 soundminded

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Posted 26 January 2009 - 09:27 PM

An audible reduction in background noise when I unplugged my wireless router was my first clue. Further reductions by terminating unused RCA jacks was the next. Unfortunately, I ran out of things I could try to reduce RF intrusion and still had noise. The HK amp had none of these symptoms.

I haven't had a chance to try another AR unit since, so it's possible that there were failing or failed components in that one, but I didn't notice any of the other usual signs of that.


Power supply noise induced by RF into the power distribution system of your house is one possible culprit. Terminating unused jacks by installing shorting plugs does not suggest the AR amplifier is inherently sensitive to RF noise either. An sheet metal enclosure around an amplifier, preamplifier, or receiver creates a Faraday cage which makes a good sheild. RF induction is often the result of pickup on interconnect cables especially at the phono preamp level. The AC power distribution system in your house also makes an excellent rf antenna especially if your house is wired with Romex. I just devised a capacitive/inductive RF coupling to the power cord of my bedside table radio to boost weak radio station signals. I always shield all my phono cables with a wrapping of aluminum foil around a bare copper wire grounded to the chasis. This wire is called a drain wire. This is one method well shielded manufactured coax and even twisted pair wire uses only you pay a lot more for it. If you have a hum or noise problem with your phono inputs, try it. Also keep signal cables away from power cables if possible.

#14 genek

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Posted 26 January 2009 - 10:06 PM

Power supply noise induced by RF into the power distribution system of your house is one possible culprit. Terminating unused jacks by installing shorting plugs does not suggest the AR amplifier is inherently sensitive to RF noise either. An sheet metal enclosure around an amplifier, preamplifier, or receiver creates a Faraday cage which makes a good sheild. RF induction is often the result of pickup on interconnect cables especially at the phono preamp level. The AC power distribution system in your house also makes an excellent rf antenna especially if your house is wired with Romex. I just devised a capacitive/inductive RF coupling to the power cord of my bedside table radio to boost weak radio station signals. I always shield all my phono cables with a wrapping of aluminum foil around a bare copper wire grounded to the chasis. This wire is called a drain wire. This is one method well shielded manufactured coax and even twisted pair wire uses only you pay a lot more for it. If you have a hum or noise problem with your phono inputs, try it. Also keep signal cables away from power cables if possible.


Yeah, I went through the usual checklist of things to try, ultimately culminating in trying another amplifier (the HK) that turned out not to have any of the issues that AR unit did. There might have been other things I could have tried, but plugging in another amp and not experiencing any problems with it turned out to be as far as I went.

The obvious problem of auditioning vintage gear is that unlike new you usually can't go back to the store and get another unit of the same model to try, and since you don't own it yet you can't open up the case and test for potential issues inside (not that I would have been qualified to recognize any). None of my experiences necessarily apply to all units of the model, and if I ever have the opportunity to try another I probably will, because the idea of having one has still not lost its appeal. It's just something that someone who's looking at the possiblity of buying one might want to watch out for. Offhand, I would think that if you go look at one and don't observe any of the issues I described, there's probably not much reason to worry about it.

All that rust on the back is another matter. Where do people put stereo equipment that it rusts? It's never happened to anything I ever owned.




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