Amplifiers for classic AR speakers.

[Guest]

Over the past few months there have been several discussions about amplifier power. This post is to centralize and further this discussion.

Up until this year I did not believe that I could hear the difference between a 55W/ch amplifier (Onkyo TX4500 .ca'77) and a 105W/ch amplifier (Onkyo TX8500 .ca'77 or Adcom 545 II). I can not tell between the TX8500 and the 545 II - driving AR91.5 or AR9 speakers (or for that matter AR7 HiRes).

The extra ~3dB of headroom/speed that the 105W/Ch gives over the 55W/ch is most noticeable to me a LOW listening levels. At higher levels, the difference is less!!

The effect here may not be the power, and may be the speed or voltage slew rate. The above three amplifiers have similar full power bandwidths, and thus the voltage slew rate of the TX4500 is 40% less. Sansui made a big thing of this characteristic bake in the early 1980s.

I have my AR9 speakers in a small room, with an Onkyo TX8500 drivng them. People are amazed by the sound quality and clarity from very low levels to rather high ones. My friends that have listened to them range from semi-pro musicians to non-musically interested. The more knowledgable/experienced with music, the more they noticed the qualities of the system.

My are AR91.5 speakers are on loan to friends that have them in a good sized living room with cathedral ceiling. The are also driven by a TX8500. They sound better - the room is four times the square footage, which is a better match.

Suggestion: borrow an amplifier with around twice as much power as you are currently using to drive your AR speakers, and see if you can here the difference at low volume levels. Listen carefully.

NOTE: make sure that the amp you borrow is up to driving AR speakers properly. It should be capable of driving very low impedance loads (2 ohms preferrably) and have a power bandwidth in excess of 50KHz.

If you can, there are many fine amplifiers on ebay at reasonable prices.

I invite comment, please site your experience on this issue, not just second hand opinion.

Nigel

[Guest]

I'm not technically knowledgeable about Audio equipment, but I know what I like..........

I've got Ar2ax's, Infiniti Quantum JR, and Advents, all old speakers.

My story is about the Infinitis. I have a 1969 Kenwood Amp (70watts RMS/ channel) and it soumds great with all my speakers, but headroom is a little lacking,so I tried a 160watt/channel Rotel.........It sounded clearer, but not "as good" as my Kenwood. Moral- LISTEN TO THE COMBINATION AT HOME BEFORE MAKING A SWITCH.

The two best things I have invested in.....a set of Audiophile speaker stands and turntable stand by "Target" of England. The sound improved by maybe double ! (no kidding).

(PS.I also have a CD player)

That's my two cents.

I'm sure more power is generally better, but listen first .

Eugene.

[Guest]

I am using a yahama p2200 - amplifier (200watts per) with a set of AR2a's. I just bought a set of AR3's at a estate sale for $50.00 that was being used in the home. Can I pair it up with a crown dc300a amplifier. How do I bi amp the amps to worh with both the AR2a and AR3's.

Thanks,

Evon

[soundminded]

I used to think the same thing everybody else is told, namely that you can't have too much clean amplifier power. But no more. I now believe that this theory is flat out wrong. Once an amplifier is capable of putting out as much power as will ever be used in a particular installation, additional reserve power capability is IMO of no value whatsoever and providing it for its own sake is a waste of money and bad engineering. Obviously when listening at low levels, power capability plays no role in the perceived difference of sound. However, crossover notch distortion does. So does frequency response. I'm convinced that the laboratory tests used to evaluate amplifiers and the specifications we use to characterize them are relics of a time when they showed up gross differences between one piece of equipment and another but today, since all of them measure textbook perfect, our measurements are inadequate to tell us very much any more. I'm also convinced that different amplifiers do sound different. I know my AR amplifier sounds different from the Dynaco 120 I had until I blew it up and both are different from the Mosfet 120 I built to replace it with. It also puts out up to 60 wpc but I did have to re-equalize the system, a process which takes about a year or two. I use that amp to drive my AR9s in a room that's about 400 square feet, nearly 4000 cubic feet and on the live side. It can drive the AR9s to deafening levels over the entire audible range and then some especially in the bass without any audible distortion. And if the impedence of the AR9s isn't low enough already, each one is in parallel with three additional 3/4 inch Audax tweeters crossed over at 6khz. But the Mosfet 120 doesn't complain. It doesn't even get hot under the collar...or under its heat sink fins.

[Guest]

The Crown DC300A is a powerful and stable design that should work very well with your 3a's...its substantial power supply is a big plus. Can you explain what you mean by bi amp?

[Guest]

As a general statement: You need approximately a 10x increase in power(wattage) to gain a additional 3 decibal increase in volume. These assume all other things equal. Most people thinks a bigger amp mean loud, for the most part all you really gain is better control of your the drivers. =ing better sound quality. At normal listening levels your amp is probalbly pushing a 1-2 watts. I have an anthem MCA 20 225 watt,an HK avr-30 60watt reciever, an hk 550I 45 watt reciever and a old techinics sa-500 50 watt reciever. The total volume difference between the three is minimal.

Driver control and less chance of clipping is all you gain.

Bottom line is put your money in to the quality of the watt not the number of watts.

ED

[Guest Bret]

>I invite comment, please site your experience on this issue<

For years and years I lived in a home with AR3a's being driven by a Heathkit AR-15 receiver. It's about 60w/channel. The room is about 20x25 with a high cathedral ceiling and a 3/4 rear wall (about 10') with a hole in the middle (about a 5' doorway). On the other side of that 3/4 wall you go another 12' before reaching the "final" wall. The left side of the room is open (railing) and a hallway and foyer are over there. The other "side" of the room is one long curtain, the floor is brick. The speakers are about 30" off the ground in a bookshelf. That's a lot of air. I always thought it sounded fine.

Then he got a Carver receiver with something like 120w or 200w/channel (the big receiver, not the original one). I thought it sounded better. Then the Carver died and went to the shop. The AR-15 was re-attached to the system and I listened for a bit. The next time I heard the system I thought the AR-15 was still on it and was really, really surprised by how great this Vivaldi CD sounded (moderate volume). It was the Carver back from the shop.

The recent experimenting with a friend's 10pi's. 65w/channel receiver, they sounded pretty doggone good. An Adcom 555Mk II was added and they sounded. . . well, amazing really. SAE A502 amplifier, that also sounded amazing. Then a Threshold 400A was substituted - they sound awe-inspiring. The Threshold is LESS wattage than either the Adcom or SAE and sounds better BUT the Threshold is rated with about 5db headroom, soooo, in fact, they are all of similar power.

BUT, any of the three "BIG" amps has one heckuva power supply.

So, although it takes twice as much juice to produce a 3db greater volume, and although the math says that the biggest amp should have been less than 6db "louder" than the receiver (or 6db *more* dynamic at most), the fact is that it made a huge difference in BOTH the way the speakers sounded at modest volumes and in the perceived average volume prior to amp "compression."

Soon I'll be able to run this "test" using a 125w/channel Pioneer receiver and a 250w/channel ESS power amplifier (essentially a slightly goosed Phase Linear 400). There should be a 3db headroom difference, right?

I know from experience when using the Pioneer receiver as a pre-amplifier to the big ESS amplifier driving my AR-9's there is a big difference in the way the ESS amplifier sounds compared to the Pioneer's own amplifiers.

But a watt is a watt and if I'm listening at 2 watts average and that's got me at about 90db, then I shouldn't run out of "watts" unless I get a spike to more than 108db. 108db is LOUD. So getting that big-ole amplifier instead of the receiver allows me to get 'em to 111db if called-for. 111db is not appreciably louder than 108db. But the bigger amplifier sure sounds better.

So, I come down on both sides of the argument. I think it's more the quality of the wattage than the wattage. But I think it's entirely possible that the bigger the amplifier the more likely the power-supply is up to the task of giving the amplifiers all the current they require. So, I say "Get a bigger amp" because I suppose the bigger amplifier will be more robust, not merely rated at a higher wattage.

I think I have proven this to myself with the Yamaha receiver to Adcom amplifier change and the Pioneer receiver to ESS amplifier change and the Heathkit to Carver (both receivers) change I've experienced. But note that all three changes were made on three different pairs of AR speakers.

It's probably useless to note at this point that back in the days when I was selling this stuff, the speaker-switching room was powered by two amplifiers - the biggest thing Accuphase made at the time and a Phase Linear D/500W. Everything from AR-11s, JBL-L150s, 4311s, L40's, and some three-way JBL about the size of a 3a that was incredibly expensive. . . I don't remember the model, ESS AMT-1b's, AR-14's, Phase Linear panels, even some Cerwin-Vegas I haven't seen a pair of since, big Kosses, and other stuff, ALL got the BIG amplifiers for A/Bing. We didn't have those big amps in there for nothin'. Or did we? I think the Accuphase may have only been rated at something less than 200w/channel. Either amplifier was plenty and way, way more umph than any receiver in the shop including the big Kenwood and Pioneers (with the possible exception of the SX-1980). But then a KA-9100 Kenwood integrated amplifier had more "umph" than receivers that were rated at higher wattages.

By the way, the Cerwin Vegas were "honky" but, my deity, would those things play loud. OH my. They had circuit breakers instead of fuses. And beautiful cabinets. They were really pretty. And loud.

Bret

[JeffS]

I'll add my own experience to this thread.

About four years ago I purchased a pair of 303's and drove them with my NAD 3150. The NAD is rated at 50 WPC into 8 ohms, with high current design and 3dB of dynamic headroom. This combination worked fine.

A couple of years ago, I came across a Kenwood KR-9050 receiver from the high power receiver era of the late 1970's.($75, and in excellent condition!) This unit is rated at 200 WPC at 8 ohms, and 250 WPC into 4 ohms. There is no 2 ohm rating.

According to the published specs, I've gained 3dB over my NAD's dynamic output.

I connected the Kenwood's power amp to the output of my NAD 3150 preamp, and drove the 303's. They sounded fantastic! That amp brings those speakers to life and gave me a whole new appreciation for them! I couldn't believe that 3dB would make that much difference.

A couple of weeks ago I acquired an NAD 7100 receiver that is rated at 60 WPC into 8 ohms, with high current design, but with 6 dB of dynamic headroom, instead of the older units' 3dB. I'm thinking that now I have the match for the Kenwood's output, and a remote control, too!

After listening for a week, I'll say that while the NAD is a fine receiver, I still hear compression on some peaks. I still prefer the Kenwood. (sonically, if not aesthetically).

I also bridged the outputs of both NAD units, and connected each one to a 303. This gave me the same visceral impact of the Kenwood, and using a Radio Shack SPL meter that I had on hand that day,I measured 107dB on peaks.

My conclusion is that if I were to buy a new amplifier, I would purchase one with a high current design, and the highest power per channel I could afford, instead of a lower power per channel and higher dynamic headroom.

(Constuction of these units seems to be commensurate with output. The Kenwood weighs 53 pounds, and though this weight includes some wood and a big faceplate, fully 2/3 of the space inside the unit is devoted to a torodial transformer, output transistors and their heat sinks. The newer NAD unit weighs 24 pounds.)

I'm currently using the Kenwood to drive a pair of recently acquired newer 2ax's that are in excellent condition, but it is more than they would ever need, and will end up back with the 303's.

Ken Kantor, if you happen to read this, thanks! I love the 303's!

[ninohernes]

I have a hafler TA 1600 amp driving my AR-2 speakers. This is the 60 watt per channel model. It is 60 watts into 8 ohms and 75 into 4. The thing has massive heatsinks on both sides and very large transformers.

This setup is used in my recording studio. Big tip, I leave this one running all of the time, I just turn the gain control on the front all the way down. This unit has been on steady for about 3 months now. This allows me to start working immediatly and not have to wait for the unit to warm up. They recomend a one hour warm up period before its up to max spec. If you leave it on, you never have to wory about this. They even recomend it.

Here are the speces. This amp only costs 200 bucks. It sounds stellar!

150 Watt 2-Way Trans•ana Professional Power Amplifier

The circuitry used in the TA1600 is the latest refinement of our patented Trans•nova (TRANSconductance NOdal Voltage Amplifier, US Patent 4,467,288) circuit. It has been proven to offer sound quality to satisfy the most analytic audiophile or the most demanding professional. The natural sound and realistic reproduction have made Trans•nova amplifiers the choice in critical installations. They have proven extremely fault tolerant even in abusive situations. This ruggedness enables the amplifier to drive reactive speaker loads without the performance and sound penalties imposed by elaborate protection schemes.

Features

MOSFET Outputs: Deliver higher output current, rugged reliability, superb sound quality.

Trans•nova: patented output stage configured for "power gain" allows simpler front end circuitry, dramatically lower cross talk and noise.

Soft Start Circuit prevents sending potentially destructive turn-on and turn-off transients to speakers.

Thermal Sensing Network monitors heatsink and transformer temperature and shuts down amplifier to protect from excessive operating heat.

Output Sensing Circuit monitors the output signal and shuts down operation detecting a short in the output load.

LED Status: allows you to monitor the operating status of each channel.

TA1600 Specifications

Power Rating 60 Watts/channel @ 8 Ohms

75 Watts/channel @ 4 Ohms

Power Rating @ 1kHz, 0.1% THD

Total Harmonic Distortion (THD) n/a

Signal-to-Noise >102dB below rated output “A” Weighted

Full Power Bandwidth 1.0Hz to 300kHz (+0/–3dB)

Slew Rate 100V/µs

CMRR (Common Mode Rejection Ratio) >65dB at 1kHz

Input Impedance 47k Ohms per phase balanced/47k Ohms unbalanced

Gain +29dB maximum

Input Sensitivity Range 0.390V (@ 8 Ohms) per phase balanced

0.310V (@ 4 Ohms) per phase balanced

Damping Factor 350 (to 1kHz)

150 (to 10kHz)

18 (to 100kHz)

Power Consumption 60VA @ 120VAC (quiescent)

Indicators Power

Dimensions 19"W x 8.5"D* x 3.5"H (2-rack spaces)

(48cm x 25cm x 8.9cm)

Net Weight 22 lbs. (9.98kg)

The attachment is a picture of it. (its kind of small)

Visit haflers website to view all of thier amps.