Best Amplifier for LS3/5a

Happy New Year All!  Seeking advice from LS3/5 enthusiasts!  I have tried a number of these speakers (Graham, Harbeth, Falcon and KEF LS50's (if that counts)) - and to me the Falcon Gold Badge really stood out. It's been a while now since I did the comparison, so I don't remember all the details - but I felt that the Falcons were the most musical, engaging, open and did NOT have bloated bass (important for a small room)!  I've held on to a pair for my bedroom system, but I don't think that my current bedroom amps (AGD Audions, which I love with my current Raidho XT-1 monitors) are the best match for them.  I get a bit too much sizzle on the top and some associated sibilance.

Herb Reichert (Stereophile) seems to love these speakers, and his review notes that the Parasound A21+ was too dry with these speakers, but he really liked the Line Magnetic LM-518 IA.  That's not going to work for me!  In this bedroom system I keep the amp(s) under the bed and generally leave them on 24/7.  If possible, I prefer a balanced design, as I want NO HUM in my bedroom and my DAC/Pre (Weiss 501) has both balanced and RCA outs.

Based on the intended setup, I think balanced solid state would make the most sense. Amp selection might be influenced by the speakers having 15 ohm input impedance.

Any suggestions?  Thanks, Peter


By the way - not seeing this thread come up on my main page for the Agon forum makes me wonder which threads get seen and which do not!  How does one know if their thread is actually seen, or posted in a place where people WILL see it?

@clio09 Yep.  I guess my question is how do threads show up in the general feed rather than getting stuck in a specialty forum. Perhaps it's number of people who have responded.

I’d get a Purifi amp. Plenty of power, excellent sound and run cool. Buckeye and VTV are both USA made and quite reasonable. Plenty of power and current which the LS3/5a’s like. What preamp will you be using?

@rdschicago   Thanks for the suggestion.  I like the fact that it's balanced and that VTV offers a 30-day audition.  I'm not intimidated by it being Class D - because my current amp (AGD Audion) is Ganfet Class D.  I think that the AGD is an amazing amp.  So my question is - is there something special about the Purifi that would beat the AGD ganfet? Definitely the Audion is less power (170W, 4ohm (>30A max current capability)).  Thoughts?

I’ve never heard the AGD, so can’t compare. I happen to love my Purifi amp which I’m using in my second system. They can drive virtually any speakers with good, clean power and current and very low distortion, without losing musicality. I’ve never found the amp to be too clinical or harsh. 

I can recommend the Schiit Tyr monoblocks, which pair great with my Harbeth P3ESR-XDs. The LS3/5a is a sealed box mini-monitor that is inherently reticent, but the Tyrs bring out a full, dynamic sound. I'm also struck by how good they sound at low volume, a testament to how well they control the woofers. The Tyr is on Stereophile's Class A recommendation list.

Ran vintage LS 3/5A 15 ohm and currently run Weiss 501.  I've run the Rogers LS 3/5A with Sugden A21SE to great affect.  They require as you know lots of quality high current, not wattage.

Class A is magical with these.  Sugden is not balanced but I do not believe that would improve over unbalanced in this application.  Best success.

@celtic66  thank you for your input. I noticed that several of the Sudgen amplifiers do have balanced inputs… But seem maybe either too big for my bedroom or not powerful enough for the speakers in question. The reason I gravitate towards balanced connections is because I want absolutely no noise in the bedroom, so I figure I have a better chance of not getting hum with balanced over single ended. Any thoughts about the sapphire model, and whether 40 W of class a would be enough to run these speakers? Thanks! 

More than enough.  People continually underestimate well designed Class A.  My wife’s system runs Luxman 509X at 110 wpc Class A/B.  Speakers are ATC 20s.  Closed cabinet, difficult load.  The Luxman has enough current to control everything well.

I slotted my Sugden A21SE (17 years old) Class A 33 wpc and it more than held its own.  In fact I might prefer it.  But not by much.

The LS 3/5A presents a tortuous load to mediocre designs with unstable current. The sound stage will collapse and dynamics suffer.  It all seems lifeless.

Best wishes solving this challenge.

In this bedroom system I keep the amp(s) under the bed and generally leave them on 24/7.

@peter_s Would you want to do that with a Class A amp?

Hi Peter,

I have set up, must be over ten LS3 5A systems. I worked in a high end store when the Rogers was released back in the late 70s. 

The LS3 5A is VERY inefficient, like 83 dB/watt @ 1meter. If you are not using subwoofers I would recommend a 200 watt/ch SS class A amp. HOWEVER the only way to use LS3 5As is with stereo subwoofers and a two way crossover, preferably digital. You want to cross at 100 Hz. Taking that bass away from the LS3 5As lowers distortion DRAMATICALLY and increases headroom also dramatically. You can also get away with a smaller amp, a 100 watt class A amp, tube or SS will do fine. I would use a Pass XA100.8. Another great amp would be the Parasound JC 1+ 

@mspot is correct about 24/7 powered up.

@mijostyn gives accurate information about the LS 3/5A characteristics.  I just do not know how crazy loud or how much bass you will demand for a bedroom system from an understandably small monitor meant for near field moderate levels.

Thanks All.  I agree that a Class A amplifier left on 24/7 under my bed is a bad idea!  The bedroom is small, and mostly I'm trying to TAME bass nodes.  That's a benefit of the Weiss 501 - I am able to use the built in DSP for that purpose.  With my current Raidho XT-1's, I also tune the bass by adding a small KEF subwoofer. 

I would like to also be able to use my LS 3/5A's in the bedroom system. I think they sound very good with the AGD Audion (that's why I kept them), but I am dealing with a little bit of sibilance.  So the question is: is the sibilance a characteristic of the Falcon Gold Badges or is there something about the amp/speaker combo that can be improved (no sibilance with the AGD's driving my Raidhos).  I was thinking that maybe it is the impedance matching, or maybe the LS 3/5A's were designed for an amp with less high frequency extension.

@celtic66 - you nailed it.  Small bedroom, lots of bass reinforcement... don't need much output.  Perhaps that changes the amp matching discussion just a bit...

@mijostyn if I ever use these speakers in a "normal" sized room, your approach sounds good.  Right now my room is 8x12 - pretty small.

But the theme here is very consistent - lots of current needed! 


Then you use small subwoofers. You are doing this as much to lower distortion as to add bass. The LS3 5A was envisioned as a monitor for remote set ups. Imagine a couple of guys in a van like the Rolling Stone Mobile Studio. 

@mijostyn I'm currently using a KEF KC62.  To quote the promo "it’s connection options allow it to be used with almost any audio system, with KEF SmartConnect and speaker level inputs eliminating any connection issues. Line output with High Pass Filter (HPF) allows for exceptional fine-tuned integration, and KC62 is also compatible with the KW1 for simple wireless compatibility."  With my current system configuration, I'm using the speaker level inputs sourced by my AGD amplifiers. I can't put a high pass filter in front of the AGD's, because it would also affect the subs.  I don't believe I can feed the subs with a line level from the Weiss 501 (I believe its "smartconnect" is proprietary). So with my current system, I don't see a way to employ high pass in front of the Falcons.  Maybe with another setup - I'm sure I'll be playing with these speakers for a while. Unless you have another suggestion....  Thanks!  

@dekay I'm not sure if this is a bonehead idea, but I'm curious whether the Quads can be bridged into monoblocks and whether bridging can be used to convert them to balanced.  


The solution is to get a stand alone two way crossover either analog such as the JL Audio unit or digital such as the MiniDSP unit. You connect the preamp outs to the crossover then the crossover to the amplifiers and on to the speakers and subs. This is not an imaginary tweak. This is a seriously big improvement. You will gain at least 10 dB in headroom (twice as loud) and lower distortion in the Falcons by an estimated 50%. 

The best sounding amplifier that I used with my 15 ohm Rogers LS3/5A's was a pair of Naim 135 monoblocks along with a Naim 72/Hicap.  Driven by a Naim CDi, that system was so musical! 👍

Don't know about bridging 306's, but on the cheap the "listed" 306 will get you going.

If you like the sound have it refurbished.

It's the last amp I tried with 15 ohm Roger's.

I liked it and I am not a SS fan.

Much better than the 303 I tried early on (late 1970's) and almost as enjoyable as my Dynaco and McIntosh tube amps.

Hell of a match with ESL 57's (per the system I borrowed it from).

In such a small room I doubt that more power and/or balanced cable will be "a thing".



@dekay in my experience, a balanced cable has been useful and eliminating or reducing hum that I get with a RCA cable. Because I want absolutely no hum in the bedroom, that’s why I would go with balanced. But these amps are inexpensive enough that I could try it out and see how it goes. 

I used a Tandberg 3012A integrated with a 15ohm set of Chartwells - it was fabulous.

@dekay I don't know for sure that there would be hum with RCA connections.  There has been in the past, with different equipment.  I know that it is absolutely silent with all the balanced amps I've used, and I don't like to have any background noise in my small bedroom (not even mechanical transformer hum).  

LS3/5a are not difficult speakers to drive and you don't need a lot of watts to get reasonable listening levels in an average room. I've driven them with amps, both tube and ss, from 15 watts to 140 watts per channel.

Presently, my best results are with a restored vintage Quad 405-2 with a Quad tube preamp. Completely silent at idle, as long as I correctly keep power cords away from interconnect cords at the back.

More important, I think, is the character of the amp. The ls3/5a need a lusher kind of amplification to mine the tonal richness available, and to fatten instrumental timbres. I used class D for a few years, but the top end can become brittle and dry. I would also avoid passive preamps. An active preamp adds good body to the tones.

So, vintage, perhaps?

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@sumaato Thanks for that.  I am definitely interested in trying out the quad amplifiers.