SET amplifier recommendation

I drive a pair of Sonus Faber Electa Amator II (88 dB efficient) with a Cary CAD-301SE amplifier (8 watts/ch).  While the amp is admittedly a bit underpowered the sound is absolutely mesmerizing with the type of music I listen to (chamber, choral, and orchestral).  

Folks, this thread is from July 2019, and likely OP has decided which way to go already.
@cygnus_859, what did you end up doing and how did it work out for you?

BTW, the passing of almarg in 2020 is yet another very sad aspect of this year. I will miss you around here!

I agree with others you have wrong speaker for SET!

I would get a high powered push and pull tube amp on a speaker you're intending to use.

Ultimately an OTL would sound the best on a wide variety of musical genre. OTL would be my first choice as over time SET romantic sound kinds of works best on some musical genre. 

If you're fixated on SET change your speakers to Horns.

...  its not enough power on speakers like that unless the intention is to have the music mostly in background or serious listening at lower levels.

I would add to Ralph's comment that the dynamic range of the kinds of recordings that are listened to (i.e., the **difference** in volume between the loudest notes and the softest notes) will dramatically affect how much power is required. For example, many well engineered minimally compressed classical symphonic recordings require **many** thousands of times as much power to reproduce brief dynamic peaks as to reproduce their softest notes. While many and probably most pop and rock recordings are dynamically compressed such that they require no more than around ten times as much power to do likewise.

Regards,
-- Al

Just out curiosity, I plugged the ACA into my 89db efficient Sound Lab electrostatics (the 805 is 88db), and my Vision Acoustics Soloist (air suspension 88db), and yes it will drive the B&Ws, and probably quite well.

No doubt! But its not enough power on speakers like that unless the intention is to have the music mostly in background or serious listening at lower levels.

+1 mountainsong's suggestion on Mastersound. 

I'm driving a very difficult load Sonus Faber Elipsa 4ohm (88 db effective)
with 30W 845 SET to satisfying levels in my large room without a subwoofer. I'm talking about concert hall levels with no distortion. Check out some videos on youtube with Mastersound driving B&W speakers. Numbers aren't everything. 

@atmasphere Just out curiosity, I plugged the ACA into my 89db efficient Sound Lab electrostatics (the 805 is 88db), and my Vision Acoustics Soloist (air suspension 88db), and yes it will drive the B&Ws, and probably quite well.

@jdl57  6 watts isn't going to do it on the 805. Quite simply you need some power.

@cygnus_859 Also, I know DIY isn't for everyone, but if it does sound at all attractive, I would just ask the community over at:  https://www.diyaudio.com/forums/pass-labs/ which amp build would best fit your speakers.  A lot of very knowledgeable people over there (including Nelson Pass himself).  I kind of wonder whether they might recommend an amp with light feedback for your speakers... 

@jdl57 A speaker change to Coincident PREs (from Coincident Super Eclipse IIIs) caused me to have to change amps from Coincident Frankenstein 300bs.  Eventually I built my own First Watt F4s and find them excellent.  I was very surprised, because I had previously demoed a Pass Labs XA25 and did not end up keeping it (although it was excellent). 

The F4s are certainly not SETs, but surprisingly, I don't really miss my Franks at all. The F4s create a ton of space and have excellent tonality.  A touch of sweetness while also being incredibly transparent.  They don't distort at all and play better at the extremes with the PREs (94db and supposedly a flat 8ohms).  Plus, as you point out, DIY does save a lot of money.  I built two monoblocks and vertically bi-amp my speakers so each driver gets its own 25 watts.  Under $1800 total cost.  I sold my Franks and upgraded tubes for around $4000.

I have an idea that might work, emphasis on the word might. This amp right here: https://diyaudiostore.com/collections/amp-camp-amp/products/amp-camp-amp-kit?variant=7072933085218 is an easy to build single ended transistor kit. It sells for $327, but if I recall shipping is expensive because the case comes from Europe somewhere. It is designed by Nelson Pass, and has a true single ended sound without the impedance and damping problems a triode tube would have, but it is still only 6 watts. Although I bet this amp would drive your speakers, it would not be ideal. I agree with the consensus that different speakers would be a requirement for true single ended nirvana. The trick is; it is a few hundred bucks rather than a few thousand and it would give you a taste of what the single ended craze is about. You would have to learn to solder if you don't know how already.

After I built my first S.E.T. amp (45 tube, 2 watts per channel), I spent 20 years looking for a true full range speaker for it. I wound up building a large, make that very large (even I wouldn't have it in my living room), Altec based horn speaker with a RAAL ribbon tweeter. The system is tri-amped. I use this amp right next to my S.E.T.s ,for driving the tweeters.

Line Magnetic, KR and NAT. NAT makes some incredible sounding SET gear that used may fit your budget and will drive the snot out of those B&Ws.
Good luck!

I own 804S and when searching for amps I listened to them in the same room and setup with McIntosh MC252 (250W SS) vs MC275 (75W tubes), and preferred the 275.

Also, the 804S is not the same thing as the original Nautilus 805 stand mount speaker, which is what I assume the OP is using.  I have never met a tube amp that could provide speed or decent bass with the any of the original B&W Nautilus line.

@lewinskih01

Thanks for the mention!

Regarding your experience with the MC275, it’s worth noting that it has a considerably lower output impedance (and correspondingly a considerably higher damping factor) than most other high quality tube amps. So the likelihood of adverse impedance interactions with the speaker’s impedance variations over the frequency range, that I referred to for the 805 in an earlier post, would be minimized with that amp compared to most other tube amps.

For example, Stereophile measured the output impedance of the MC275 version 5 at most frequencies as being only 0.33 ohms for the 4 ohm tap and 0.57 ohms for the 8 ohm tap. And version 6 is specified at the McIntosh website as having a damping factor of 22, which theoretically corresponds to an output impedance of 4/22 = 0.18 ohms for the 4 ohm tap, and 8/22 = 0.36 ohms for the 8 ohm tap.

In contrast, the damping factors of the majority of high quality tube amps are in the single digits, and some SETs have damping factors in the vicinity of 1 or even less. With the corresponding output impedances being much higher than those of the MC275.

So in terms of the tonal effects resulting from impedance interactions with the speaker those numbers suggest that the MC275’s behavior will approach solid state territory, rather than being representative of the behavior of most high quality tube amps.

All of that is not to say, though, that no tube amp having a relatively low damping factor/high output impedance can work well with these speakers. For example Ralph’s amps fall into that category, but I don’t doubt for a second that the reports of good customer experiences he has cited involving pairings of his amps with these speakers are accurate. But generally speaking, obtaining good results pairing a tube amp with these speakers figures to be less predictable and a good deal more doubtful than with a solid state amp.

Best regards,
-- Al

The B&W speakers are voiced for SS amplification and are never going to sound their best with tube amplification; possibly with the exception of a pair of Atma-Sphere OTL monoblocks.

Sorry, but I disagree with this statement. I own 804S and when searching for amps I listened to them in the same room and setup with McIntosh MC252 (250W SS) vs MC275 (75W tubes), and preferred the 275. My system has evolved quite a bit since and now the 804S run as active speakers with 400W class D driving their woofers, subs under them, but the MC275 still drives mids/tweeters. 
In my journey I veered towards building my own active speakers and looking to drive mids and tweeters with SETs, but doesn't mean good PP powerful tubes can't drive 805 well.

OTLs could very well be it. BTW, thanks Ralph and Almarg for the informative exchange!

There's a Dennis Had SEP amp for sale (not mine, but similar) here...that could sort of solve any Coincident issues.

And since some of the information is buried in the thread, here's a quick rundown:  all you do is set your volume at the max listening level you use, then play the provided -12db 120hz test tone while measuring voltage at the speaker terminals. Square that value and you’ve got the maximum watts needed. Plenty to read at the link...

@cygnus_859 If you're curious how much power your speakers are using and have (or are willing to buy) a multimeter, you can use the technique at this link to actually measure how much power you'll need..

https://www.diyaudio.com/forums/multi-way/204857-test-voltage-power-speakers.html

I'll add my two cents here, as I had the B&W 805 speakers (D2, not the current D3) a few years ago, and while I no longer have them I'm considering going to SET with my current speakers.  I moved from B&W to Wilson speakers - first the Sabrina and very recently with a used pair of Sasha (series 2, not the new DAW).  In addition to my solid state amp in my main setup (D'Agostino Classic Stereo - 300W at 8 Ohms, 600W at 4 and 1200 at 2) I have a Cary CAD300SEI integrated in my office setup.  The Cary is rated at 15W.  Enjoying what the 300B SET does for my office speakers (Omega Compact Alnico - single full range driver and 94.5 dB sensitivity), I had some friends over to compare it to my solid state driving the Sabrinas.  There was certainly something magical about the midrange, and I didn't really feel the volume or dynamics was lacking, but we agreed the solid state power amp had better control of the bass.

The Sabrina has a sensitivity of 87 dB and a pretty challenging impedance curve.  So it was an interesting experiment but not really a serious contender for replacement.  The Sasha's, however, are a different story.  They also have a difficult impedance curve, but with 92 dB sensitivity they're not as challenging.  Same comparison, but this time I'm thoroughly entranced by the SET amp driving these speakers.  There was plenty of volume and dynamics for me, and I didn't feel there was anything lacking in the bass compared to the solid state amp.

I should also mention that my listening environment (my living room - not a dedicated listening room) is pretty lively, with hardwood floors and, though softened with rugs and cloth upholstered sofa and chairs and drapes over windows, I've done no special sound treatments.  I know that when I've auditioned new gear at my local hifi dealer with the exact same components I have at home I use a much lower volume setting on my preamp than I do in the dealers highly treated room.  I also have to position the speakers fairly close to the front wall (less than two feet between the back of the cabinet and the wall).  The point is that the room is going to have an effect as well.

To me the bottom line is that I'd suggest you find amps that you can try in your setup at home.  There's really no other way to tell if it might work for you.  To add to the fun, if you could find other speakers to audition you might really have a fun few days.  (Auditioning gear is what I miss most about having my system mostly sorted out).

You have gotten plenty of input, but I thought I would chime in because I have 805's and have hooked them to many different amps.  The sensitivity is definitely an issue.  I have had them hooked to even some higher power tube amps(not SET) like Cary, McIntosh, etc, and they just didn't sound good.  They definitely sound significantly better with more power.

As far as replacing them, if you really like the B&W sound, you won't be happy with vintage Klipsch, IMHO.  But getting new speakers is a whole different ball game :) Good Luck!

I have tested a B&W 805 with an Ayon Mercury 300b Set amp (20W). Very bad match. 

Do NOT buy anything from Coincident. I made that mistake a few years ago, and will never consider it again.
the dynamo is a cheaply made Chinese crap, with the cheapest parts and terrible workmanship. I’ve had issues with it from day 1, and the customer service I received from Israel was appalling. He did not own his warranty for an amp that arrived defective, tried to blame me for it, and wouldn’t even pay for return shipping for the repair, even though after I sent the amp back he admitted that it was faulty. If you want a Chinese SET, get a cheap one one on eBay. Quality will be the same, price will be 1/4 of the dynamo, and most Chinese sellers provide customer service orders of magnitude better than Israel.

I recently built the Elekit TU-8600R-VK with Lundahl OPT's and TKD pot.
I'm running Gold Lion PX300B, Tele 12AX7 and RCA Cleartop 12AU7.

It is sublime!!! Amazing amp and would costs $1800 for the upgraded kit, a few hundred more for the tubes I mentioned, or you can go with EML or Elrog 300B within your $3000 budget.

Not that it matters too much but Herb Reichart reviewed it for Stereophile and compared it to $20K amps, landing into the list of recommended components.
https://www.stereophile.com/content/gramophone-dreams-27-elekit-tu-8600r-amplifier-kit

The issue of bandwidth becoming more limited as the total output power is increased happens with any amplifier with an output transformer. In SETs this issue is exacerbated.

Thanks, Ralph. That would say that in the case of tube amps having output transformers published frequency response specs should be taken with grains of salt, unless the power level they correspond to is clearly stated (with that basis preferably being full power). (And also, as with the frequency response or bandwidth specs of any amplifier, grains of salt should be applied if the amount of rolloff the stated response corresponds to is not indicated).

And if I may say so, the specs provided at your site are exemplary in those (and other) respects.

Best regards,
-- Al

That’s an interesting point, Ralph, which I presume derives mainly from the bandwidth limitations imposed by output transformers when they are used in SET configurations.

Would the bandwidth limitations you refer to apply to the small signal bandwidth as well as to the bandwidth at or near full power? Or just to the latter?

The issue of bandwidth becoming more limited as the total output power is increased happens with any amplifier with an output transformer. In SETs this issue is exacerbated. To give you an example, a Harmon Kardon Citation 2 which makes 60 watts has bandwidth at full power from 10Hz or so to well past 60KHz; a 300b SET which makes only 7 watts can't go as low or as high. This is why lower powered SETs like the 2A3 and the type 45 have gained ascendancy-  they have more bandwidth. But speakers with the efficiency needed to bring out their qualities are considerably more limited- you need well over 103 dB in most rooms to make amps like that work. Even with a 300B I would not be using a speaker of less than 99dB for the simple reason that if you use more than about 20% of the total amplifier power the distortion becomes unacceptable (that increased distortion is responsible for that 'dynamic' quaility for which SETs are known).

So I have made the entire journey across 30 years from SET to High Power and back to SET.  I do own the Coiencident Frankenstein Mk-II's and must concur with those above regarding the poor match to the B&W 805's which I use in a separate surround system driven with significant power.  

I recommend that you determine the sound priorities your are looking for and start matching from there.  In the world of SET the speaker options are somewhat limited and need to match your priorities.  This does not mean limited volumes or dynamics or base extension but has to be carefully thought through to wisely use the ~8 watts available.  My fife can run me out of the house on our system listening to rock at 100db.

Do have fun with the journey!

300Bs and other lower powered tubes vs. 805s - 845s - 211s - T100s have pretty significantly different sound profile. 

The 300B, 2A3, PX25 has this lush midrange that borders on addictive.  It is amazingly musical and is what most people think of when they here a SET.  

805s, 845s, 211s, etc... have a different sound profile.  It is less lush and more dimensional IMO. Delivers tighter bass and a less pronounced midrange even compared to and EL34.  As someone who has an 845 SET and 845 Push Pull and use less sensitive speakers (current pair in my system has an SPL of 84dB paired with Push Pull) I am a fan of its sound profile. To me, there is far more difference between tubes than there is going from Push Pull to SET using the same tube.  

The Line Magnetic you are talking about is an interesting amp in that it is 3 stage instead of 2 stage and there are 300B Driver Tubes to help deliver a more lush sound.  I did a ton of reading on it today for a customer or mine.  It is lovely out of the box but can be improved by rolling in just the right tubes. 

Also, high SPL speakers are a completely different animal.  They can sound great.  Klipsch are wonderful.  Depending on the model, some require being place in a corner.  The Cornwalls are great speakers, work in most rooms and are wonderful with a 300B.  Zu also makes some great speakers and Tekton, assuming you like larger units, has some great units.  

If you really love your 805s, I mentioned above.  You might want to look at a push pull with a different tube compliment.  

With SETs, the bigger the amp the less bandwidth. 300b is about as powerful as an SET can get and still be considered ’hifi’ as far as bandwidth goes.

That’s an interesting point, Ralph, which I presume derives mainly from the bandwidth limitations imposed by output transformers when they are used in SET configurations.

Would the bandwidth limitations you refer to apply to the small signal bandwidth as well as to the bandwidth at or near full power? Or just to the latter?

Thanks. Best regards,
-- Al

How different is the sound between 300b and 805 (LM 508AI, etc)?  

With SETs, the bigger the amp the less bandwidth. 300b is about as powerful as an SET can get and still be considered 'hifi' as far as bandwidth goes.

https://www.audiogon.com/listings/lis9g44j-zu-audio-soul-superfly-full-range

I would rather recommend Zu Audio speaker with small footprint.

Height: 38” [96.5cm]
Footprint: 12-9/64”square [30.8cm square]
Weight: 54 pounds [24kg]
Bandwidth: 30 – 25kHz
Efficiency: 101 dB-SPL 1W, 1m
Impedance: 16 ohm
Power Amp Range: 2 – 300 watt

You can drive above with 300B SET to enough volume.

But you may get nice sound with your current PP amp.

Thank you for all comments. I also have some concern about sensitivity of 805. I do ask Israel regarding the sensitivity (both B&W 805 and Polk Audio LSi7). His answer is OK. if the speaker is an issue, i need a pair of high sensitivity ones. Is vintage Klipsch a good option? i heard they are highly colored speaker. But the sensitivity is very high. How different is the sound between 300b and 805 (LM 508AI, etc)?  

@cygnus_859: My mistake: the correct name is: Golden Tube SE40. Brain fog strikes! There are some good owner reviews on: audioreview.com

The B&W speakers are voiced for SS amplification and are never going to sound their best with tube amplification; possibly with the exception of a pair of Atma-Sphere OTL monoblocks.

We’ve got several customers that are very happy with this combination.

Our amps have a lot in common with SETs- quite literally, they are two SETs wired together differentially, with the output bridged. Triode, class A, with a character like SETs of distortion falling to unmeasurable as power is decreased. Unlike SETs they have about 1/10th the distortion, much higher power and wider bandwidth. The cost of replacement for a full set of power tubes for a pair of M-60s is similar to one good 300b.

The B&W speakers are voiced for SS amplification and are never going to sound their best with tube amplification; possibly with the exception of a pair of Atma-Sphere OTL monoblocks. My recommendation is to stay with SS or, if the OP really wants to do SET, change the speakers to something more appropriate.

+1. (Although Ralph/Atmasphere is of course much better positioned than I am to comment on the suitability of his amps for this particular speaker).

And it’s not just a matter of having enough power. Given that the speaker is presumably voiced with solid state amplifiers in mind, which almost always have a near zero output impedance, the interaction of the very wide impedance variations of this particular speaker (see Figure 1 of JA’s measurements) with the relatively high output impedance of nearly all tube amps will result in a tonal balance that was not intended by the speaker’s designers.

Regards,
-- Al

Get a Golden Sound SE-40 PSE amp.

roberjerman2, do you mean the ubiquitous Golden Tube Audio SE-40?  If so, my guess is two of these bridged might work with the OP's B&W 805s but that's a hard row to hoe.  These amps need to be rebuilt and matched in order to extract the best sound and run reliably (ask me how I know this).

The B&W speakers are voiced for SS amplification and are never going to sound their best with tube amplification; possibly with the exception of a pair of Atma-Sphere OTL monoblocks.  My recommendation is to stay with SS or, if the OP really wants to do SET, change the speakers to something more appropriate.

Mastersound. King of the road.

One Golden Sound SE-40 per channel with its two outputs connected in parallel would give you a very respectable 36 watts of SE power! 

I do have a possible candidate - if you are willing to buy used! Get a Golden Sound SE-40 PSE amp. I have one also - forgot to mention it in my above post! This uses three 6L6G's in parallel per channel. About 18 wpc! Capable of driving many more speakers than the sub-10 watt SE amps! And the 6L6G's are cheap and plentiful because they are a popular guitar amp power tube. Though in guitar amps they are used in PP pairs. The SE-40 is single-ended parallel. And is no longer in production. They are still available on the used market for around $700. You could buy two for $1400 and parallel the outputs - giving you a respectable 36 wpc - for a reasonable price! I of course bought my SE-40 used. So there you have it - a SE amp that could drive your B&W's - especially if you buy two of them!

i second the linear tube audio suggestion. they have SET magic with  oomph (:

Don't fall for the SE tube hype! PP tube amps can be just as good! And a lot more practical! I have both - and high-sensitivity speakers to use with the SE amps (Klipsch Heresy's). The SE amps are: Sanei 560A (2A3's), Will Vincent 45 and a custom-buit SE amp using one 6BG6 tetrode per channel (6 watts). I have many speakers at hand - but only the Heresy's are suitable!

Take a look at the Audio Mirror 45w SET mono blocks. Over your budget, but maybe used price would meet your spend. There are also a couple of reviews links on the Audio Mirror website. 

I agree with other people’s opinion that B&W805 is not a good match with SET amp.

About 20 years ago I had driven B&W Nautilus 801(15 inch woofer) with Jadis 500 (350 tube watts) with explosive dynamics and deep bass.


I recommend OP to sell B&W 805 and get the SET friendly speaker with high efficiency above 94 db.

After driving it with ARC PP for a while, OP can try to get SET amp suitable for the speaker as a next step.

I am happy to drive Lansche 4.1 (99db/w spec) with either Line Magnetic 508 and Silbatone 300B SET in open space of 25ft wide, 20 feet deep, 15ft high loft.

The nice thing of SET sound is vocal music.

Both Elvis and Eva Cassidy sounds natural with spooky presence.

I don't know the current situation but approx. 15 years ago a local dealer told me that Coincident SET amps were made in China. If this is true, I understand why they don't accept returns.

I have a Cary CAD-300SEI and run via Watkins Gen 4 speakers near field - on my desk.  I also have an REL sub.  Way more power than I need for a small room, even a bigger one.  

+1 for @verdantaudio  Lots of great info there

Border Patrol also makes 300b PP amplifiers, but they are in the 10,000usd or more price range.

Agreed, wrong speakers for an SET amp. If you are wedded to the B&Ws and want something that sounds like a very good SET but with balls then take a look at the Linear Tube Audio ZOTL 40. Should be enough power and also give you that special magic of the SET.