Powerful Tube Amp for SF Strads?

I am looking for recommendations for a powerful tube amp for my Strads. A powerful tube amp which truly excels at palpability, musicality but also has very good bass control (though bass control is not as 'mission critical' to me as palpability).

My current amp (see below) sounds great to my ears!...but runs out of steam much too soon.

My system today:

Zanden 5000S DAC
CJ Act 2
CJ MV60 (EL 34 tube)
SF Strads (4ohms, 92db sensitivity though impedence does dip to 2.5ohms)
Velodyne DD-18 (run in parallel)
Transparent Ref/Ref XL cabling throughout
Purist Audio Dominus PC

In addition to recommendations, any thoughts are welcome on Wavac, Audio Note, Zanden, VTL, CJ LP275...or monoblocking MV60 (EL34)? Thanks!

You are going to get a lot of suggestions, and since this is Audiogon, most of them bad.

Only a tiny handful of tube amps have output transformers and power supplies of the quality necessary to drive speakers that drop below 3 Ohms in the bass, and they are all extremely expensive. If I were running speakers that present a tough load and just had to do a tube amp, I would look only at the CAT amplifiers, which have the best output transformers I am aware of. They are a real hotrod design, however, and require soldering when tubes fail due to resistors frying upon tube meltdown (which happens frequently because it is a hotrod design). Other options would be the Air Tight Reference and VAC's Renaissance 140's. My guess is that the VTL Siegfried would also work. Generally, you have to be most careful in choosing a high-powered tube amp, as almost all of the well known ones are not as capable of driving low impedance speakers as their ratings would suggest (I also find that high powered tube amps as a rule do not sound very good).

All of that said, I would forgo a tube amp entirely with that speaker in favor of a darTZeel, which will give you better overall sound barring some bizarre synergy issue with the rest of your equipment (I have no reason to think that would occur).

LLoyd, I'd look into a used pair of Cary V12 monoblocks. Those are VERY comfortably driving a friend's Infinity Beta ribbon panels. The V12's are also very musical amps a la Cary tradition..I'd think they would fare well with your Strads. The Beta panels are rated at 86db sensitivity while the Strads are 92db's and they both have a lowish impedence drop, so I guess you won't have any problems there.

Hope this helps..


Try a pair of McIntosh MC275 run in Mono w/ upgraded tubes (Genalex KT 88 Gold Lion 6550 and selected 12XA7 types). Or just buy MC2301 monoblocks rated at 300 watts @ 2 ohm.
I previously owned SF Extrema and now own SF Amati, and in both cases use CAT JL-1 Mono amps. Ive owned the amps now for about 5 years and they just do everything right. they are semi user friendly where occasionally will require you to solder in a resistor pack in the event of a failed tube but this happens very infrequently. I own a solder gun and do this myself as you can too once you become familier with the amp. Amps are very stable and i usually get about 2000 hours from a set of power tubes. If you have any questions feel free to email me.
Since you're set on tubes and to second two suggestions above, go for CAT's tubes, and I hope you like the sound. (I did, immensly)
There was really no problem driving a difficult load in my home. I.e., impedance drops, medium sensitivity, etc etc were not an issue.
Besides the above suggestions, you should also check out the Lamm M1.2 and M2.2 hybrid amps. Do some research, the reviews and user comments seem universally positive. Also check out the new Pass XA160.5 or XA100.5 amps - although they are not tube amps, the reviews always seem to mention that the sound has "tube like" qualities. Good luck.
Wow! Thanks for the quick responses! Appreciate the advice. Have also received from direct emails from fellow A'goners looking to help...thanks to you as well.

I have been invited to audition Wavac MD805s. I will try to find place that carries VTL, CAT and VAC (in London UK).

As for Pass, i've seen many A'Goners like Pass with SF's. Personally, i do love the earlier SF speakers (Electa Amator, Extrema) with SS like Krell...OTOH Guarneri, Amati and Strad i somehow associate with tubes. Given Ackman00's recommendations, i will keep an open mind...SS with the extreme palpability of a great tube could be perfect! Thanks again to all.
...oh and Cary & Wolcott of course! Thanks, Audiograils and Unsound.
I would think a VAC Phi 300.1 or two would do the job nicely.

CAT JL2 or 3 for sure, I think they can handle most any load and with 100 watts of Class A, Triode power they avoid what Raquel alludes to regarding high-power tube amps, they tend not to sound as good as their lower-power bretheren (assuming the lower power remains sufficient power to drive the speakers).
I must say that is quite a challange. A tube amp with moderately resistive speakers but not near the tubes output impedance, instead it drops precipitously and creating a worsened output mismatch and less power.
There is an easy fix. Simply buy the tube amp with a monster power supply and if possible an output coupler. In common terms this means get a tube amp with the biggest transformers you can and ignore total or rms wpc. Those watts mean nothing. My 60 wpc Jadis DA-60 just doesn't clip although I haven't tried to make it explode it handles everything I want it to. Also The Kilovolt power trannie 211 or 845 PP amps provide plenty of foundation. Honestly That is where the music is -in the trannies once the major obstacles are met then subtleties can come in and do their thing.
Thus I congratulate you on the wisdom of thinking Wavac and LLam. Those are perfectly good examples of "transformers make the music."
Forum mate Downunder is using McIntosh MC2102's monoblocked with the SF Strads, check with him.
I have heard the Mac 275's in mono with the SF Elipsa's and it was truly beautiful. With the Strads, I would think the Mac 2301's a better choice.
The Art Audio quartet monoblock are hook up with the
Andra I Eggleston,the power is more than enough,and they
excel in palpability, and musicality,they have good bass
too.You can email Joe Fratus from Art audio.You can also
email Markr1,who own the system,Ive heard.
Thanks for the further responses and advice! Mechans - that is consistent with i am starting to learn about tubes and amps in general. Yes, there is something about watts, but it is both current and voltage which matter. (e.g., there are some great and powerful sounding low wattage tube amps...high current designs.) I will try to check out the Wavacs this weekend.
Jamnesta/Jmpwme - spoke with Downunder who owns the strads and the 2102s. Jayctoy - will email Markr1...thanks!
The nice thing about the Mac tube amps is that you can run them on 2ohm taps, 4 ohm taps or 8ohm taps. Parallel or bridge them and they can run at full power into loan from 1ohm to 16ohms. The ACT 2 will drive them fine as well.

I run my 2xMC2102's parallel into 2 ohms at the moment at they sound great.

Running a quality subwoofer allows one to have that little bit of SS slam and extension without any of the drawbacks.

personally I could not see dartzeel power amp controlling the Strads very well, from memory they don't like driving low impedance loads .
SS amps don't really gel with the Strads IMO. I will howver be trying the enigmatic Arye MX-R's in a couple of weeks.

That said I would luv to hear the CAT tube amp.
Thanks Downunder,

Yes, i agree. Earlier SF's and modern SF's (other than Homage series) mated well with good SS like Krell. But the Guarneris, Amatis and Strads seem imho to mate much better with Tubes.

I auditioned the Strad with ARC CD7, ARC Ref 3 and Krell Evo 402...don't get me wrong. i heard some pretty incredible sound, and the 402 is one heck of an amp. I guess i missed that absolute palpability that the STrad is capable of producing (but which also typically requires a tube to get the full measure of that palpability in my experience so far.)

Meanwhile, I heard the Evo 402 with the Grand Pianos and other SFs...outrageously good synergy.

then again...have heard the Ayres are pretty incredible in palpability! Pls let us all know how the Ayres do with the Strads! thanks.
To expand a bit upon the above posts and my own post regarding the CAT amps and their transformers and power supplies, the original CAT JL-1 100 watt/channel monoblocks are gnarling beasts. They contain outrageous hand-wound transformers that weigh 55 lbs. each, the power supplies are something like 1,000 joules per monoblock, and each monoblock weighs 192 lbs. By comparison, the "monster" 500 watt/channel Audio Research 610T monoblocks weigh 170 lbs. each (as transformers and power supplies are both heavy and expensive, the quality of a tube amp can largely be gauged by its weight and cost). I almost stripped a gear helping my friend carry his JL-1 Limited Edition's from one side of the room to another.

Speaking of the JL-1 Limited Edition, it was point-to-point wired and had unbelievable parts quality - it retailed for $50,000 and Ken Stevens only made about a dozen of them (not to be confused with later "Signature" versions of the JL-2 and JL-3 that use circuit boards and cost $20k less). It has incredible finesse and resolution, but at the same time, sounds subjectively more powerful that a 500 watt/channel Krell. I am not aware of a more potent tube amp or a better sounding high powered tube amp. All of that said, like a Shelby Cobra, it was high maintenance and frequently blew output tubes, which took out resistors that had to be soldered out and new ones soldered in - my friend nicknamed them the "Popcorn Poppers" and would not leave them unattended.
I agree with Raquel. There is unlikely to be a tube amplifier with the drive and current of a CAT, but I also agree that they are much like a Ferrari (a Cobra) too, they are super high performance, but they are not drop in and forget'em amps. But they are hard to beat for one of the very best sounding amps you will ever hear, espcially when you need High Watt SS bass with SET midrange delicacy. I would like fuse protection for tube failures, but then it wouldn't be a CAT.
I had some Manley Neo Classic 250's driving my Eidolons effortlessly. Or some hard to find MFA mono's.
Thanks for the further posts! I read a review in this month's issue of HiFi+ about the new David Berning Quadature Z 200w OTL tube monos. They went crazy in the review, saying it was hands down the best amp they had ever heard, effectively redefining their view on musicality, muscle and refinement.

David Berning Zh270 has a very loyal following, and i remember reading in STereophile (Jan 05) that Franco Serblin of Sonus FAber had Stereophile at the factory, listening to a ZH270 running the SF Strads.

Any thoughts on the new Quadature Z's would be welcome! i have contacted the company and will post if i find a way to hear them. thanks.
Hi. I will be auditioning the Berning Quad Z monos! Will update.

Aren't the Bernings 30k??
Vac has several amps that would easily drive the SF speakers. I have Thiel CS1.5 speakers that are 87db sensitivity and operate between 4 and 3 ohms. The amplifier I use is the VAC PA90.

Good hunting!
ANother vote for VAC here. I would recommend the current statement piece, the Phi 300.1. Really amazing sound, especially bass, speed and musicality. Driving my VSA VR-7SE's to new sonic heights every day without ever breaking a sweat... a phenomenal amp, as other owners have attested.
I hope I can be of some help,though not directly.

Last April,I was lucky enough to attend a superb demo of VAC,Zanden,and VTL electronics....

All A/B'd against each-other,on the JM Labs Nova Utopia speakers.This was in a good sized room,and we used both CD and LP's.A very good demonstration,based on the not so hot demoes I've attended over the years,in that room.

I think the Novas are about as sensitive as the Strads,and also dip in impedence in the bass freq.This should be a very similar speaker in sensitivity to different amps,I assume.

Bottom line,and quite surprising(to me).....

The 100 wpc VAC sounded superb and room filling.NO weakness on both CD or the LP's,being played.Loved the line,and especially the classy way the company owner handled himself.Real class!!

The VTL(BIG amps,and fuul line of pre/phonostage)sounded OK,but did not have the magic of the VAC,to me(I know many love the stuff).....Other attendees loved the bigger bass,but I felt it was a bit too dry.I got bored with the VTL's handling of timbre,but others liked the BIG sound.It did not float my boat,like the VAC stuff did.

The Zanden full line up(45wpc mono amps,pre/phono stage and CD player) was amazingly lifelike.Oh boy,this was nice!!

Of course we got the "full monty" treatment with the RIAA aspects of the fabulous phonostage.However the REAL surprise came by way of the ZANDEN mono amps.

These non high powered,but highly musical,amps "absolutely" filled a very large room (I'd guess about 20x30x12) with a huge sound stage,and had superb bass response.Very controlled,and very convincing in virtually all important areas....to me!Especially in timbral aspects of music,where I am a bit finicky.

Hope this helps.

Good luck...you won't need it -:)
Wow...Thanks Sirspeedy. Sounds pretty incredible. I will say the Zanden 5000S captured me, after only 5 minutes. I had struggled to do the DCS Elgar Plus 3x before ultimately deciding it was not for me in spite of how great it was.

I will look into the 9600s.

And yes, Downunder the Bernings are 30K. Nevertheless, i am someone who likes to listen to pieces like this so that either a) i determine i am going to keep looking, b) i understand the totality of what is achievable today, c) i decide i am either going to do something crazy like get them, or wait until a more sensible time to spring for them.

I bought my first boombox in 86, my first system 93-96, and have started the first upgrade in '05-'08. i have upgraded each component ONCE, and do not expect to look back for another 10+ years.

Thanks to the A'Goners, i have many things to audition before i decide: at the moment,

Berning Quad Z
CJ LP 275
Zanden 9600

will be an adventure for sure!
Consider Audio Valve challenger 180 watt class A, built like a German tank. Amp, tubes fully protected, auto bias, tells you if tubes are weak. Sound is amazing bass best Ive heard out of a tube amp. Can run differant tube types. Can drive most any loudspeaker including electrostatics
Thanks JohnK! Will look into it!
The Audio Valve amps are indeed superb and I should have included them in my discussion (I usually do, but forgot). The 400, I believe, is one of the rare high-powered tube amps that truly sounds good. They will be expensive with the current exchange rate (assuming you are in the U.S.).
has anyone heard the Pass XA.5 upgraded class A amps??

I wonder how they would go with my Strads and how similar they sound to nice tubes in the upper frequencies.
Hi Downunder,

I have heard others say the Pass bridges the gap btwn solid and tube. I have heard the same of the CJ Premier 350...read Martin Collom's review on the net. Wow...until the Premier 350, the Krell 700cxi was one of his fav SS amps. He said the 350 bettered it by being more musical...130-point rating by Martin. 600 watts/channel into 4ohm load so plenty of power/effortless volume for a 93db efficiency Strad.
The XA.5 series is the best SS I have heard, and their 30 watt amp should be more than enough to drive the SFs plenty loud in most rooms for most people - I think it is very conservatively rated at 30 watts. THe .5 iteration is much better at delivering current into low and volatile impedance swings - should do very well with the SF in that regard. It worked superbly well with the Merlin VSMs (a much easier load the SF), and would expect the same with the SFs. Is it tubes, no - but it sure sounds good.
Funny you mention the CJ 275,because my dear friend has just gotten that amp.He has all CJ ART components,and a fully loaded VPI table/arm/Lyra Titan-i cartridge,but the speaker is different from those mentioned here.

Thsy are highly modded Infinity RS-1bs.In truth(when modded "fully",including a crossover rebuild)these are about as revealing,and dynamic as anything "popular" today!Classic design.

The CJ 275 will only run the midbass/midrange/tweeter panels(the woofer towers are run by SS Krell).They'll start to come in at above 110 hz,or thereabouts.

Previously his sound,with the older CJ big boys has been superb,and he is an old school,extremely experienced 'phile!A great listening room as well....because.....

Regardless of what one thinks the particular sonic success of "any" system is the absolute combination of room/amp/speaker.....That's it,in a nutshell!!

They are not independant of oneanother!

He is currently experiencing some set-up problems,but I should be getting in some serious listening very soon.

Hi Lloyd

I owned the cj prem350 for about 6 months. Did not like it at all at the end and was very happy to sell them. Just sounds like SS, expecially in the bass which is lean and tight and not lifelike.

Don't get me wrong, it sounded better than other SS amps I tried at the time including Pass X350.5,Parasound JC-1, Simaudio, Cary 500MB's, Krell 400cxi but ultimately if you prefer what tubes do you won't be able to live with any of them, and i am a big cj fan
Hi Sirspeedy, have read and respect your posts from before. Very helpful. Between your post and Downunder's plus lots of listening and reading, I've refined my thinking for my SF Strads. I am a tube guy and love my CJ MV60's EL34s for midrange palpability. If I am looking for tube midrange and effortless power and volume, I am narrowing it down to CJ LP275, Berning Quad Z, possibly Wavac 833 1.3s. Thanks for posting!!!

sounds like a wondeful choice of tube amps to choose from. Hopefully you can hear them in your system so you can decide best for you.

BTW, my local dealer is getting a pair of cj LP275's in a couple of weeks. That will be an interesting comparison with my 2xMC2102's if I can arrange it. Almost scared to ask
A friend has the Strads in a medium sized dedicated listening room (designed from the ground up by Rives). He powers the speakers with a pair of custom-built output transformerless tube amplifiers. The sound is very good. If I have one issue with the speaker, it is that it is not super fast and dynamic. While it is not a slug, and compares fairly with other dynamic speakers of its type, it is certainly not in the "speed" range of elctrostatics or horns or even fast dynamic speakers like the Magicos.

I would personally be looking for amps that can provide a little kick-in-the-ass quality. I have not heard the combination myself, but I would, if it were in my system, look into Atmasphere OTLs. The bass may seem a touch lean with the Atmaspheres, but, it will be tight and fast and will add some helpful "jump" to the music.
Wow, Downunder...please let me know if you listen to them!!! It is tough/impossible to get CJ in UK where I am.

Thanks, Larryi...have read your posts and learned from them. I will try to look into Atmaspheres here in UK.
Thanks, Larryi. I've seen your posts before and learned from them. I agree with you on Strads. Compared to Wilson Grand Slamms or Maxx 2s, the Strads are more about "feeling the roisin of the violin strings' than dynamic attack and speed. I prefer my Strads to the Maxx2 because while I care about hip hop, Deep House and orchestral, I listen most critically to jazz, female vocals, and string quartets where the emotive feel of the Strads is remarkable. That said, the Grand Slamms are in their own league.

Thanks for your advice. I'll look for Atmaspheres in London....and hope the Berning Quad Zs (also OTL's) will be a good match.


I too really like the sound of Strads. I hope you find an amp that really works well for you. The Strads do not strike me as being particularly tempermental so you should not have too much difficulty finding a good match.

Let me make it clear that I have not actually heard an Atmasphere amp with this particular speaker, although I've heard and really liked their amps in general. I've also heard, and liked the Joule OTLs. The Joules struck me as being warmer sounding (richer upper bass), but the particular unit I heard had problems with bad tube sockets (caused an intermittent, but extremely loud BANG), so I can recommend Joule on sound quality, but I would be concerned about reliability.

I am generally partial to OTLs when it comes to higher power from tubes. I personally have found some higher powered pentode tube amps to have a brittle edge to the sound and a "glassiness" that is worse than most solid state amps. OTL's can sound a bit rough and tumble and they may have a bit of brittleness too, but, the compensating payoff with OTLs is their unmatched liveliness and vividness.
The top line VTL monoblocks--the Reference or the Siegfried. This is the best-sounding, most seductively addicting and at the same time most dynamic amp I have *ever* heard.

They give you the best of everything: Magic of tubes, wickedly powerful, and regulated by a complex solid state circuit that maintains proper bias, speed, and linearity.
Have you considered the McIntosh 2301 dual mono pair?

They come straight to mind when you say powerful and tube in the same sentence! :-)
Try the new Eternal arts OTL amp. Just got a rave review in German mag "image hifi". I bought one 6 months ago and it is simply amazing. Best of both worlds: tube sound with Dartzeel speed. Look it up at www.audioclassica.de. I run mine withg Audionote AN-E loudspeakers, Bliss.
I don't question the quality if the Eternal Arts - never having heard them, but I would stick with Atma-sphere for OTLs which are outstanding soundwise, U.S. made, very reliable, can repaired here in the US should it ever need it, and has a healthy afetermarket if you should ever tire of it. In fact you can by used here and sell back for roughly the same should it not be your cup of tea.
What about a pair of CJ LP140s or push the boat out further with a pair of LP275s?
Hi jskg,

thanks...i am a big CJ and SF fan, as apparently you are as well. As i have the ACT 2 preamp and CJ mv60 amp at the moment, i am very seriously considering either of the 2 amps...am leaning towards pushing the boat out, as you say, and getting the 275 monos.

Have you compared the 275 to the 140? would love to hear your impressions about what the 275 gives you. thanks!
Have owned and listened to different Stradivari set up at friends.
have listened with many poweramps and one of the best matches turned out to be the accuphase P7100.
have listened to Wavac 833 1.3 too, Lamm M1.2ref and some others.
the Stradivari needs the best, and it needs a dominant amp.
with Lamm M1.2ref it was nice as for sound, but this did not bring out what a Strad is capable of.
the big Zanden mono's are superb match soundwise, but if you really want fireworks: TENOR hybrid or Accuphase.
I have owned the Stardivarius for sometime and I could not find a tube amplifier that mated well with them. Although they sounded nice with tubes, after you hear the scale and dynamics of these speakers with a good power amplifier such as a Krell FPB700 or a cj Premier 350 you find you regret what you are missing with tubes.
Since you have an ACT2 I would suggest a Premier 350 - they can be found at nice prices at audiogon. Also consider factory upgrading your ACT2 to series 2 - it is expensive, but worthwhile. The new preamp is more musical and is even more spatial than the previous one and will match perfectly with the Stradivarius.