Tubed Monos for Focal Aria 948s

I'm considering a pair of tubed monos for my Aria 948s. Given that their efficiency is at 92.5 it seems that I could swap the 130W SS monos for the warmer tube sound in the 40W range and not have any issues. Any ideas how much bass would be lost? Do I need to factor gain into the equation? Already have a tube preamp and like the way that sounds, even like the the way the SS monos sound but since the Focals are so clear my thought is that tubes would pair very well.

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A nicely restored pair of Dynaco MkIII's would work well. About 70 watts from a pair of KT88/6550's. I have a pair in my collection. Still among the best tube amps ever!
The biggest issue with similar speakers, and Focal in particular, is they tend to have an impedance dip right where you don't want it, around 100 Hz.

This makes them "discerning" of amplifiers, meaning that they will require a low impedance amp to drive them without loosing bass drive.

This is not the same model, but it is typical in this range for Foral:
Sorry, I never got to my point.  My point was that when auditioning amps, listen in the lower to mid bass for any weakness. Decide accordingly.
That may be a 92.5db/w/m speaker but it's a crossover intensive, multi-driver speaker. Few modest-power tube amps will resolve that Focal's problems (or challenges) and you don't want the mega-massed-tetrodes/pentodes 200w+ tubes monsters. What can you actually spend on amplification? I'm a tube loyalist but sometimes you have to accept a solid state alternative. IF you can afford to, the SST Ampzilla 2000 Second Edition (temporarily $5200/pair on promotion) would give you tube warmth and scintillating solid state resolution + faultless bass control. Magnificent on that speaker. Also the SPL S800 stereo power amp.  And for much less, the m2tech Crosby, either as a 60/60w stereo power amp or as 180w monoblocks (8 ohms), would obliterate most tube amps on that speaker. The Crosby is $1300 for stereo, $2600 for a pair of energetic, high-grip monoblocks. Tube smoothness with transistor assertiveness and control in an 8 lbs. per monoblock compact package. What are you game for?

Thank you everyone for the replies. As I expected, there is a good bit more to understand before making a selection and your information cuts down on research time.

@erik_squires I was wondering where that part of the signal went. I love the sound of these speakers but always felt that they needed a little something extra. Thank you for defining the problem.

@213cobra I was under the impression that the crossover design made it easier for amps to drive the speakers. If that is incorrect then I will have to take that into consideration. I was looking at a pair of Prima Luna Dialogue 7 monos ($4800) or the EVO 400 which are twice as much. The 7s I could get in a month, the EVOs would be 4-6 months but I am going to look into your recommendations now. I have the Odyssey Kismets hooked up at the moment so SS is not a deal-breaker at all. I'm looking at tubes just to see if I can warm things up a bit but as Erik pointed out, whatever I choose will have to compensate for the 100Hz dip.
Check out Quicksilver's new 120 watt mono amps...
@oddiofyl You are the second person to recommend the Quiksilver 120. I will send a message to the company and explain what I have. Erik_Squires mentioned the 100 Hz dip so now I'll be focused on that as well.

Again, thank you everyone for the information.
+2 for Quicksilver Mono 120s. Got some too. Love them :)

Also, I helped my sister to acquire Focal 948s and for her we chose a simple 100w Peachtree integrated (with tube input) for her family room. Goes plenty loud, and I’m certain QS Mono 120s would be plenty, I’ve heard them with large 7 foot tall IN-effcient electrostatic and large multi-driver speakers. Mono 60s could work too, with a bit less grunt than Mono 120s. 948s are known to be bass heavy so pick your poison with QS Mono amps.

Mono 120s are what I use for my own multi-driver electrostatics in my main system now. Takes a while for tubes and caps to burn in. Once that happens, they really take on a nice smooth sound.

Mono 120s have the finesse of lower power amps with large transformers and proper circuit and plate voltage to drive the KT150s.
I’m a 40-year mosfet solid state amp guy and love these amps. Mike did a really nice job on them, switch on the front and AC/speaker on the back, with KT150s and quality build and I’ll say it again, large-quality transformers in a well known proven circuit design. They run 12AU7 input and 12AT7 drivers, so tubes are not crazy expensive if you want NOS or boutique tubes. I’m running NOS 1960s Mullard input/drivers elevating the sound to true high-end, totally 3-dimensional, nice midpoint sound stage, dead quiet. Again, need to burn them in 200+hrs.

Mike’s standard Linestage preamp (non-remote) version is a nice preamp for them, great value too. However, I run a different 6SN7 based preamp (already had it), and it pairs sooooo nicely with these Mono 120s. Comparable CJ KT150 based amps are $19k, over 4x the price. I’d put these up against it all day long. Value$ !!!

Keep the bias at 40ma and they run COOL! Any of my former Class-A, or better Class A/B solid state amps ran warmer than my Mono 120s. The more I listen to the KT150s, the more I really like them, more than I thought I would and I tend to generally like EL34 sound. The KT150s have more top-air, more bottom end, and the right amount of midrange without being syrupy in these amps. Mike nailed it with Mono 120s for my custom speakers.

Not sure what your budget is, but Rogue Audio's monoblocks are fantastic. I have the M-180s. No experience with those speakers, so can't say how they would match up. When I had my Legacy Audio 20/20s (94db efficiency if I remember correctly), it was intense! They're great with the Harbeths I have now also. 
@decooney I agree with bass on the 948s. I thought Focals were a bit light on the bass by nature but not these. I'm using a Prima Luna Dialogue HP for the preamp and love the sound.

@big_greg I figured that I would need around $5k for a good set of tubed monos so the Rogues are possible.

Just read a post about speaker impedance and amps which should help. Looks like a lot of math but that should narrow the parameters considerably 

"OP: "I could swap the 130W SS monos" ...


@decooney I agree with bass on the 948s. I thought Focals were a bit light on the bass by nature but not these. I'm using a Prima Luna Dialogue HP for the preamp and love the sound."

Are you running 130W SS amps or Prima Luna Dialogue HP now?

What are you not getting out your current amps you hope to get out of new tube monos respective to your Focal 948 speakers?

@decooney I have a Prima Luna Dialogue HP pre amp that is connected to a pair of Odyssey Khartago mono blocks. They sound fine as is but the Focals are so clear that it sounds a little lean in the bass. As erik_squires pointed out, there is a dip in the upper bass range so my thinking is that the warmth of the tubes may help the tonal balance. Is this is incorrect? thinking is that the warmth of the tubes may help the tonal balance. Is this is incorrect?

No, not incorrect but I will say there may be other areas to mess with before jumping to tube mono amps to remedy the leanness. Sure a pair of tube mono amps with smooth sounding EL34 tubes can "round off" the highs a tad to accentuate the bass some but you may have other options to try before you try other amps... tape a paper towel over your tweeter on your speakers as a cheater simulation test...: heheh.

I took a look at your amps, torroid transformer, notable power quad caps and while don’t know much about your amps sonically - but know a few locals with them that did go to tube amps later but for sonic reasons OTHER than adding the weight and fullness you seem to be looking for (below 200hz) with your Focals. With that said, I think you might look at some other areas if you want to keep your Odyssey amps. They are kinda nice. Perhaps restarting with 1) your preamp/upgrades, preamp tubes, preamp caps and 2) maybe even some softer and more rolled off interconnect cables next to cheat some...a tradeoff some times (chat via private message), gotta few ideas there too from my own hybrid tube preamp / ss combos. And, if you have not already done so. 3) maybe look at adding a little REL subwoofer is a nice cheater fix to fill in that dip. They can sound nice. I build my main speakers and custom subs and a good sub can help fill that void particularly for low volume level listening and permit your mains (to work less hard) to resolve better too in a large room. Look at what some of the more expensive Wilson Audio speakers are doing the past decade, see the lower half of he speaker :) Just a few other thoughts, feel free to send a private message. Gotta a few other questions for ya. Your preamp has the triple 12AU7s per side, correct - or older version. The new PL labeled input tubes in those preamps look like rebranded PSVANE tubes, sort of. Also noting the Mundorf caps in the newer version pre - I run those same caps in a tube DAC, but there are other caps that are warmer, less tinny, the EVO supremes are fuller, IMO. You may have other areas to work on IF you keep those amps you have now.

To the extent this is helpful - 

I used 60 watt per channel Allnic 300B XLS amps to power Focal Sopra 1s, and it worked like a dream, more bass than I ever would have imagined. I could play it loud. However, I never cranked it alllll the way.

I currently use a pair of Conrad Johnson's that put about 180 watts into 8 ohms, and they power my Sopra 2s perfectly. Extension in both directions, more than enough power to play very loudly.
@gmercer I'll bet that sounds great. If the Sopras sound half as good as they look you must be pretty stoked. I heard a pair of Kantas at a dealer's home and that's what got me hooked on Focals. The clarity and detail was like nothing I've ever heard so when an opportunity to score some 1.5 year old 948s came up at the price they did, I jumped. I figured they would be lean in the bass like the Kantas but they are not at all. They just need that something extra to push them across the finish line.
I hace the 948. Very good speakers at budget prices these days. New and used. New if you get the walnut. I preferred black gloss. Looks good with a jl fathom gloss sub. But anyways i currently have a audio research ref 75. Sounds great. But the amp i had before and wont sell because i got it for a grand is a krell kav 2250. It sounded just as good as the arc. You can find one for a grand somewhere and its built like a tank. But my preamp is a audio research ref 5. So maybe the krell and arc preamp matched just as well as the arc tube amp.
Hace2 denafrips pontus dac and my arias sound really great. If you havent gotten some isoacoustics gaias yet. Go ahead and grab those. It cleans up a already clean sound and youll notice right away. I bought some used gaia iii for my aria 948 even though the arias are a little over the recommended weight if the gaia iii at 70 lbs. Save some money they work fine with arias. 
I started out woth electra 1007be and it sounded very good and detailed. Then someone sold me a pair of used chorus 836v focals. And wow, i realized that towers sound so much better. Or at least it did to me. I will not be selling my chorus or krell amp. Ill put them in another setup someday. Im currentky wanting some sopras in blue. But they cost way too much. So im currenttly carbon fiber vinyl wrapping my chorus 836v. It's gonna turn out pretty sweet. I got my blue speakers one way or another. I feel like you cam get the focal sound in the basic models just as easy.
The budget line of focals is where its at. Feel like kanta 2 may be a hair better than my arias but im paying for looks and not sound at this point

The arc amp is nice but that krell held its own. And it weights 70 lbs so its not a pushover amp

I did get the isoacustics you mentioned. They do make a bit of a difference. Overall, I love these speakers. I was considering the Kantas but when the opportunity to get these popped up I jumped. Very glad I did. I’d love to try the Sopras some day just to hear the difference 
Well i finally found a pair of focal sopras in blue and pulled the trigger. They were the sopra 3. Definately too large for my room. Compared to the 948 using my audio research ref 75 amp. Main difference was bass. The sopra has midbass for days. I could honestly sell my sub now. When using the 948 the bass was nice and tight but still needed some sub help. The sopra 3s dont need any sub help. They look stunning. But i may be getting a tad bit better detail but the bass was the hugest impact. As soon as i turned a track on i was stinned. I went to check what i had the sub on. Because sometimes at night i would lower the knob of the sub. It was in the very low setting. It felt like the sub was cranked to what setting its initially at. During the day that is. Nights ill lower it. 
Ill be honest the aria 948 can hold its own in the midrange and highs. The sopra you do get a more presents. Like it has more authority. Its Definately a better speaker. It should be it costs more than quadruple its price. Im now considering selling my audio research gear and getting naim or micromega integrated. Since those brands mesh well with focal. Audio research sounds great but whats funny is when i crank up the ref 75. The watt meter barely goes over 5 watts. Its hard to get them to go over 10 wattts. 
It doenst take much to drive focals. I feel the arias were harder to push than the sopras according to the vu meters. 
So im at the point that maybe a integrated would push these sopras fine in class a/ab amp like a micromega m150 or naim nova. Decision decisions.
The krell was sooo good it makes me think i could do without a tube amp. And maybe its because my preamp is so good. Best of luck to you. Arias are still a great product line. Sopras have more definition, presents, authority... Best way to describe it. Thanks
Congratulations on the Sopras. They are beautiful speakers. I've been playing around with placement of the 948s. I positioned them a third of the way into the room and set them 3.5 feet off the side walls without toe-in. The soundstage really developed nicely after that. I've been using Tool's Fear Inoculum to test it. Could always hear the guitar and bass directly from the left and right speakers respectively before but since spreading them further apart, the band is all in the center now. I raised the front of the speakers about 5mm to raise the soundstage a bit and the bass really came to life. On cello soloist music it's like I can feel the vibration of the wood body now. I don't think I will mess with the amps now. I'm going to enjoy this for a bit.
Glad to hear you're enjoying the Sopras
Micromega M150 would be a great match for Sopra N3, I have M100 and looking into Sopra N1. or N2. However, beware of Micromega, LAN on my M100 stopped working, and I've tried to contact Micromega every way I can, they do not respond..........
Speakers are efficient yes, 
dontmshort change yourself on a low,powered amp.
get something with power.
your ears will thank you.
My past experience with Focals is that they can develop a distinct L, C and R image, but without the ability to fill in between.  I was able to fix this with just a little toe in. 
@arctikdeth I'm running a pair of 180w mono blocks into them now. I would like to keep the wattage up there if possible.

@erik_squires That's exactly what I noticed too. I spread the speakers further apart and removed the toe-in which seems to have worked in my room.
If no-one's mentioned it, that speaker should be on the 4-ohm tap if using tubes. The woofer array is nominally 4 ohms- that's where you power is.
@atmasphere First I've heard of it. The amps don't have a 4 ohm option otherwise I'd give it a try
@zyphryx  A transformer-coupled tube amp without a four ohm tap??

No worries- a set of ZEROs ( can fix that. If the speaker is bi-wirable you can try putting the ZEROs just on the woofer section. 
@atmasphere Can't bi-wire these speakers and the preamp is tubed not the mono blocks. They are solid state. The whole post was about switching the mono amps from SS to tubed and what the trade-offs would be.I've added a TT into the mix recently, so I may just leave everything as is now. The sound is great right now except for minor placement tweaks
Ah. Well if you ever do get a tube amp, try both the 4 and 8 ohm taps and see which works best over a variety of material.