Suggestion used tube amp between $1,500-2,000

Honestly, in your price range I think you would be better served getting a tubed integrated amp. Look for a used PrimaLuna DiaLogue Premium HP, or Cary SLI-80. With your speakers I think you would probably need the 80 wpc in Ultralinear, but if your room is small enough, maybe you could use the triode mode,

I’ve owned the ARC LS-7, and it’s not a very good preamp to be honest.
Integrated amps get a bad rap sometimes, but they really do give you more bang for the buck in your price range and even much higher.
I’m currently running a VAC Sigma 160i integrated amp, which lists for $10K, and handily beat the $20K of separates that I replaced with it.
Not only is an integrated amp more bang for the buck, but it’s one less power cord and pair of interconnects to buy too.
Personally, I wouldn't head into the separates market unless I was looking to spend over $30K.

Cheers,
John

Look for Cayin or VAS items, great value and great sound, new or used.  Most of its products are knock offs of vintage Mc, HK and Marantz designs, updated for SOTA parts.  I have purchased a few Cayin products and I found them better then stuff costing three and four times the price.

I'd echo John's recommendation of an integrated. The Cary Sli-80 build quality is excellent, it's easy to bias and gives you a large range of output tube options to tailor the sound to your liking. The small tubes and rectifiers are common types, meaning lots of choices in a wide range of prices. Having service and advice available within the U.S. is a bonus, as well. Most important, it sounds wonderful and is a pleasure to use.

Why buy used?
http://www.quicksilveraudio.com/products/midmono.html

I agree with the integrated option being a better bang in your budget range. They’re making a comeback for very good reasons many given above by John. A real problem can be finding the ideal preamp/amp/speaker interface that will suit you, it might prove hit and miss going forward. With an integrated your biggest concern is that the amp and speaker match up and that you’ll have enough power for your application and room size as noted.

The QS amps are great values and performers at their price and well beyond, I'll testify to that. The question is will the QS or any amp recommended be an ideal and satisfactory match to you with that LS7? 

For $2k, you can pick up a used Music Reference RM-200 (the original, not the Mk.2). It is well-suited for passive pre-amp use (input sensitivity, gain), so you can dispense with the LS-7 and get a better-sounding passive if you wish. Over twice the power of the good Quicksilver suggestion from yogiboy---100w at 8 ohms from only a pair of KT-88's per channel. And unlike any other tube amp with which I am familiar, more power into 4 ohms! 

I noticed that in your other recent thread you indicated that at an early stage of their breakin the new SF speakers have been sounding bright. Presumably that will improve as more hours are accumulated. But I want to caution that a tube amp, somewhat counter-intuitively, may not be helpful in that regard, and depending on the particular tube amp may actually increase the brightness.

The reason I say that is that the impedance of your speakers, as shown here, varies from less than 4 ohms in the mid-bass region to very high values, more than 20 ohms, in much of the brightness region (e.g., 2 to 5 kHz). The relatively high output impedance of most tube amps (compared to nearly all solid state amps) will interact with that kind of impedance variation in a manner that will give greater emphasis to the frequencies at which the speaker impedance is high. The degree of that effect will depend on the output impedance of the particular tube amp.

The RM-200 which bdp24 suggested has significantly lower output impedance than most tube amps (see Stereophile’s measurements), especially on its 4 ohm and 1 ohm taps, and so in that respect, at least, it would seem like a good choice. I’m not so sure about the other amps that have been suggested. However the 15.4K input impedance of the RM-200 is less than the 20K minimum load that is recommended for your ARC preamp.

I’ll mention also that nearly all solid state amps have output impedances that are near zero, and so with your speakers would not emphasize the brightness region as a result of the effect I described above. However many solid state amps will intrinsically tend toward brightness, compared to many tube amps, in part due to their tendency to incorporate greater amounts of feedback than many tube amps. So it may be matter of picking your poison.

I don’t have any particular suggestions to offer that are within the price range you indicated, but those are some thoughts I would consider. And before making any decisions about amplification it would probably make sense to wait until the breakin process of the speakers is further along.

Good luck. Regards,
-- Al

I would second the VAC 160. I recently heard this amp in a head to head with Aestetix amp and it was much more pleasing tho my ears. 

Where can one get a Vac 160 for $1.5-$2k? 

Another vote for Quicksilver and there is always Rogue Audio to consider in this price range.  I do disagree slightly with people recommending higher power tube amps though.  That will depend on your room size.  My speakers are 90 db sensitive in a 14' x 19' room and I rarely exceed 5 wpc, it gets uncomfortably loud at that level.   I know this because I keep old amps with power meters around.  So what is the room size and how far is your listening position?

Regarding power requirements, I would add that in addition to room size, listening distance, and individual volume preferences, a very major variable is the dynamic range of the type of music that is listened to.  Dynamic range meaning the difference in volume between the loudest notes and the softest notes.

Many and probably most pop and rock recordings are compressed to dynamic ranges of less than 10 db, meaning that less than 10 times as much power is required to reproduce the loudest notes as is required to reproduce the softest notes.  While many recordings in other genres, such as classical symphonic music, can have dynamic ranges of 30, 40, or even 50 db. A 30 db dynamic range means that 1,000 times as much power is required for the loudest notes as for the softest notes. A 40 db dynamic range means that 10,000 times as much power is required for the loudest notes as for the softest notes.  And music having wide dynamic range will generally be played at levels such that brief dynamic peaks reach much higher volumes than the peaks of music that never gets much above its average level.

Which is one reason that like most recommendations for amplifier power that are provided by speaker manufacturers, SF's recommendation for the Venere 2.5 (40 to 250 watts) covers a very wide range.

Regards,
-- Al

The input impedance of the RM-200 is 30k via it's XLR inputs, I believe.

Thanks bdp24. But note that the LS7 preamp only provides unbalanced RCA outputs. And using an adapter to put the unbalanced signals into the amp’s XLR inputs would most likely still result in the LS7 seeing a 15K load, as the 30K figure most likely reflects the sum of the impedances of the two legs of each of the balanced inputs.

Regards,
-- Al

would manley stingray be powerful enough? cary sli80 used ...both around 2500...

I'm getting cronus magnum 2 for 88 db totem sttafs...

usatubeaudio swears by ayon it seems, more poewrful than what I needed and pricey new...

jolida, cayin used would be easily below 2k...


I mean I hardly know what I'm talking about tho...just got into this...

Nighthawk MK2 integrated amp by Raven audio for $2600 new.  Check it out.  Call the owner, Dave and he will be a tremendous help to.  I agree with the above posters on going the integrated amp way.  

Ah yes Al, unbalanced only on the LS7. Of course, if Eddy goes passive, he could get a passive pre with balanced out. They are available, aren't they? Not that Eddy indicated any dissatisfaction with his LS7, but when I see a system with a single line level source, I think passive pre. Roger recommends that route with the RM-200. An even better course of action, if the source allows it, is to install an attenuator right in the source component. No impedance match to worry about, and one less interconnect! Ric Schultz of EVS used to make a great attenuator, of discrete resistor-ladder design. VERY transparent.

Thank you everyone for helpful suggestions.  LS7 I bought it used and it is on the way to me but if it is not good then I might try it for a week and will put it on eBay.  And will look for tube integrated amp.  

I have a pair of Quicksilver Mid Monos I bought used for $1000 and they are great amps.   They are good stock with EL34s but sound even better with KT66.   The best thing about them is you can use many different output tubes,  you just have to bias for each type.  They have been rock solid reliable and sound great .  Not my first tube amp, I've had several tube amps in the 40 to 50w range but the best value even new at $18965 I would consider them a bargain.

I am using my old Acurus 200x3 amp that been on the shelf collecting dust right now.  And will replace my ADCOM preamp with the AR LS7 that will be here on Tuesday?  I was thinking to keep my speaker for a year and if you guys think that I should get rid of LS7 and then purchase integrated amp to make better sound, I really like Cary SLI-80 and that might be the one I am going to get.  Suggestion please.  

you cant go wrong with Cary sli-80.

The Audio Research VS-55 is the answer!  This is the best bang-for-buck of any tube amp out there.  It can we had for around $1500 used--even less.  It's the lowest cost tube amp to re-tube of any out there.  I've had one for 4-years and I'll NEVER sell it!  My system sounds world-class for a fraction of the bucks of many of these audiophile setups.  If you're near San Diego, you can come by and audition it with me if you want.  I'd love to show it off.

btw, I did put it head to head with a McIntosh MC-75 and my VS-55 cooked it.  I was amazed!  I almost made a mistake by buying the MC-75 but the seller let me audition it in my setup first.  (Caveat, I have no idea what state the MC-75's tubes were in.  But I wasn't going to buy all new tubes for it to find out if that would improve it or not).

Now, all that being said, everything matters!  Source, speakers, preamp and amp--all of it.  I had to sift though a few pieces before I hit on this setup.  But, for me, the setup I have now is reference.  I will only change pieces out if it can improve what I already have by auditioning said piece before I buy it.  I've already made one mistake by going by reviews for a piece that didn't really cut it.

Thank you and now you makes me thinking again between Audio Research VS-55 with LS-7(sure will change to better preamp when I have more money) and Carry SLI-80!!!!!. 

Any other suggestion between this two options?

I have an ARC Classic 60 that was recently gone through by a tech I really trust. It used to be my main amp, but is used as a spare now. It sounds wonderful. They go for reasonable prices these days.

Well the ARC and Cary sound are very different. Both have their fans, but only you can decide whether you want the transparency of the ARC or the warmth of the Cary.

Thank you.

Had you looked into a rebuilt H/K Citation 2?

The Citation had/has excellent bandwidth even be today's standards. I mention this amp as it is still a contender and a fellow named Jim McShane is well-known for excellent rebuilds which will challenge any modern amplifier, and they seem to be at the right price point.