Tube amp for Sourcepoint 8?

Well on paper it looks like they would perform very well with a good powerful (150-200watts) and clean musical sounding solid state amplifier. Although tubes are not out of the question here, so here again it needs to be a amp of at least 50-75 watts per side of magical tube power and very musical and clean electronics must be used.

From Stereophile’s measurements section of their review…

The SourcePoint 8's specified sensitivity is 87dB/2.83V/m; my B-weighted estimate was the same. The SourcePoint 8's nominal impedance is specified as 8 ohms, with a minimum value of 6.4 ohms. I measured the speaker's impedance magnitude and phase with Dayton Audio's DATS V2 system, but for consistency with Stereophile's presentation of impedance graphs for the past 33 years, I created fig.1 with the Audio Precision System One software. The speaker's impedance magnitude (solid trace) is greater than 8 ohms for almost all the audioband, dropping to 7.47 ohms at 120Hz. If this speaker is used with tube amplifiers, the significantly higher impedance in the treble compared with that in the midrange will tilt up the high frequencies. With the high average impedance, the equivalent peak dissipation resistance, or EPDR (footnote 1), is generally greater than 4 ohms, though it does drop below that magnitude between 197Hz and 341Hz, with a minimum value of 3.83 ohms at 242Hz. Even so, the SourcePoint 8 is an easy load for an amplifier.

It's an easy load, just not very loud.

Thanks guys..I appreciate the comments. I've read the reviews and seen the numbers, but that doesn't always tell the whole story. That's why I'm hoping to hear from someone who has actually heard the speakers in situ with a tube amp. 

As for loudness, in my current set up the volume pot is at less than half and it's more than I can handle...I can't imagine volume would be an issue with a push-pull tube amp in the 30+ watt range, at least for the way I listen. 

If you listen at low decibels (many of us do), then a normal 40-50 wpc push-pull tube amp should do you well. Most advisors (dealers) assume you will want the ability to turn it up really loud when they tell yo to buy a 300-500 wpc amp.

Yes, I rarely listen above 70-75 DB. I'm not looking to peel the paint off the walls, but  ideally I would like to add some body and texture without losing control in the bottom end. 

Quicksilver KT Monos...AWESOME amps with stock KT88s and deadly quiet, too. Plenty of power, drive, and bass that can drive 4 ohms no problems at all.

Thanks Bojack…Quicksilver gear is great, but I’m looking for an integrated.  No space in my NYC apartment for monos and a pre. 

BTW, have you heard the Quicksilvers with the Sourcepoints, or are you making an educated guess based on specs or similar pairings?

FWIT , there is a review of your speakers on the Darko site. They are paired with a Prima Luna integrated. Upscale Audio is involved and sells both Prima Luna and MoFi. It might be worth a call to see what they think. I like a tube pre with a SS amp, but they need to play well together. I understand you’re not looking for that, but maybe consider one of the better sounding hybrids. I have Rogue gear but the pre in the integrated falls short of separates. People praise Raven amps, you might contact them. Happy Hunting , Mike B. 

Mdemaio, totally get the limited space and was recommending the KT Monos as a current owner of these and the fact that they are a low-impedance design and thus will  likely play well with the Sourcepoint 8s.

What’s your budget, and are you looking for new or used?  It’s really almost irrelevant what tube amps other people have run with your speakers because their taste may be, and probably is, different from yours so really the thing that matters most is what specific sound characteristics you’re looking for from the amp. 

Pure tube amps usually do not have a tight bass unless you a bit more.

Normally, a tube preamp + SS amp would give you what you are looking for. So likely a hybrid tube integrated might be a good option.

The Krell k-300i integrated has a warm sound “…output up to 150Wpc into 8 ohms and 300Wpc into 4 ohms, with its iBias technology allowing the amp to deliver up to the first 90W in class-A…”(Stereophile)

If this speaker is used with tube amplifiers, the significantly higher impedance in the treble compared with that in the midrange will tilt up the high frequencies.

@soix This is a good example of how Stereophile comments are not always correct. If the amp is designed properly its very likely the output of the amp will not increase at all. This can be true even if the amp lacks feedback.

@mdemaio   Since this is a lower efficiency speaker of only 87 dB (quite common with speakers of this size) you will need some power. But you may not need all that much. I would expect a Dynaco ST70 to do quite well on this speaker. The load is benign so you have a wide range of amps that will do the job.

But just to be clear a lot will depend on how you play your system and the size of the room. My speakers in my bedroom system are the same efficiency and I drive them with a 5 Watt/channel integrated stereo tube amp that has no problems playing plenty of volume; in fact I've never run it out of gas. My bedroom is not that small; it takes up the entire second floor of my home.

Dynaco made a small integrated amp called the SCA35 which might be a consideration. I don't know if they still make it; if you get an older one it will have to be refurbished. But you could do that for under $1500.00.

Well, given you like the Exposure (nice amp BTW) and are just looking for a little more meat on the bones you might be looking for more of a neutral sounding tube amp rather than a more conventional and warmer “tubey” sounding amp.  I’d put the PrimaLuna more in the latter camp and would be a little concerned you might miss some upper octave detail and energy.  With what you stated you’re looking for I’d check out the Rogue Cronus Magnum iii for a tube amp and the Unison Unico series that are hybrid integrated designs with tube pre and MOSFET solid state amp sections.  Sound Approach sells the latter with a 10% discount and a trial period, which is nice.  Either should do a great job filling in what you’re missing in the upper mids while retaining what you like about the Exposure.  Just some ideas to ponder FWIW, and best of luck. 

GanFET amps have a “warm” presentation, but not sure if it’s offered in an integrated

Thanks for all the thoughtful responses, guys. 

Soix, we are very much aligned - the two amps that have risen to the top of the  consideration set so far have been the Cronus ("Dark" version) and the Unison Unico Nuovo (or Due). Just not sure how much of a step up they are from the 3510. I'm going to give the speakers another 100+ hours before I think about this at greater depth. 

Atmosphere, I have my dad's ST70 in storage. I had upgraded it with Curcio mods a while back, so it's a little less euphonic than the original (which works in my favor here). I wouldn't want a 50+ year old amp to be my main rig, but at least it can give me a starting point for differences. It's more likely that I'd have better sonic luck with a KT88-based amp than with the EL34s of the ST70, but I can at least contrast. 

Thanks again!

I'd suggest the Cary SLI 80HS and the Margules I-240. Plenty of tube power and sweetness. 

I currently have the Cary paired with Volti Razz, such a great combo for my taste. I like that Cary changed the rectifier stage to SS, (apparently helps with the syrupy nature of previous generations but keeps the warmth of the tubes). Also with the Cary one can switch between Ultra-linear and Triode mode on the fly.

I have heard the Cary with Sourcepoint 10's and enjoyed the session very much. It reminded me of when I worked at our local HiFi shop and we sold Cary and Tannoy. They were a very pleasing combo in my book.  

Thanks, Doyle. I love the Volti stuff - I got to hear a pair of Vittoras a few years ago at Rocky Mountain and was floored (that's where I first heard the Border Patrol DAC, which someone will pry from my cold, dead hands;).

I've always. been intrigued by the Margules. The 10s are a little more fussy in terms of pairing than are the 10s, but still manageable, I think, for either of the amps you mentioned. I appreciate the suggestions! 

I wouldn't want a 50+ year old amp to be my main rig

@mdemaio Why? As long as the power supply has been properly refurbished its a pretty competent amp and also reliable. Plus it can give a decent spanking to a fair amount of new amps.

BTW in the case of the ST70 the bias rectifier should also be replaced.

You can reduce distortion by installing an adapter to allow you to use a 6GH8 as a driver tube instead of the 7199 The 6U8 is the same as a 6GH8. No other modification required.

The weakness of that amp is the 5AR4 rectifier which can't really handle two pairs of EL34s at full power. But as long as you don't push the amp hard it holds up fine. 

Thanks Atmasphere. I've really only kept the ST70 for sentimental reasons (my dad built it when I was in utero). It sounds great, but runs hot, needs to be biased frequently, is cosmetically OK but not particularly beautiful, and most of all I don't have space for an amp and preamp. So it's fine for what it is, but it's not the long-term answer. 

It sounds great, but runs hot, needs to be biased frequently

@mdemaio If it needs frequent biasing there's something wrong with it. One of the things that can cause that is that bias rectifier I mentioned. The original is a selenium device which in short is terrible. It can be replaced with a UA4007 which is a 15 cent part.

If you are wanting an integrated tube amp this is what you're up against. The ST70 is a good minimum power for your speakers unless you are in a smaller room (which might be the case if space for the amp is that tight; if that's true skip the next part). The space needed to make that kind of power means that if the amp is integrated its going to take up some room (unless it has really cheap output transformers), more than an ST70.

Do you need a phono section? If no, you might be able to run everything through your DAC.

If you skipped the stuff above, a smaller amp will work if your room is smaller. You might be able to get by on only 15-20 Watts/channel. I mentioned the Dynaco SCA35 earlier; its compact and a nice sounding amp if properly sorted out (there may be new ones around too). You might also look out for a Sansui AU-111. Sansui made this amp in the 1960s but reproduced it in the 1990s due to popular demand. Very nice design and it makes 40 Watts/channel.