Tube amp for Sourcepoint 8?

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.

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. 

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.