First foray into tube amps

treepmeyer

Pure Audio Project speakers are terrific, and a great value for the quality of sound they produce. I'll be adding another pair of speakers (high sensitivity) later this year, and they will be on my short list....as will Volti.

The important thing with the Pure Audios is to find out which tweeter design you prefer.....horn, Voxactiv full range, or 10" coaxial. They all sound very different, though I usually lean towards the horn or the new coaxials

Reading through the posts here, I can see how it can seem intimidating. But think about it this way... you could easily asked the question about buying your first solid state amp or preamp and gotten similar detailed and contradictory information. Looking at your first post... you had a good short list. 

The most important step for you will be to use your best judgment and get your first tube amp. After nearly forty years of solid state amps I bought my first tube amp about ten years ago. I am soooo sorry that I did not do it earlier. I have experienced no failures. I have changed to tubes in my amp once. All of my components have been tubed for the last seven years of so. I would never consider going back to solid state. 

So, my recommendations are to do it. Once you own one... well, the difference between zero experience and owning and using one is the biggest step you will ever take. Your level of experience goes from none to nearly infinite more than zero. Stick with highly reputable companies... Audio Research, Conrad Johnson, or MAC and go from there. 

Basically, tube amplification achieve even harmonics and more pleasant listening so some people say.  And solid state produces odd harmonics which some people say is edgy and not as comfortable to listen to. But very good solid state amplifiers are really quite good to listen to if done well.

@emergingsoul This isn't correct. The difference is that tube amps make lower ordered harmonics which are able to mask higher ordered harmonics. Solid state amps that sound harsh and bright tend to suppress the lower ordered harmonics (2nd and 3rd) and so can have unmasked higher orders. In addition, the use of feedback can result in distortion rising with frequency above a certain point (often around 1KHz) due to a more mysterious property called Gain Bandwidth Product (or actually the lack of it), where the feedback employed is not supported in the design well enough, so at some frequency the feedback decreases on a slope, thus causing distortion to rise and thus be unmasked.

What this also means is that if the designer understands this and knows what he is doing, he can design a solid state amp that will be just as smooth and revealing as the best tube amps. 

@treepmeyer Depending on your room size, you might want to consider a more efficient speaker. Your speakers are 87dB, which is on the low side of things. In a smaller room you might be fine but in a larger room you could easily run a 50 Watt amplifier out of gas.

This is important because if you really want to hear the 'magic' of tubes the best way to do that is with lower powered amps, due the effects of the output transformer (there are also output transformerless amps to which this does not apply). In a push pull amp the sweet spot is about 20-25 Watts. At this point you've got some power to play with and the output transformer can have very wide bandwidth. This is important because if you want to limit phase shift (which robs bass impact in the lows and can cause colorations in the highs) you have to have wide bandwidth, since you can't apply enough feedback in a tube amp to correct the phase shift otherwise. 

There's no reason that a speaker that is 10dB more efficient would not also be just as revealing. It will be larger though. A speaker 10dB more efficient needs 1/10th the amplifier power to make the same sound pressure. That means a 50 Watt amp on your present speaker could be replaced by a 5 Watt amp if the speakers were 97dB. 

There have been some comments about SETs. Two things you need to be aware of if going in that direction:

1) Most SETs cannot make full power in the bass- to get the most out of them, bass frequencies should be prevented from entering the amp. The reason for this is technical, having to do with the output transformer. I can go into depth on this if you like.

2) If the SET is zero feedback, only about 20-25% of its power can be considered useful. Above that level, harmonic distortion will cause the amp to sound 'dynamic' (if you've read about how SETs sound so dynamic this is what I'm talking about; its an interaction between the way the ear perceives harmonics and the distortion of the amp; I can go into more detail). A push-pull zero feedback tube amp has much higher usable power- more like about 90%.

You will probably read about how 'engaging' SETs are. This can be quite true, but if a push pull tube amp is properly designed, it can be every bit as engaging and musical with no downside. 

Good Luck in the quest!!

@atmasphere I think you are right about the speakers.  I almost gave up on trying a tube amp after reading Agon comments on your GaN monoblocs.  There was a good price on a used pair on TMR, and if I did that I could keep my LS3/6’s.  Someone beat me to it and I am back to thinking about more efficient speakers, like the Volti Razz, a Klipsch Cornwall or a Pure Audio Project Duet.

I like the Stirling LS3/6 but I am for now committed to the Bacch4Mac crosstalk elimination system from Theoretica.  That works best speakers that have a narrow dispersion, which the Stirlings don’t.  I think the Duet and Cornwall fit the bill, not sure about the Razz.

Then, after sorting out the speakers, I can return to the amp issue and have many more options, including SET amps.

Thanks for your comments, and to everyone else on this thread.  I’ve learned a lot.

@tuberist 

I second the motion. However, the Galion TS120SE may be on back-order until September. Mine are driving Cornwall 4's.