Tube Amps Watts vs SS amp

Roberjerman, I went back and looked at the Heresy's timeline. It does date back to 1957 but it was called the H 700. It was given the Heresy name with an update in 1972 which was probably the year I got them as they were marketed at the time as new speakers. The K horn is the longest running production speaker of all time! I remember listen to them at the store I eventually got the Heresys at. They were being powered by Marantz Model 9 mono amplifiers and a Model 7C preamp. The turntable was a Thorens TD 124 with an SME arm. I don't remember the cartridge. That was the absolute State of the Art at the time. It had no problem doing realistic volume levels.

My understanding is that the concept of “bandwidth” is very important. Perhaps more important for tube amps than solid state. But I have a First Watt SIT-3 which is a low watt solid state amp. It apparently has some bandwidth to it because it drives my Magico A3s well. They have a sensitivity of 88dB, an impedance of 4 ohms and recommended minimum power of 50 watts. The SIT-3 drives them just as well as my Bryston 4B3, which has a lot more power. But what I would like to know from the group is: how is bandwidth measured? How do you calculate bandwidth?

Bandwidth is important to keep phase shift at a minimum. To this end, phase shift is minimized if bandwidth is 10x the maximum frequency to be amplified (20Hz, so 200KHz required) and also 1/10th the lowest frequency to be amplified (20Hz, so 2Hz response required). Bandwidth is measured by either a sine wave or square wave; with a sine wave the signal is applied to the circuit and the output observed to be within usually + or - 1/2dB to be considered ’flat’; with a squarewave rounding of the edges can be seen to show a rolloff at high freqencies and tilt on the top of the squarewave shows a rolloff at low frequencies. This is fairly easy for transistor amps, and there are tube amps that meet the ’2Hz-200KHz’ requirement too, but to my knowledge they are all OTLs (Output TransformerLess).


Keeping phase shift linear has to benefits: more accurate presentation of the soundstage and more accurate presentation of tonality. As an example of the latter, if there is a rolloff at 10Hz, phase shift will cause a lack of impact up to about 100Hz despite the amp measuring flat to 20Hz on the bench. This is why if there is a problem at 50KHz it can often be heard as well, since phase shift artifacts will exist down to 5KHz. Again, this will be interpreted by the ear as a tonality.


So one takeaway: three things affect tonality: actual frequency response (which is different from bandwidth), distortion and phase shift. 

The tubes vs SS discussion should focus more on the type of music one prefers rather than the technical merits of each amp. I have multiple tube and SS amps that I interchange frequently. If you primarily listen to Jazz, voice, acoustic music of any kind there is nothing better than a quality tube amp.

The only time I would caution someone about moving toward tubes is if they primarily / exclusively listen to rock & roll at higher volumes. i don’t feel the benefits of tubes are realized in that case. I prefer listening to that type of R&R music on my SS amps. But that being said, most guitar amps use the EL34 tubes so when I listen to earlier R&R with guitar emphasis they sound more live on my EL34 amp.

The reason tube watts seem louder than SS is not because tube watts are more "powerful" but because you can listen to tube amps louder than SS without as much fatigue. The listenable / enjoyable wattage range of tube amps is greater than an equal SS amp.

I would also recommend an EL34 tube amp as a starter / first tube amp because the EL34 really hits the sweet spot of tubes. If budget is any consideration, you can buy a quality used one very reasonably and latter upgrade to a new tube amp if you find that tubes are for you. That is what I did and got a very good price on a Cary V12R EL34 amp and then latter bought a new tube amp. I still own the V12R and enjoy it daily.

I have two listening systems one with difficult to drive speakers. I bi-amp them both with a tube amp on top and a SS amp on the bottom pushing the woofers. This works very well with difficult speakers that demand more power.

This is what you want.  Monobloc pair at $125 watts each.

http://www.tubes4hifi.com/bob.htm#M125

You can buy it as a kit and build yourself, saving a fair amount, or buy it fully assembled and tested.

kit - no tubes:  $1778
kit - with tubes:  $2213
Wired - no tubes:  $2595
Wired with tubes:  $2935

Wow, what a thread!  OP, there is a ton of misinformation here.  Read some articles by experts to get an answer to your question.  I'm not an expert but I do know that with a tube amp, it isn't about the wattage, it's about the output transformers, and their bandwidth and power output.  

But, the real question you are asking is about those particular speakers with tube amps.  This is the right answer! 

05-07-2019 9:17amyogiboy2,778 postsYou are better off using that speaker with solid state. It is not an easy speaker to use with tubes!
http://www.thevintageknob.org/acoustic_research-AR9.html

As it happens, I have a Primaluna HP Integrated tube amp that I love, and think sounds fantastic with every speaker I've heard with it.  It puts out close to 100 watts with KT150 tubes.  

However, a local friend invited me over to listen to his AR9s.  He has them connected to vintage NAD mono blocks and they sound great in his room!  But, he is thinking about updating his amps to tubes.  His dealer brought over a Primaluna HP Integrated to listen with his speakers.  

It was not a good match.  I don't know the technical reason - it was definitely plenty of output power.  But the bass was kind of flabby and weak, and overall the speakers sounded flat and uninviting.  I was shocked.  This amp has never sounded so poorly with any speakers I've heard.  

The dealer wanted to bring something else along to listen to.  So, he connected an Anthem STR 200 wpc integrated, with room correction, and the speakers sounded much better.  Tight bass, smooth overall sound, and really good overall.  

Hooking the NADs back in the mix (I think they are 200 wpc) and the sound was very similar to the Anthem.  The speakers sound fantastic.  Deep, taut bass, wonderful midrange, just fantastic.  I was shocked that the SS both beat the PL.  The NAD and Anthem had very similar sound signatures, and worked very well with these speakers.  He decided to keep the NADs and save his $4500.  Instead he had the NADs refreshed with new caps, etc.

Point is, as pointed out by @yogiboy these speakers aren't a good match for tubes.  At least not Primaluna tubes, which I consider to be top notch equipment.