Tube amps - what 3 things…

As a guitarist, I’m probably overly attached to tubes.  I own over 30 tube guitar amps.  I also own several solid state - digital and analog- guitar amps.  They’re inferior - except for portability and consistency. Tonally, there’s no comparison.  Tubes rule. 

I also own McIntosh, Prima Luna, Manley and several SS  Marantz - Ruby, Reference and a 2230 - hi fi stuff.  

The Manley Stingray  is EL84 based.  In guitar world, EL84 is known to be easier to drive, suitable for low wattage amps and possess a desirable chime at lower volumes.  The Manley fits the bill.   It sounds great, gets to the sweet spot without cranking it up but the bass response is weak.  EL84 based systems require efficient speakers.  Still, a great sounding integrated from Manley.  They build amazing stuff.    But I would probably pass on an another EL84 amp.  

6L6 is my favorite in both hi-fi and guitar sound.  It’s clean, robust, powerful and has a ton of headroom before it gets flubby.  Tubes are easy to find.  The McIntosh integrated is 6L6 as is the Prima Luna separate.   My main guitar amp, a Two Rock, uses 6L6.  In guitar world, what are considered the best clean tones are almost always 6L6 based.  

The Prima Luna integrated uses EL34, 6L6 or KT88.  The KT88 is a fantastic sounding tube but I stopped using them due to reliability issues.  They’re harder to find and their manufacture seems inconsistent.  I’ve had several crash on me for no reason other than I installed them.  But, when working, they were the most hi-fi, clean, round bass, beautiful mids of all the tube types.  

EL 34, which is very popular in guitar, is probably my least favorite in hi-fi.   They’re overly warm, with too much emphasis on the midrange.  But other people swear by them. They’re able to handle a lot of wattage and they’re known for their reliability in demanding, high plate voltage environments.  

My advice, if you’re young, is to buy whatever sounds best in your budge but try to get a system, like Prima Luna, that can handle different tube types.   If you get bored, just roll tubes,  it’s like getting a brand new system.  Chasing tone through tube swaps is a life long endeavor.  I have boxes and drawers full of old tubes.  It’s a great hobby.  Enjoy!!! 
 

Many great suggestions mentioned. I might suggest you watch Roger of Rogers High Fidelity YouTube videos on tube amps & what he feels are important. There are a few really good ones . He knows his stuff! Obviously, he’s also promoting his own brand but very worth it.

His offerings are relatively expensive but in his case, you get what you pay for. I have now for a year his EHF 200 Mark II integrated amp & it is outstanding! Very powerful w/great detailed beautiful tone w/ very good extension at both frequency extremes. It does run hot operating in full class A producing a true 100 watts + / channel but that’s the price you pay for that design & the sound quality it offers.  
 

I’ve owned tube amps & preamps for 40 years; Conrad Johnson, Audio Research, Melos, New York Audio Labs, Art Audio & enjoyed them all. The build & sound quality of Rogers handily beats them all. 
 

My thoughts on important aspects of a a tube amp are: 1- high quality, large power oversized transformers, 2- point to point wiring w/ good wire ( much easier to diagnose & repair should a problem occur) , 3- solid, non resonant  physical construction w/ high quality input & speaker connectors. 
 

enjoy the tubes! Warning once you go there, there may be no turning back. 

If you are planning to use a tube amp, do yourself a favor and avoid low impedance speakers. Your amplifier dollar investment will thank you.

Tube amps using output transformers can lose as much as an octave of bass response going from an 8 Ohm load (using the 8 Ohm tap) to a 4 Ohm load (using the 4 Ohm tap) and the output transformer will run hotter (since more of your output section power will be heating it, not a good use of that power). The amp will make more distortion too and the speaker cables will play a far more important role (and will need to be heavier).

In the old days when tubes were the only game in town, speakers were much easier to drive- they were more efficient. Efficiency is helpful because you get less thermal compression in the voice coils- a more vivacious sound results (IOW this is both measurable and audible).

So a speaker of 8 Ohms (particularly in the bass, so be careful of speakers using dual woofers that might be rated '8 Ohm compatible') or better yet 16 Ohms, along with higher efficiency (+90dB) will help you get the most out of your tube amplifier investment (this is helpful for transistor amps too, since they also make less distortion into higher impedances...).

If you are planning an SET, its helpful to be aware of what you're getting into: If you want the most out of an SET, your speakers must be so efficient that the amp never makes more than about 20-25% of full power. At power levels above that, the higher ordered harmonics start to show up on the transients (where the power is), causing the ear to perceive the transients as 'louder'. This is why you read so much about how 'dynamic' SETs are; it really distortion masquerading as 'dynamics'. To avoid this you need a speaker efficient enough to prevent this phenomena occurring. Of course, SETs have troubles with bandwidth when built to make more power; usually the bass is curtailed in favor of higher frequencies in the output transformer design. This is why the lower powered SETs are known for better sound.

My advice is that the mark of a good system is that it doesn't sound 'loud' even when it is. The dynamics comes from the recording, not the electronics! To that end, the speakers must be easy to drive so that the amplifier is spending most of its time loafing.

@hilde45 My experience as well. My PrimaLuna has been EXACTLY like owning a solid state amp with maintenance so far. None. I have had it 3 years with average amount of use. I haven't changed a tube yet. It sounds GREAT.  I would not want to mess with manual biasing.