Output tube types - need some opinions


I'm starting to think about my next DIY project and would like to build a push-pull tube amp (monoblocks) with a single pair of output tubes. I do not plan on using any global feedback, but will probably include the option to run ultra-linear if the tubes support it. 

I don't have much experience with different tube types, so I would like to get some opinions about differences in SQ strengths and weaknesses of different types. I am currently using a pair of 300B parallel SET amps I finished last year (see my virtual system for some details) and like what they do. For this next amp, I'm hoping for more headroom (at least 30W), a bit better macro-dynamics, and maybe a touch less warmth. 

I'm not looking for kit suggestions. I plan to build these amps from scratch. But I don't want to work with voltages any higher than 600V which rules out some options. 

I listen mostly to jazz, folk, electronica, classic rock, and enjoy vocals. Excellent vocal performance is probably most important to me, but nice soundstage and decent imaging is also a priority. I use powered subs to cover the bottom couple octaves, so deep bass performance isn't too important, but good midbass performance is. My high frequency hearing isn't what it used to be, so extension out to 20khz and beyond will be lost on me. 

I've been thinking about using KT150s but I don't really know whether these are a good choice. I would appreciate some help deciding. Thanks. 

128x128jaytor

Showing 2 responses by jasonbourne52

I recall a magazine article from years back about building a PP 300B amp using output trannies from a HK Citation II. It might have been in Vacuum Tube Valley. This would be worth checking out! It was an impressive article!

Since you've already worked with pairs of 300B's I suggest building some amps with a pair of 300B's in PP. This configuration will give you about 25 watts of triode power! Using the common tetrode/pentode types (6L6, EL34, 6550, KT88 ...) requires feedback for low distortion/linearity. Then problems arise with instability due to feedback. Stick to triodes! Get the best output trannies you can afford - like Tango/Tamura. The output iron is the limiting factor in any tube amp's sound quality - much more so than the brand of the output tubes.