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Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
I find it a bit odd that a selling point for these new devices is that they introduce a lot of the rich harmonics you enjoy from valve gear. However, for another application, I've been digging around into the development of valve amplifiers in the 50's, and one of the great advantages of the beam tetrode, KT66 and the like, was that it could be used in so-called 'super-linear' mode. The screen grids were powered not from a fixed supply, but from 43% tappings on the output transformer, which straightened up the transfer characteristic. So the valve and amplifier designers thought straighter was better! Just sayin'.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Dr. Slack wrote ...
I find it a bit odd that a selling point for these new devices is that they introduce a lot of the rich harmonics you enjoy from valve gear. However, for another application, I've been digging around into the development of valve amplifiers in the 50's, and one of the great advantages of the beam tetrode, KT66 and the like, was that it could be used in so-called 'super-linear' mode. The screen grids were powered not from a fixed supply, but from 43% tappings on the output transformer, which straightened up the transfer characteristic. So the valve and amplifier designers thought straighter was better! Just sayin'.
I was under the impression (and I'm no expert on valve amps) that during the 50's 'push pull' amps became common because they were more powerful, but they did introduce some distortion (compared to 30's style 'single ended'). I understood that the 43% (or whatever) was to correct the distortion from 'push-pull'.
I'm using a beam tetrode 'voltage regulator' tube in a single ended amp I'm building as they are supposed to be extremely linear. It is the first valve amp I've built, though.
EDIT: I'm not sure how much the 'rich harmonics' bit is just 'audiophile speak', to appeal to people who prefer the sound of valves. Silicon is generally far from linear, always has the associated forward voltage drop, and takes time to respond.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
I'm with Dr.Slack ! How many other new components have added distortion as their main selling point ? push-pull was both for increased output power and reduced harmonic distortion 'super-linear' (Ultra-Linear) was for even lower distortion (high power, wide frequency response and low distortion were the selling points for amplifiers!) so for design engineers the goal was a wide flat frequency response with minimal distortion BUT various folk liked the 'sound' of particular amplifiers class-A with rich even harmonics seem preferable (odd harmonics sound harsh, even harmonics make a tone into a pleasant chord with a rich mellow sound)
even today with almost perfect solid state amplifiers and A/D, different microphones that have definitely non-flat frequency responses are used for their particular sound.
This kind of discussion usually goes nowhere because engineers are 'trained' to go for flat frequency response with negligible distortion but audio is a subjective thing.
Since my hearing has long ago lost Hi-Fi ability it no longer matters to me.
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
Sulaiman wrote ...
BUT various folk liked the 'sound' of particular amplifiers class-A with rich even harmonics seem preferable (odd harmonics sound harsh, even harmonics make a tone into a pleasant chord with a rich mellow sound)
As a poor impecunious student, I gradually built up my hifi gear bit by bit, so at one stage I had a decent deck, decent amp, and a pair of tiny unmatched car door speakers. I had one particular track that sounded glorious, Annie Austere from The Prince of Heaven's Eyes. A year later, I looked forward to listening to it through my newly-built KEFs (50 watts, 120 litre cabinets). This was gunna sound good! I turned it up, and it was OK, I turned it up some more, and kept turning it up until my ears were hurting, and it still just sounded OK. A quick A/B test with my tiny old speakers confirmed that the glorious sound was the swathes of distortion from the little speakers thrashing themselves against the endstops. Ho hum!
@Ash, no offence, but even allowing for the fact that valves might have a tame and repeatable distorting charcteristic that sounds pleasing, why anybody would use a tube for a voltage regulator, or power supply rectifier is beyond me. It can only be for the bling of having extra warm bottles to show off. Now you're not you're not going to get that bling with these new, presumably field-emission cathode, vacuum devices.
Registered Member #11591
Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556
The only two positive things I can think about Vacuum Tubes, are very low susceptibility to EMPs and the visual appeal. (These are good enough for me) Extra distortion (which I cannot hear) isn't a particular selling point!
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Low power tubes
