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SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream. |
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SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream. |
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In Reply to: RE: Nobody here ever said tubes don't need break in. (nt) posted by morricab on August 25, 2015 at 15:33:54:
The problem with early transistor preamps was lack of dynamic range which tubes are superior by default. Better silicon technology has greatly improved this however I will agree a tube mic preamp is still superior. It's the old question of if modern transistor preamps are good enough. For most pro applications, they are.As for single ended amplification, I was referring strictly to SET power amps. Look at any OPAMP circuit. Sure they are push pull output but the VAS stage is most always single ended. I am not denouncing single ended amplifier stages at all. I am denouncing $10,000 plus SET amplifiers with greater then 10% THD at a few watts of power and poor PSRR to boot! They are only made commercially by very small manufactures and sold in very unique stereo shops - often on special "made to order" policies. Not to many people buy them hence the cult status. Outside of table radios and low cost TV output stages, the audio industry abandoned SET since the 1940s and there is no evidence of it ever coming back en masse.
The Otala feedback theory is a farce and has been denounced many times since it's publication.
The physics and electronic theory is dead on. You cannot correct a fast rise time signal by measuring it after the distortion is applied. TIM can be demonstrated in most any feedback amplifier using a cheap square wave generator. And many audio magazines have shown the scope shots. But for all the electronics genius of Otala, many have overlooked the 800 pound gorilla in the room.
Show me a musical instrument or any natural or man made sound that can produce a fast acoustic rise time at over 10khz in our 15psi atmosphere? Beyond that show me a mechanical microphone that can respond that fast if such a pressure wave was even possible.
While TIM is real and can easily be simulated, no audio amplifier will ever be called upon to reproduce such a signal in sound reproduction. TIM in audio amplifiers is an academic exercise, nothing more.
The real issue with early transistor power amps was crossover distortion caused by early semiconductor limitations. This is no longer a problem for at least the past 20 years.
Otala's work did however bring to our attention stability issues. His work led us to superior feedback compensation design. This is why HF square wave testing is still very important in audio amplifier design, especially with today's commodity wide bandwidth power transistors.
Read Morgan Jones, Douglass Self, Rod Elliot, Randy Sloan for power amp design expertise. I have and my power maps, a 9.2.4 HT system are all DIY. I built some tube ampssp over the years as well.
Edits: 08/25/15 08/25/15 08/25/15
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Follow Ups
- RE: Nobody here ever said tubes don't need break in. (nt) - gusser 20:43:22 08/25/15 (1)
- RE: Nobody here ever said tubes don't need break in. (nt) - morricab 01:17:23 08/26/15 (0)
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