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In Reply to: RE: Went to a hifi show today in Switzerland... posted by Disbeliever on October 21, 2014 at 05:27:21
The engineer didn't say HOW the transistors get low distortion...it is with copious amounts of negative feedback! Read Crowhurst and others about the effects that has on subjective sound.
Your numbers, especially for preamps, are way off...there are a number of good tube preamps on the market that will produce less than 0.2% distortion and even a goodly number of tube amps that will do so at low power.
Low distortion is a red herring anyway when pursued with the wrong strategy to reduce it (i.e. lots of negative feedback).
Triodes are MUCH more linear than any transistor...its fact not speculation. Combining more and more non-linear devices does not make a circuit magically more linear. It is ONLY through the use of negative feedback that it a complex transistor circuit can be made to behave.
Which hybrid did you use? Give names or stop pretending.
Enjoy your underdesigned JOB...I am sure you will tire of having weak bass due to a weak power supply.
Follow Ups:
For Morricab:I refer you to my previous answer to your statement 7th April 2014. I answered you fairly but you decided that Geddes et al overode any other arguments.. What Geddes has discovered is neither new or unusual but is however contextual. So I will make a suggestion and you work it out for yourself and not let others do it for you. The music you listen to has gone through many stages, one which is the control desk. This has many op amps.I.C's using bucket loads of negative feedback. These devices are for the most part unconditionally stable even at unity gain, that is with 100% feedback. many WELL designed amplifiers are using a similar architecture as the op amp and the feedback used does other things than just reduce distortion, we know about crossover distortion so run the output in a few watts of class A before driven into AB or B this is all very basic, you seem to want to take matters out of context to prove your position, like the assumption that valves are not used with negative feedback, they are, regularly but in the pre-amp you cite uses current negative feedback that is undecoupled cathode reesistors and often with global feedback. Some very good pre-amps like Audio Research use hybrid configurations with transistors where this would enhance the overall performance. You can readily find adverts for single Triode O/P amplifiers which regularly exhibit up to 10% distortion at full power and around 5-7% normally, yes I know sounds just like dads old radiogram easy on the ear, but that is also because the frequency response is limited to not much above 10-12 kHz and is rich in second harmonics much favoured by the ear... I suggest you look at the time Geddes wrote his papers, today we have exceptionally fast transistor devices and Mosfets which enable amplifiers to operate up to much higher frequencies without the kind of difficulties that Geddes was referring to. Stating that feed back is bad shows a kind of stubborness, you must check your references in the right context. You, with respect are not the only man in the world that has good hearing as if I have even to mention this. Humble
Edits: 10/22/14
I will pass on your comments to the electronics engineer. The hybrid preamp long long time ago was a Radford SC-22, I believe the first hybrid. I have criticised the weak power supply of the Job 225, IMO 225 VA is insufficient, I will get it modified if necessary.
Edits: 10/21/14
"I have criticised the weak power supply of the Job 225, IMO 225 VA is insufficient, I will get it modified if necessary.
"
IMO, that product is a fail for that reason...even if it sounds good, which I doubt it does.
The amp arrived today ,just set it up, from switch on it sounds better than my old stereo amp from cold, will have to see how much it improves over the next few days.
Edits: 10/22/14
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