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Old 25th October 2012, 01:19 AM   #5501
Salas is offline Salas  Greece
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Good news. Don't give up on the follower transistor yet, if it can fit in steadily, it boosts the performance. You may do a before and after listening test and decide better when finished. Can you upload a shot of your interesting total configuration?
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Old 25th October 2012, 06:35 AM   #5502
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Normally the R core gives better mains isolation due to completely separate primary and secondary

It seems that's rarely the case. From what i understand most R-cores are wound in a balanced manner.
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Old 25th October 2012, 09:10 AM   #5503
AndrewT is offline AndrewT  Scotland
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That's what I have read when the manufacturer divulges his trade secret.
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Old 25th October 2012, 10:30 AM   #5504
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A while ago I compared an R-core transformer with some toroid transformers in an experimental tube preamp project. Although R-cores have much lower capacitance between primary and secondary, there was not a big difference in sound quality between the R-core and a toroid of about the same VA rating. But there was a distinct difference when I compared bigger VA ratings. The bigger the transformer the better the sound! And this was not by a small margin. This pre was never built but I ended then with a 500VA (230V sec.) toroid with fast rectifiers and only about 50uF of smoothing capacitance before the voltage regulator and it sounded wonderful!

Peter
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Old 25th October 2012, 10:47 AM   #5505
mikelm is offline mikelm  England
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Hi Peter,

Any theories about why the bigger transformers sound better ?

Does this extend to Power Amplifiers also ?

My only comparison of transformers was between similar specified torroidal & EI transformers when developing a power amplifier. They were about 200VA & 18VAC + 18VAC. In this A/B comparison the EI transformer sounded MUCH better.

These days I always used comprehensive filtration in all legs after the bridge and this makes the different types of transformer almost indistinguishable but I am interested to understand your findings more.
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Old 25th October 2012, 11:36 AM   #5506
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Hi Mikelm,

Yes this also extends to power amplifiers. In power amplifiers it is better beef up your transformer than to enlarge smoothing capacitance (generally). I can not proof that with theory, but I think that it is an advantage to have fast charging times. So: big transformers, fast (soft recovery) rectifiers and just enough capacitance.

Peter
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Old 25th October 2012, 12:43 PM   #5507
mikelm is offline mikelm  England
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Well, Peter that is an interesting perspective which I will definitely check out . . . . but it makes be laugh a little bit to hear this because it is so different than that which I would expect to be the case but I know from experience that I can believe your advice.

My personal PSU philosophy is more along the lines of " if the type of transformer can make a difference . . . . then the post transformer line regulation measures to filter out mains noise / diode switching / secondaries resonance etc . . . just aren't working well enough ".

Funny we should chat again today because only yesterday I was trying to implement a LM285Z-2.5 that you recommended to me when we were discussing LDR volume controls. Only in this case I could not get a good result from it - in fact in this case - a green LED gave much better measured result. I will PM to you - perhaps you can tell me if I made an error.

thx

mike
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Old 25th October 2012, 06:43 PM   #5508
RCruz is offline RCruz  Switzerland
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. But there was a distinct difference when I compared bigger VA ratings. The bigger the transformer the better the sound! And this was not by a small margin. Peter
I do agree with you.... That corresponds to my findings
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Old 25th October 2012, 09:01 PM   #5509
orelli is offline orelli  Italy
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+1
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Old 25th October 2012, 09:03 PM   #5510
orelli is offline orelli  Italy
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also paralleling two secondaries help the sound (of the same voltage, of course)
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