John Curl's Blowtorch preamplifier part II - Page 3656 - diyAudio
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Old 10th March 2013, 06:33 AM   #36551
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I guess I would come back as a cow then....
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Old 10th March 2013, 06:38 AM   #36552
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I guess I would come back as a cow then....


se
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Old 10th March 2013, 08:20 AM   #36553
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I guess I would come back as a cow then....
Or a sheep.
An electric sheep !
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Old 10th March 2013, 08:35 AM   #36554
RNMarsh is offline RNMarsh  United States
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Richard,
. I might not be a circuit designer but I do have a good idea what not to do when testing live equipment.
Its a headsup for everyone... your working on power transformers will eventaually lead to other areas for solutions which can be followed by readers of the forum. So for them it was meant. And, for all the other projects they build. -RNM
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Old 10th March 2013, 09:02 AM   #36555
bcarso is offline bcarso  United States
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Or a sheep.
An electric sheep !
Do androids dream of electromagnetic compliance?
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Old 10th March 2013, 09:39 AM   #36556
gk7 is offline gk7
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... In my recent experience, I tried adding one to improve the input noise for a certain limited number of MC cartridges. However, the distortion at the very low frequencies, finally put me off. No big deal, there are other, equally expensive approaches to do the same thing, and I can do them. ...
Well, I don´t argue with this as a design decision, but the test case was completely unrealistic.
BTW which levels of distortion would a non feedback MC stage (like in the Vendetta) produce
under the _very same_ test conditions (200 mV(!) in at 10Hz I believe it was) ?
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Old 10th March 2013, 11:26 AM   #36557
gpapag is offline gpapag  Greece
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Don't make a mistake while working on something like that, you only get one mistake and then you don't have to worry about that ever again!
I am a transmutated creature, charged for ever,after surviving an 145kV capacitance one side discharge blow.

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Been in effect since 2003. Ditto EU
Correct.
But whether UL rated or not, with time and use, HV circuitry and heat generating areas will suffer from dust attraction. My experience with dissecting damaged equipment, tells me that regular cleaning these areas would have prevented catastrophic and dangerous failures.

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Attached are the FFT results for six different transformers of different construction but all about the same ratings. They are imposing a voltage on the chassis as shown in my test setup (Prior Post.)

ES
Ed thanks for sharing.
Wide spreading of freq. peaks suggests edges on the waveform.
Studying the shape and location of distortion in the waveform may tell a lot.

The spectrum of the unloaded case indicated the magnetic core is saturated by the magnetizing (idle) current. Check the waveform for flat top and bottom peaks. Increasing ~10% the primary turns usually cures it.

3rd, 5th and 6th attached FFTs show quite a difference in loaded condition rel unloaded. I am not sure on this but I suspect close primary/secondary winding coupling and/or load is high for the trafo.

George

PS Test lead shown here
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.
form a large loop. This way your set-up is sensitive to other magnetic pick-ups in addition to the intended one (voltage across the chassis). Shielded separate leads may be better for the purpose.
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Last edited by gpapag; 10th March 2013 at 11:34 AM.
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Old 10th March 2013, 01:45 PM   #36558
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I guess I would come back as a cow then
Convince me you haven't already.
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Old 10th March 2013, 02:32 PM   #36559
Mooly is offline Mooly  United Kingdom
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Convince me you haven't already.
Been there, done that
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Old 10th March 2013, 03:06 PM   #36560
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Joao, I would appreciate it if you understood me better. OF COURSE, experienced musicians LISTEN and EVALUATE my products. They don't do it in the design process, how could they? But after the design is done, or even if the design is still a prototype, we will send a component out to music schools and such for evaluation. In fact, I am soon getting for my own use, a newly designed power amp that has been evaluated in just this way, and not only with other designer/audiophiles. We just sent another amp to Germany for independent evaluation.
However, personal approval from a symphony conductor or such will not cut much weight with this audience who think that virtually all good amps sound the same. ALL my amps and preamps measure very well, so many here think that they should sound the same as any other component that measures very well. It isn't my experience, but many here discredit my experience, as propaganda or hallucination. '-)
John, thanks for the explanation that I can understand your steps in the way of designung.

It's normal that most designer "idealize" their practice how it has to be done. Anyway what meaures very good must not sound good - sometimes there is a difference.

However,sometimes I like to get some statements during the prototype phase as well and it could be helpful.
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