John Curl's Blowtorch preamplifier part III

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Tournesol said:
I am really shocked by the way Mr. Marsh was treated here. He has, probably, made more measurements than most of us, here, and i doubt many are so well equipped with measuring instruments than him: it is obviously his passion.
A number on an instrument is just raw data. To turn that into a measurement you need to add correct interpretation. It is the interpretations we sometimes question, not the number displayed on the instrument.
 
No. All sorts of rationalizations ----- I dont use dblt only because it doesnt work for ME. I have to listen to my system and I do not take advice on what something does or does not sound like or will sound like. I listen and decide for myself on my own system, only.

That says it all right there, too much to lose. Decide on your own system only as long as you have the answer ahead of time. DBLT has nothing to do about your own system or any "advice" on how something should or should not sound, it just means you don't know.

At least thanks for clarifying that none of your opinions are based on anything more than the usual uncontrolled sighted listening tests.
 
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From what I have read, the Orange Drop and similar caps are made by winding on a hollow bobbin, then squashing them. This leaves the construction less tightly wound than straight wound (cylindrical caps).

Wouldn't this result in worse distortion for the orange drop vs cylindrical caps?

Good question.

No. In fact it is just the opposite....

The best caps are those which are annealed and this process requires the cap maker to heat the cap to just the narrow window of the films plastic state.

At that point it is pressed to get out all potential air gaps or air bubble between layers which is a source of breakdown and poor reliability. When cooled this piece is now a solid bar of plastic film.... very tight and fused solid.


THx-RNMarsh
 
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That says it all right there, too much to lose. Decide on your own system only as long as you have the answer ahead of time. DBLT has nothing to do about your own system or any "advice" on how something should or should not sound, it just means you don't know.

At least thanks for clarifying that none of your opinions are based on anything more than the usual uncontrolled sighted listening tests.

Thats fine to say. I have the choice to do it either way and i choose the one which works best for me and allows me to do more in less time. Maybe with more mistakes but enough successes to opt for the time element. I do not need to be perfectly right all the time... to make real progress even.

Now if it was life and death issues or a scholarly work for publication.... Ok. Or high dollar invested. OK. or my job is on the line. In other words-- important enough to need near 100% certainty..... Otherwise, i'm taking the fast route to get where i want this to be and I have learned how to make it successful most of the time.

And nice spin in the comment.... broad stroke painting. I do a lot of testing first. Listening last. Not just listening, only.

Feel free to ignore anything I say as merely guess work.


-RM
 
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Bought an Teac UD503 USB dac (it has an isolated USB input) :)
The question was about how to totally isolate each element of a system to avoid any parasitic leakages (ground loops).
I have CD, DAT, minidisk, Revox, Nakamichi, PC, Preamp, active crossover and filter with DAC, amps.
Jan Didden pretend it is easy. But he did not propose any solution.

What I have done:
1- Switch the grounds of the analog Equipements in my preamp, in the same time than the signal inputs.
2- Chose the AC sens of each power plug to minimize the phenomena.
3- Use digital optical connexions when it is possible.
What i will do:
1- Replace the PC with an other digital source.
2 Replace the big linear power supplies of my amps with switching ones.
But, as i have limited financial ressources ...

May-be i will consider to modify each analog gear to be totally symmetrical.
But 600/600 transformers has their own flaws and are expensive, and active is not so efficient. I tried SSM2142 etc, but was not fully satisfied with the way they sound.

PS: I am not interested in comments that says the problem does not exist. Or that i have HF oscillation problems in my amps
 
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But Richard, what you have just described is your 'preference'. Unfortunately what often comes out is preaching 'this is the only way'. No one has a problem with preference, as it's a hobby after all.

it may seem that way from short sound bites here. But trust me a lot has gone into it... testing mostly and for years -- then i drop the bottom line only.

I am old... not going to spend my last years going back and covering the details of why and how. just cant and dont want to. So, just realize I did more than it appears. you can then think about it or try it or what ever with it.


THx-Richard
 
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Somewhat on-topic. Was cleaning out stuff, found my notes from a distant AES convention, a presentation on capacitor non-linearities resulting from - gasp - electro-mechanical forces in a wound film cap. I cannot remember the presenter but it was possibly Clarity cap.

The measurements were done on a 4.7uF wound film xover cap with a laser vibro-meter.
My notes say:

Measured mechanical effects at the top of the audio band (14-20kHz);
Compression from internal electrostatic forces due to voltage on layers: compression 10's of pico-meters; forces of 6.5N inside, 23.3N outside. Internal forces cancel due to each layer seeing two opposed forces.

Electrodynamic force due to current flowing inside the 'sheet' much less, ball-park 1.3 x 10^-5N.

Main mech resonance caused by 'squeeze' from outside layer. As force is always attractive, the vibration is at double signal frequency.

For whatever it is worth, but should be good for another 10k pages here. Am looking forward to the 1st guy who sees money in non-compressive capacitors ;-)

Jan

Good memory jogger for me ... I noticed the effect as changes in C. wrote a paper showing C changes with freq of compression etc. I'll see if i can find it. IMO comes from loosely wound cap construction. isnt there with the annealed and compressed caps. Only ones wound very fast which traps air between layers and makes plates possible to move.

Also known as a microphonic cap?

side note -- one way to reduce cap costs is -- time is money -- make them (wind them) as fast as possible. High thru-put. But this traps air between layers. One of several reasons REL Caps (and some others) are more expensive is slow, tight winding. And annealing time. many dont do that at all. ... really time consuming.

THx-RNMarsh
 
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Sorry, these grounding issues are funny and they just complete the image.
PMA, when you will have 50% of my experience and background in the domain of professional recording and audio design, my professional area, i will take care of your comments.
Welcome, you too, in my ignore list (4 inputs now). Just let me say you something, as an answer to your ad hominem : I have made a little tour on your web site and many inputs from you in this forum: nothing new, nothing interesting, and a very agressive attitude.
 
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^ Honestly no one cares. Just block whomever you'd like and don't respond to them. The more you make a deal out of it, the more you just look like you're interested in drama. Plus, professional recording and audio design folk aren't the only ones with grounding issues. Pretty sure PMA worked on power electronics, which means that ground is a part of the circuit versus a triangle at the bottom of the schematic. ;) I.e. don't be so quick to dismiss people out of hand and try to pull the experience card. Too many people can call you on that.

As to your grounding problem: have you successfully broken it and now need to find a less intrusive way to do so or are you stuck on the first part?
 
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Ground loops are a fact of life when dealing with Class I equipment. I would just avoid using unbalanced I/O.

Nowadays, ground loops are not an issue for most normal consumers as they are using HDMI sources into their AV receivers (mostly Class II anyway), which drive their speakers.
 
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Ground loops are a fact of life when dealing with Class I equipment. I would just avoid using unbalanced I/O.

Nowadays, ground loops are not an issue for most normal consumers as they are using HDMI sources into their AV receivers (mostly Class II anyway), which drive their speakers.

Most? Are we forgetting how many now also stream off the internet? Another grounded system.


-RM
 
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