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Author Topic: A quandry from the Mackie manual.  (Read 7820 times)

John Roberts {JR}

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Re: Correcting wrong information
« Reply #20 on: April 19, 2011, 09:53:17 am »

You got corrected because what you posted was completely wrong. In these forums the difference between correct and incorrect information actually matters. Sorry if that offends you.

Mac

It doesn't offend me at all Mac, what offends me is the presentation of said correction. There is a tactful way of correcting someone and labeling my post 'stupidity' is not a tactful way of doing that.

I appreciate that my knowledge has been challenged and I learnt something from this today, I also take back what I said about not caring. However I don't deserve to be called stupid because I accidentally slipped the wrong information whilst trying to be helpful to the OP.

If that is your idea of knowledge, I guess I was challenging it. I'm sorry if I appear harsh to you, I was not trying to hurt your feelings, but more concerned about informing the larger audience. If misinformation is not corrected promptly, it becomes somebody else's incorrect knowledge. 

I'm glad your learned something, I did too. Apparently Alto mixers are so poorly engineered that their own mics kill them. 

JR


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John Sabine

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Re: A quandry from the Mackie manual.
« Reply #21 on: April 19, 2011, 11:55:09 am »

I've actually gotten some inexpensive microphones in that had unbalanced XLR cables shipped with them so yes, they do exist.




Yes Joun.  I understand the science.  I just can't conceive the the circumstances where an unbalanced mic could become connected to an XLR, without considerable home build effort. 
Having said that, my day job does involve the phrase "industrial stupidity". The warning is a good call.
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Dave Potter

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Re: A quandry from the Mackie manual.
« Reply #22 on: April 21, 2011, 03:25:25 am »

The word "stupidity" was mentioned only by me, and the context was very clear:- 
One does not need to BE fundamentally stupid to DO a stupid thing.  I had already stated that I work in an environment of the creativity stupid - despite the best attempts on designers.  We all do the stupid things.  Its our right as human beings.  The incorrect wiring post only confirms this.
The only questions that remain are: "Is any one dumb enough to blow up a mixer, smart enough to understand the warning?"  and "What can designers possibly do about it?"
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John Roberts {JR}

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Re: A quandry from the Mackie manual.
« Reply #23 on: April 21, 2011, 10:41:49 am »

The word "stupidity" was mentioned only by me, and the context was very clear:- 
One does not need to BE fundamentally stupid to DO a stupid thing.  I had already stated that I work in an environment of the creativity stupid - despite the best attempts on designers.  We all do the stupid things.  Its our right as human beings.  The incorrect wiring post only confirms this.
The only questions that remain are: "Is any one dumb enough to blow up a mixer, smart enough to understand the warning?"  and "What can designers possibly do about it?"

The is a well understood failure mechanism, and explored in new and not so new (but not very old) AES preprints.


References
1)
Bortoni, Rosalfonso and Kirkwood, Wayne, “The 48V Phantom Menace Returns,” Audio Engineering Society preprint from the 127th AES Convention, October 2009; www.aes.org.
2)
Hebert, Gary and Thomas, Frank, “The 48 Volt Phantom Menace,"  Audio Engineering  Society preprint from the 110th AES Convention, May,  2001; www.aes.org.

As I mentioned the failure mode is managed for in professional recording consoles where because of patch bay use the inadvertent input short circuit is far more common.  The lower frequency of this fault, or perhaps inexperience of Alto's designer, means that mixer was unprepared for the stress.. That killer mic would not break every console, but make a few uncomfortable...

I don't consider an operator hot plugging a mic into phantom as stupid (perhaps a little inexperienced), as this is a rather subtle design quirk of phantom power. I do consider it very stupid for a manufacturer to make such a mic with one input shorted as this is a disaster just waiting to happen.

While Kristian didn't say, I hope the mics were not also made by Alto, that would be inexcusable, and they would surely have figured it out their mistake pretty quickly. I suspect some music dealer or distributer put the killer mic together with a weak mixer, in a "how cheap of a system can we assemble" exercise.
 

JR

PS: A common newby design mistake is to make the input phantom caps rather large, thinking bigger is better, but the transient fault current increases linearly with cap value, so the protection needs to be scaled up along with cap values, or smoke can get out. 
 
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Re: A quandry from the Mackie manual.
« Reply #23 on: April 21, 2011, 10:41:49 am »


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