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Old 14th February 2010, 04:00 PM   #7071
sekess is offline sekess  United States
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Thanks for all your answers guys. I got it now. The voltage available number was screwing me up.
Thanks,
Steve
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Old 14th February 2010, 09:39 PM   #7072
ichiban is offline ichiban  United States
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Question fat metal tabs

Quote:
Originally Posted by bear View Post
Why do some polypropylene caps have fat metal tabs coming out the end, and not wires?
_-_-bear
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Old 15th February 2010, 11:50 AM   #7073
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by sekess View Post
ok bobodioulasso,
So, if I'm following you correctly:

-- Let's say you've got +-24 volt rails. That would give you 48 volts total.
-- Let's take off 8 volts for various losses. I'm not sure if this is a good approximation or not. I just chose it so that we have an even 40 volts available at the rails.
-- So, if we have 40 volts as Vmax, we can now divide by 1.414. This would give you 28.29volts.
-- Now, using (V*V)/R as the calculation for Power, we get (28*28)/16 = 49 watts.............
Hi,
you have a dual polarity power supply. This is exactly equivalent to two power supplies, one that is +24Vdc relative to zero volts/ground and the other one is -24Vdc relative to zero volts/ground.
You have a speaker connected to ground on one side and to the amp output rail on it's other side.
What is the maximum voltage that the positive supply can apply to the speaker?
What is the maximum voltage that the negative supply can apply to the speaker?
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Old 15th February 2010, 12:05 PM   #7074
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by bear View Post
Why do some polypropylene caps have fat metal tabs coming out the end, and not wires?
Quote:
Originally Posted by ichiban View Post
fat metal tabs are shorter than wires, generally.
Short links = low inductance = lower impedance at HF.

That's why the two pin capacitors inserted into a PCB have relatively low inductance for their 10mm pin pitch.
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Old 15th February 2010, 04:20 PM   #7075
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Quote:
Originally Posted by AndrewT View Post
fat metal tabs are shorter than wires, generally.
Short links = low inductance = lower impedance at HF.

That's why the two pin capacitors inserted into a PCB have relatively low inductance for their 10mm pin pitch.
Andrew,

Thanks for giving an answer.
However the question was not aimed at someone who is "highly knowledgeable about all matters electronic", rather for others to go and look, question and research. So, it would be better if you would restrain yourself from being didactic in many cases?

_-_-

PS. So, why not just short wires then?

PPS. I posit that I don't know squat.
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http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
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Old 15th February 2010, 04:38 PM   #7076
a.wayne is offline a.wayne  United States
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Andrew ,

With all due respect to Bear , thanks for the clear and concise answers , 2 many times answers to questions are given with smoke and mirrors which leads to more confusion , where only those in the know can follow , the opposite of the actually intent to help i suppose.

regards,

Last edited by a.wayne; 15th February 2010 at 04:50 PM.
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Old 15th February 2010, 05:07 PM   #7077
AndrewT is offline AndrewT  Scotland
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there are times (many of them) when I too pose directed questions to the enquirer. I think I make it clear when I expect the enquirer to do the homework to come to an answer.


I do not play mind games with other Forum Members and I would respect more those that do play with me/us.

Clarity is important.

Just to go off topic.
Essay set in year8 (11/12years old).
Describe how you would build a model aeroplane.
I had previously read a book on precisely this subject.
I looked up my grammar text book and found out how to write a technical essay.
I submitted my essay and it came back with a zero. The English teacher refused to mark it. We never got the chance to discus his issue. I suspect he thought I had copied the book verbatim. He went on to become a university lecturer that I met again some 30 years later, when he retired and moved back to Edinburgh.
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Old 15th February 2010, 06:17 PM   #7078
a.wayne is offline a.wayne  United States
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Had many teachers like that myself ... i guess it's an requisite when preparing for 'O' Levels...
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Old 15th February 2010, 08:08 PM   #7079
sekess is offline sekess  United States
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Hey Andrew,
If for simplicity we assume no losses and that the positive and negative halves can output the full respective +24 and -24 volts, then the maximum voltage that the positive supply can apply to the speaker is +24 volts and the maximum that the negative can supply is -24 voilts (with respect to ground).
So theoretically, I would think that the driver could move -24 volts in the negative direction and +24 volts in the positive direction. This would give a total voltage swing of 48 volts from the bottom of the driver's movement (inward) to the top of the movement (outward).
This is what I had originally thought was the maximum theoretical voltage available to the driver (48 volts - minus losses and circuit limitations). But I was informed that - since the output is a sine wave - for calculating wattage, you use some fraction of the peak to peak voltage. I think it's the RMS voltage value. But, I'm not 100% sure that it's RMS. This is the part that had me somewhat confused.

Thanks,
Steve


Quote:
Originally Posted by AndrewT View Post
Hi,
you have a dual polarity power supply. This is exactly equivalent to two power supplies, one that is +24Vdc relative to zero volts/ground and the other one is -24Vdc relative to zero volts/ground.
You have a speaker connected to ground on one side and to the amp output rail on it's other side.
What is the maximum voltage that the positive supply can apply to the speaker?
What is the maximum voltage that the negative supply can apply to the speaker?
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Old 15th February 2010, 09:18 PM   #7080
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Audio power - Wikipedia, the free encyclopedia
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