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Mathematics how to solve integration of exp^x square with lower limit=0 and upper limit=infinity

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  • Ronald Tisdale
    Ronald Tisdale May 11, 2010

    prove that the integral of exp(-x^2) from zero to infinity = square root of pi??

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Drag the red point. at link below
http://www.ies.co.jp/math/java/calc/int_e/int_e.html

The following program computes exp(x) for an input x using the
! infinite series of exp(x). This program adds the
! terms together until a term is less than a specified
! tolerance value. Thus, two values are required:
! the value for x and a tolerance value. In this program,
! he tolerance value is set to 0.00001 using PARAMETER.
http://www.cs.mtu.edu/~shene/COURSES/cs201/NOTES/chap04/exp.html

Posted on May 06, 2008

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Well..first thing I'd do, is pour a tall cold one, and ponder the importance of this equation..then I'd navigate my belly button with my fingers, and in that process, enlightenment would arise, with the proper Fixya Solution set, no?

Posted on May 05, 2008

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In need of a infiniti x885 cross trainer manual


Have you looked on the Infinity website?

May 22, 2014 | Amplifiers & Preamps

1 Answer

I have a Yamaha preamplifier CX-800/U where the Powertransformer is defect which let the primary 220V transform into secondary voltages.I know the transformer is no longer available but i would like to...


I asked for more info, but I have replaced many hundreds of unobtainable transformers. All the voltages can be found by a bit of logic thinking & observation. If I have the item in front of me I will have the solution in minutes.
Double red with black, expecially together is normally a X-0-X winding, identified by the rectifier & smoothing caps. The voltages on them will give some indication, but tracing the voltage to an regulator is an accurate solution.
What are the voltages used for?
Normally the one winding will be a low voltage like 12-18 volt for the pre-amps mixers etc. This very often will go through oner or more voltage regulators. Their voltage is written on them,and they will have have small heatsink on them & live near the rectifiers & caps. Look for three legged items marked something like 7812. This is a 12 volt reghulater while a 7809 is a 9 volt regulater. The split voltage say from 20-0-20 to 80-0-80 max will drive the power amp. A 20 watt stereo amp will most likely use two integrated circuits. Luckily you can find their operating voltages very easily by typing in their number like TDS2005 into google. As for an output stage like a 60 to 100 Watt amplifier, a voltage like 60 0 60 and 80 0 80 is used. If in doubt, go a bit lower & play safe. All you will loose is a few watts. If logic (computer circuitry) is used, all computers use basic only 12 volt and 5 volt. Very easy.
Before you give up or look for a new transformeer, just check!!!!!
Most *** xformers have a secret fuse inside them which is easily replaced if you know how!
Send photos! (under 60Kb)

Sep 04, 2011 | NAD C352 2-Channel Amplifier

1 Answer

Not a problem probably but my stereo integrated amplifier is playing louder lately with CD, phono and tapes at less volume settings. Why and is this an issue? thanks!


You have absolutely right, the typical audio level output for the tape is 775mVolts and the cd is about 1000mVolts(=1Volt). This is not a problem the audio input that you connect the cd player can handle the difference, but indeed there is an audible difference. I don't know your preamplifier (or integrated amp), but some models have a separate cd input with an input a little bit lower than the tape, tuner, aux e.t.c. Take a look if there is an input like this at your amp. A good idea also is to set the line out volume level at the cd a little bit lower (not available at all cd players), although after the power off -power on the level will come to default. In case you are familiar with soldering tools and connectors I could suggest you a simple schematic for an attenuator. If you desperately need an attenuator like this let me know to make a research for you.

In case of a problem or clarification or further details needed, don't hesitate to post me a reply before rejecting my answer.
If you are satisfied, rate my solution with the "thumbs" or (even better) add a testimonial.

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Stelios
direct fixya link: http://www.fixya.com/users/technical114

Feb 08, 2011 | Amplifiers & Preamps

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How manny watts per channel??


I'm guessing the 200w are the Speakers maximum input, right?
Is the sub passive or active(=integrated Amp)?

If it's a passive sub:
If it's a 2-Channel Amplifier, you're talking about, you won't be able to connect all 3 - unless you can live with one speaker being significantly louder than the other or your amplifier going up in smoke...

As to the power required, if it's 250W PER CHANNEL the amp will blow your speakers, if it's 250W combined you may not be able to drive them to their absolute limit but they will be loud enough (they probably reach their db-limit with less than 200w but if they reach it with 200, you'll only get ~6db less than that with 125w per channel)

The Watt-numbers on (passive) speakers only tell you how much they can take before they are damaged, the relevant numbers for your problem are the efficiency (the unit is db/W or db/2,83V) and the maximum db-level (most floorstands can produce between 100 and 110 db at one meter distance)

If your speaker produces i.e. 87db/W at 1 meter distance (which is the standard measuring distance), it will produce ~97db at 10W, ~107 at 100W, etc. - unless it reaches it's limit before that. Most speakers can take a lot more power, than they need to reach their limit but they won't get any louder if you keep turning up the volume beyond that (they'll probably produce more distortions though, so don't)


As to the sub:
if it's passive, you'll need another amp (there are special amp-modules for subs, but any amp with enough power will do)

if it's active, you can connect it to the sub-out of your preamp (I'm guessing the PA Amp you mention is a Main Amp, not an integrated one) or your integrated amp via cinch (a tape-out works too)

OR you can connect it to the speaker outputs and than connect the speakers to the sub - in that case the sub is still NOT driven by your main amp but you can use it's crossover to separate low frequencies (--> SUB only) form higher frequencies (--> SPEAKERS only).

Most active subs can be connected both ways, if yours can't your stuck with one.

Rarely there is a third way, which only works if your sub supports it and if you either have seperate Pre- and Main-Amp or if your integrated amp has a Pre-Out and a Main-In (in that case in can be split into preamp and main amp)

IF you want to use your subs Crossover (which is good idea, provided it has one), you'll have to connect it between Amp and Speakers (works with allmost all active subs) or between preamp and main amp (works only with a few)



I hope this is helpful

Jan (Hamburg, Federal Republic of Krautistan)

Mar 17, 2010 | Radio Shack 250 Watt PA Amplifier...

1 Answer

I have a Teac a-R600 integrated amp. The muting light strarts to flash after about an hour playing and mutes the sound until unit is switched off and re started. Any ideas . Thanks Ian


YOU ARE GOING TOO FAR IN VOLUME CONTROL AND YOUR AMPLIFIER TRY TO PROTECT ITSELF BY MUTING-MAKE YOUR VOLUME LITTLE BIT DOWN.IF THE PROBLEM REPEATED WITH LOWER VOLUME SETTING YOU WILL HAVE INTERNAL PROBLEM.ANYWAY CHECK YOUR CABLES FOR GOOD CONDITION.

Dec 19, 2009 | Amplifiers & Preamps

1 Answer

What is the maximum speaker wattage for a NAD c340 integrated amplifier?


The specs say 2x50W into 8 ohms. I could not located the 4 ohm specs, but it is logical to assume that you can run 2x100W into 4 ohms.

The back panel seems to imply that 4 ohms is a limit for speakers.

So any speaker over 100W capability should be fine, either 4 ohms or 8 ohms.

Oct 30, 2009 | NAD C340 Integrated Amplifier

1 Answer

Infinity ERS640 speakers impedance


Your speakers are acutally rated at 4 ohms. Your connection will be just fine. No need to worry.

Here is the manual for your reference.

Jan 19, 2009 | Infinity Amplifiers & Preamps

1 Answer

The volume will not turn down


Do the volume controls on the stereo itself (not the remote) work? Try using a universal remote to lower the volume.

Dec 28, 2008 | Teac Amplifiers & Preamps

1 Answer

Vintage Stereo Connection ???


Hi spanky

Where to start :) I am excited thinking about them :p You got 2 totally cool pieces of classic vintage gear there in the C2 and the Marantz. I have a C2 preamp myself (gathering dust but wont sell it cos its excellent) and the marantz would be totally cool to have(but then I am a little biased towards 70's vintage marantz). They ruled the roost in HiFi amps throughout that decade.

Because they are both integrated amps, you could use them as standalone systems with a pair of speakers, and just plug your favourite gear into them. If you just wanted to run up a nice sounding HiFi, I would sell the kenwood gear and just keep the Marantz. The Kenwood kr1100 has the edge in power, so if it is grunt you are looking for use that. Because vintage sound is all about stereo, you only really need an integrated amp to get great results.

the specs are
# Kenwood Model Eleven G (KR-11000G) Receiver
120W per channel min RMS, both channels driven, at 8 ohms from 20 to 20.000 Hz with no more than 0.03% total harmonic distortion.
Dynamic power output 440W at 4 ohms
Power bandwidth 5 Hz to 70.000 HZ
Frequency response 5 Hz to 100.000 HZ -1.5dB
Signal to noise ratio 115dB

The marantz is a little lower in power at 75rms a channel, but will have the sonic edge in vintage sound over the kr1100. Look them up on ebay and you will find that they do have some value to collectors and people seeking nice tone. There is an 1152 for sale here for AU$900

Best bet is to fire up the 2 integrated amps,and see how they are going. Run them for several hours to be sure there is no strange noises and crackles. Then decide if you want power or finesse.

You could also run both amps from the C2 preamp by connecting to the Amp in connections to the rear of the integrated amps.

happy to talk to you more about it, hit me with a Fixya if my advice was helpful to you. I would keep the marantz, use that and sell the rest and buy some nice speakers:)

regards
robotek

Jul 20, 2008 | Amplifiers & Preamps

1 Answer

Integrated Amplifier - Volume Control Problem


Hi there, get down to your local electronics supplier and buy a tin of spray switch cleaner. Try and spray some into th v/control and do the other controls at ther same time, this should solve the problem

Aug 27, 2007 | Amplifiers & Preamps

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