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Old 28th March 2004, 02:42 PM   #11
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Default time domain

This may be useful for understanding square wave analysis.

Time Domain Audio Measurements

Michael
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Old 28th March 2004, 03:28 PM   #12
EC8010 is offline EC8010  United Kingdom
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Default Don't trust anything!

Yes, I should also have said don't trust your meter! Most <100 DVMs measure AC very poorly, whereas older equipment based on moving coil meters can be quite good. The AVO8 is useable to 15kHz. My (second-hand) Levell microvoltmeter is -3dB at 3MHz, and I used to have an ancient Marconi meter that was flat (-0.1dB) to 50MHz.

Don't forget that a 20MHz oscilloscope means -3dB at 20MHz.

You really need to know the limitations of your test gear.

To be fair, measuring noise is a very tough test, and it is perfectly possible for two meters to give different (legitimate) readings.
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Old 28th March 2004, 04:03 PM   #13
stormy is offline stormy  United Kingdom
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Default Re: time domain

Quote:
Originally posted by audiobot
This may be useful for understanding square wave analysis.

Time Domain Audio Measurements

Michael
Hi,
thanx for posting this link, it ilustrates some good examples,
and saves me making a fool of myself in paintshop hehe
i hate paintshop :0)


Regards stormy
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Old 28th March 2004, 04:24 PM   #14
Bryan is offline Bryan  United States
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Thanks Guys!
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Old 28th March 2004, 05:16 PM   #15
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Default Re: Don't trust anything!

Quote:
Originally posted by EC8010
Don't forget that a 20MHz oscilloscope means -3dB at 20MHz.
Not necessarily. I seem to remember my 475 is rated -1dB at 200MHz...

Tim
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Old 28th March 2004, 10:20 PM   #16
EC8010 is offline EC8010  United Kingdom
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Well, I don't have a manual for a 475, but the definition of bandwidth is -3dB.
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Old 29th March 2004, 02:13 AM   #17
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In general, if not specified. I could spec my amplifiers at 5Hz to 200kHz if I wanted, but it would be +1dB/-20dB in reality. MOST BW specs have variation at -1.5, -3 or -6dB (and little care towards any rises).

Lemme see...ok. Manual seems to imply -3dB point for BW (in any position).

Tim
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Old 29th March 2004, 05:47 PM   #18
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Hi there..... I've enclosed some links for those who need volts/dBu's/dBm's clarifying:
Starting out in test ? get hold of this lot......

At www.sowter.co.uk ........ scroll down to Decibels:
www.rane.com/note145.html
www.jimprice.com/prosound/db.html

learn and memorise the lot.....

rich
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Old 29th March 2004, 05:53 PM   #19
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Apol's site should read www.sowter.co.uk
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