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Old 12th November 2006, 07:43 AM   #1
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Default Proposal of new test signal for amplifiers, with regard to HF interference

My proposal and first results are here, looking forward your comments:

http://web.telecom.cz/macura/mixtest.html

Cheers,
Pavel Macura
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Old 12th November 2006, 12:40 PM   #2
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Any opinion?
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Old 12th November 2006, 01:18 PM   #3
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Sine mixed with square?
Such signals were used to measure TIM in 70's.
If your square is steep enough, you can actually observe slew limitation at output of some circuits. I think that 30kHz square should be at least 100 times lower in amplitude then.
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Adam
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Old 12th November 2006, 01:23 PM   #4
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Adam,

I know DIM30 and DIM100 signals. They consist of 3.18kHz square and 15kHz sine. Square amplitude is 4:1 to sine.

May goal is very different. To simulate HF content at player output. 30 kHz corresponds to switching frequency of DC-DC converter. Square simulates harmonic content of fast impulses with 30 kHz repetition. Small square amplitude corresponds to interference amplitude related to useful signal.

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Pavel
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Old 12th November 2006, 02:06 PM   #5
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Still, I'd prefer triangle.
First it is more similar to SMPS voltage ripple, second there is no fear of slew overload a circuit with a triangle. One the other hand it has -12dB/oct spectrum vs. -6dB/oct for square.
Just my suggestion.
regards
Adam
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Old 12th November 2006, 03:02 PM   #6
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Adam,

I do not think so. The HF impulse residuals at CD player output have rise time of 10ns. Just a derivative of square. Triangle is integral of square and thus very easy signal for amplifier.

I am not afraid of the slew rate limitation. Square amplitude in my test is 30dB under sine amplitude.

For me, amplifier must whithstand square wave test, 10kHz at 50% power for one hour into load. If not, the amplifier is not worth any consideration for me.

Cheers,
Pavel
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Old 12th November 2006, 04:11 PM   #7
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Hi, PMA,

Good one
Since the disturbance is unadvoidable in home audio environment these days, could this thread gives solution how to advoid those HF intermodulation with music signal?

BTW, this is about square wave and audio signal (sinusoidal signals)
http://www.diyaudio.com/forums/showt...689#post806689
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Old 12th November 2006, 04:24 PM   #8
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Quote:
Originally posted by lumanauw
Hi, PMA,

Good one
Since the disturbance is unadvoidable in home audio environment these days, could this thread gives solution how to advoid those HF intermodulation with music signal?
David,

this is what I have been permanently trying to work on. Recommendations would cover construction, wiring, input filters. Unfortunately, audio is only my hobby and my time for it is limited. On the other hand, I design instruments for operation in harsh EMI invironment as my professional job. I will try to give some recommendations, after I have time to translate them from my similar document in Czech language.

Regards,
Pavel
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Old 12th November 2006, 04:28 PM   #9
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Right now, my colleague Vladimir has made a similar test on commercial SONY amplifier. Test signals were 6kHz sine + 31kHz square, amplitude ratio same as in my measurements. 16W into 4ohm load. Please compare with my Symasym measurement in post no. 1 of this thread.
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Old 12th November 2006, 04:31 PM   #10
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This is Symasym for 1kHz sine + 34kHz square:
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