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Old 22nd September 2011, 16:42   #16
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Default Re: Setting amplifier gain without DMM or Oscilloscope

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Originally Posted by navin View Post
Iso since at the amp's lowest setting you cannot hear any clipping whne the HU's output is at max the HU is working within it's limits. Which is expected.
Kudos to Pioneer for manufacturing HU which doesn't clip even at maximum, so I can safely set it to any level at that front.

As the max voltage would be 4v and normal amp gain marking is for 2V, and the curve looks like logrithmic, i should be safe if i set it at middle of the 6.5 and normal(2v) marking.

Well, that solved the problem of procuring a DMM and oscilloscope, I guess.
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Old 22nd September 2011, 16:53   #17
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Default Re: Setting amplifier gain without DMM or Oscilloscope

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That said I prefer to use A-weighted noise as this is closer to how the humar ear hears that either pink or white noise.

Do you think using grey noise instead of pink noise would help in identifying clipping as it's an inverted A-weighted noise giving the perception of equal loudness across the spectrum?

Last edited by glidealong : 22nd September 2011 at 16:56.
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Old 23rd September 2011, 12:06   #18
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Default Re: Setting amplifier gain without DMM or Oscilloscope

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Do you think using grey noise instead of pink noise would help in identifying clipping as it's an inverted A-weighted noise giving the perception of equal loudness across the spectrum?

Ha grey noise. Is that what they call it nowadays. Yes what I meant was an inverted A weighted curve it used to the closest curve to fletcher-munson.

But no grey noise is not applicable for your test.

1. what device are you trying to clip?
2. why?

Almost any HU+AMP combo can be "forced" to produce a clipped singal (at output of amp) if one setns the gains accordingly. The question is that we need to set the gains so the amp does not clip even with the HU at full output. Making an amp clip is easy - just turn teh sensitivity (gain) all the way up!

A power amp (car audio amps are mostly power amps) is like a black box with a certain gain ratio. Push the input too hard and some stage inside the power amp (usually the output stage) will get overdriven and clip.

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Originally Posted by glidealong View Post
Kudos to Pioneer for manufacturing HU which doesn't clip even at maximum, so I can safely set it to any level at that front.

As the max voltage would be 4v and normal amp gain marking is for 2V, and the curve looks like logrithmic, i should be safe if i set it at middle of the 6.5 and normal(2v) marking.

Well, that solved the problem of procuring a DMM and oscilloscope, I guess.
Please remember that the output voltages are nominal. A Hu that is speced at 4V output wont produce 4V at all times. The output level will vary. What it means is that the HU produce up to 4V without clipping.

As far as the amplifier setting is concerned: What you need to ensure is that the HU does not force the amplifier into clipping when the HU's volume is maximum. Since the amplifier is usually rated to produce it's max output with a 1V signal (check this rating for your specific amplifier) even keeping the gain level in the middle will do.
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Old 23rd September 2011, 16:32   #19
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Default Re: Setting amplifier gain without DMM or Oscilloscope

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1. what device are you trying to clip?
2. why?
1. Head units
2. To make sure electronic circuits work properly in their intended range to give the listener a good experience, so that I get good clean audio signals through the speakers while I am listening to ambient music like Helios where the bass can be quite deep and loud in parts. I don't want my HU to clip those in first place.


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Originally Posted by navin View Post
Making an amp clip is easy - just turn teh sensitivity (gain) all the way up!

A power amp (car audio amps are mostly power amps) is like a black box with a certain gain ratio. Push the input too hard and some stage inside the power amp (usually the output stage) will get overdriven and clip.
True, I don't want this either.

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Please remember that the output voltages are nominal. A Hu that is speced at 4V output wont produce 4V at all times. The output level will vary. What it means is that the HU produce up to 4V without clipping.
Agree.
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Originally Posted by navin View Post
Since the amplifier is usually rated to produce it's max output with a 1V signal (check this rating for your specific amplifier) even keeping the gain level in the middle will do.
I beg to disagree.
IMHO, I would have to get the highest voltage output from the head unit, which is better because a higher voltage signal would be better at resisting induced noise. Amps might have filters to filter them out, but more powerful the original signal is more efficient would be the filters to cut out these noise. I don't want noise to get in between me and my music, be it ground or electromagnetic interference or any other.

And I don't want to clip either even if i turn the volume knob to the max. Hope I am making myself clear here.

Last edited by glidealong : 23rd September 2011 at 16:47.
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Old 23rd September 2011, 17:06   #20
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Default Re: Setting amplifier gain without DMM or Oscilloscope

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And I don't want to clip either even if i turn the volume knob to the max. Hope I am making myself clear here.
OK now I get what you want....

Ok the simplest to do this (without the use of instrument) is to start with the amp's sensitivity turned all the way down so that even at the HU's max volume the amp is producing as little output as possible (in your case I think it is 6.5V).

Now with the HU still at full volume slowly turn the sensivitity up till you hear distortion. This distortion might most likely be from physical excursion of the drivers or from the amp clipping but it is distortion nontheless. This will give you a level from the HU that ensures best S/N ratio from the HU.
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Old 23rd September 2011, 17:22   #21
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Default Re: Setting amplifier gain without DMM or Oscilloscope

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This will give you a level from the HU that ensures best S/N ratio from the HU.
Exactly, best Signal To Noise Ratio... that's the term. I should have originally put the thread as "Setting amplifier gain without DMM or Oscilloscope for best Signal To Noise Ratio"


Last edited by glidealong : 23rd September 2011 at 17:23.
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