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Classe Sigma AMP5 Multichannel Amplifier Review

PeteL

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Most amplifiers do not have clip indicators so it is easy over-estimate the need for power. I always did, opting for the ATI AT6000's over the AT4000s. In reality, there was only a 1 dB advantage.

Critical listening will occur at 1 watt and below, that is if you think amps can and do sound differently, of course.

- Rich
Wouldn’t it be the opposite? no clip indicator means you don’t know if your peaks are clipped, may lead you to think you have enough power when you don’t?
 

anmpr1

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Most amplifiers do not have clip indicators so it is easy over-estimate the need for power. I always did, opting for the ATI AT6000's over the AT4000s. In reality, there was only a 1 dB advantage. Critical listening will occur at 1 watt and below, that is if you think amps can and do sound differently, of course.

Yes. The requirement for 'raw power' is a) loudspeaker dependent, b) room size dependent, and c) how loud you want to listen. If your living room is four thousand square feet, and you have Apogee ribbon loudspeakers, you pretty much have to have a thousand watts into one ohm. If your loudspeakers are Klipsch (or some other horn loaded design) then twenty or thirty watts is probably enough for most listening situations.

I get what @restorer-john is saying, at least on an absolute level and given what can be had in the marketplace for limited dollars. But I can't accept his exclusionary definition of what constitutes a 'serious' power amplifier. I think Thomas Colangelo (and Curl?) was thinking seriously when he designed these.

ml2.jpg
 

PeteL

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Yes. The requirement for 'raw power' is a) loudspeaker dependent, b) room size dependent, and c) how loud you want to listen. If your living room is four thousand square feet, and you have Apogee ribbon loudspeakers, you pretty much have to have a thousand watts into one ohm. If your loudspeakers are Klipsch (or some other horn loaded design) then twenty or thirty watts is probably enough for most listening situations.

I get what @restorer-john is saying, at least on an absolute level and given what can be had in the marketplace for limited dollars. But I can't accept his exclusionary definition of what constitutes a 'serious' power amplifier. I think Thomas Colangelo (and Curl?) was thinking seriously when he designed these.

View attachment 87672
You are right, I would also add 2 points to your list tough d) the type of music you listen to (pop music has limited dynamic range) e) The fact that class D designs has no dynamic headroom at all (if a peak is clipped, it's hard clipped, and peak power is the same as continuous)
 

RichB

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Wouldn’t it be the opposite? no clip indicator means you don’t know if your peaks are clipped, may lead you to think you have enough power when you don’t?

It is possible to determine the power requirements with digital sources.
I measured a 2.83 volts playing a 0 DBFS sine-wave (400Hz, 1kHz, and 2kHz) at my listening position and found that -31 on my processor produced 86 dB at my 11 foot listening position (in a 30' room). The Salon2s are basically 4 Ohm speakers so this computes to 2 watts.
This means the maximum power at processor volume -31 is 2 watts in my system.

The AHB2 delivers 180 watts into 4 Ohms.
Using a simple spreadsheet, -13 produces a maximum of 104 dB with 128 watts. -10 produces a maximum of 107 dB with 256 watts.
Processor volume -11 is about the maximum volume settings that is guaranteed to NEVER clip.
This type of analysis can be performed in room with a volt meter, 0 DBFS sine-wave file, and SPL meter.

I watch movies and stream mostly at -20 and have gone as high is -12 and that is very loud.
For music, I can predictably clip the amps between -13 and -10 but don't listen at these levels.

This is not a complicated analysis that any enthusiast can perform.
You can know volume level on your processor and where clipping can occur with sources that reach maximum volume.

For me, I absolutely know what volume setting does not clip and also know that it is loud enough for me.
There is no need to fret about power and clipping. The AHB2 clip indicators confirm this analysis,

- Rich
 

RichB

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You are right, I would also add 2 points to your list tough d) the type of music you listen to (pop music has limited dynamic range) e) The fact that class D designs has no dynamic headroom at all (if a peak is clipped, it's hard clipped, and peak power is the same as continuous)

This is true, but with digital sources, you can determine the maximum volume required and know when you amp could clip and when it cannot.
If set to maximum non-clipping volume you may need more amplifier. All this assumes you have speakers that sound good at these levels.

Compressed with signals at 0 DBFS is normal for pop so predictably will clip the amp when playing at the computed maximum volume.
Classic and highly dynamic sources may increase the desire to turn the volume up, but again will not clip unless the maximum determined volume is exceeded. I suspect that most actually do not clip anywhere near as often as they fear.

Personally, I have tried more than one AVR driving the Salons and they don't sound good even at modest volume levels but that is a different discussion.

- Rich
 
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PeteL

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It is possible to determine the power requirements with digital sources.
I measured a 2.83 volts playing a 0 DBFS sine-wave (400Hz, 1kHz, and 2kHz) at my listening position and found that -31 on my processor produced 86 dB at my 11 foot listening position (in a 30' room). The Salon2s are basically 4 Ohm speakers so this computes to 2 watts.
This means the maximum power at processor volume -31 is 2 watts in my system.

The AHB2 delivers 180 watts into 4 Ohms.
Using a simple spreadsheet, -13 produces a maximum of 104 dB with 128 watts. -10 produces a maximum of 107 dB with 256 watts.
Processor volume -11 is about the maximum volume settings that is guaranteed to NEVER clip.
This type of analysis can be performed in room with a volt meter, 0 DBFS sine-wave file, and SPL meter.

I watch movies and stream mostly at -20 and have gone as high is -12 and that is very loud.
For music, I can predictably clip the amps between -13 and -10 but don't listen at these levels.

This is not a complicated analysis that any enthusiast can perform.
You can know volume level on your processor and where clipping can occur with sources that reach maximum volume.

For me, I absolutely know what volume setting does not clip and also know that it is loud enough for me.
There is no need to fret about power and clipping. The AHB2 clip indicators confirm this analysis,

- Rich
Yes, you can do this, so let's put this in perspective. You have in your case 107 dB with 256 watts. That's your 0 DBFS, If you want to be sure never to clip. Now, what is the rms level of your recording. It's not rare for dynamic recording to have this value around -20 dBFS but can be as high as -30dBFS, dB SPLs are an averaged value. Movies have large dynamic range. It's not bad practice to have that much headroom if you want to be absolutely sure. So with your metric, let's say you like to listen to movie loud, like 85 dB SPL, you MAY have peaks at 115dBs, for very short transients (not hurtful for your ears),IF your recording is VERY dynamic. Also, you should also have for good measure check at 80 Hz, do you still have 86 dBS at 2.83 volts, probably, but does it have the current reserve to linearly translate at higher voltage, you are not sure of that, since measurments are normally done at 1k. That said, those are extreme cases. If it never clips for you, well it never clips and you have enough power.
 
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RichB

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Yes, you can do this, so let's put this in perspective. You have in your case 107 dB with 256 watts. That's your 0 DBFS, If you want to be sure never to clip. Now, what is the rms level of your recording. It's not rare for dynamic recording to have this value around -20 dBFS but can be as high as -30dBFS, dB SPLs are an averaged value. Movies have large dynamic range. It's not bad practice to have that much headroom if you want to be absolutely sure. So with your metric, let's say you like to listen to movie loud, like 85 dB SPL, you MAY have peaks at 115dBs, for very short transients (not hurtful for your ears),IF your recording is VERY dynamic. Also, you should also have for good measure check at 80 Hz, do you still have 86 dBS at 2.83 volts, probably, but does it have the current reserve to linearly translate at higher voltage, you are not sure of that, since measurments are normally done at 1k.

Reasonably sure because the AHB2 have excellent per-channel clip indicators. The AHB2 does well into load where the power requirements are greatest. There is no short or long, there is only 0 dBFS and the determined maximum volume setting.

A processor with a maximum volume setting could be set to the the computed value for the amplifier and therefore never clip.
The only question is with dynamic material will the volume be enough. That is based on preferences. There need not be guess-work.

When I had only one AHB2, I watched Aquaman at -17 which at least 2 dB from what I found comfortably loud. The Salon2s were set to full range and the woofers were moving quite a bit during the Kraken scene ad there were no clip indicators. I found this strange which is why I embarked on the analysis.

I have enough AHB2s to bridge which would remove all doubt (at nearly 500 WPC) but I don't need that power. I have reached an age to have developed an interest in preserving my hearing.

I have found that power calculators can easily lead to the conclusion that 4 times more power is needed. I encourage folks to do the analysis from their listening position.

Since I drive my 5.1 system with 4 AHB2s and 3 dedicated 20 amp circuits (left over from the ATI AT6000 days), there will not no compression or limitation based on channel count and common supply.

- Rich
 
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PeteL

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Reasonably sure because the AHB2 have excellent per-channel clip indicators. The AHB2 does well into load where the power requirements are greatest. There is no short or long, there is only 0 dBFS and the determined maximum volume setting.

A processor with a maximum volume setting could be set to the the computed value for the amplifier and therefore never clip.
The only question is with dynamic material will the volume be enough. That is based on preferences. There need not be guess-work.

When I had only one AHB2, I watched Aquaman at -17 which at least 2 dB from what I found comfortably loud. The Salon2s were set to full range and the woofers were moving quite a bit during the Kraken scene ad there were no clip indicators. I found this strange which is why I embarked on the analysis.

I have enough AHB2s to bridge which would remove all doubt (at nearly 500 WPC) but I don't need that power. I have reached an age to have developed an interest in preserving my hearing.

I have found that power calculators can easily lead to the conclusion that 4 time more power is needed than is accurate. I encourage folks to do the analysis from their listening position.

Since I drive my 5.1 system with 4 AHB2s and 3 dedicated 20 amp circuits (left over from the ATI AT600 days), there will not no compression or limitation based on channel count and common supply.

- Rich
I fully agree with this. I was not insinuating that you didn't have enough, I was presenting edge cases, you know when you look at your preamp or processor and realise, why am I that loud? I NEVER need to turn it up that much! It's the recording. Also was just clarifying what headroom is, for some less technically savy people by reading your second paragraph may lead to think that you could listen at 107 dB spl with 256 watts, it obviously don't mean that but you know that.
 
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RichB

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I fully agree with this. I was not insinuating that you didn't have enough, I was presenting edge cases, you know when you look at your preamp or processor and realise, why am I that loud? I NEVER need to turn it up that much! It's the recording.

I have an Oppo UPD-205 connected directly to an AHB2 driving a pair of Revel M126Bes. With the AHB2 at mid-gain, 4 volts is used to generate full output. The 205 generated 4 volts at the max volume setting of 100%. Again, this will not clip. The M126Be's are the limiting factor. I have no desire to listen to them at maximum volume. If I want more, I'll use the Salon2s.

It is possible, to use voltage to determine the maximum volume. In this case, the amplifier is not the limiting factor, it is the reasonable output and distortion profile of the speaker.

A dealer once told me that he found amplifiers a mostly "male" obsession, much like muscle cars.

- Rich
 

anmpr1

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A dealer once told me that he found amplifiers a mostly "male" obsession...
That is interesting about the amplifier. And probably true. I mean, when you consider the difference between the sexes, a woman is really like a very complicated hi-fi preamplifier, whereas the man is definitely more the basic power amp.

mw.jpg
 

RichB

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That is interesting about the amplifier. And probably true. I mean, when you consider the difference between the sexes, a woman is really like a very complicated hi-fi preamplifier, whereas the man is definitely more the basic power amp.

View attachment 87747

Who says men don't like knobs :p

- Rich
 

Koeitje

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Bwmr

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When Amirm writes that there is an Analog to Digital conversion happening in this amp: are we talking about the actual analog audio signal being converted to digital? So there is a 5-channels ADC and DAC in this amp?
Is this "common" design in a power amp? Which other power amp brand (without DSP) would do such an ADC?
Forgive me if this question sounds naive, this is the first time I learn of a pure power amp without DSP does an ADC.
 
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amirm

amirm

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When Amirm writes that there is an Analog to Digital conversion happening in this amp: are we talking about the actual analog audio signal being converted to digital? So there is a 5-channels ADC and DAC in this amp?
Yes. I have only seen this in Pro amps that then allow DSP (crossover, filtering, etc.). I have not seen it done with no user facing features.
 

RHG55

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I'm so happy that I chose to buy the NAD M27 amp instead of this classe sigma-5 amp, when I was on the market for a multi-channel amp a few years ago. I got a great deal in buying the M27 used form a local AVR installation shop that was undergoing a remodeling.
 

Descartes

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