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Review and Measurements of NAD C 320BEE PWR Amplifier

amirm

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#1
This is a review and detailed measurements of the NAD C 320BEE power (speaker) amplifier. It is on kind loan. The C 320BEE is a vintage product, dating back to 2003 I think. The BEE designation is apparently a reference to Bjorn Erik Edvardsen who was one of their designers. Can't tell if he designed this version or this is based on work he did years earlier. Either way, I am told it is a "classic." I don't keep up with such things but I am sure some of you will set me straight if that is, or isn't so. :)

From what I can tell the original cost was US $399. So quite a budget piece for a mid-tier brand like NAD.

The C 320BEE is typical of NAD design language which is maintained to this day:

NAD C 320BEE Integrated Amplifier Audio Review.jpg

There are set of tone controls and balance which I appreciate in this day and age when it is removed from most gear.

I did not seek out the manual and remain unsure how this thing powers on. You hit the power button but nothing happens until you press one of the input buttons???

Here is the back panel:

NAD C 320BEE Integrated Amplifier Back Panel Audio Review.jpg

It is an old school layout with non-removable power cord, jumper set for pre to power map. And a set of RCA jacks lined up.

The unit appears to run cool but there are large holes on the bottom where the amplifier heatsink is and if you touch that heatsink, it gets quite hot.

In testing, without undue stress, the unit went into protection and would not reset until I cooled it off with a fan and left it off for a few minutes. Most amps survive my testing without going into protection mode since I only push them to max power for seconds.

Also, in the process of changing my setup for 4 to 8 ohm, the unit went into oscillation, producing 107 watts on its own with no signal. So there is some instability in the design. This happened when I changed my load impedance to 8 ohm so perhaps you won't see it if you don't mess with speaker output while the unit is on.

To be on the safe side, for the last few tests I put a fan on top to keep it cool and that got it to run very reliably.

Amplifier Audio Measurements
Let's start with our usual 5 watt dashboard into 4 ohm:
NAD C 320BEE Integrated Amplifier Audio Measurements.png


The highest distortion product is at -100 dB. Since out SINAD (signal to noise and distortion), is only 90 dB, it means there is 10 dB of noise that is degrading that. All else being equal, noise is less of an audible problem than distortion so that is good. Take at its value, the C 320BEE clocks much better than many other amplifiers we have measured in this regard:
Best Audio Amplifiers Reviewed and Measured 2019.png


Drilling into the 1 kHz tone spectrum we see the nice clean output of classic AB amplifier:
NAD C 320BEE Integrated Amplifier 1 kHz Audio Measurements.png


Those of you who hate class-D spectra in ultrasonics, can rejoice now. :)

Signal to noise ratio is good but is power dependent:

NAD C 320BEE Integrated Amplifier Dynamic Range Audio Measurements.png


I think the spec is a few dBs better than this but I am sure you can mess with levels and volume control position to get there. Either way, this is plenty clean for CD/16-bit playback.

Crosstalk is unremarkable compared to state-of-the-art:
NAD C 320BEE Integrated Amplifier Crosstalk Audio Measurements.png


Fortunately, this should not be an audible issue as there is plenty of separation between channels here.

Frequency response is broad and quite flat in audible band:
NAD C 320BEE Integrated Amplifier Frequency Response Audio Measurements.png


Even at 100 kHz, the response is only down 1 dB. So your high-resolution music can sing without the amplifier truncating their bandwidth.

Let's look at intermodulation distortion (two tones at 60 and 7 kHz) versus power output:

NAD C 320BEE Integrated Amplifier IMD Audio Measurements.png



This is a well-behaved amplifier until it gets to its limit and then clips hard as amplifiers tend to do. Of note, there is a "soft clip" light but I did not see it come on in any of my tests.

We can run the same test but with two high frequency tones of 19 and 20 kHz:
NAD C 320BEE Integrated Amplifier IMD 19 + 20 kHz Audio Measurements.png


Forgetting about the ultrasonic ones around 38 kHz, the distortion sidebands remain at -100 dB which is very nice. You can play your 16 bit content without worrying about any distortion above its noise floor.

Most important test is power versus distortion. Let's start with 4 ohm load:

NAD C 320BEE Integrated Amplifier Power into 4 ohm  Audio Measurements.png


This is very modest level of power but no strangeness in its response. We can run the test again but compare to modern "streaming" amplifiers of today:
NAD C 320BEE Integrated Amplifier Power into 4 ohm vs SONOS Amazon Nuforce Audio Measurements.png


We have very clean power compared to them but less power as compared to either SONOS or Amazon Link Amp. The NAD does outperform the NuForce STA-200 though in every respect.

Switching to 8 ohm gets us this:
NAD C 320BEE Integrated Amplifier Power into 8 ohm  Audio Measurements.png


I am puzzled that power output remains identical in both cases. Something must be controlling that.

The graph of distortion versus frequency at power levels is quite messy as it typically is:

NAD C 320BEE Integrated Amplifier THD vs Frequency vs Level Audio Measurements.png


Putting aside the light pink which is at or near clipping, the amp if well behaved with only a modest rise in distortion as power levels increase.

To keep things exciting :), I added a new measurement to this test. It is the "dynamic" power according to CEA-2006/490A designed to keep car audio amplifier companies honest with peak power:

NAD C 320BEE Integrated Amplifier Peak Power Audio Measurements.png


These are burst power measurements. Let me know if you like them and I will run them in future reviews. I think there is some merit to measuring this way as music is not continuous sine wave.

Conclusions
Nice to go back in time and test amplifiers which were simple to understand and simple to measure. The NAD C 320BEE seems to have been competently designed for modest power delivery at a budget price. In that regard, it completely succeeds in its mission.

Personally, I think 67 watts is not enough for home listening. Today's speakers have become smaller in size and shrunk in efficiency, needing fair bit of power to get them to produce proper dynamics. If you disagree otherwise, or have sensitive speakers, the NAD C 320BEE seems to be a good unit to buy. It certainly does away with any anxiety you may have with using class-D amplification.

------------
As always, questions, comments, recommendations, etc. are welcome.

My wife is leaving town this weekend so I plan another big party again. Only panthers are invited this time so you can't attend. But you can help fund purchase of ton of meat with need for the even using:

https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

amirm

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#3
The owner told me there is a switch in the back that enables "soft clipping." This is what it does:
NAD C 320BEE Integrated Amplifier Soft Clipping Audio Measurements.png


Performance was identical at lower power levels so I zoomed into upper range. As seen, it does exactly what is advertised: it allows a much more gentle distortion rise instead of a sudden hockey stick. You pay for that in the form of higher distortion though before you reach the limit.
 

Blake Klondike

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#7
This is a review and detailed measurements of the NAD C 320BEE power (speaker) amplifier. It is on kind loan. The C 320BEE is a vintage product, dating back to 2003 I think. The BEE designation is apparently a reference to Bjorn Erik Edvardsen who was one of their designers. Can't tell if he designed this version or this is based on work he did years earlier. Either way, I am told it is a "classic." I don't keep up with such things but I am sure some of you will set me straight if that is, or isn't so. :)

From what I can tell the original cost was US $399. So quite a budget piece for a mid-tier brand like NAD.

The C 320BEE is typical of NAD design language which is maintained to this day:


There are set of tone controls and balance which I appreciate in this day and age when it is removed from most gear.

I did not seek out the manual and remain unsure how this thing powers on. You hit the power button but nothing happens until you press one of the input buttons???

Here is the back panel:


It is an old school layout with non-removable power cord, jumper set for pre to power map. And a set of RCA jacks lined up.

The unit appears to run cool but there are large holes on the bottom where the amplifier heatsink is and if you touch that heatsink, it gets quite hot.

In testing, without undue stress, the unit went into protection and would not reset until I cooled it off with a fan and left it off for a few minutes. Most amps survive my testing without going into protection mode since I only push them to max power for seconds.

Also, in the process of changing my setup for 4 to 8 ohm, the unit went into oscillation, producing 107 watts on its own with no signal. So there is some instability in the design. This happened when I changed my load impedance to 8 ohm so perhaps you won't see it if you don't mess with speaker output while the unit is on.

To be on the safe side, for the last few tests I put a fan on top to keep it cool and that got it to run very reliably.

Amplifier Audio Measurements
Let's start with our usual 5 watt dashboard into 4 ohm:
View attachment 31497

The highest distortion product is at -100 dB. Since out SINAD (signal to noise and distortion), is only 90 dB, it means there is 10 dB of noise that is degrading that. All else being equal, noise is less of an audible problem than distortion so that is good. Take at its value, the C 320BEE clocks much better than many other amplifiers we have measured in this regard:
View attachment 31498

Drilling into the 1 kHz tone spectrum we see the nice clean output of classic AB amplifier:
View attachment 31499

Those of you who hate class-D spectra in ultrasonics, can rejoice now. :)

Signal to noise ratio is good but is power dependent:

View attachment 31500

I think the spec is a few dBs better than this but I am sure you can mess with levels and volume control position to get there. Either way, this is plenty clean for CD/16-bit playback.

Crosstalk is unremarkable compared to state-of-the-art:
View attachment 31501

Fortunately, this should not be an audible issue as there is plenty of separation between channels here.

Frequency response is broad and quite flat in audible band:
View attachment 31502

Even at 100 kHz, the response is only down 1 dB. So your high-resolution music can sing without the amplifier truncating their bandwidth.

Let's look at intermodulation distortion (two tones at 60 and 7 kHz) versus power output:

View attachment 31503


This is a well-behaved amplifier until it gets to its limit and then clips hard as amplifiers tend to do. Of note, there is a "soft clip" light but I did not see it come on in any of my tests.

We can run the same test but with two high frequency tones of 19 and 20 kHz:
View attachment 31504

Forgetting about the ultrasonic ones around 38 kHz, the distortion sidebands remain at -100 dB which is very nice. You can play your 16 bit content without worrying about any distortion above its noise floor.

Most important test is power versus distortion. Let's start with 4 ohm load:

View attachment 31505

This is very modest level of power but no strangeness in its response. We can run the test again but compare to modern "streaming" amplifiers of today:
View attachment 31506

We have very clean power compared to them but less power as compared to either SONOS or Amazon Link Amp. The NAD does outperform the NuForce STA-200 though in every respect.

Switching to 8 ohm gets us this:
View attachment 31507

I am puzzled that power output remains identical in both cases. Something must be controlling that.

The graph of distortion versus frequency at power levels is quite messy as it typically is:

View attachment 31508

Putting aside the light pink which is at or near clipping, the amp if well behaved with only a modest rise in distortion as power levels increase.

To keep things exciting :), I added a new measurement to this test. It is the "dynamic" power according to CEA-2006/490A designed to keep car audio amplifier companies honest with peak power:

View attachment 31509

These are burst power measurements. Let me know if you like them and I will run them in future reviews. I think there is some merit to measuring this way as music is not continuous sine wave.

Conclusions
Nice to go back in time and test amplifiers which were simple to understand and simple to measure. The NAD C 320BEE seems to have been competently designed for modest power delivery at a budget price. In that regard, it completely succeeds in its mission.

Personally, I think 67 watts is not enough for home listening. Today's speakers have become smaller in size and shrunk in efficiency, needing fair bit of power to get them to produce proper dynamics. If you disagree otherwise, or have sensitive speakers, the NAD C 320BEE seems to be a good unit to buy. It certainly does away with any anxiety you may have with using class-D amplification.

------------
As always, questions, comments, recommendations, etc. are welcome.

My wife is leaving town this weekend so I plan another big party again. Only panthers are invited this time so you can't attend. But you can help fund purchase of ton of meat with need for the even using:

https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Your comment re: 67 watts not being enough power for home listening is interesting. I have the Technics C-700 integrated (75 watts) and have not been able to find any speakers that produce compelling sound through it. Would you say the wattage is a limiting factor? If not, any thoughts on what speakers folks with these amps might check out?
 

amirm

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#9
Your comment re: 67 watts not being enough power for home listening is interesting. I have the Technics C-700 integrated (75 watts) and have not been able to find any speakers that produce compelling sound through it. Would you say the wattage is a limiting factor? If not, any thoughts on what speakers folks with these amps might check out?
Yes, it is the power availability which can limit performance. Look up the reviews I have done previous to this for other options. In general, class-d amplifiers provide copious amount of power that one usually needs.
 

pjug

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#10
No, it is both channels driven.
Thanks. So this is an example of so many NAD amps where the claim is that the dynamic power is a better indication of power available for real music. But you seem to feel that the 67 watts continuous power indicates not enough power. Does this mean you don't buy into the dynamic power argument?
 

Blake Klondike

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#12
Yes, it is the power availability which can limit performance. Look up the reviews I have done previous to this for other options. In general, class-d amplifiers provide copious amount of power that one usually needs.
One question for folks: I have a 35w Cambridge Audio AM-10 and I just plain haven't been able to find ANY speakers that sound competitive with it. Plenty that are OK, but nothing with any body or resolution. Is that the case of the AM-10's 35w making it ineligible for consideration as an amp for serious listening? I get the impression it is more of a kitchen counter system.
 

PuX

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#13
nice, I wouldn't have expected a very old low-end model to perform this well.

I suspect other pure stereo amps would also show decent performance, so I hope there will be more old/simple amp measurements in the future.
 

VintageFlanker

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#14
I had this back in the days, one of my first stereo amp. Bought it for 100€ used if I remember well.
 
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#16
I have two 50W integrated amps, one in the bedroom other in the living room and i never pass half the volume. One system is a denon with kef speakers, the other a marantz with monitor audio speakers. My father has a 100W yamaha with b&w speakers in his living room and maybe sometimes we go to 5/12, but it's normally on 4/12 of the volume. So i don't get the lack of power. The 3 systems are older than 10 years.
 

audio_tony

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#17
I have two 50W integrated amps, one in the bedroom other in the living room and i never pass half the volume. One system is a denon with kef speakers, the other a marantz with monitor audio speakers. My father has a 100W yamaha with b&w speakers in his living room and maybe sometimes we go to 5/12, but it's normally on 4/12 of the volume. So i don't get the lack of power. The 3 systems are older than 10 years.
Same here - my listening room is 12ft x 14ft and I use a variety of speakers, from large floor standers (Paradigm Monitor 7) to standmounts (Dynaudio 52) and rarely do I use more than 5w!! In fact I'd say my average listening levels are 1w to 2w.

And for years (since mid 70's) I've believed that 50w per channel is more than enough, and I still believe that.
 

Dialectic

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#20
Hi,

ASR lurker for some time.. this 320BEE review encouraged me to register :)
First of all thank you @amirm also for all other reviews, measurements here and great concept for this forum.

This NAD was actually my first serious amp (cca 20y ago). I've purchased it together with two nearfield passive monitors. I thought it was really great amp for its "budget" category. At least to me, when I compared it to some other contenders back then.. Especially apparent clarity and "heft" it provided among small amps. It was quite common and recommended setup for lot of people around me. So I definitely subscribe to its "classic" status :)

Later, when I got some standalone DA converter with adjustable output level (and it become my sole audio source), I tried to bypass its pre, removed jumper and feed its power amp directly. As I can recall, it seemed to be like improvement at the time over built-in preamp.. and later found, quite a few other NAD owners used it the same way.
Honestly I'm curious, what it really did :) Can you try to measure, what that do with noisefloor.. say in your 5W THD+N test?

All the best,

Michal
 
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