What's the difference between a company's amplifier series?

[Robert94]

Company's always have different series of speakers, amplifiers, DACs - you name it - usually with a significant price difference between each. I'm specifically interested in amplifiers, which there seems to be a split of opinion on whether there are sound differences between 'good amps' where some believe that a good amp should sound the same as another good amp as they should evenly amplify a full audio spectrum.

Let me give a specific example:
Cambridge Azur 351A (351 series): ~ £300

• Power output45W RMS into 8 Ohms
• THD (unweighted)< 0.02% @ 1kHz, 80% of rated power
  < 0.15% 20Hz - 20kHz, 80% of rated power
• Inputs5 x RCA, 1 x USB (type B), 1 x 3.5mm MP3 input
• OutputsSpeakers A & B, 1 x Rec Out, ¼'' headphone out,
• USBUSB audio 1.0 16-bit 32kHz, 44.1kHz, 48kHz
• Frequency response5Hz - 50kHz
• S/N ratio (ref 1w)>92dB (unweighted)
• Input impedance47k Ohms
• Max. power consumption320W
• Bass/treble controlsShelving, ultimate boost/cut +/-10dB @ 20Hz and +/-6dB @ 20kHz
• ColourBlack or silver
• Dimensions (WxHxD)430 x 86 x 340mm (16.9 X 3.4 X 13.4 ")
• Weight6.0Kg (13.2lbs)

Cambridge Azur 651A (651 series) ~ £450

• Power output75W RMS into 8 Ohms
• THD (unweighted)< 0.002% @ 1kHz, 80% of rated power
  < 0.03% 20Hz - 20kHz, 80% of rated power
  < 0.02% 20Hz - 20kHz @ 10W
• Frequency response5Hz - 50kHz (-1dB)
• S/N ratio (ref 1w)>92dB (unweighted)
• Input impedance47k Ohms
• Power amp damping factor>100 at 1 kHz
• Max. power consumption600W
• Standby power consumption<1W @ rated mains
  Shelving, ultimate boost/cut +/- 7.5dB @ 20Hz and 20kHz
• USB audio inputUSB audio 1.0
  16 bit 32kHz, 44.1kHz, 48kHz
• ColourBlack or silver
• Dimensions (WxHxD)430 x 120 x 350mm (16.9 x 4.7 x 13.8")
• Weight8.4Kg (18.5lbs)

Specification wise the only real difference here seems to be more power and slightly less THD (probably less than human hearing anyway). So does the extra cost between series all go into improving the circuitry so that the output power can be higher (I suppose this would require more robust heat sinks and things like that) or is it likely to 'sound better'? Perhaps this might only be noticeable when driving the amp at high power where clipping may be encountered by the lower power amp but won't be encountered by the more powerful amp? Feature wise there is no difference so in this case that doesn't contribute here.

Anyway I'm interested in everyones opinion on this and experiences.

 

[TheWarrior]

You've opened a huge topic. Lets clarify, are you looking to purchase a new amp and are trying to determine what best suits your needs? Because that is ultimately the deciding factor for any amp purchase; what speakers does it need to drive, in what room, at what volume?

 

[Robert94]

You've opened a huge topic. Lets clarify, are you looking to purchase a new amp and are trying to determine what best suits your needs? Because that is ultimately the deciding factor for any amp purchase; what speakers does it need to drive, in what room, at what volume?

I was interested generally in what goes into the larger price. And partly I'm interested because my mate is looking for an amp and I have the older equivalent of the 351A (340a) and I found the older equivalent of the 651A (640A) for under £100 second hand. So I suggested that I would exchange my amp + £35 for the 640A if he bought it as he has Wharfedale diamond 9.1 speakers and I have some B&W 685 S2 speakers, which are larger so thought it would work quite well but was also interested in whether I'd notice a small gain in performance. That being said I've never had my 340a at max volume (I don't really know how far is too far to push a pair of speakers really - I usually stop when there is quite a lot of cone movement which is still very loud I might add) and I don't think i would notice a particular difference.

As for the room it's probably roughly 9ft by 11ft.

EDIT** Perhaps the 640a would provide upgrade potential when I inevitably buy some floor standers in the future although this might not be for a few years so not a major factor.

 

[TheWarrior]

Size of speaker is irrelevant. Most important is speaker impedance; the lower the value, the more difficult to drive (simply put). Many B&W's are low impedance speakers, and therefore difficult for a Receiver to power above moderate volumes. So you've done well by buying an amp!

I like your thinking with getting an upgrade for only a small fee, while helping your buddy upgrade! That said, it takes massive wattage to achieve any appreciable difference in volume. Are you hearing issues that are making you want to upgrade? Because that could be suggestive of something other than amps hindering your experience.

 

[Robert94]

According to the specs my speakers have 8 ohm impedance with a minimum of 3.5 ohm. By any chance do you know an equation that describes the impedance/wattage/difficulty to drive a set of speakers.

I mean the wattage would be nearly double what I currently have but I don't go to max volume so perhaps a tad more headroom - more volume isn't necessarily the reason for this idea. Maybe if I were to pick anything the treble can be a tad harsh at high volume (this is being very picky however).

I am mainly interested in the difference between different amp series excluding power output - do manufacturers (generally) improve other components aside from those that are required to handle a larger power output.

 

[fmw]

I would say you have a decent basic understanding of things. The major difference would be the added headroom of between 2 and 3db. As you say, since the distortion in both units is inaudible, that specification is immaterial. The specs would indicate that the higher priced unit probably has a heftier power supply with a larger power transformer. That is not likely important in your situation.

I use a 40 watt integrated amp in my exercise room. It is more than powerful enough. With your speakers, I think the smaller one will do fine for you.

 

[Robert94]

I use a 40 watt integrated amp in my exercise room. It is more than powerful enough. With your speakers, I think the smaller one will do fine for you.

This pretty much confirms what I was thinking. Quite a large price difference for a larger power transformer - although I don't really know how much these things cost. Thanks!

 

[Adam]

Hi, Robert. There's definitely more differences between the 351A and 651A than just the output power. For example - connections. The 651A has two Rec Out connections versus one, has pre-amp outputs and a sub out, has connections for a control bus, and has an IR emitter jack.

The internal architecture is different, too. From the outside, you can see the orientation of the connections on the back is flipped left-to-right on the models. You can also easily find photos online of the internal hardware of those units (I just did a Google image search). I can't say if the changes are meaningful, but it's more than just a different power transformer.

The 651A also weighs about 40% more than the 351A, and it's not all in the chassis.

As a general question about differences between the amp models/lines for any given company, it's impossible to give a generic answer. Different companies approach things differently. Some go with different topologies, add features, improve build quality, add better aesthetics, and so on.

 

[PENG]

According to the specs my speakers have 8 ohm impedance with a minimum of 3.5 ohm. By any chance do you know an equation that describes the impedance/wattage/difficulty to drive a set of speakers.

It is complicated, though if you assume everything else being equal, a 4 ohm load will draw twice as much current as an 8 ohm load. The equations you asked about would involve the following:

Ohm's law: V=IZ, or I=V/Z).

Power formula: P=VI*PF, or I^2*Z*PF.

V - Voltage, I - Current, Z - Impedance, PF - Power Factor

Power Factor = Cosine of the angle between the voltage and current phasors (commonly referred to as vectors).

From the power formula, you can see that everything being equal, the 4 ohm load would demand twice as much power as an 8 ohm load. In practice, there are many other factors so everything is not equal. That means a 4 ohm speaker may or may not draw twice (could be more, or less) the power that an 8 ohm speaker does. For one thing, the impedance of a speaker typically varies with frequency and different speakers have different impedance versus frequency and phase angle versus frequency characteristics. As an extreme example, it is possible that certain 8 ohm rated speakers could be more difficult to drive than certain 4 ohm rated ones.

I am mainly interested in the difference between different amp series excluding power output - do manufacturers (generally) improve other components aside from those that are required to handle a larger power output.

Not always, but in many cases, the higher series do have higher quality components in them. The 651A also has at least one useful additional feature, the pre-outs, that allows you to use an external power amplifier. It also has a sub out, though I don't find that too useful, but is an added convenience.

 

[Robert94]

From the power formula, you can see that everything being equal, the 4 ohm load would demand twice as much power as an 8 ohm load.

Thanks for the detailed explanation along with the formula. I guess this is why you can get clipping at certain frequencies when pushing an amp and why it is therefore useful to have some headroom to allow for intermittent drops in impedance, rather than running at full whack all of the time