Sonos amp power

NAD amplifiers have a reputation for “soft clipping”, but they annoy me.

If an amplifier is overdriven it usually misbehaves either by obvious shutdown or gross distortion. If you watch the output using an oscilloscope it is obvious that the tops and bottoms of the waveform have reached a limit and are simply straight horizontal lines. This is known as “clipping”. Amplifiers such as NAD speak about “soft clipping”. This implies that some compression starts at about 70% of maximum power, avoiding hard clipping. If you watch this on an analyzer you can clearly observe an increase in distortion and reduction of dynamics as the compression kicks in. There are obvious tradeoff’s with this technique. While gross distortion is avoided when the the amplifier is operating near (and potentially above) the limit, there is usually excess distortion, resulting in a fatiguing sound for some listeners. If the amplifier would emit some sort of gross sound or shut down, it can communicate its situation with the user. An amplifier can also flash a warning light.

If the user habitually overdrives the unit, soft clipping can result in a more pleasant sound, but a more powerful amplifier or a user who can learn to back off a bit, will have superior results.

But this is more than doubling the 8-Ohm draw. What if the amplifier protection circuit shuts down hard at the 4-Ohm current? Even though rated at 4-Ohms, some amplifiers will tolerate short 2-Ohm excursions. AMP is in this class, CONNECT:AMP is not.

Hmm...news to me. I thought that the Amp will do better with a speaker that drops to 2 ohms because it has more grunt that the Connect Amp, not also because the Connect Amp will cut out.

In general: where does this characteristic show up in a typical amp spec? 

This sort of detail does not usually show up in a spec. You can infer a little by looking at the 4-Ohm/8-Ohm power ratio. In the case of CONNECT:AMP the protection circuit is very literal and quick responding.

There are two limits for a power amplifier, current and heat. If the current limit is exceeded, even briefly, the amplifier will fail catastrophically. If the amplifier has some excess current capacity, a brief higher current excursion will not cause dangerous overheating. The published ratings give the running forever limits.

Let’s look at this from a different angle. Say the output stage can safely deal with 10A, but the cooling, for various heatsink size, fan or no fan, etc, considerations, can only support 8A continuously. This amplifier will be rated for the 8A case, but an occasional 10A excursion is not a major issue.

Transistors are rated for a certain number of temperature cycles. A cycle begins at ambient, rises to the operating temperature, then returns to ambient. The deeper the cycle, the fewer the unit will tolerate. This is why leaving a unit running perpetually is not a big deal because this is a single cycle.

In the 10A/8A case above the occasional 10A excursions will simply widen that cycle a bit, but this is not a major issue for a relatively low number of cycles. A single 11A attempt will be the end of the line for that transistor.

Making it even more fun, while the power supply temp is directly related to the power being provided the output stages of an amplifier can actually run hotter at lower levels than at full power.

That is a big part of the industry grief over the RMS power specs as the 1/3 power pre-conditioning stage caused amps that had no problem reproducing much louder music to have cooling issues. I believe that was mostly a class B amp issue.

Something else to consider is the actual volume differences you get at the various power levels, often what looks like a big difference in Watts is pretty minor in dB. There are a lot of on-line calculators and charts to use in making your comparisons.

Which is why I think active speakers, with dedicated amps per driver make much more sense. The manufacturer is better equipped technically to install the right amps than over 99% of users can left to their own devices. All the user then has to do is to see if the sound is to one’s liking and can go loud enough for the room with some headroom on the volume control knob - something that all users can do.

I recently bought a Pioneer DJ monitor pair to serve an Echo Dot/Bedroom TV for about USD 135. It has the vital auto standby and wake functions, and took me less than five minutes to wire up. Pioneer has the amp power quoted in the spec somewhere, but that is not an essential thing to know. Brilliant bit of kit for sound quality, form factor and value for money.

For the audiophile, powered speakers are no fun. The fun is chasing the ultimate speaker and the ultimate amplifier. Even though passive crossovers take a toll on the sound, audiophiles seem to prefer separate amplifiers.

A problem with the whole concept of passive speakers is that they must be designed to deliver balanced sound, ‘flat’ if you like, when driven by a ‘flat’ (frequency response) amplifier. Drivers and boxes are not particularly ‘flat’. From a system standpoint a complimentary amplifier-driver-box approach yields better results. 

I can recall a speaker that was sold in two versions. A passive version and an active version intended for autos. The amplifiers used in the bi-amped active version were not notable, but the active version sounded much better than the passive version -- regardless of the amplifier used to drive the speaker.

And there is the audiophile speaker wire chase. Active speakers eliminate the speaker wire.

It may even have been that the same amp modules were used in amps used to drive said passive version, but once they are surrounded by all the eye candy of cabinets and dials, who is the wiser? 

Which is another reason why actives can also be a lot cheaper - all that expensive, usually heavy  cabinetry isn't needed. Ditto for speaker cables.

As to audiophiles, that is also exactly why Sonos is a turn off. Nothing to play with and cheap enough for the Joneses to own as well. Although the tech inside Sonos speakers - and I am not referring to the wireless multiroom tech but the core audio tech - is at least a couple of decades ahead of that of tech in passive kit.