Specifications - let's get them out of the way

All general audio posts go here.
User avatar
TheMadMick
Posts: 437
Joined: Tue Jan 31, 2017 9:50 am
Location: SOUTHPORT, UK
Has thanked: 3 times
Been thanked: 141 times
ST_PATRICK'S_SALTIRE

Re: Specifications - let's get them out of the way

Unread post by TheMadMick »

I've been avoiding this for some time simply because it's almost impossible to identify and isolate all the variables. Please let me explain:

It is possible to have something that measures badly yet "sounds good". But sounds good to whom? In life folks have adopted measurement to get a handle on "sounding good". However, not all things that can be measured are worth measuring and there are more things that go on than we can sensibly measure.

Thus, I take the following view. Most anything I buy should measure acceptably. That means it won't go unstable, go on fire, put a lot of DC through my speakers etc. After that, to avoid nugatory expenditure, I see what others think weighting that with the level of confidence I have in that individual (or group). I then go and try it - a test drive, a demo, a loan (preferred) or whatever, to see if the cost benefit equation works for me and my taste.

That does not mean that everyone will agree with me. That's their problem. The downside is that every so often I go down a blind alley and cost myself money that would be better spent elsewhere. But that's called learning!

As I've said before on this forum, your perception is your reality. Be confident in that.
Blusound Vault 2, P50SA, A80's, BMU, TIS, LS7, MA PL200, Meridian 506 (18 bit).

Lurcher300b
Posts: 933
Joined: Tue Jun 14, 2016 1:58 pm
Has thanked: 0
Been thanked: 16 times

Re: Specifications - let's get them out of the way

Unread post by Lurcher300b »

Most anything I buy should measure acceptably. That means it won't go unstable, go on fire, put a lot of DC through my speakers etc.
I agree, unfortunately none of the measurements that are normally published for a amplifier will cover any of those cases. There are a number of things you do during design and in R&D testing that will check the stability of the amp to loads other than a 8 ohm resistor, but will have no direct bearing on how it sounds driving a simple crossover via a low capacitance speaker cable. In fact, "unconditional" stability, not catching fire and speaker protection circuits will all likely negatively affect the sonics of a amplifier. Not a simple question with a simple answer. CE level safety testing works on the basis of one part failing (or a single external influence) and how the device handles that condition. It doesn't need to survive the test, it just needs to fail in a safe (to the consumer) way. Strictly speaking, outputting DC is not an unsafe condition, especially if its not above about 50v as long as the amp doesn't become unsafe while doing it. The amps job after all is to output voltage.

Geoff.R.G
Posts: 1562
Joined: Thu Aug 11, 2016 2:46 pm
Location: Denham UK
Has thanked: 132 times
Been thanked: 476 times
Great Britain

Re: Specifications - let's get them out of the way

Unread post by Geoff.R.G »

Specifications are very useful, but the ones prospective purchasers look for can be meaningless. As an example; the thickness, stiffness and coper thickness of the circuit board matters in that it determines the effect of vibration and heat, amongst other things, on the behaviour of the finished product. The specification of the resistors used in the stepped attenuator is important too. None of which is of any value to the prospective purchaser and will never be revealed in advertising.

What our potential customer wants is Power output, distortion, frequency response and other equally meaningless, on their own, details. Power output without a lot of information on how it is measured means nothing. Distortion likewise. The vast majority of amps boast a flat frequency response but what matters more is where it rolls off and how fast or how it changes with different types of load. I have never seen an amplifier specification sheet that contained sufficient detail to allow any meaningful comparison between products.

The story goes that when Rolls Royce were asked the engine power of one of their cars they responded "sufficient".

I suspect the person who wanted to know the capacitance of the interconnect cable hadn't a clue how it affected the sound or why. I use a lot of cable but my criterion for choosing it has more to do with how it will stand up to being abused than its technical specification. I will only buy Neutric connectors because they can withstand the conditions in which they are used and, if a cable gets damaged, can be reused many times over.

I would rather not have, for example, a power output rating than have a meaningless number what does 150 Watts "peak music power" really mean anyway.

Post Reply