Amps - Whats in em and why?

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Daniel Quinn
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Re: Amps - Whats in em and why?

Unread post by Daniel Quinn » Tue Nov 12, 2019 2:15 pm

Personally I like just to piss about and learn something a long the way.

Lurcher300b
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Re: Amps - Whats in em and why?

Unread post by Lurcher300b » Tue Nov 12, 2019 2:55 pm

Daniel Quinn wrote:
Tue Nov 12, 2019 2:15 pm
Personally I like just to piss about and learn something a long the way.
Thats how you end up with opinions instead of anything close to evidence.

Daniel Quinn
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Re: Amps - Whats in em and why?

Unread post by Daniel Quinn » Tue Nov 12, 2019 5:53 pm

That why I don't offer them.

Geoff.R.G
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Re: Amps - Whats in em and why?

Unread post by Geoff.R.G » Tue Nov 12, 2019 7:31 pm

Lurcher300b wrote:
Tue Nov 12, 2019 11:53 am
That is an excellent example of intelligent troubleshooting, something I have found rare amongst some, so called, professional engineers.
I have spent much of my working life fixing software and hardware, you can't fix a bug unless you know what's causing it. To do otherwise is to just cover it up and possibly give yourself twice the number of problems.
I found that younger engineers tended to rely on what the computer was telling them rather than knowing how the system worked. In one case the computer regularly faulted an actuator, the real cause was that the output of the drive circuit had failed. Changing the actuator was a couple of hours work but changing the box took minutes.

The reason the computer failed the actuator was that it fed a signal into the drive circuit and looked for the actuator to move but it didn't check that there was actually an output to the actuator. That was in 1989, for all I know it is still that way.

keepitsimplestupid
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Re: Amps - Whats in em and why?

Unread post by keepitsimplestupid » Sat Nov 16, 2019 9:39 pm

Anything beyond a specification and materials list in an advert is hyperbole, including descriptions of the sound. Nva pricing structure would fall into this category if we're being strict.

Geoff.R.G
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Re: Amps - Whats in em and why?

Unread post by Geoff.R.G » Sun Nov 17, 2019 10:39 am

keepitsimplestupid wrote:
Sat Nov 16, 2019 9:39 pm
Anything beyond a specification and materials list in an advert is hyperbole, including descriptions of the sound. Nva pricing structure would fall into this category if we're being strict.
Specification can be extensive and, to the uninitiated, confusing, more so if you don't actually know which bits are important to you. As an example, amplifier a has an output of 300 W into 8 ohms, amplifier b has an output of 50W RMS into 6 ohms, what is the difference? The fact is that they could be the same piece of equipment simply using a different means of measuring the output. Unsurprisingly, many people would put amplifier a higher on their list than amplifier b.

The point of an advertisement is to show the product in the best possible light and to highlight its features. In the world of Hi-Fi the specification can easily be hyperbole too.

keepitsimplestupid
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Re: Amps - Whats in em and why?

Unread post by keepitsimplestupid » Sun Nov 17, 2019 10:50 am

Both of those are meaningless numbers. You need watts load and distortion all together to form part of a meaningful spec. But you know that, just like we all know some people cant read, but it doesnt mean we shouldn't ignore the 99.9% who can.

Lurcher300b
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Re: Amps - Whats in em and why?

Unread post by Lurcher300b » Sun Nov 17, 2019 11:24 am

You need watts load and distortion all together to form part of a meaningful spec.
Even then its close to meaningless, all its telling you is how much power you would not want to be getting from the amp. Lets say it produces 0.1% distortion at 50W into 6 ohm. Ok, does that tell you anything about what it does at 45W into 6 ohm?

Also, you need a frequency adding to that, 50W at 1kHz into 6Ohm at 0.1% distortion. Even then doesn't tell you anything about 50W at 50Hz or 10kHz

Also real loads are not resistive, test ones normally are.

Also real signals are not single sine waves, some test ones are. At least for the above spec.

And so on.

Geoff.R.G
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Location: Denham UK
Great Britain

Re: Amps - Whats in em and why?

Unread post by Geoff.R.G » Sun Nov 17, 2019 11:47 pm

Lurcher300b wrote:
Sun Nov 17, 2019 11:24 am
You need watts load and distortion all together to form part of a meaningful spec.
Even then its close to meaningless, all its telling you is how much power you would not want to be getting from the amp. Lets say it produces 0.1% distortion at 50W into 6 ohm. Ok, does that tell you anything about what it does at 45W into 6 ohm?

Also, you need a frequency adding to that, 50W at 1kHz into 6Ohm at 0.1% distortion. Even then doesn't tell you anything about 50W at 50Hz or 10kHz

Also real loads are not resistive, test ones normally are.

Also real signals are not single sine waves, some test ones are. At least for the above spec.

And so on.
I agree.
I have driven speakers rated at 35W with an amplifier rated at 150W, the speakers are still fine. That is because most of the time, with "real" signals you aren't using all that much power*.

*I also made sure that there were no signs of distress and kept the levels down.

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