Amps - Whats in em and why?

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

Unread post by Geoff.R.G » Sun Nov 10, 2019 11:44 am

keepitsimplestupid wrote:
Sat Nov 09, 2019 9:28 pm
Paralleling output devices is hardly new, or controversial.
Far from it but paralleling drivers does bring potential problems if there is any phase shift between the two drive transistors.

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Hemmo1969
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Re: Amps - Whats in em and why?

Unread post by Hemmo1969 » Sun Nov 10, 2019 1:25 pm

karatestu wrote:
Sun Nov 10, 2019 7:42 am
Are you any the wiser now Chris ?
Not sure I’m wise :) but enjoying the comments and yes I can easily see how companies put so much hyperbole in their adverts.

valvesRus
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Re: Amps - Whats in em and why?

Unread post by valvesRus » Sun Nov 10, 2019 1:29 pm

Hemmo1969 wrote:
Sun Nov 10, 2019 1:25 pm
karatestu wrote:
Sun Nov 10, 2019 7:42 am
Are you any the wiser now Chris ?
Not sure I’m wise :) but enjoying the comments and yes I can easily see how companies put so much hyperbole in their adverts.
Can you think of ANY companies (NVA accepted) that don't use hyperbole in their adverts ?

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

Unread post by Daniel Quinn » Sun Nov 10, 2019 1:49 pm

Despite selling through mcru, longdog audio are pretty factual.

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karatestu
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Re: Amps - Whats in em and why?

Unread post by karatestu » Sun Nov 10, 2019 2:07 pm

I still think of myself as an electronics numpty who knows just enough to be dangerous, so take any of my views with a pinch of salt.

Yes all adverts are full of marketing nonsense. Some are worse than others.

If you are looking to learn more about what makes up an amplifier then you need to do a lot of reading and asking of questions. That will get you to a point where you can understand what people are talking about. You could then put say a power supply on some amplifier boards, wire it all up correctly and not blow anything up. Very satisfying.

To get to the real nitty gritty you need to study general electronicsi think. Ohm's law, what resistors, capacitors, diodes, transistors etc do.

A quick overview of what is in a solid state amp to help you understand

Power supply - can be linear or switch mode. Linear involves a transformer ( big donut ) to reduce 240V AC down to a usable level (say 30V for eg). Then there is a rectifier (which is usually made from diodes) which turns AC to DC voltage. Then comes the big smoothing / reservoir capacitors which filter out some of remaining AC noise and other crap and supply power to the circuits. Some amps use regulators for all or part of the amplifier. Most (?) don't use one at all (NVA). A regulator is there to provide a steady, low impedance, constant DC voltage to the amplifier circuit .

The amplifier circuit - can take many forms and include various stages. Class A, AB, D etc etc.

Switches, potentiometers, relays, transformers for volume & source selection (if integrated amp), power on off

Any active preamp circuitry or buffers

The case and heatsinking, input and output sockets, signal wiring, power supply wiring

Other bells and whistles like output protection (to protect the speakers), circuits to prevent over stretching the output transistors, remote control, soft start circuits to prevent the turn on surge from tripping consumer units blah blah etc etc.

It can be a bit daunting getting to grips with all this. Sometimes it helps when a friendly, helpful person on the internet takes the time to explain things in understandable language. Often they forget they are talking to a beginner or they can not be bothered to take the time to explain it.
DIY inspired by Richard "The Doc" Dunn RIP

Lurcher300b
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Re: Amps - Whats in em and why?

Unread post by Lurcher300b » Sun Nov 10, 2019 3:00 pm

Power supply - can be linear or switch mode. Linear involves a transformer ( big donut ) to reduce 240V AC down to a usable level (say 30V for eg). Then there is a rectifier (which is usually made from diodes) which turns AC to DC voltage. Then comes the big smoothing / reservoir capacitors which filter out some of remaining AC noise and other crap and supply power to the circuits.
The above is just about true for a switch mode as well. The only difference is the mains is rectified and filtered, and then converted into a high frequency wave with switching (efficient) transistors, that goes through a transformer to reduce it to the required level, then its rectified, smoothed and passed to the rest of the amp. Because its done at high frequency (say 200kHz) instead of 50Hz the transformer can be much smaller, and the smoothing caps smaller. But other than that, they are not as different as you may imagine.

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

Unread post by Geoff.R.G » Mon Nov 11, 2019 6:35 pm

karatestu wrote:
Sun Nov 10, 2019 2:07 pm
I still think of myself as an electronics numpty who knows just enough to be dangerous, so take any of my views with a pinch of salt.

Yes all adverts are full of marketing nonsense. Some are worse than others.

If you are looking to learn more about what makes up an amplifier then you need to do a lot of reading and asking of questions. That will get you to a point where you can understand what people are talking about. You could then put say a power supply on some amplifier boards, wire it all up correctly and not blow anything up. Very satisfying.

To get to the real nitty gritty you need to study general electronicsi think. Ohm's law, what resistors, capacitors, diodes, transistors etc do.

A quick overview of what is in a solid state amp to help you understand

Power supply - can be linear or switch mode. Linear involves a transformer ( big donut ) to reduce 240V AC down to a usable level (say 30V for eg). Then there is a rectifier (which is usually made from diodes) which turns AC to DC voltage. Then comes the big smoothing / reservoir capacitors which filter out some of remaining AC noise and other crap and supply power to the circuits. Some amps use regulators for all or part of the amplifier. Most (?) don't use one at all (NVA). A regulator is there to provide a steady, low impedance, constant DC voltage to the amplifier circuit .

The amplifier circuit - can take many forms and include various stages. Class A, AB, D etc etc.

Switches, potentiometers, relays, transformers for volume & source selection (if integrated amp), power on off

Any active preamp circuitry or buffers

The case and heatsinking, input and output sockets, signal wiring, power supply wiring

Other bells and whistles like output protection (to protect the speakers), circuits to prevent over stretching the output transistors, remote control, soft start circuits to prevent the turn on surge from tripping consumer units blah blah etc etc.

It can be a bit daunting getting to grips with all this. Sometimes it helps when a friendly, helpful person on the internet takes the time to explain things in understandable language. Often they forget they are talking to a beginner or they can not be bothered to take the time to explain it.
That isn't actually a bad explanation.
Protection is usually for the output transistors rather than the speakers. I came across what happens if you overdrive speakers recently, someone else had use one and when I went to use it nothing happened. Some time later I took the drive units out and both were open-circuit. Obsolete Sony units so now I have to work out what to do with it.
It is actually pretty difficult to protect a speaker in the amplifier as there is no way the amp can know how much current a speaker can take. That is the user's job.

Lurcher300b
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Re: Amps - Whats in em and why?

Unread post by Lurcher300b » Mon Nov 11, 2019 6:49 pm

Protection is usually for the output transistors rather than the speakers
Normally both. Protection for the output devices in the case of overload caused by a short circuit, or some other out of spec occurrence. Protection for the speakers in the case of a fault in the amplifier. Normally DC if one of the output devices fails, or one of the rail fuses blows. Also excess HF in the case of instability (not many check for that).

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Re: Amps - Whats in em and why?

Unread post by Geoff.R.G » Mon Nov 11, 2019 7:18 pm

Lurcher300b wrote:
Mon Nov 11, 2019 6:49 pm
Protection is usually for the output transistors rather than the speakers
Normally both. Protection for the output devices in the case of overload caused by a short circuit, or some other out of spec occurrence. Protection for the speakers in the case of a fault in the amplifier. Normally DC if one of the output devices fails, or one of the rail fuses blows. Also excess HF in the case of instability (not many check for that).
Good point, speakers don't like DC. I hadn't thought of either of those because my experience is that transistors fail open circuit but obviously the can have other failure modes. Instability is something many designs try very hard to avoid, and Richard chose not to protect against with additional circuits.

I must be getting out of practice because that's twice in this thread that I have missed the obvious.

Lurcher300b
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Re: Amps - Whats in em and why?

Unread post by Lurcher300b » Mon Nov 11, 2019 7:27 pm

is that transistors fail open circuit
Maybe, but often it can be a driver transistor that can fail causing the output to go to one or other rail. Its never the obvious failure that happens, its always the cunning sneaky one that bites.

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