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PostPosted: Mon Nov 12, 2018 4:16 am 
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No one ever mentions them in amplifier reviews. Manufacturers never say a word about them.

Why?

Are they simply accepted as a given or were they never required in the first place?


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PostPosted: Mon Nov 12, 2018 6:05 am 
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PBB wrote:
No one ever mentions them in amplifier reviews. Manufacturers never say a word about them.

Why?

Are they simply accepted as a given or were they never required in the first place?

First a general observation...

In the days of old, "reviews" consisted largely of facts (weights, dimensions, features) and measured results, with the occasional opinion / interpretation thrown in. Most so for power amplifiers.

Nowadays there's no room (or budget - or even ability) for reviewers to generate, or have access to, test results, so a review consists mostly about feelings, and how well a phrase can be turned from the same old subjective quiver of descriptors.

Now of course I generalize. But that's the trend / change that I have seen.

An amplifier review would have its physical characteristics and appearance described (with perhaps the addition of "attractive" thrown in). Then its class, published specs (usually in an industry-wide accepted standard way of doing so - mostly mandated by government rules) and then any special features - which would include things like protection circuits. Then would come the testing - and comparison with the published specs (ie. did it do what it said it could do). And then, especially if something were "off," there would be a brief description of how it sounded - and since, to a great extent all amps sound the same, comments were usually something like how loud and "clean" it could drive sound out of a chosen set of speakers. That was it.

And back to the OP, and protection circuits: yes they are absolutely required - assuming one values one's speakers!

But since they just sit there doing nothing until they are needed, contributing nothing, nor taking anything away from the sound, today's reviewer, searching for yet more verbiage to describe something that sounds the same as everything else, usually ignores it completely. And I don't blame him for doing so. (I can't recall reading a car review wherein column inches are dedicated to the parking brake. I just assume that every car has one and that it will work when I need it. And yes not completely analogous, but it illustrates the point.)

Jeff

ps. Speaking of published specs... I was in a Canada Computer store yesterday and happened to look at the box for a surround receiver that they were selling. It had a very visible sticker proclaiming that it was "175 Watts/channel." But also on the sticker was printed the disclaimer "6 Ohms, 1 KHz, 10% distortion, one channel driven." I pity today's consumer!

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PostPosted: Mon Nov 12, 2018 6:11 am 
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Well we still have John Atkinson measuring things to a degree, at least last time I checked.


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PostPosted: Mon Nov 12, 2018 7:13 am 
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We're still changing over to being internet based.

Where the spilling of prose is the easy part, and is free. If not a revenue generator.

whereas with print, each word has a cost and that cost must be associated with revenue. Revenue from pages of advertising, that is paid for, and on the given printed pages. Each word or paragraph, is dear, in this scenario.

with the interwebs, new prose to view and take in, is a flick of a mouse away and the costs are minimal. Very much so. Close to zero.

The new trick, or new aim/reality is to get the reviewer to wax poetic and spill ink. More internet pages to be viewed by the reader and thus more adverts to be witnessed by the given reader.

The numbers and how they occur, are slightly but notably different.

Print and website versions of audio reviews, for a given rag or entity that has both print and website...are currently ...identical. I expect that to change. If it hasn't, it should.

Measurements are a web page that can occur in a way that it pays for itself, via views. all kinds of opportunities here, with the extensive test records that entities like Stereophile have made over the years.

... ... ...

I believe in measurements, but I also believe in my ears, and my ears and preferences and my intellect tied to the given hearing takes precedent over measurements, in the final vote. All sensible people who make audio gear in this high end world, feel and act this way, almost to the last individual.

Science does the same. Observation is first and observation remains king. It's a simple statement to cover the large complexities of senses vs measurements vs intellect, so don't take that literally in how you interpret the words. It's tied to the prior paragraph, obviously...

As for protection circuits, they do indeed impact the sound quality in some audio gear in some cases. A slight increase in sound quality, overall, across the board, in all amplifiers as a set, would occur if protection circuits were absent. Depends on implementation, etc.

If we are talking about fusing (which is a protection circuit), then overall, with fusing absent....a notable step forward in sound quality would occur. Fusing will remain, though. It's origins are legal and mandated in the original sense and also adopted, over time, in attempts to be as protection circuits.

-- 12 Nov 2018 11:27 --

PBB wrote:
Well we still have John Atkinson measuring things to a degree, at least last time I checked.



John's measurements are largely as extensive as any manufacturer's own internal gear and analysis. So extensive that some manufacturers of audio gear tested at Stereophile -have less capacity and commit to less measurement than Stereophile does. John uses an Audio Precision SY2722 test bed. Audio nerds drool over this stuff. I've used them before. Totally awesome toys - ahem, work tools. True audio nerds want one of those under the Christmas tree. Except for the problem of 'New car or an Audio Precision test bed' being the core decision tree.... most audio nerds would have such gear.

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PostPosted: Mon Nov 12, 2018 7:49 am 
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Great post Ken, great post!

All I wanted was to see if my hunch was right (1) that there is nothing new in protection circuits; and (2) that the great fever that such circuits affect audio quality had now broken.

Blew the doors right off of my silly question and I now understand that speakers no longer don't mind a healthy dose of DC.


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PostPosted: Mon Nov 12, 2018 8:10 am 
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Quote:
I now understand that speakers no longer don't mind a healthy dose of DC.


No speakers I know likes or behave good under theses ''dose of DC''

Protection circuits exist for protecting
1- speakers
2- complete meltdown of the drivers and output stages
3-both above conditions

Protection circuits will operate if current limits are present. Short circuits or extreme low impedance and limit of drive or all theses variables.

Certain amplifier do have intrusive protection as current limiters or other design withstand a lot of current and instantaneous power.
all related to circuits design and what you want to achieve.

A good old Naim NAP250 could push a 6dB headroom while other only could push 1dB of dynamic signal over their rated specs.
But a Hifi amp is not design to be a tour band amplifier....
Both DC offsets are to be as low as possible , 10-20 millivolts or lower for push pull transistor amp is good.


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PostPosted: Mon Nov 12, 2018 11:07 am 
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PBB wrote:
Great post Ken, great post!

All I wanted was to see if my hunch was right (1) that there is nothing new in protection circuits; and (2) that the great fever that such circuits affect audio quality had now broken.

Blew the doors right off of my silly question and I now understand that speakers no longer don't mind a healthy dose of DC.


My sarcasm detection meter is a bit wobbly and confused, thus it seemingly indicates you've got some quality product, there.....

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PostPosted: Mon Nov 12, 2018 1:39 pm 
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Teo Audio wrote:
PBB wrote:
Great post Ken, great post!

All I wanted was to see if my hunch was right (1) that there is nothing new in protection circuits; and (2) that the great fever that such circuits affect audio quality had now broken.

Blew the doors right off of my silly question and I now understand that speakers no longer don't mind a healthy dose of DC.


My sarcasm detection meter is a bit wobbly and confused, thus it seemingly indicates you've got some quality product, there.....



I thought yours was pretty good to, you know your first paragraph left me speechless. :roll:


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PostPosted: Mon Nov 12, 2018 1:49 pm 
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PBB wrote:
All I wanted was to see if my hunch was right (1) that there is nothing new in protection circuits; and (2) that the great fever that such circuits affect audio quality had now broken.

AFAIK, there haven't been any particularly new idea's in protection circuits... They basically boil down to three types. There's the SOA or IV limiters, which aim to protect the output devices by limiting the wattage they're being asked to dissipate. That's the type most notorious for negatively affecting audio quality, particularly if they're set at the "safe" end of things, and you're using low impedance/high current demanding speakers. There are thermal shutdowns, which turn the amp off if it gets too hot. And finally there are the DC offset type, which can operate in a few different fashions (turn the amp off, open an output signal relay, or crow bar the output).

Part of the problem as I see it, is that there are fewer and fewer reviewers that actually have any sort of technical knowledge, and wouldn't recognize an IV limiter if you circled it on a schematic. They plug it in, and wax poetic about the "inner bloom", "bass slam", and how low the jitter must be, without a real clue about what circuit design might get you there, or why there's no such thing as jitter in a non-switching amplifier.

That's my two cents, for what they're worth! Cheers, Dave


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PostPosted: Mon Nov 12, 2018 3:26 pm 
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There was an older tech I spoke with who recommended an inline fuse on speaker cables. He thought that when transistor amps blew there was almost always speaker damage. The built in protection on most amps isn't fast enough. He also said that he "replaced more transistors than tubes".

I can't say that I followed his advice. I did stop buying old vintage transistor amps.


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