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Old 7th February 2012, 06:23 PM   #1981
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Originally Posted by dvv View Post
However, now that you mentioned it, I seem to remember that in an interview, Mr Johson did mention that he and his colleague Mr Conrad did actually design some of their first products ...

Is that too hard to bear?
Not at all, rather, if the very early stuff I had to fix was designed by economists and bankers it would explain the "interesting features".

Ciao T
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Old 7th February 2012, 06:29 PM   #1982
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T, at least you pointed out WHY we, in the PA industry, used limiters. We needed them to PROTECT the loudspeakers! The idea of needing them for home hi fi is almost a joke. Just get a slightly bigger amplifier, OR bi-amp. That will fix your problem, properly.
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Old 7th February 2012, 06:41 PM   #1983
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Quote:
Originally Posted by john curl View Post
T, at least you pointed out WHY we, in the PA industry, used limiters. We needed them to PROTECT the loudspeakers! The idea of needing them for home hi fi is almost a joke. Just get a slightly bigger amplifier, OR bi-amp. That will fix your problem, properly.
No, it's not a joke. Home users often don't have a slight idea how often their equipment clips. They don't understand that they don't have a headroom they want. They just think that equipment is bad. When my limiter works it flashes overload LED on the front panel. Compression sounds less nasty than clipping, and if the user does not want it he/she would follow the advice to decrease signal level when bright red light starts flashing.
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Old 7th February 2012, 06:46 PM   #1984
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I guess I just use bigger amps, because my hi fi does not clip very easily or often. The smallest amp that I use is over 100W/ch.
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Old 7th February 2012, 06:58 PM   #1985
bcarso is offline bcarso  United States
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Quote:
Originally Posted by john curl View Post
T, at least you pointed out WHY we, in the PA industry, used limiters. We needed them to PROTECT the loudspeakers! The idea of needing them for home hi fi is almost a joke. Just get a slightly bigger amplifier, OR bi-amp. That will fix your problem, properly.
When I worked on the electronics for OEM computer speakers, the primary objective was to avoid having a customer call and complain. So if the typical source, the computer soundcard, had an output sufficient to drive the amplifier into clipping, this could prompt calls unless there was some way of limiting. Somehow the knowledge possessed by most everyone in the home hifi arena about turning the volume down when you heard unacceptable distortion just went out the window in the computer domain.

There was usually not enough power to damage the actual drivers, although with process and design issues for these one can indeed get into trouble.

And of course, any whole system had to be dirt-cheap. However, the volumes justified spending a good deal of time optimizing things. If you are going to ship a few million units, saving a few pennies is warranted even if it takes a few days of work.

My favorite design managed to get a full-wave detector with complementary polarity outputs out of one transistor, which in turn drove a four-transistor current-steering cell wrapped around a power amp which incorporated a two-pole underdamped highpass, whose low-frequency boost got attentuated preferentially when things began to compress. A little bit of mid-dip EQ compensated for the 2Pi-4Pi transition in the midrange, and overall it was a pretty decent pair of speakers to flank a monitor. One of the nicest parts was that the industrial design was, for once, something good for acoustical directivity, with smooth, rounded features that minimized diffraction.

I can listen to music through them without fretting, casually, although obviously with limited low-frequency extension and overall SPL. Anything but high-end though! The bill of materials cost was shockingly low.


Brad

Last edited by bcarso; 7th February 2012 at 07:00 PM. Reason: word order clarify
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Old 7th February 2012, 07:11 PM   #1986
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Hi,

Quote:
Originally Posted by DF96 View Post
It turns out that economic systems can exhibit behaviour analogous to phase transitions. To some extent this explains the world crash, which most economists did not see coming.
Absolutely. Economics as now generally practised attempts to throw a corrective feedback loop around a non-linear system, with considerable stochastic non-linearities, "memory distortion" and it does so not in any direct way, but attempts to do so by adjusting power- ... ooops... money-supply, creating both massive lag (phaseshift) and leverage (loop gain)...

So, if anyone wants to know what is "wrong" with negative feedback, take the current economic troubles as an illustration what a badly designed feedback system does.

Indeed, one might argue that rather than trying to control the economics systems perceived non-linearities via global feedback systems, it may actually yield better results to simply abandon such feedback systems and where corrective action is needed to apply this on the most local level possible, in favour of maximising the accumulated non-linearities and to then use massive leverage to try to correct things when they really get off track.

But perhaps this is where the analogy breaks down.

The Economy is actually not a simple mechanical system (as theorists would an Amplifier be) or even highly complex mechanical system (as the practicians find real amplifiers to be), but involves large numbers of both irrational (pun intended) and easily influenced elements which are so irrational that in the trivial pursuit of any short term gain they can be easily made to act deliberately against their direct own long term interests...

Thankfully Amplifiers are generally rather devoid of such elements, lest you live too close to a Training centre of the Church of LRH and your Amp is pre-clear. In which case it is entirely possible it was taken over by one of the Body Thetans that got shed by the Clear's progressing to OT Level VIII, who now thinks it's a transistor, capacitor or resistor in your amp - in that case all bets are off...

Ciao T
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Old 7th February 2012, 07:14 PM   #1987
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Quote:
Originally Posted by john curl View Post
I guess I just use bigger amps, because my hi fi does not clip very easily or often. The smallest amp that I use is over 100W/ch.
Pyramid prototypes I made are used with Magnepans that are not efficient, and according to one user 80W / Channel is not enough for his taste, but he keeps it because it sounds better than all he tried before. Though, the same amps driving line arrays on campgrounds were adequate.
All depends on efficiency of speakers, room sizes, and individual tastes. If I can add some fool-proof so the user would not blame on me for own mistakes, when such mistakes are common, I will do that.

The only case when such protection was considered as bad, when one DJ tried to get "right sound" from my amp. I helped the guy pulling down master faders on console, pushing up faders on channel strips that have sharp diode limiters. He was satisfied.
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Last edited by Wavebourn; 7th February 2012 at 07:16 PM.
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Old 7th February 2012, 07:17 PM   #1988
bcarso is offline bcarso  United States
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Quote:
Originally Posted by ThorstenL View Post
Hi,

[snip]


Thankfully Amplifiers are generally rather devoid of such elements, lest you live too close to a Training centre of the Church of LRH and your Amp is pre-clear. In which case it is entirely possible it was taken over by one of the Body Thetans that got shed by the Clear's progressing to OT Level VIII, who now thinks it's a transistor, capacitor or resistor in your amp - in that case all bets are off...

Ciao T


They are NOT getting their hands on my amplifiers!
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Old 7th February 2012, 07:21 PM   #1989
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Hi John,

Quote:
Originally Posted by john curl View Post
I guess I just use bigger amps, because my hi fi does not clip very easily or often. The smallest amp that I use is over 100W/ch.
I guess I just ratchet up the Speaker Efficiency instead.

The highest efficieny speaker I have used long term was 104dB/1m/1W (not 2.83V, but 1W) the lowest ones often hover in the lower 90's...

Of course having a really quiet 150WPC or bigger Amp on a pair of near 100dB efficiency Urei's or similar main studio monitors is seriously silly grin inducing.

I occasionally clip my 35W Tube amp into my current 91dB/W/m speakers, but it's a tube amp with no global looped feedback so it can be overdriven quite hard before it goes from sounding "peak compressed" to "distorted", probably on the region of 6dB peaks above nominal power...

When the Amp goes from compression to obvious distortion I usually fear the neighbours in my Condo will pull my fuses.

Ciao T
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Old 7th February 2012, 07:23 PM   #1990
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Hi,

Quote:
Originally Posted by bcarso View Post
They are NOT getting their hands on my amplifiers!
In the interrest of accuracy, BT's do not HAVE hands, though they may think they ARE one of your hands, while not having any physical form. Well, according to the teachings of the Church of LRH anyway...

Ciao T
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