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Old 24th October 2012, 05:26 AM   #1
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Default Soft Clippers versus expectations. They're not magic.

Update: Please see Sreten's informative post (#6) as soon as possible.
If I understood that post correctly, the layman's (my) expectations of a soft clipper is that which provides tube amp like softer clipping and headroom benefits; but, unfortunately, that isn't what typical soft clipper circuits do. Actually, except for being quieter hard clippers, real typical soft clipper circuits are not a desirable audio effect.

Therefore, please bear in mind that the goal of this thread is Non-Typical soft clipper circuits that are actually on-demand halfbreed compressors (for attempting some tube amp features and headroom). Thanks AndrewT, for mentioning Bob Cordell's Klever Klipper at post #3. As Mr. Cordell's creative spelling indicates (engineer humor there), Klever Klipper does compress-before-clip, which is prettier than a regular soft clipper.

Goal:
I have hopes that multiple slightly ineffective aka non-clipping, elementary soft clipper circuits can be stacked to do compress-before-clip (a Klever Klip) without op-amps or optocouplers.

See also Esperado's post #30.
More information at post #34.

The soft clipper is faster and costs less than a typical compressor; however there's a treble difference if the two are compared.
Some examples. . .

Here's Elvee's 4N25 Soft clip + Limiter for Circlophone. (a protector, not an audio effect)
What is shown is a protector with soft clip pattern; however, the detector shown on the far right is generally applicable, can use zeners as low as 5.6v and could be re-deployed to drive a compressor (not shown).
Click the image to open in full size.
.

Here (below) is my diode based ltp soft clip (partially a compressor), inspired by Ken.
The feedback resistor, R17 is unaltered
The feedback-shunt resistor, R16 is replaced with a voltage divider or trimmer
The soft clip (partially a compressor) is connected from in- to in+ of an ltp
The circuit also fluctuates compensations thereby altering harmonics.
A trimmer at R16a, R16b can be dialed in so that compressor occurs while the amp is beginning to clip; but, if you push it harder, soft clip occurs.
Click the image to open in full size.
.

Here (below) is my overload stopper. No matter if that is called a hard or soft clip, that protector is quite useless as an audio effect. However, it shows that a voltage detector at input of power amp, doesn't remove headroom (in normal conditions).
Click the image to open in full size.
Reduces the big loud bang of awaking the computer from standby power saver.
Maybe that circuit can be modified in order to answer this question:
Quote:
Originally Posted by Esperado
Please, i'm looking for a nice and simple idea to clip an input signal, and to can tune-it just under the clipping point of any amp. I would be very pleased if you have some idea better than my adjustable zeners's ones in the input line.
Here goes with sneaking up on the signal (a prettier effect). The high precision square corners of Zeners may sound like a square wave; so, instead of that distortion, an LED knee voltage is more gentle, and more current reliant, which gives softer corners for a prettier soft clipper (prettier = more like a compressor).
Click the image to open in full size.
Variable resistor settings, lowest current on left side, higher current on right side.
Diode options:
1N34A, ECG109, SK3090, 1N60, BAT86, BAT85, 1N5711, fast/soft silicon diodes, and LED.
Tested: 1N34A, BAT86, LED's aren't as harsh as regular diodes.
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Last edited by danielwritesbac; 11th December 2012 at 08:21 PM. Reason: subtract picturesque from intro. change the word noise to the word distortion.
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Old 25th October 2012, 08:40 PM   #2
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I understand why we can use a clipper to protect an amp.
But why to use a "soft"-one ?
If it used to reduce disagreeable distortions effects during high levels's party's, why not to use a limiter, instead, with less distortion when after the limit ? Because of the less complicated and expensive circuit ?
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Old 26th October 2012, 11:27 AM   #3
AndrewT is offline AndrewT  Scotland
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I don't have a limiter.
I suspect most listeners don't have a limiter.
A bit difficult to add a limiter and set it up when we don't have any.

I tell a lie, I do have a DCX 24/96 and it has limiters of some type inside.

Could Baker Clamps be termed a soft clipper?

Cordell shows a soft clipper, he called it Klever Klipper.
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Last edited by AndrewT; 26th October 2012 at 11:30 AM.
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Old 26th October 2012, 11:58 AM   #4
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Quote:
Originally Posted by AndrewT View Post
I do have a DCX 24/96 and it has limiters of some type inside.
Could Baker Clamps be termed a soft clipper?
Modified DCX ?
I believed Becker Clamps was for fast switching ?
In fact, i am in need for a perfect limiter, for a protection circuit. Witch add no noise nor distortion before it clips...
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Old 26th October 2012, 12:15 PM   #5
AndrewT is offline AndrewT  Scotland
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Baker clamp.
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Old 26th October 2012, 12:44 PM   #6
sreten is offline sreten  United Kingdom
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Hi,

A thread that starts with a load of misinformation about "palatable clipping"
and ignores the general principles of the way dynamic range management
is usually done in subs, AV kit and PC speakers is somewhat doomed.

(Also the way its done for film, TV and radio, as well as music mastering).

Assuming circuits are a fix to a problem and describing them in those terms
doesn't cover what they really do and don't do, and thus will mislead a lot.

rgds, sreten.
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Old 26th October 2012, 01:07 PM   #7
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Quote:
Originally Posted by AndrewT View Post
Baker clamp.
My typo mistake, those diodes, yes.
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Last edited by Esperado; 26th October 2012 at 01:22 PM.
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Old 26th October 2012, 01:18 PM   #8
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Quote:
Originally Posted by sreten View Post
A thread that starts with a load of misinformation about "palatable clipping"...
In a way, i was uncomfortable with this "palatable" as well as "soft". But did we have to discuss about producing an acceptable (intelligibility) movie sound track for both TV (listened at low level in noisy ambiance) and movie theater (with enough dynamic effects) ?
About what kind of peaks we can limit without we can notice the loss of "ease" to increase a subjective level in a CD ? It would take hundred of thread's pages and should be untitled with "limiter or compressor" in the subject.

So i believe the first poster limit its goal to speaker reproduction, and that its attempt is, not touching the gain curve, to reduce the subjective effects of rare clipping when playing a program at the limit of amp's headroom ?
While my own interest is just clipping without signal deterioration under the limit.
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Last edited by Esperado; 26th October 2012 at 01:30 PM.
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Old 26th October 2012, 01:30 PM   #9
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Quote:
Originally Posted by sreten View Post
Hi, A thread that starts with a load of misinformation about "palatable clipping" and ignores the general principles of the way dynamic range management is usually done in subs, AV kit and PC speakers is somewhat doomed.
(Also the way its done for film, TV and radio, as well as music mastering).
Assuming circuits are a fix to a problem and describing them in those terms
doesn't cover what they really do and don't do, and thus will mislead a lot.
rgds, sreten.
Feel free to write a nice short concise intro for what soft clippers do and don't do, and I'll remove my intro and paste your quote at the top of post 1.

Right now I'll go attempt a re-edit to something less picturesque, but if that won't do, simply tell me something that will do.
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Old 26th October 2012, 02:11 PM   #10
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Quote:
Originally Posted by Esperado View Post
. . . to reduce the subjective effects of rare clipping when playing a program at the limit of amp's headroom? While my own interest is just clipping without signal deterioration under the limit.
I had 4 thoughts about this:
A clip (of short duration) happens more often than expected at normal playback volume. References:
-Sound Impairment Monitor (SIM) - Is This The Answer?
-ESP SIM (Sound Impairment Monitor)
I'm trying to say that you don't want to activate a hard clipper several times per minute during normal volume playback.
If signal encounters a hard clipper, the result is always increased noise; however, a soft clipper is less noisy.
A visual indicator could explain more than anything I could type.

". . . without signal deterioration under the limit." probably favors a soft clipper instead of a hard clipper. You can use both simultaneously, if the hard clipper is set to a higher switch-on voltage, to allow the soft clipper room to work. For example a standard overload blocker (hard clipper) installed on an amplifier that is also equipped with Bob Cordell's Klever Klipper (soft clipper).

Quote:
Originally Posted by Esperado
. . .why not to use a limiter, instead, with less distortion when after the limit ? Because of the less complicated and expensive circuit ?
A compressor/limiter usually has a capacitive delay and sometimes misses the leading edge of signal but almost always gets the trailing edge just fine. In my experiences, it is nice to use both the compressor/limiter and soft clipper--The compressor/limiter's treble may be prettier but the soft clipper is faster. They can work together nicely.
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Last edited by danielwritesbac; 26th October 2012 at 02:29 PM.
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