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Old 27th October 2012, 06:53 AM   #21
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Excellent communication. Totally understandable. Thanks!!
Quote:
Originally Posted by Esperado View Post
You can set delays for different feels. With a fast attack and a long recovery, you can reduce the volume of any loud signals.Volume decrease at the attack and stay at a lower level. After the average high level material of the signal has stopped, the gain will slowly increase.
The "VR1" (compressor for television) from AudioVox, Terk, does that. It generally works but often sounds disturbing when the volume suddenly changes. It is better than either fiercely loud commercials or unintelligible voice tracks on movies, but not attractive for music.
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Originally Posted by Esperado View Post
On the contrary, using slow attack and fast recovery, you can let the peaks, and reduce volume after. Adding attack to a bass that way is a common practice in mixing processes.
The ClipNipper (compressor for boosting small amplifiers) does that. It is unable to reduce bass impact. The frequency response stays level. It doesn't make the typical compressor "YAAAA!" sounding effect. Maybe it doesn't make that noise because the bass is as loud as the vocals? Thanks for the clues!
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Originally Posted by Esperado View Post
About what I'm looking for, is a clipper able to clip a signal in a identical way that following amp can do. Of course, because it is supposed to be a protection, even in high end amps, it is requisite that this clipping circuit will not deteriorate the quality of the signal in any way.
Such a perfect circuit will just remove little percent of the peak power capability of the amp.
Clip the amp before it may do worse. Sounds just like the amp clipping normally (maybe sounds just like a tube amp clipping normally). Removes only a little bit of peak power without affecting the normal signal range of operation. Oh, we're back on topic--I think you've just named a soft clipper.
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Originally Posted by Esperado View Post
For the moment, I'm on this simple idea: + 2 adjustable zener Diodes. The interest is that it has no action before the threshold, because just a resistance in the signal path.
Click the image to open in full size.
Adjustable like this? ZR431 Zener shunt reg
Slight problem: The voltage tolerance is so tight that there's very little curve and a lot of flat. I like the adjustable idea, but we need "more roundness, less flat" You might want to build a clipping indicator to see that real music signal is so very dynamic, that your device will be giving peaks an audible flat top more often than expected.

Can you do this multi-step approach?
A mild (tiny current) soft clipper takes effect first, followed by. . .
A medium current soft clipper takes effect next, followed by. . .
A strong soft clipper, takes effect last, followed by. . .
A hard clipper with a non-audio voltage setting for surge overload protect.
*Only the 3 soft clippers are doing an audio processing task.

Mild current soft clipper is set for lower voltage (the amp has almost begun to clip),
medium current soft clipper is set in the middle (the amp has begun to clip),
strong current soft clipper is set for highest voltage (the amp is clipping).

the roundness is increased--the duration of flat top is decreased
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Old 27th October 2012, 09:38 AM   #22
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Default More limiters than easter eggs. :)

Quote:
Originally Posted by AndrewT View Post
A bit difficult to add a limiter and set it up when we don't have any. . . . 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.
Thanks for the Bob Cordell references. I enjoyed reading those parts of his book. On reading some of his interviews and papers I guess that he puts the Baker Clamp into the soft clipper category along with Klever Klipper. But, what I'm actually sure of is that they're mentioned together.

A few compressors for comparison. . .
Here's Rod Elliot's spin on a compressor Audio Amp Power Limiter
I think it interesting that Rod Elliot proposes handmade DIY optocouplers. It is also possible to use the 10mm led's file the top of the led flat, glue it to a CDS cell (with clear glue) and paint the device black. You can make a Rod Elliot limiter (compressor) a ClipNipper, a lightspeed attenuator (that you can automate) or even a Volumax for your border blaster.

My ClipNipper uses a similar approach to Rod Elliot's circuit, but I found that the current reliant LED were more likely to predict what needs doing for helping small size amplifiers.
It seems to be a matter of scale:
He has 100u delay and 10k input loss. I have 22u delay and 1k input loss. Neither offer fast peak protection--LDR and cap delays allow peaks to pass prior to LDR activation. Both offer protection against constantly high current. His compressor is more dramatic (more effective = less transparent). I think he designed for big amp (he mentions 500w) while I designed for small amp (10w to 25w).

And now adding the soft clipper. . .
Neither compressor can block x-max or peaks unless set to severely reduce the amplifier's power output. That might be okay if using Rod Elliot's 500w amplifier, but it is a fail with my T-amp. Instead of setting the compressor to reduce output power greatly, I would prefer to add the fast soft clipper to block x-max and block peaks as needed to catch what the compressor didn't do.

I guess that the soft clipper's zero delay (fast attack) combined with the compressor's pattern gets very close to doing the job thoroughly. And both can be set mildly for transparency (low disturbance). I believe that what we don't want to hear is the flat top of normal clipping or hard clipper. Soft clipper also has a flat top, just not sharp edges. By adding the compressor the trailing edge is restored to almost normal for music signal and the flat top is gone.
Unfortunately, there were optos to make or buy, and that is slightly inconvenient.
Quote:
Originally Posted by AndrewT View Post
I don't have a limiter. I suspect most listeners don't have a limiter.
In a broader definition, I see a few limiters in use: Transformer throttling, CRC resistor, some types of amplifier compensations, current dumper cable, flexy bridge rectifier (KBPC1610, Stealth), SMPS safety limiting, LM3875 LM3886 NatSemi Overture Spike System screeching harder limiter, TDA7293 TDA7294 soft limiter (decreases bass). Well, I think we all have limiters to some extent, but they might not be as attractive as possible.
Therein is the motivation to do something differently.

The Bob Cordell Super Gain Clone with Klever Kilpper example is great because, I believe that NatSemi made the unfortunate mistake of assuming that music transient peaks of significant height, don't occur during normal playback. In addition to a clever topology, he also sets the Klever Klipper to take effect before the chip amp's disturbing Spike system activates. He put a Klever Kork into NatSemi's noise generator.

Not everyone use a Klever Klipper
Some of us want more simplistic circuit.
But, with a more simplistic circuit, there's a caveat in that effective is not transparent, but transparent is a lot less effective.
And the simple options. . .
For the normal amplifier (those without inbuilt clippers), the soft clipper if set aggressively, looks just like a hard clipper except for ineffectively rounded edges (sounds like Spike) or the soft clipper if set mildly looks like a rather ineffective headroom boost (imitation tube/valve clipping in addition to regular clipping). Instead of choosing between bad or bad, what I'd rather do is have load at the input dynamically adapt to the current requirement of the given signal.--Instead of a flat top haircut, I'd like greater resemblance to normal music signal.
Done without op-amps.
Done without optocouplers.
Done without complex sensor.
Done without cutting output power severely.
At the very least, I wish to have the simple soft clipper altered to reduce the duration of the flattened portion of the signal (via curving the edges more). Without actually building compressor circuits with op-amps and/or optos, the best I can think of at the moment is multi-stage soft clipper also employing at least one current reliant diode.

And simplified works, but there's a problem.
Even with the fast circuit at the bottom of post 1, I can't quite seem to avoid a bit of treble hash and unlevel frequency response. The bass gets cut first. The switching pollutes the treble. This needs a filter, but I haven't managed it yet. It seems to need a voltage activated addition that would engage a "tone control" as needed and concurrently with soft clipper activation. Maybe each stage that switches on can also engage a really mild RC enough to affect a partial compensation?

I'm in search of something simple, but that wasn't simple.
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Last edited by danielwritesbac; 27th October 2012 at 09:43 AM.
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Old 27th October 2012, 11:24 AM   #23
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Quote:
Originally Posted by danielwritesbac View Post
Adjustable like this? ZR431 Zener shunt reg
You got-it.

Can-you precise your goal, danielwritesbac ?
You do not allow on a high end system that clipping never occurs. A simple clipping indicator would be sufficient to warn-you that you have to reduce your level for no distortion, don't you think ?
Of course, this implies that your speakers are efficient enough for high SPL, and your amp powerful enough.

Rare clippings, only on the top of half a period on the attack of an instrument, are not really a problem. It will gives-you the feeling of more "punch", and your brain will not have time to analyses the distortion as so. I doubt that softening of the clipping would change the landscape in a drastic way. If you use commercial recordings, (CDs) the limitation of those rare peaks are already done during mastering in a transparent way (digital limiters).

So, did you want a soft clipping for frequent overdrive of your amp ? (no fidelity expected )
Means less dynamic and more average level ?
A compressor will give-you more agreeable results, i think. That you can bypass when you want a linear reproduction.

PS: About adding attack on an instrument with a compressor, that can be done only with a multi track recording, where all the instruments are separated, so you can apply this to one single instrument alone.
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Last edited by Esperado; 27th October 2012 at 11:35 AM.
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Old 27th October 2012, 12:05 PM   #24
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Quote:
Originally Posted by Esperado View Post
A simple clipping indicator would be sufficient to warn-you that you have to reduce your level for no distortion, don't you think? Of course, this implies that your speakers are efficient enough for high SPL, and your amp powerful enough.
You got it. My amp isn't powerful enough. It isn't 768 watts, and I don't have rare high efficiency speakers either.
Quote:
Originally Posted by Esperado View Post
Rare clippings, only on the top of half a period on the attack of an instrument, are not really a problem. It will gives-you the feeling of more "punch", and your brain will not have time to analyses the distortion as so. I doubt that softening of the clipping would change the landscape in a drastic way.
I disagree, partially. Clipping indicators, from Rod Elliot and others, show that clipping is very, very frequent. I agree that it is short duration.

If this meets a typical aggressive soft clipper, it gets worse distortion, and I don't want that.

Decreasing the distortion for a soft clipper means decreasing the current of the soft clipper (decreased effectiveness). That's good! Then it has a mild, low distortion, very gentle, effect on the signal. That's not very helpful, but it is a lot less harmful.

I think "a lot less harmful" is the useful place to start.

After that point, there's a game of increasing effectiveness without increasing distortion. For that, I propose to set an additional mild, low distortion, very gentle soft clipper at slightly higher signal voltage. The signal has again been curved gently--yes it has now been curved gently twice.

EDIT:
I'd like to see really gentle times three different stages, and all low distortion and adjustable.
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Old 27th October 2012, 04:02 PM   #25
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A soft clipper means you'll loose more linear power than with a "hard" one. Because if it as action in the last 3Dbs (half of power), the last half of your power will make distortion to the signal, whatever this signal would have been clipped or not.
And if it has less margin action, i believe the difference will not be obvious.
I don't know if i make this clear... my poor English...
But you didn't had answering my question about your context. High end system ?
What is your amp ?
Why are-you limited with power of your amp ? Can't you use a more powerful amp ?
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Old 28th October 2012, 04:52 AM   #26
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Quote:
Originally Posted by Esperado View Post
A soft clipper means you'll loose more linear power than with a "hard" one. Because if it as action in the last 3Dbs (half of power), the last half of your power will make distortion to the signal, whatever this signal would have been clipped or not. And if it has less margin action, i believe the difference will not be obvious. I don't know if i make this clear... my poor English...
But you didn't had answering my question about your context. High end system? What is your amp? Why are-you limited with power of your amp ? Can't you use a more powerful amp ?
The amp is whatever I happen to be making at the moment.
A non-defective soft clipper will give you a headroom boost.

Perhaps the topic is not clear until after building a few options for comparison?
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Old 28th October 2012, 09:17 AM   #27
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Quote:
Originally Posted by danielwritesbac View Post
.............A non-defective soft clipper will give you a headroom boost.................
No !
if the Vpk is limited by the Rail supply and the losses through the output stage, then implementing a soft clip circuit will reduce the headroom before the distortion sets in, i.e the clip starts earlier than if the soft clip circuit were not fitted.
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Old 28th October 2012, 01:08 PM   #28
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Quote:
Originally Posted by AndrewT View Post
No !
If the Vpk is limited by the Rail supply and the losses through the output stage, then implementing a soft clip circuit will reduce the headroom before the distortion sets in, i.e the clip starts earlier than if the soft clip circuit were not fitted.
The current setting is overly aggressive if soft clipper is causing brick wall errors like that.
Peak height and duration are individually adjustable.

A "mild" soft clipper is for pinching the top of square wave to decrease duration of clipping peaks, without cutting the height of the peak.
It is a compressor's poor cousin.
Decreasing the duration of the peak looks good for output device SOAR.
Decreasing the duration of the peak allows faster power supply recharge.

Long term test almost done:
Since Thursday, May 03, 2012, according to the date stamp locked into the forum attachment, the ltp soft clipper has been in active service protecting real amplifiers without reducing useful headroom. It will have 6 months active service by November 3, 2012.

P.S.
Thank you for the helpful post that illustrates the typical soft clipper problem; however, there are many choices and I'm focusing on uncommon soft clippers that can't brick wall within the useful range of the amplifier. We might agree that the amplifier's normal clipping pattern is usually better than adding a problem.
You have so many, many choices for soft clipper,
And their qualities vary. Mostly awful. Few good.
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Last edited by danielwritesbac; 28th October 2012 at 01:36 PM.
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Old 28th October 2012, 02:54 PM   #29
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Soft Clipper in common language is a device that ABSOLUTELY MUST: Provide the more favorable clipping pattern of a tube amplifier along with the implied headroom increase. Anything that fails the expectation is necessarily considered poor quality and possibly something to avoid.

Is there, perhaps some alternative and highly malicious definition specific to engineer-speak? Is the term "soft clipper" used as an "inside joke" to catch the unwary? Why is everyone promoting slightly softened circuits overly similar to hard clipper behavior? Does talk of soft clipper automatically incur hazing? What's going on? And, where is the quality control? Did I accidentally request something unexpectedly bad?
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Old 28th October 2012, 03:20 PM   #30
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Quote:
Originally Posted by danielwritesbac View Post
a device that ABSOLUTELY MUST: Provide the more favorable clipping pattern
That is where lie our reactions: we think clipping has never to occur in a hifi system.
When highest quality 400W amps (like hypex N400) are available and affordable, (and some other, a little less good for 1/10 of its price), we tend to look, instead, at this kind of solution.

Anyway, we are curious to heard from your experiments.

But, once again, if for some reason, i had to respond at that kind of technical requirement (increase the average level with not excessive distortion), i will look limiters side.
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Last edited by Esperado; 28th October 2012 at 03:25 PM.
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