Soft Clipper Central Station?

[RCruz]

Clipping input:
At location "C4" put a series pair of FR diodes "facing up" and another series pair of FR "facing down" so there's 4 diodes total. A series pair of FR = 1v (and you'll need two series pairs--one pair is backwards polarity). OR, series pair of 1n400x is 1.3v.

Measure and adjust the value of C4 smaller so that the total of parasitic (diode body) and normal (c4) capacitance of that location is the same 1n as previously (or similar).

You will then get normal operation when the input is 1v or less, or some distortion if the input is more than 1v. Add an additional FR for upswing and an additional FR for downswing, if you want 1.5v (which will also have lower capacitance--diodes in series is like little capacitors in series, less capacitance that way).

If the FR diode body capacitance is still too high, you can switch to bat86 diodes instead (0.3v each), but signal schottky types are more frail and thus the series resistance, R6, may need to be greater to help protect them.
You can probably use up to 330R at R6 without affecting the audio. In that case, 2 pair 1n4148 clippers (0.7v+0.7v=1.4v clipper parallel with C4) is an easy option.

Usage, for example, computer music source, when the computer switches on or awakes from standby, the ranchy blast from its output, sometimes 12v, will be cut off to 1v by your input hard clipper.

*alternative to the input hard clipper protection is an active circuit, such as Cordell's Klever Clipper and many many other options. But none are as simple as antiparallel diodes with the voltage threshold set higher than desirable signal. These don't work very well alone, but can work rather well as the shunt leg of a voltage divider (your R6 is the other piece).


Clipping amplification:
But if you had needed to clip the amplification, then you'd need a much different circuit, such as an ltp soft clipper.
For this, change R22 to a 2k multi-turn trimmer in parallel with an 18k resistor, resulting in the original value of 1.8k. Next attach series two antiparallel pairs of BAT86 (0.3v + 0.3v = 0.6v clipper with very low capacitance) to the wiper of the 2k trimmer, and next, a 1k multi-turn trimmer (as a variable resistor) goes between the BAT86 clipper and the positive input. The 2k trimmer is clip voltage, the 1k trimmer is clip current. This describes an LTP soft clipper. Startup positions of the trimmers is half (wiper at centerpoint).

Usage, for example, a surge high enough to cause the outputs to stick (or severe hfe droop, or other non-linear range), has INSTEAD, clipped the inputs, which can recover instantly and rather easily (there's a big difference in the current of the clip--tiny at inputs or huge at outputs).

*I have not used the ltp soft clipper on a dc/mixed coupled amplifier; however, if there's trouble, it is possible to put a capacitor series to the 1k trimmer so that the clipper won't switch on for DC. If you undersize the cap, it will ignore some of the lowest bass pitches and appear to function as a rudimentary form of compressor instead of the intended function.
**The LTP soft clipper circuit will relocate your imaging linearity sweet spot to take effect during somewhat louder volume playback than previously, just as the LTP soft clipper has begun to catch a few peaks infrequently, is just about when the imaging will kick up to bigger and the tone will foobar slightly in identical proportion to the imaging boost. To swamp a bit more of that, you may want to double up your power decouplers, C5, C8, 100u||100u (200u, an orthodox value anyway).
***Alternative to the ltp soft clipper circuit is: baker clamps can be used instead.


I did use both the input clipper and the LTP clipper on my circlophone. Those two clippers do different tasks.

P.S.
Also suggest changing C3 to approximately 2uF, although 1uF may do fine or better; however, the currently 50uF input coupler could have too much discharge force, like a tiny tazer.

P.P.S.
I suppose there's some 100u in your parts box. Quadruple parallel 100u (400u low loss) would not sound bad if put in series between R22 and ground (400u as a coupler). It would be a worthy experiment to see if ac coupling will yield a more sturdy amplifier with louder and more lifelike dynamics (as expected).

Thank you so much for your answer.

I will try the diodes in antiparallel in the input.

PS: I do not use C3 in my actual build and I do have a good cap between R22 and GND (the schematic I posted is not up to date).

 

[AndrewT]

RC,
can you explain the quote you posted?

 

[RCruz]

Andrew

A picture is better than 1000 words.

Here you have an updated schematic

 

[AndrewT]

Not your schematic.
What is the quote in your post41 talking about?

explain the quote you posted

 

[RCruz]

Thank you so much for your answer.

I will try the diodes in antiparallel in the input.

PS: I do not use C3 in my actual build and I do have a good cap between R22 and GND (the schematic I posted is not up to date).

Look at my last schematic.... I put four diodes in antiparallel in the input and also have a cap between R22 and gnd (in the feedback circuit)

 

[RCruz]

Andrew

Just sent you a PM but you have your mail box full..... Need your input on a new amp.

 

[AndrewT]

RC,
there is another option.
Open a Thread and ask for input to your new thoughts.

 

[RCruz]

Just opened a new thread regarding the "Assemblage Power Amp" http://www.diyaudio.com/forums/solid-state/258549-assemblage-power-amp.html#post3978099

Looking forward for your input.

 

[FdW]

And here is an other soft clipper. A possible candidate for the mosfets (right side circuit) is
http://www.onsemi.com/pub_link/Collateral/NTUD3169CZ-D.PDF

 

[danielwritesbac]

And here is an other soft clipper. A possible candidate for the mosfets (right side circuit) is
http://www.onsemi.com/pub_link/Collateral/NTUD3169CZ-D.PDF

Is that a soft clipper or a form of compressor? Well, I'm asking because if it doesn't sound like a clipper, then it probably isn't a clipper.

Problem: A compressor circuit used without activation delay (milliseconds), can make noise like a clipper (if/when insufficient delay) (Fix: a little delay resistor-cap is normally used so that treble treble signal isn't rapidly altered)

Problem2: A compressor circuit that makes switching noises can also make noise like a clipper (Fix: JFETS and optos are preferred for compressors).

Or, there's the point of these things, which is really different:
(typical usages)
Hard clipper, surge-protect the input transistors
Soft clipper, protect the Output transistors against sticking
Compressor, play a lot louder (doesn't provide peak protection)

 

[FdW]

Sorry for the late answer, but it is a soft clipper as shown in the graphs.

Is that a soft clipper or a form of compressor? Well, I'm asking because if it doesn't sound like a clipper, then it probably isn't a clipper.

Problem: A compressor circuit used without activation delay (milliseconds), can make noise like a clipper (if/when insufficient delay) (Fix: a little delay resistor-cap is normally used so that treble treble signal isn't rapidly altered)

Problem2: A compressor circuit that makes switching noises can also make noise like a clipper (Fix: JFETS and optos are preferred for compressors).

Or, there's the point of these things, which is really different:
(typical usages)
Hard clipper, surge-protect the input transistors
Soft clipper, protect the Output transistors against sticking
Compressor, play a lot louder (doesn't provide peak protection)

 

[FdW]

Here is an other (better ) graph, and a better circuit. Until 1.8V in there is no influence of the clipper (near -200dB ). From there on (the last step shown is 2V) it start to clip and the output shows a nice rounded top and rounded corners. The whole thing is extremely fast.

 

[danielwritesbac]

That looks nice, but it gave me questions because the average computer doesn't do high fidelity beyond 0.9v output and I, personally, have only high gain amplifiers (necessarily). So, in my case I wouldn't be using the 1.8v~2.0v activation threshold because I just don't have it.


In other news, I'd be tempted to build your device into a preamplifier of some sort and impose a ~15ms delay on activation so as to shorten the duration of clipping (rather than remove all clipping) and without the cost of reducing initial bass impact; however, that describes a compressor, not a soft clipper. The concept may need a capacitor added to generate a delay but it could sound quite attractive (which is what clippers don't do).