LDR Limiter for TA2020, TA2024, spirited playback without clipping. - Page 2 - diyAudio
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Old 11th April 2012, 03:24 PM   #11
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hi, is this ok? Click the image to open in full size.
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Old 12th April 2012, 12:32 AM   #12
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Default Schematics

Thank you for the schematic. I have revised it. See the attachments.
Input:
We need an input load resistor because the 1k to 50k LDR optocoupler could (varies) go nearly open circuit when off.
Sensor:
We need to set the sensor's voltage range suited to TA2020, TA2024,
We need to do without a ground tap for sensor (bridge amp doesn't have an output ground),
We need to set the sensor so that the amplifier plays louder and still clean (unusual for a limiter)
Noises:
We need to reduce the effectiveness of the limiter enough to remove obvious pulsing noises,
We need to reduce the effectiveness of the limiter enough so that we don't require high gain/preamplifier noise.
Frequency Response:
We need to use LED and Schottky voltage drops because their sloppy knee voltage region will make a more transparent rendering and LOUDER BASS than abrupt zener.

Please check the attached schematics for polarity. I did test these actual components with the real amp. A 3.1v LED is an ordinary white or warmwhite LED ("on" voltage varies by current). You can fine tune voltage drop to match your amp by either subtracting 1 schottky diode or adding more schottky/fast silicon diodes.
Attached Images
File Type: gif ClipNipper-FullWave.gif (13.4 KB, 2336 views)
File Type: gif ClipNipper-HalfWave.gif (11.0 KB, 682 views)

Last edited by danielwritesbac; 12th April 2012 at 12:51 AM.
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Old 12th April 2012, 03:15 AM   #13
Eva is offline Eva  Spain
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My recommendation: Sense a too low voltage drop from one output to the positive rail or to ground rather than just a too high output voltage. Why? To allow for any supply voltage and sag.

Nice idea otherwise.
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Old 12th April 2012, 04:22 AM   #14
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hi daniel,some friend of mine say that at high frequency the LDR will be less responsive,because LDR has 200-500us response time
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Old 12th April 2012, 04:31 AM   #15
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Quote:
Originally Posted by Eva View Post
My recommendation: Sense a too low voltage drop from one output to the positive rail or to ground rather than just a too high output voltage. Why? To allow for any supply voltage and sag.
Nice idea otherwise.
Thank you!
I couldn't quite figure out how to do that type of sensor with a bridge amp and still make it play louder instead of quieter.
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Old 12th April 2012, 05:01 AM   #16
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Quote:
Originally Posted by ionutzxpo View Post
hi daniel,some friend of mine say that at high frequency the LDR will be less responsive,because LDR has 200-500us response time
You can try 4n25 instead of LDR for soft clipper -or- try the full wave version of ClipNipper since that a mild limiter with a nice smooth treble response.
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Old 13th April 2012, 12:54 AM   #17
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Default Gain management documentation

The Easy way--For higher gain, you could set RI (Tripath datasheet RI resistors are located "chip side" of the input cap) to 10k (instead of datasheet 22k) for a "gain mod" boost of replacing 2 SMD resistors with two ordinary resistors. I used this method personally, on the real TA2020 amplifier. It was easy on that amp. I also needed a thick (good quality) shielded input cable, which is a normal requirement for TA2020.
-or-
Modest/slight difficulty--Changing the schematic's input resistor to lower figure, like 470R instead of 1k, and also increase 22k input load resistor on the schematic up to 33k as these steps are just like turning up a volume knob's proportions. You don't want excess at all, but you do have the freedom to adjust this spot. If your weakest source still can't light up the LED's then either replace the amp gain SMD resistors or give a weak source its own preamplifier.
-or-
Extra complicated--You can automate a Lightspeed Attenuator by powering it from my sensor that is on the schematic. This prospect can reduce the input loss except for when the sensor is lit up. Since LED's don't directly parallel, a Lightspeed Attenuator uses two private voltage drop sections and TWO private drainer resistors but may be powered from just one bridge rectifier.
-or-
Zero loss method (auto gain ride)--Instead of LDR optocouplers at the input, the very first edition of ClipNipper did nip parallel to the gain settings (inert except for removing clipping) on a discrete amp, but I avoided it this time because there isn't board space available except for amplifier re-design.
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Old 13th April 2012, 07:32 AM   #18
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Default Question answered, Studio compression/clipped recordings, make audible pulsing.

Modern InGan LED retrofit lighting bulbs will burn down an RV that has a half wave converter because of 13.5vdc AND ~6.5vac, but most InGan see the total sum of ~20v or more. Since clipping has similarities to dirty DC, most InGan react extra strongly to clipped audio signals. It makes a great detector that sometimes works too well.

It can be used for detecting clipping and blare, but it could also detect static/fuzz via exacerbator op amp active detector. Then we have ldr, cds, optotransistor and solid state switching technologies for which to apply feedback and thus cancel any of those noises.

I can't do anything about ClipNipper overreacting to music that was recorded hot with clipping and compression, except. . .
I will soon be attempting to integrate the BlareBuster at the input to ClipNipper and automate the engagement points by using the new detector. By removing a small amount of studio compression first, then ClipNipper can be free to work more accurately, without the noticeable pulsing that sometimes occurs on highly compressed tracks. It can be done with 4 or 5 passive parts per channel and not consume battery power. Zero energy consumption simple design won't remove clipping at low volume playback. The stand-alone prototypes are complete, interoperable and producing results. Integration and automation remains to be completed. Now that we can play loud, the next logical step is the BlareBuster, because "can play loud" and "want to play loud" are two different things.

There won't be any attention getting theater like effects--the effectiveness will be decreased as much as necessary to achieve transparency, because of the belief that noise removers must not add noise.

P.S.
Since I'm not a formally educated audio engineer, but rather more like going through Edison's 1000 ways of not making a light bulb, expect another delay since that process is slow and then expect another "steam punk like" simple circuit already working and running, before a schematic is published.
Sorry for the delay in redeploying the hi-fi uncompressor to fit T-amp.

Last edited by danielwritesbac; 13th April 2012 at 07:35 AM.
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Old 13th April 2012, 07:55 AM   #19
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Here's a radical idea: use the clipping (overload) pin on the amp chip to do something. Whoever lays out those boards deserves a kick to a delicate part of the body for not bringing that pin out to a terminal, preferably through a buffer to drive an LED.
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Old 13th April 2012, 02:22 PM   #20
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Quote:
Originally Posted by dangus View Post
Here's a radical idea: use the clipping (overload) pin on the amp chip to do something. Whoever lays out those boards deserves a kick to a delicate part of the body for not bringing that pin out to a terminal, preferably through a buffer to drive an LED.
If you can drive an LED, you can drive an LDR or a 4n25, which both do contain leds. But, I don't know if their onboard detector is abrupt or variable or slow or fast. Have you tried it?
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