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Old 15th July 2007, 07:09 PM   #1
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Default distortion in silonex limiter with nsl32sr3

hi,
I have build the limiter http://www1.silonex.com/audiohm/limiter.html

instead of the BSN10 I have used a 2n7000 mosfet.

the distortion is very high and audible especially with subwoofer signal input (100hz low pass filter).

someone can help me to reduce the distortion?

thanks to all
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Old 15th July 2007, 07:13 PM   #2
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I presume that this distortion occurs while the circuit is not
limiting the signal?

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Old 15th July 2007, 07:38 PM   #3
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no, the distortion occurs only when the limiter is limiting (the led light on)
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Old 17th July 2007, 07:04 PM   #4
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You need to use a low gate threshold Fet like the BSN10 specified. The 2N7000 is not a good equivalent.
Its a good idea though to use a limiter to avoid damage to a subwoofer I was thinking of using the same idea myself.
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Old 17th July 2007, 07:48 PM   #5
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Quote:
Originally posted by davide86
no, the distortion occurs only when the limiter is limiting (the led light on)
You will naturally see distortion when it's limiting, because that's
the basic function of the limiter. As per the Silonex application
notes, you can vary this effect by adjusting the attack and
decay time constants, and of course the threshold and amount
of limiting, all of which are adjustable.

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Old 17th July 2007, 11:13 PM   #6
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thank you very much! ;-)

I will try with an other fet.

I have been able to remove most of the distortion adding a capacitor in the feedback of the ic1b (integrator circuit) but the sound is not very good.
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Old 19th July 2007, 09:20 PM   #7
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Default Re: distortion in silonex limiter with nsl32sr3

Quote:
Originally posted by davide86
hi,
I have build the limiter http://www1.silonex.com/audiohm/limiter.html

instead of the BSN10 I have used a 2n7000 mosfet.

the distortion is very high and audible especially with subwoofer signal input (100hz low pass filter).

someone can help me to reduce the distortion?

thanks to all
Try reducing R7 to 1k or 220ohms and see if you get a reduction in distortion. This resistor allows some unfiltered rectified audio to control the LDR to create increased attack/release time for quick transients. In a subwoofer limiter application, this would be undesireable, as this would allow tracking of the low frequency waveform, creating distortion.

In fact, you may want to go as far as removing shorting R7, so one end of C1 sits at ground potential. This will still give you a fast release time for a bass limiter (about 150ms). You could then try increasing the value of C1 in small increments up to 2uF. If you use a polarized cap (electrolytic) make sure (-) is at ground.

You may also try experimenting with shorting C2 and see how that sounds. Also, reducing the value of R11 and see how that sounds. This would adjust the gain reduction ratio of the limiter. With C2 and R11 installed, it looks like it would be a very high ratio limiter, with peaks having a lower ratio (due to the filtering action of C2/R11 in the feedback loop.

Hope this helps.
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Old 25th July 2007, 08:14 PM   #8
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the most important reduction of distortion is to place a capacitor bethween anode of D4 and chatode of D1. for the bass frequency I place 1uF and for mid-hi freq 100nF.

i have shorted C2 and substitute R11 with 100k to reduce ratio and R10 with 2k2 resistor to increase the attack time and to soften the sound.
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Old 13th February 2012, 03:58 PM   #9
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Hi all,

I am digging this old thread as i am building a limiter based on Silonex's design and I just can't figure out what is the purpose of DZ1 and D4...
It is said on Silonex's webpage that : The resulting output voltage is then compared with a threshold reference by IC1B, the output of which normally sits at approximately 3.3V lower.
I guess that the 3.3V difference is set by DZ1 and D4 but why should that be usefull ? If the threshold is set to 5V or more than Q2 would always be on, right ? What am I missing here ?

Thanks to all !
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