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Old 27th February 2005, 01:10 PM   #1
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Default hiss

I have a drv134 driving 8 lm3886(4+4)Im getting hiss

each chip has one 220uf and one .1uf on each rail

The chips are inverted with 4k input resistor and 100k feedback resistor


Suggestion needed
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Old 27th February 2005, 05:49 PM   #2
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I suppose that's a bridge/parallel arrangement.
You are using too much gain.
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Old 27th February 2005, 07:49 PM   #3
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Carlosfm:


that was my guess too.

Thanks
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Old 27th February 2005, 07:56 PM   #4
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Carlosfm:


I would like to use a snubber in my power supply,but the lowest value resistors I have are 2.7ohms. 2.7ohm resistor and a 33nf cap will it work
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Old 27th February 2005, 09:06 PM   #5
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Quote:
Originally posted by jaudio
2.7ohm resistor and a 33nf cap will it work
I don't think so.
You need to buy the necessary parts.
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Old 27th February 2005, 09:08 PM   #6
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Quote:
Originally posted by jaudio
Carlosfm:
that was my guess too.
Thanks
Change the 4k input resistors for 8.2~10k.
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Old 28th February 2005, 04:39 AM   #7
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Do you have any more capacitance than the 220uFs on each chip?

and I hope you have 220uF on both positive and neg rails?
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Old 28th February 2005, 10:20 PM   #8
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The 220uf caps are on chip rail pins.

I have 136000uf per rail for each monoblock,housed in a separated power supply
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Old 1st March 2005, 08:38 PM   #9
macboy is offline macboy  Canada
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Reduce the gain! preferably by reducing the size of the feedback resistor, not by increasing the input resistor (smaller resistors make less noise!).

Also try adding a single 0.1 uF or so cap directly across the V+ and V- supply pins of each '3886 (not to ground). Make sure that it is rated at an appropriate voltage (100 V will do).
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Old 1st March 2005, 09:14 PM   #10
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Quote:
Originally posted by jaudio
The 220uf caps are on chip rail pins.

I have 136000uf per rail for each monoblock,housed in a separated power supply
nice... just checking.

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