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Old 13th March 2006, 05:34 AM   #1
ostie01 is offline ostie01  Canada
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Default optocoupler to eliminate ground loop

Hi, would like to know if it's possible to eliminate ground loop problem
with optocoupler or can it be used in amplifier input.Are they stable enough. Can I use this device to transfert analog signal like in audio circuit. Thanks everybody for your time.
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Old 13th March 2006, 06:09 AM   #2
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Look at datasheets of CP Clare....
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Old 13th March 2006, 06:49 AM   #3
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There are analog optocouplers but the quality isn't enough for audio I'm afraid. Check for instance IL300 from Vishay. I have used it in a 4-20mA loop and for this purpose it's OK.

http://www.vishay.com/optocouplers/list/product-83622/
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Old 13th March 2006, 06:52 AM   #4
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There are some instrumentation isolators that may be good enough for audio, using a pwm system across capacitors.

Linear modulation of an IR diode driving a PIN diode works fairly well except at very low frequencies where I have seen strange non linearity and memory effects.

A transformer may be your best solution.
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Old 13th March 2006, 07:07 AM   #5
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Seriously, I think it better to solve the casue of the ground loop problem. Have you built the gear or is it bought?
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Old 13th March 2006, 07:54 AM   #6
ostie01 is offline ostie01  Canada
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Hi, thanks for these great reply.Not built anything yet.It's for my 4way active crossover project.When I hook it up to a power amplifier, I got some hum in the speaker.Tried some tricks like disconnect ground from one end of interconnect but this is the worse I can do, more hum.tried some other interconnect with same result.


Just take a look at this link, this is my crossover project.Every cables is sheilded, separate transformer, each board has it's own filtering caps and voltage regulator. All capacitors are polystyrene or polypropylene for the bass output. all ICs are NE5532.Each ICs has a 22 Ohm resistor and a 22uF capacitor at the neg and positive input. Just let me know what you think. Thanks

http://img98.imageshack.us/img98/187...ssover17pl.jpg

http://img117.imageshack.us/img117/8...ssover20de.jpg

http://img95.imageshack.us/img95/565...arleur18eh.jpg

The last pic is a picture of my 4way speaker that I've built.

All my power amp are Rotel exept for the 15 inches drivers this are power by an Harman Kardon citation 7.1 with 450 watts/channel.

My crossover is built in a Rotel power amplifier case that has been modified, reduce in height to match the height of my Rotel line conditionner.Still have to finish the front(sanding and painting to match other Rotel components.
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Old 13th March 2006, 08:02 AM   #7
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I suspect that your problem lies in an issue with your grounds within your crossover. When you have separate regs for different boards it can become tricky to keep everything starred properly.
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Old 13th March 2006, 08:08 AM   #8
ostie01 is offline ostie01  Canada
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HI, I know what you mean but the 2 boards have the same ground path.Each boards is grounded to the case.
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Old 13th March 2006, 08:15 AM   #9
ostie01 is offline ostie01  Canada
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Here is my design for the 4way crossover, should sound great if everything is O.K.



http://img92.imageshack.us/img92/103...sover114ai.jpg
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Old 13th March 2006, 08:42 AM   #10
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If things are grounded to your case, have you used isolated input and output sockets? Also when you say grounded to the case, do you mean a star ground at ONE point on the case for ALL boards?
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