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Preventing Hum/Noise in Amplifiers
Preventing Hum/Noise in Amplifiers
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Old 13th April 2017, 10:42 AM   #21
udok is offline udok  Austria
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Preventing Hum/Noise in Amplifiers
I don't like the idea with diodes in the safety connector as this is not
"the state of the art" as defined by official organizations like DIN and VDE.
And many safety testers will recognice your amp as faulty.

There are better methods used in industry for over 50 years.

Udo
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Old 13th April 2017, 10:52 AM   #22
AndrewT is offline AndrewT  Scotland
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Quote:
I don't like the idea with diodes in the safety connector............many safety testers will recognice your amp as faulty................
The "Safety Connector" is the PE wire directly and mechanically connected to the Chassis/Enclosure.

The testing equipment will recognise this DIRECT PE connection and pass the equipment as compliant.
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Old 13th April 2017, 10:53 AM   #23
AndrewT is offline AndrewT  Scotland
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Originally Posted by udok View Post
..............There are better methods used in industry for over 50 years..............
Could you link us/me to these better methods?
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Old 13th April 2017, 12:06 PM   #24
udok is offline udok  Austria
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Preventing Hum/Noise in Amplifiers
Quote:
Originally Posted by AndrewT View Post
The "Safety Connector" is the PE wire directly and mechanically connected to the Chassis/Enclosure.

The testing equipment will recognise this DIRECT PE connection and pass the equipment as compliant.
Any touchable metal part should be tested, including touchable connectors...

Does any one of the big hifi companies use this diode trick? And if not why?

Last edited by udok; 13th April 2017 at 12:08 PM.
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Old 13th April 2017, 02:42 PM   #25
Walkalone is offline Walkalone  Viet Nam
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Thanks Andrew,

I try to summarize from my knowledge as pic below,
Your opinion seem do not same as it, please describe your opinion as pic to easy understand.

Thank you,
Attached Images
File Type: png Ex.png (21.5 KB, 146 views)
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Old 13th April 2017, 04:30 PM   #26
dadod is offline dadod  Croatia
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Originally Posted by Bonsai View Post
Thanks

Yes - I have gone over to returning the speaker 0V to the amplifier PCB and not directly to the central ground - neater and you also get a smaller loop area. I might commrnt further on this in later updates - it will remain a 'living' document no doubt.
Hi Andrew,
Do you have measured proof that it's the better way to connect 0V speaker wire?
I tried both way with mixed result.
BR Damir
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Old 13th April 2017, 05:50 PM   #27
Bonsai is offline Bonsai  Europe
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Hello Damir,

You can return the speaker 0V to either the main central ground, or return it to the PCB and from there a 0V wire that goes back to the central 0V. I have used both methods (e.g. sx and nx amps go directly back to central 0V)

In both cases, the idea is to minimize the loop area, so I recommend that if you use the latter method, you run the speaker return wire next to the speaker + wire (twist them) back to the PCB and then continue the speaker 0V wire back to central ground.

I have gone over to returning the speaker 0V back to the amplifier module 0V (which is arranged in a STAR GND) and then a single 0V line to the central ground. I have not picked up any problems and am getting no observable difference in performance. Note that on the main PCB, I have local decoupling of 2 x 220uF 100V per rail per amplifier module (4 devices per amplifier module). This is important in order to keep the loop area small.

Anyway, can you share what you have found?
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Old 13th April 2017, 06:03 PM   #28
Bonsai is offline Bonsai  Europe
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Quote:
Originally Posted by udok View Post
Any touchable metal part should be tested, including touchable connectors...

Does any one of the big hifi companies use this diode trick? And if not why?
If you touched the mains on any part of the chassis it would trip the RCB - there is a direct connection to mains PE as AndrewT has pointed out.

If you touched mains on any connector it would trip the RCB or blow open circuit.

I have used a GL on the sx, nx and e-Amps with no problems.

Note, you must use a good quality 25/35A or better diode bridge. The ones I used on the sx and nx amp are 600V PIV and 400 Amps surge current.

If you are not comfortable using a ground lifter (GL), then my recommendation is DON'T.

I do not know of any commercial audio companies using this technique.
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Old 13th April 2017, 06:05 PM   #29
Bonsai is offline Bonsai  Europe
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"There are better methods used in industry for over 50 years."

Udo, please share these techniques - we can add them to the existing methods in use - good to discuss this.
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Old 13th April 2017, 06:27 PM   #30
Mark Whitney is offline Mark Whitney  Netherlands
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Walkalone, Join 2,3 together and place 4,6,7,8 so that their paths are very short and wide.
For best results, you should place the feedback loop parallel to the speaker without introducing any other currents within that loop.
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