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amp in metal case, 2 questions
amp in metal case, 2 questions
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Old 4th September 2014, 02:35 PM   #1
gychang is offline gychang  United States
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Join Date: Feb 2005
Location: Davis, California
Default amp in metal case, 2 questions

1. I will be using 3.5mm audio input terminal as attached on the metal case, what is the easiest way to isolate it from touching the case?, I can see the correct size plastic/rubber washer but how about the "core" touching the case?

2. I noticed many builds have cables twisted to speaker terminals from the amp, should this be done on the audio input signal to amp also?, what is the reason?

thanks,
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Old 4th September 2014, 02:45 PM   #2
gychang is offline gychang  United States
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Join Date: Feb 2005
Location: Davis, California
Default amp in metal case, 2 questions

1. I will be using 3.5mm audio input terminal as attached on the metal case, what is the easiest way to isolate it from touching the case?, I can see the correct size plastic/rubber washer but how about the "core" touching the case?

2. I noticed many builds have cables twisted to speaker terminals from the amp, should this be done on the audio input signal to amp also?, what is the reason?

thanks,
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Old 4th September 2014, 03:13 PM   #3
rayma is offline rayma  United States
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Join Date: Apr 2011
Quote:
Originally Posted by gychang View Post
1. I will be using 3.5mm audio input terminal as attached on the metal case, what is the easiest way to isolate it from touching the case?, I can see the correct size plastic/rubber washer but how about the "core" touching the case?

2. I noticed many builds have cables twisted to speaker terminals from the amp, should this be done on the audio input signal to amp also?, what is the reason?

thanks,
Use either an insulating shoulder washer/flat washer combination (preferred), or in a large hole mount an insulating panel with mounting hole for the socket.

Send/return lines should be twisted, if they're not in the form of a coaxial cable. This is for shielding, to reduce interference and/or feedback from the output circuit.

Last edited by rayma; 4th September 2014 at 03:43 PM.
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Old 4th September 2014, 11:36 PM   #4
gychang is offline gychang  United States
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Join Date: Feb 2005
Location: Davis, California
Quote:
Originally Posted by rayma View Post
Use either an insulating shoulder washer/flat washer combination (preferred), or in a large hole mount an insulating panel with mounting hole for the socket.

Send/return lines should be twisted, if they're not in the form of a coaxial cable. This is for shielding, to reduce interference and/or feedback from the output circuit.
very helpful, where can I get "shoulder-washer" combo (sounds ideal).

not sure what u mean by send/return lines, (no coaxial). Audio input wires to amp?, speaker wires to RCA terminal?
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Old 4th September 2014, 11:42 PM   #5
rayma is offline rayma  United States
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Join Date: Apr 2011
Quote:
Originally Posted by gychang View Post
very helpful, where can I get "shoulder-washer" combo (sounds ideal).

not sure what u mean by send/return lines, (no coaxial). Audio input wires to amp?, speaker wires to RCA terminal?
Yes, these are made by companies that make electronic hardware, like:

Flat Washer, Shoulder Washer, Nylon, Fibre: Keystone Electronics

The fiber types are much more rugged and temperature tolerant than the nylon types.

An unbalanced input has two wires, hot and cold. These should be twisted together on their way to the pcb, for example.
Think of the current as flowing in a loop. You want to keep that loop area as small as possible. The twisting averages out the effects of external fields.

Last edited by rayma; 4th September 2014 at 11:45 PM.
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