wire connection of audio signals from circuit board to jacks on chassis

Thread Starter

PeteHL

Joined Dec 17, 2014
340
Can I use hook-up wire to connect input/ output line level audio signals from a circuit board to jacks that are chassis mounted? The maximum length of wire making such a connection would be 9 inch or 23 cm. There is a signal transformer (part of the +/- 15VDC power supply, 100 mA) in the piece of equipment that I'm assembling located about 6 inches or 15 cm distant from the connecting wires.

My original plan was to use shielded cable for all connections from the board to jacks, but the greater flexibility of 22 AWG stranded insulated hook- up wire would be better and easier to install than shielded cable.

Also, if I were to use hook-up wire rather than shielded, would it be beneficial to wind a length of hook-up wire connected to ground around the length of hook-up wire carrying the signal?

Thanks for your advice in advance,

Pete
 

KeithWalker

Joined Jul 10, 2017
1,031
Can I use hook-up wire to connect input/ output line level audio signals from a circuit board to jacks that are chassis mounted? The maximum length of wire making such a connection would be 9 inch or 23 cm. There is a signal transformer (part of the +/- 15VDC power supply, 100 mA) in the piece of equipment that I'm assembling located about 6 inches or 15 cm distant from the connecting wires.
For that short distance, with line level signals, you should not have any problems if you use hook-up wire from the board to the jacks. Use twisted pairs - in other words, twist each signal wire together with it's associated ground wire. You don't need to twist them very tightly, about three turns to the inch will be OK.
Regards, Keith
 

Wolframore

Joined Jan 21, 2019
1,748
Sounds like an easy test, it depends on the amplifier, personally I like shielded wiring to help reduce EMI... you might be ok, you might not... hard to guess.
 

Thread Starter

PeteHL

Joined Dec 17, 2014
340
Thanks @KeithWalker and @Wolframore for your advice. Testing with the connections made with hook-up wire is what I will try.

Craig Anderton in his book Electronic Projects for Musicians says that when shielding a signal conductor, connect only one end of the shield to ground. What do AAC members think about that strategy?

-Pete
 

Wolframore

Joined Jan 21, 2019
1,748
Could you post pictures of your project and the case? I’m not sure I‘m picturing this correctly. I thought it was from device to device but now it sounds like it’s internal. If it’s internal I agree with @KeithWalker, just twist the pair together.
 

DickCappels

Joined Aug 21, 2008
6,454
Without a detailed description of the environment and potential noise sources it would be difficult to predict how much interefence you would get. As a precaution, you might want to twist the pairs of wires between the circuits and the jacks then try it. If it is too noisy replace with shielded twisted pairs.

The proof is in the pudding.
 

KeithWalker

Joined Jul 10, 2017
1,031
Craig Anderton in his book Electronic Projects for Musicians says that when shielding a signal conductor, connect only one end of the shield to ground. What do AAC members think about that strategy?

-Pete
If the connections are from the circuit board to jacks, as stated, you need both ends of the ground wires connected or you will not have a complete circuit. e.g.:

Keith
 

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Audioguru again

Joined Oct 21, 2019
1,575
I always use good speakers that produce deep bass. Then I use shielded audio cables for everything to avoid hum.
If you use squeaky little speakers that do not produce bass then hum interference picked up by ordinary unshielded wires will not be heard, but buzzing might be heard.
 

Thread Starter

PeteHL

Joined Dec 17, 2014
340
Could you post pictures of your project and the case? I’m not sure I‘m picturing this correctly. I thought it was from device to device but now it sounds like it’s internal. If it’s internal I agree with @KeithWalker, just twist the pair together.
This is about connecting from a circuit board to input or output RCA Jacks attached to the enclosure for the board. Connecting this component to other components will be done with shielded audio cable.


Regards,
Pete
 
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Thread Starter

PeteHL

Joined Dec 17, 2014
340
I always use good speakers that produce deep bass. Then I use shielded audio cables for everything to avoid hum.
If you use squeaky little speakers that do not produce bass then hum interference picked up by ordinary unshielded wires will not be heard, but buzzing might be heard.
What I'm building is a line level processor to be used with a good quality stereo system, i.e., one that produces your "deep bass", if you consider a corner frequency of 40 Hz to be that.

Thanks,
Pete
 

MisterBill2

Joined Jan 23, 2018
6,297
Shielding of signal wiring is almost always a good choice. But the quality of the cable is important, some cables act like big parallel capacitors between the center conductor and the grounded shield.
 

MisterBill2

Joined Jan 23, 2018
6,297
60 Hz hum is always a challenge.
In some cases the connector grounds should be through the shield back to the circuit board, because the voltages on the metal chassis include noise or hum or both. Not really a "ground loop" issue but it gets called that if there is a problem. Really it is a pickup-loop sort of problem when it happens.
 

Thread Starter

PeteHL

Joined Dec 17, 2014
340
If the connections are from the circuit board to jacks, as stated, you need both ends of the ground wires connected or you will not have a complete circuit. e.g.:

Keith
CA doesn't explain, but I'm sure that what he means is don't connect the ground lug of the jacks to ground by the shield, but rather connect the lug to ground of the circuit board with a wire. Then connect one end of the shield to ground of the circuit board, or the other end to the ground lug, but not both.

What does the circuit that you posted a photo of do?

Regards,
Pete
 

KeithWalker

Joined Jul 10, 2017
1,031
This is about connecting from a circuit board to input or output RCA Jacks attached to the enclosure for the board. Connecting this component to other components will be done with shielded audio cable.
Regards,
Pete
The picture I posted showing the twisted wires from the circuit board to the input and output jacks is of an IR remote programmed audio attenuator and input selector that I made for linking my TV audio, radio and auxiliary inputs to to my analogue amplifier.
Regards,
Keith
 

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MisterBill2

Joined Jan 23, 2018
6,297
In a low noise area, with lower impedance higher level circuits, twisted wires can be adequate and even work well.
As for the shields, my intention was to suggest NOT using the chassis as a ground connection, but instead returning the connector ground by means of the shield. Of course, then the shield will need to be connected to the right ground point on the circuit board, and the connector will want to be isolated from the chassis/case/panel, (whatever).
 
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