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Closed VS Open Circuit Jack

post #1 of 5
Thread Starter 

I'm currently in the process of designing my own desktop version of the Objective2 amp, and have pretty much everything sorted, except for what type of 1/4" jack I want to use. I see that there are open and closed circuit jacks, and to my understanding a closed circuit jack incorporates a switch that closes when the connector is removed. Am I right in thinking this?

 

I have read that if the switch is used to ground the channels when the connector is removed it eliminates noise that could be caused by the unoccupied jack. I know I wouldn't normally need this, because it is an output, but I plan on keeping the 3.5mm jack originally specified in the design and adding the 1/4" jack as well. Would having the closed circuit jack (i.e. grounding the channels on the 1/4" jack when it is unoccupied) affect the 3.5mm jack in any way?

 

Thanks.

post #2 of 5
Quote:
Am I right in thinking this?

 

Yes.

 

 

Quote:
Would having the closed circuit jack (i.e. grounding the channels on the 1/4" jack when it is unoccupied) affect the 3.5mm jack in any way?

 

Assuming you are putting the 3.5mm and 1/4" jacks in parallel on the output, shorting one will short the other.

 

Closed-circuit headphone jacks are far more commonly used in devices where plugging the headphones in cuts another circuit out, like the speakers in a boom box, or the RCA outputs in a preamp.

post #3 of 5
Thread Starter 
Quote:
Originally Posted by tangent View Post

 

Yes.

 

 

 

Assuming you are putting the 3.5mm and 1/4" jacks in parallel on the output, shorting one will short the other.

 

Closed-circuit headphone jacks are far more commonly used in devices where plugging the headphones in cuts another circuit out, like the speakers in a boom box, or the RCA outputs in a preamp.

Thanks for the information, will be going for the open circuit jacks.

post #4 of 5

Sometimes the jack you want to use is only available with the extra closed-circuit lugs, and this is fine. You simply don't hook anything up to them.

 

Actually, it occurs to me that in this particular case, you could hook the 3.5" jack up to the 1/4" jack's closed-circuit lugs. That way it wouldn't allow you to plug headphones into both at once; when then something is plugged into the 1/4" jack, it would cut out the 3.5mm. Call it a feature, since the amp isn't intended to be a distribution amp.

 

You'd effectively be designing the amp to give the 1/4" output priority when there is a conflict.

post #5 of 5
Thread Starter 
Quote:
Originally Posted by tangent View Post

Sometimes the jack you want to use is only available with the extra closed-circuit lugs, and this is fine. You simply don't hook anything up to them.

Actually, it occurs to me that in this particular case, you could hook the 3.5" jack up to the 1/4" jack's closed-circuit lugs. That way it wouldn't allow you to plug headphones into both at once; when then something is plugged into the 1/4" jack, it would cut out the 3.5mm. Call it a feature, since the amp isn't intended to be a distribution amp.

You'd effectively be designing the amp to give the 1/4" output priority when there is a conflict.

Thanks for the idea, that's very smart. Switchcraft does offer both closed and open circuit jacks, but I guess there's no harm in buying a closed circuit jack regardless.
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