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[Steve Garris]

Can someone enlighten me on this? A question from a local guitar player friend with a Marshall SV20H head:

On a dual input speaker jack for chaining two cabs together ...
If the positive pole on the first jack is wired to the negative pole on the second jack and the negative pole on the the first jack is wired to the positive pole on the second jack ...
Is that series or parallel ?

[Geoff Doane]

Can someone enlighten me on this? A question from a local guitar player friend with a Marshall SV20H head:

On a dual input speaker jack for chaining two cabs together ...
If the positive pole on the first jack is wired to the negative pole on the second jack and the negative pole on the the first jack is wired to the positive pole on the second jack ...
Is that series or parallel ?

As you've described it, it's parallel.  But the polarity is reversed. Perhaps it was a mistake (botched repair), or maybe there is a practical application for it.

If you wanted to add a second cabinet in series with the first, you would need to use a jack with a normally closed contact as the "out jack" to the extension cabinet.

GTD

[Steve Loewenthal]

Perhaps it was a mistake (botched repair), or maybe there is a practical application for it.

I think "mistake" is the more probable of the 2. (and I will concur that the rest of Geoff's answer is correct.)

[Art Welter]

As you've described it, it's parallel.  But the polarity is reversed. Perhaps it was a mistake (botched repair), or maybe there is a practical application for it.

Different guitar amplifiers, and even different channels of the same guitar amp may have different input to output polarities.

One practical application for a reversed polarity speaker output would be when combining that amp/speaker with another amp/speaker, by changing the speaker jack output, polarity reversals between two amplifiers could be corrected. That said, botched repair or factory wiring is more likely, as the 5 output jacks on the Marshall SV20H normally would have the 8 ohm pair and 4 ohm pairs wired in normal, not reversed polarity.

Art

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