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I have a guitar amp that has one output that can handle either an 8 or 16 Ohm load.

I have a cabinet with two 8 ohm speakers (each with a separate input). I could wire the speakers in series, and get 16 Ohms.

The way I want to do this is by adding a second output jack to my amplifier chassis and use a DPDT switch to toggle between parallel and series wiring. Easy enough (see schematic).

Paralell/series switch

My question is: is it really necessary to add a separate switch? Could I not install two female stereo jacks in my amp and use the ring connection as a switch?

Then if both (mono) speaker jacks are inserted, I get a series connection, but if only one is connected it, it just passes the signal through without any splitting?

I tried to draw this up but couldn't figure how to achieve this using audio switches in place of the DPDT? Perhaps it can't be done?

Can anybody help?

Vidar
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1 Answers1

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schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. Your three options with your kit.

schematic

simulate this circuit

Figure 2. Single or series connection using switched jacks. The inserted plug makes contact with the free arrow while it opens the contact with the touching arrow.

enter image description here

Figure 3. A switched jack socket with NC switch contacts clearly visible in the forground.

How it works:

  • Connecting Speaker 1 will give the amplifier connection to the tip and the ground connection will be through the normally closed (NC) contact of the second jack.
  • Connecting Speaker 2 will open the tip contact, disconnect the ground and the first speaker will now be in series with the second.

The circuit should be as fool-proof as the original jack. There is no additional risk of short-circuits. (There is and was a risk if it is possible for the jack tip to short between tip and sleeve during insertion.)

Would it be possible to execute this using a vintage-style female jack as well, like pictured here?

enter image description here

Figure 4. OP's vintage jack.

No. Look at your image. There are no switching contacts. You need one switching contact on the tip at least.

Transistor
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  • But this won't let him connect the speakers in parallel. – hmakholm left over Monica Feb 24 '18 at 23:05
  • Hej, Henning. Read the question again. "*Then if both (mono) speaker jacks are inserted, I get a series connection, but if only one is connected it, it just passes the signal through without any splitting?*" I think I have understood the question correctly. Med venlig hilsen. – Transistor Feb 24 '18 at 23:14
  • Hmm, yes, he does write that. Perhaps I'm misunderstanding his diagram. – hmakholm left over Monica Feb 25 '18 at 10:38
  • Thank you so much for your input! Would it be possible to execute this using a vintage-style female jack as well, like pictured here? [link](https://images-na.ssl-images-amazon.com/images/I/81C%2BDF4Q2mL._SX355_.jpg) – Vidar Feb 25 '18 at 12:34
  • See the update. – Transistor Feb 25 '18 at 16:16
  • Thanks, you rock! I have made an order for the right female jack. – Vidar Feb 26 '18 at 01:56
  • Note that the original jack socket sleeve should not touch the amplifier chassis either. Figure 2 shows that the socket for Speaker 1 must be isolated otherwise it will be permanently grounded to the metal chassis and no signal will reach the socket for Speaker 2. – Transistor Feb 26 '18 at 05:27