Sunn Model A

[flyingpork]

Just a little confused when reading the schematics. I have a Sunn A212- on the schematics it has two 8 ohm speaker outputs. The two speakers that are in the combo are 8 ohm run in parallel making it 4 ohm. Is this just a terrible choice of speakers leaving the second output useless or has someone replaced these somewhere along the line?

It doesn't ave an ohm selector on back- would it be a problem switching the two 8 ohm speakers to 16 ohm series and adding a 16 ohm 4x12 cab and just running the amp at 8 ohm?

Thanks

[Tom Phillips]

Just a little confused when reading the schematics. I have a Sunn A212- on the schematics it has two 8 ohm speaker outputs. The two speakers that are in the combo are 8 ohm run in parallel making it 4 ohm. Is this just a terrible choice of speakers leaving the second output useless or has someone replaced these somewhere along the line?

It doesn't ave an ohm selector on back- would it be a problem switching the two 8 ohm speakers to 16 ohm series and adding a 16 ohm 4x12 cab and just running the amp at 8 ohm?

Thanks

You said you have a schematic but attached is the schematic I have just to make sure we are looking at the same circuit.

The "Speaker" jack is a plane 1/4" unit. When you plug into it AND there is nothing plugged into the "Ext. Speaker" jack, you are connected to the 8 Ohm tap of the output transformer.

The "Ext. Speaker" jack is a switching jack. If you plug into the "Ext. Speaker" jack then the 4 ohm tap of the output transformer is selected.

If you want a perfect impedance match, you can simply plug your 4 Ohm spreaker load into the "Ext. Speaker" jack.

The 8 Ohm marking on the chassis means that you can plug an 8 Ohm load into the "Speaker" jack or an 8 Ohm load into each jack and the amp will switch the 4 ohm tap.

Hope this all makes sense. It is confusing the way it's marked.
Note: This all assumes that your amp is stock.

Regards,
Tom

[flyingpork]

Thank you! I did not know that. So this being said it would be no problem to rewire the combo speakers to 16 ohm and run a 16 ohm cab for a less powerful 8 ohm right? I'm just not familiar with tube amps. OR should I put a piggy back jack on the cab to to run the series 16 ohm combo speakers into the cab and the cab into the 8 ohm jack? That would be a perfect ohm match right?

[Tom Phillips]

I'm not sure what you mean by "...for a less powerful 8 ohm right..."

The easiest approach is to just plug your existing combo 4 Ohm speaker load into the "Ext. Speaker" jack.

Sounds like you really want to run a big speaker stack. In that case you can wire the combo speakers to be a 16 Ohm load and use it with your other 16 Ohm cabinet as you described. You can add jacks but an alternative to keep everything stock is to make a "Y" cord to allow you to connect both cabs to the "Speaker" jack. That will be an 8 Ohm load to the 8 Ohm output transformer secondary. Remember that you should not plug anything into the "Ext Speaker" jack or the output of the amp will be switched to the 4 Ohm tap.

There are other choices of course if you want to mod the amp.

Have fun,
Tom