Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Does anyone have any experience with the uPC1188H? The data sheet says 4 ohm minimum but every amp I've seen use these has 8 ohm speakers. The data sheet lists 8 ohms as typical. I have a Fender Princeton Stereo Chorus that I'm interested in adding some cabinets to. So I was wondering if I should wire those in parallel for 4 ohms each or have them disconnect the internal speakers.

My car has a red line on the tach at 5000rpm (or whatever).  That doesn't mean I want to drive around town wound up that fast.

The chip can handle 4 ohms, but most people are more concerned over long term reliability.  8 ohms is less stressful.

Try this, wire jacks in series with the internal speakers, so any external speakers are in series with the load.  That reduces the stress on the amp and the power output.  But it works well and reliably.

In that case I think it would make more sense to just have the speaker outputs disconnect the internal speakers to keep each amp at the normal 8 ohm load.

You can do that too, but then you don't get the internals.  I thought the point of your project was to add the externals to the internals for a larger sound.

There is nothing magic about 8 ohms.  16 ohms will make the amp happy too.  It will reduce the power some, but only about 3db.