Dumb Ruby Question...

[MetalUpYerEye]

Sorry for the dumb question but I was building a stock Ruby for my younger brother and misplaced the LM386 IC I had set aside for it. This is a problem for me as I cant get to the electronics store but every 2 weeks or so, so... I got to looking around in my garage and found that when I bought the parts for a Tubescreamer i'm going to build for him (after the Ruby) I had bought an extra JRC4558D IC.

How much fun/damage/destruction/awesomeness/mayhem/anything would I create if I plugged the JRC4558D in the Rubys socket instead of the LM386?

[Cliff Schecht]

It wouldn't work. both chips have different layouts and operations.

[MetalUpYerEye]

Ah... Poop!

What if I used jumpers to correct the pinouts? Could a mini-amp be built using a 4558? Think it'd sound like anything decent?

[KORGULL]

I'm guessing that you won't get much power/clean volume using the 4558. I don't think it is nearly as capable of driving a speaker as the LM386.

[MetalUpYerEye]

Well I read the datasheets for the two IC's.

The LM386 has a typical voltage gain of 26dB, whereas the JRC4558 has a typical voltage gain of 100dB. To me it sounds like that'd yield more POWER!

My main question still stands though; Is it feasable to build an amp out of a 4558 and if so, any thoughts on what it might sound like?

[Peter Snowberg]

The thing that matters in amplifiers for speakers is the current gain.

The 4558 datasheet from Fairchild shows a short circuit current of 20mA. The output voltage swing vs. load resistance graphs don't cover an 8 ohm load, but from the curves you can see it looks like the swing would be less than a volt at 8 ohms. As a guesstimate, you'll get maybe 20 milliwatts, max.

NE5532s are built to drive low impedance loads and they work well for headphone amps, but don't expect much from a speaker and an opamp built for voltage gain.