limiting gain for LM386N-3

[gpond]

I am a beginner trying to build small amps using an LM386N-3, I need them to drive .5- 1 Watt, 8-Ohm speakers for a sound installation project. I started with the attached circuit. On the oscilloscope the pre amp seems to work properly although I am using a LM2904N rather than the LM358AN. I am generating a sine wave with my computer and outputting via the built in audio 1/8” jack into the preamp. The amplifier is clipping severely. I have built 3 other amps using the same chip but with different configurations and I get about the same results with each. I have tried to increase the voltage to the amplifiers but the clipping is too severe. I have tried adjusting the capacitors and resistors between pins 1 and 8 to control the gain but with no success- or I haven’t found the right combination. Whether I have the pre amp connected to an amp or not the signal is clipping. I know very little about electronics theory so I am having a hard time knowing where or to look and how to proceed. I am sure that there is some piece of information that I am missing but after several days of searching I am appealing for help. Please advise.

[teemuk]

With the first glance I see nothing wrong in the schematic. I recall that the LM386 had a quite low input sensitivity - something around 400 mV RMS, I don't have the datasheet at hand, though. A computer will typically output around 1V RMS so it could be you are overdriving the chip input or perhaps the diodes clip the pre amp otput signal. A pretty messy sachematic but it seems that the preamp has a gain of zero? Are you sure the chip will stay stabile at zero gain - I see no high frequency NFB that would stop oscillations, perhaps there is blocking distortion caused by HF oscillation. The LM386 is pretty low power chip and IMO it clips "severily" even at full 12V supply - especially with unefficient speakers... Could be just that.