Finally built up the circuit below that I've been designing/toying with in LTSpice and its working OK but I'm wondering if an experienced eye might be able to quickly label what/why the oddities are in the signals I see on my oscilloscope.

I'm probably missing a crucial component/layout choice and I'm hoping its a typical beginner mistake I'm making!

Circuit enter image description here

Input: 300Hz sine wave: enter image description here

  • I notice that with the 300Hz input, when I increase the input level the 'width' of the distorted parts widens - if that is a useful observation for me to diagnose my issue?

Input: ActualMusic: enter image description here

Actual Build enter image description here

  • Let me know if I can/need to explain any of the spaghetti!
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    \$\begingroup\$ For audio? Your method of creating a +Vcc, -Vcc is not wonderful, and its wasteful of power. The impedance of this power source at 20 Hz is a bit high. Where are those two 1000uF located? They should go directly from pwr transistor collectors to the 4-ohm ground point. \$\endgroup\$ – glen_geek Oct 3 at 18:05
  • \$\begingroup\$ Looks like a grounding layout problem to me. Show your layout. \$\endgroup\$ – Andy aka Oct 3 at 18:12
  • \$\begingroup\$ This is similar to the self-excitation (oscillation) of the amplifier. Try adding a 5..30 pF capacitor in parallel to R16. \$\endgroup\$ – Peter MP Oct 3 at 18:20
  • \$\begingroup\$ @Andyaka - Added an image, let me know if I can clarify any of the mess that it is :S \$\endgroup\$ – Cdevelop Oct 3 at 18:22
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    \$\begingroup\$ Possibly relevant... your output transistors are emitter followers... electronics.stackexchange.com/questions/85319/… \$\endgroup\$ – Brian Drummond Oct 3 at 18:46

Get 4 of the 6v lantern batteries. Wire as +_12v.


Regarding stability, your only gain_stage is Q9. Install 100pF or 1,000pF from base to collector.

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