Does it oscillate in LTSpice without C16? And why isn't there a cap on the BD139? I couldn't see a mention of this on Eliott's site. Looks like a bit of a hack to me.
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guys - I love the interest but if I may - please put TGM8 stuff in the TGM8 thread or I'll get all confused 😱
anyhow, need to be careful which schematic being referenced as C16 might be anything !
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In any amplifiers, the complete story is the complete compensation scheme. They are one package and cannot be seen as add-ons. The 22k resistor is part of the compensation scheme in Naim amp.
He did mention it. The oscillation happens as bursts, intermittently, in my experience. In my build I tried 47pF and I got these bursts of oscillation then I paralleled with another 10pF and it is gone. Why not on BD139? It has been taken care of by the Miller and in most situation we need to 'slow down' the bottom half.
I’d be very wary about this instability. The Naim doesn’t show it. A proper analysis is advised.
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indeed, the lower output is not the same topology as the P3a, it has the phase correction networks on the base of the driver and the Baxandal diode.
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