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'LIVEWIRE?' · 3rd Feb 2019, 12:23 pm

AFAIK the BC328 is simply an extra pre-amplifier/driver stage. The circuit(with minor variations) was used in a wide range of Blaupunkt Car radios in the early/mid 1970s ( I used to service & repair them back in those days) such as the Hamburg (MW/LW), Frankfurt mono & Frankfurt Stereo, and others. The signal at the collector of V207 will be out of phase with that at it's base, which will be in phase with that at the base of V205. I admit to have partly forgotten how these DC coupled amplifiers work, but the phase of the signal presented to the bases of the output transistors may be important. (Someone refresh my memory, please!) All such amplifiers are, so far as I know, based on an early Mullard design, which did only use 4 Transistors. I built such an amp. maybe 40 or more years ago for use in a SW Radio. This only had 4 transistors (AC127 & AC128),with a max. output of about 500mW, but most car radio amps. of that type I've seen, used 5.

3rd Feb 2019, 12:23 pm	#6
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: '71 Blaupunkt E AFAIK the BC328 is simply an extra pre-amplifier/driver stage. The circuit(with minor variations) was used in a wide range of Blaupunkt Car radios in the early/mid 1970s ( I used to service & repair them back in those days) such as the Hamburg (MW/LW), Frankfurt mono & Frankfurt Stereo, and others. The signal at the collector of V207 will be out of phase with that at it's base, which will be in phase with that at the base of V205. I admit to have partly forgotten how these DC coupled amplifiers work, but the phase of the signal presented to the bases of the output transistors may be important. (Someone refresh my memory, please!) All such amplifiers are, so far as I know, based on an early Mullard design, which did only use 4 Transistors. I built such an amp. maybe 40 or more years ago for use in a SW Radio. This only had 4 transistors (AC127 & AC128),with a max. output of about 500mW, but most car radio amps. of that type I've seen, used 5.