D1, and D2 are right. The input stage is working close to the saturation. But 0,6V Vce is enough for the properly selected transistor.
Sajti
BC550C/560C is good for this application. BC337/327 would be better, but I can get the 550C/560C easier.
Sajti
It is not so simple, look at this thread please. http://www.diyaudio.com/forums/soli...i-saturation-measured-data-5.html#post4758150
Unfortunately not so simple. But my input stage is running with 1mA bias, and both 550C can handle it, with 0,6V Vce. Anyway I use Onsemi 550C and 560C.
Sajti
You said it's easier to buy BC550C/560C for you, where do you buy them, I am interested to buy some.
Damir
From Mouser, about a year ago, maybe earlier. I had to clean up their stock, as Onsemi announced to finish manufacturing them
Sajti
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Very nice , a current mirrored cascoded VAS like my IC(eyesee) input module.
Run by a CFA front end.
The triple worries me , either decouple the driver/pre (or just the pre) with
a 4R-10R + 22u/.02uf R/C. Also make sure the driver/pre are stellar in the ft
spec ( 100mhz+) ...fast- fast !! outputs just the standard 20-45mhz variety.
Edit - I notice your passive DC blocking at the (-) CFA node. Very hard to hold offset down
since the low Z at this node (does not play well) with the passive method.
The input diamond beta be the major factor. I have always chosen a high Z positive op-amp
servo to tweak the input diamond DC bias by (as little as a few microvolts) to tweak the offset.
(below) tried this with a tested cfa one (built and ran). It seems to be the (only)
way for this type amp stage - my new one will use this. THD is still single digit
PPM with the positive FB servo.
OS
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