Electronics > Beginners

TL071 distortion - bad amplifier design?

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spec:

--- Quote from: AngraMelo on December 12, 2018, 12:54:50 am ---Spec, I soldered the resistor and pot correctly nothing I do brings the current between +rail and 5200 Collector above 0ma

--- End quote ---
Very strange. I will go back and check the circuit values.

AngraMelo:
Hero999,
Great tips!
About the mod with the pot and 1k resistor:
Im implementing the changes as they came on the thread. Im now following the attached schemaitc

spec:
CROSSED POST

The circuit and values are OK.

Are you using the new design with the PNP transistor in the emitter of the top PNP VAS transistor? Whichever way there should be 10mA flowing out of the PNP VAS collector.

The voltages on the VBE multiplier transistor (BC337) should be:
Collector 1V2
Emitter  -1V2
Base      -0V6

What are you getting?

spec:

--- Quote from: AngraMelo on December 12, 2018, 01:13:51 am ---About the mod with the pot and 1k resistor:
Im implementing the changes as they came on the thread. I'm now following the attached schematic

--- End quote ---

That may be the problem. You need to embody the latest circuit mods as shown on the reply #44 post.

AngraMelo:
Spec, I did only the following modifications:
- Changed the 2 4.7nF for 2 47uF capacitors
- Added a BC337 between the colletors of both VAS transistors
- added a 1k resistor between 1015 collector and BC337 base
- added a 1k pot between 1815 collector and BC337 base
- added a 100uf cap accross the BC337 collector and emitter

I believe that is all that is included in the schematic I posted on reply#71, am I mistaken?
Do I need to short the input to measure the current?

Hero999
The board with the new transistors is not yet made. Spec will make a layout for me and Ill etch it here.
Im bodging the components I described above on the existing board.

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