Re: 10W LInear PA: Starting build - any suggestions, thoughts, comments? #10W_PA


KEN G4APB
 

Having previously started a similar thread that seems to have close connections...I repeat..
QUESTION 3: Why the first stage amplifier (two BS170s) has a complex biasing circuit while the second stage (two IRF510s) is just done by trim pots? ?
Can somebody please illustrate how this biasing circuit works? In particular, I don't quite get the role of the 1N4004 diode (D201) in this. 

Maybe Hans could answer this one please?? 'Cos I really want to know why my amp does not perform like it should. Diode 201 was missing from my kit anyway.

.....Again a guess, it is a copy of a working amplifier, why re-design? -- ,sorry, but this does not answer the question. I'm sure Hans does not look for a wildy complex circuits and stick them in his designs with the thought .. "that 'll make me look clever...."

Also, Hans, much talk about matching the devices  .. do you supply pre-matched devices in this 10W Linear PA kit.? As I originally stated, I do not see similar bias voltages on my finals, so I wondered how much of a problem this really is.

73 Ken G4APB

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