Most metal films are 1%, and most carbon films are 5%. Metal films also have less excess noise, and better temperature stability. I would stick to the metal films in positions where 1/4w is enough.DeadSpeaker said:Thanks. I was going to use 1/4 watt metal film, but I found that I have quite a few 1/2w carbon films that will work. So I will not be using any 1/4w ones.
You have pure AC over the cap since the stage is fed from +15 V and -15 V but the AC voltage will probably be quite low so the cap will last for quite a while.DeadSpeaker said:Thanks for the tip. I just noticed that c14 is 10uf and it is non-polar. Is it possible to use electrolytic here, and if so how would it be oriented? Thanks.
If you know your load you can calculate which cap value you'll need.
f = 1/(2*pi*R*C) where
f = where the base starts to drop
R = your load (10k or more?)
C = the cap
peranders said:I hate to tell you that this is not correct. Only a couple of nA will flow through this resistor. 1/4 W will certainly do.
Both you and me were correct!
I mean R9 on power amplifier circuit (4.7k), you mean R9 on the preamp circuit (2.2k).
At 40V +Vcc the dissipation on that resistor in the bootstrap circuit would be ~150mW. That's why I recommended 1/2W rated resistor instead of 1/4W rated.
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