Quote:
Originally Posted by thermionic
As others have said, slightly increasing the values of reservoir and output coupling capacitors will be beneficial to the amplifier.
Even in the early 1970’s, larger value electrolytic capacitors were bulky and expensive, so manufacturers were keen to keep the capacitances to the minimum they could get away with.
Today we are spoilt with the availability of high capacitance, compact components at reasonable prices. However, if you want to keep the amplifier sounding as it would have done originally, then sticking with, or very close to, the original values is the way to go!
Cheers.
SimonT.
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Thanks Simon.
So can anyone tell me other than my previously considered reasons, why increasing reservoir capacitance causes problems in terms of excess bass and blowing the 1A supply protection fuse if the wicks turned up. Which is why I kept to 1000uF main reservoir?
I checked the Voltages. to the nearest Volt as it varies slightly as the mains drifts.
off rectifier across reservoir capacitor 47V
Across zener 43V
between base and collector of pass transistor 4V
between emitter and collector of pass transistor 4V
and from the positive to negative of main supply 43V
So I figure its working OK? Or have I missed a fundamental?
if my maths is right then the 4V drop across the 390 ohm resistor between Base and collector means theres about 10mA flowing through the zener and thus a dissipation of 41 mW which is well inside the diodes 1W rating and the resistors 1/2W.
I've so far also replaced the coupling caps on the disc stage and output driver, and speaker output caps. but nothing else yet.
I feel that its got to be worth working through them all though after 50 years, only the electrolytics though as all the rest are standard Mullard polyesters etc which should still be good.
A.