[Amps] The power of an oversized electrolytic capacitor /

Jim Thomson jim.thom at telus.net
Sat May 26 02:26:21 PDT 2012

-----Original Message----- 
From: Carl
Sent: Saturday, May 19, 2012 9:25 AM
To: Jim Thomson ; amps at contesting.com
Subject: Re: [Amps] The power of an oversized electrolytic capacitor /

For you folks that go on and on and on abt diminishing returns,  why don’t
you toss the arrl book in the trash..and find out for yourselves.

later... Jim   VE7RF

Since that is the only part of your statement that isnt a steady
repeat....youre starting to remind me of Rich....here is my reply.

At say 2500VDC a 25V ripple is only 1%. Who can hear it, even as an AM
linear? Sure another 10X reduction looks nice on a scope but our ears arent
so sensitive.

###  99% of ham amps are min 3+ %  ripple.   For whatever techno reason,
all the ESSB folks can easily hear the difference between  3%..and 1%.
That plus the improved dynamic regulation affect the low freq content
of essb  tx audio  for some reason.   W8JI aluded to the effect, when he 
his modified 2 tone rest, by introducing a pulse 3rd tone.   If the pulsed 
3rd tone
is done at a real slow rate, the  effects of  poor dynamic regulation show 
up asap.

Its the same with an audio amp, to a speaker or as a modulator. If the low
level input signal is clean so will the output even if the ripple isnt as
good in the amp.

### say what.  We have 2 things going on here at once, ripple and dynamic
regulation.  By using 570-800 uf caps, instead of those 200 uf caps,  you 
kill 2 x birds with one stone.    The original idea behind the bigger caps 
was to
try and improve dynamic regulation, not static reg. The redux in ripple is 
icing on the cake..and is a byproduct of using bigger caps.   Ripple redux
is  directly  proportional to cap value.  Double the cap value...and ripple 
is in half.
Quadruple the cap value... ripple is now  one quarter.   Half the cap 
ripple will double.

IMD reduces a bit as regulation improves but how much?  Ive asked you this
many times but never an answer.

##  You are the guy with all the spectrum analyzer gear you tell us.  BTW,
any normal 2 tone test wont show anything!   Why, cuz everything is in a
steady state !   Your B+ doesn’t budge, and neither does the bias V..nor 
V  etc.   So a standard 2 tone test is useless.

With most store bought amps having 8-12% idle current  to full PEP
regulation how much IMD improvement is there in each 1% improvement? The few
tests Ive done here using the eyeball and then the Peak Hold method on the
SA while inputting a voice track into the exciter shows under 1dB using a
TS-940 and TS-950SD which have excellent IMD to start with....sometimes
better than the amps published specs.

###  use a Class A yaesu to run the peak hold SA test, while inputting a 
voice track.
Ok, then run the test again.. driving the store bought amp..... GG triode.
Do it with 200 uf caps... then repeat using 600-2500 uf caps.   While ur at 
measure the pep output of the amp.   You wont get any 12% drop.

Later... Jim  VE7RF


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