[HAM] Capacitors

[Kon Zissis]

Hi David , Christoph and Keith.
 
David Anderson wrote:
>but  to claim simply that increasing the value of a plate resistor  
>increases bass is cutting far more electrical engineering corners  
>than I'm comfortable with.
 
Although I am not sure about the correct electronic  explanation  of
what is happening , I suspect  that what is happening here is that
because there is a much higher resistance between the plates of the
valve stages with the 1 Mega ohms plate resistors , the negative
feedback effect  is lessened between the various valve stages thus
allowing a causing bass response.
 
In a normal valve circuit if 1 Mega ohms plate resistors are used
instead of the more normal 100 K resistors  then the high  power supply
voltage will need to be higher than normal so that the voltage  that
reaches the valve plates after passing through  the 1 Mega ohms is at
the proper range and current rating required  for the valves . I am not
sure what the voltage drop is with 1 Mega ohms plate resistors as
opposed to 100 K plate resistors. I would have to experiment with this.
 
In the hope of getting a louder and cleaner headroom  by having a higher
voltage going to the valve plates, I did experiment with  100 K ohms
resistors instead of the stock 470 K ohms on the plates of the two 6AU6
valves and I think that I also tried out 100 K ohms resistors instead of
the stock 330 K ohms resistors  on the plates of the V4A and V4B 12AX7
valve the in the AO28 of my 1962 C3 but the 100 K ohms plate resistors
resulted in the bass response thinning out so therefore I went back to
the stock 470 K and 330 K plate resistor values for the plates of the
two 6AU6 valves and the 12AX7 valve.
 
I think that the increased negative feedback between the various valve
stages caused by the 100K plate resistors caused the bass response to
thin out.  This amateurish experiment helps to verify your statement
that the power supply is indeed in  the signal path.
 
>Off the top of my head, I might wager that, rather than increasing  
>the bass, you're actually cutting the treble due to increased Miller  
>Effect.
 
The normal setting for the six switches that set the plate resistance
for the six stages of the three 12AX7 valves  in my guitar preamp  is
the 100 K ohms setting  but when I set  the six  switches to the 1 Mega
ohms  resistors , the overall volume level of the sound remains the same
but the bass response become deeper and fatter. The higher voltage drop
of the 1 Mega ohms plate resistors causes the sound to distort earlier
than it does with the 100 K  plate resistors but  the overall tonality
does sound nicer and fatter with the 1 Mega ohms plate resistors.
 
Christoph.P.Kukulies wrote:
>I appreciate you as a - most of the time - rationally, scientifically
>thinking human. All the more I'm surprised how you can use the above
sentence:
>"little warmer..."
>What is warm sounding? 
 
By "warmer"  or "warm sounding" I mean a fuller bass and midrange
response that makes the sound fatter and thus more pleasant. "Warm"
sound is the opposite of thin or sterile sound.
 
As for audiophile voodoo terminology , what does the term "tight " as in
"tight bass" mean and what does "punchy sounding " mean  and what does
"transparent sounding" mean ? 
 
>Why not make an MP3 to let us compare "before" and "after" and do a 
>Fourier transform on the sound samples after such a rebuild.
 
A few other people have asked me to do MP3 samples of my modified C3 but
unfortunately I do not have the proper recording equipment to do this .
MP3's can be helpful for demo samples. Some time ago Dennis M Wage did
MP3 samples of all ninety one notes of his red mylar capped 1964 B3 and
the TG notes 13 to 91 of his wax capped 1961 B3 and with these  MP3
demos I can clearly hear the difference in the tonality of the two
organs, especially  the tonality of the TG notes 37 to 48 of the 1964 B3
with the R/C hum filters and the wax capped TG notes 49 to 91 of the
1961 B3. 
 
>No offence meant :-)
 
No offence was taken
 
 
Keith H Clark wrote:
>Kon, Best bet is still the replacement cans as opposed to the smaller
>individual electrolytic.  
 
Ideally the multi cap can capacitors  would be good because of the
compact size and much less soldering work , but the multi cap can
capacitors are not readily available locally and the cap cans from the
USA are very expensive just to buy them and on top of this the postage
and handling  costs to ship them over to Melbourne Australia would make
them  exorbitantly expensive , costing over one hundred Australian
dollars. The readily available ( Topcon brand )  individual 47uf , 33uf
and 10uf 450 volt rated capacitors cost me  a few dollars each and the
two 33uf cathode bypass capacitors cost less than one dollar each.
 
One real  advantage of using individual capacitors instead of a multi
cap can capacitor is that if one of the individual capacitors  fails
then I would only need to replace that one instead of having to replace
the whole multi cap can.
 
All the best.
Kon