Pearl Phono Stage Coupling Capacitors (?)

mirlo

Member
Paid Member
2002-07-12 9:55 am
San Diego
I noticed that the 0.15 uF/63V capacitor C11 pictured in the AudioXpress article aren't quite the same as the ones specified in the parts list. The cap in the parts list is a 50V Panasonic polypropylene, with a red conformal coating, but the pictured ones appear to be green, smaller and more "boxy".

The same cap is used for both coupling and power supply bypass.

So, I don't imagine that the exact value of this capacitor is too critical ...

But I'm curious about a couple things:

In the coupling application, it is in parallel with a 0.047 uF cap. Was the idea to get something close to 0.2 uF with parts on hand, or is there something subtle going on? I would think that a composite capacitor would be made from vaules that were more different than 0.15 and 0.047...

Also, just curious what dielectric, construction style, and manufacturer those boxy 63V caps are, in part because I bet they fit the board better than the Panasonic does. (Unless the board was revv'ed to fit the Panasonics since the article was published.)

If this question was already answered, please accept my apologies -- I really did search!
 
C11

C11 is part of the RIAA eq. section of the pearl.
NP (or should i say WB?) uses Panasonic 2% types.
If you cannot get them try any decent polypropylene @ 5%.
In my Pearl i used SCR caps which i bypassed with Siemens Styroflex 1% types. The results are very fine indeed.
The "green, small and boxy" are probably polyester caps (i think Tiroth is right), good for bypassing power supply electrolytics but not ideal for phono equalization.
For C10, C13, C11+C12, try to combine polypropylene with styroflex caps.

hope this helps,

Nick
 

joe

Member
2001-10-23 8:44 pm
Hamburg
Hi,
to my understanding C11 is NOT part of the RIAA-EQ. I would say its just for DC-blocking.

Here are some equations taken from: "S.P. Lipshitz: On RIAA Equalization Networks" in Journal Of The Audio Eng. Society, Vol27, No.6, 1979. Refering to the schematics in Fig1 in the Pearl article:

R23*C10=750µs
R22*C13=318µs
R23/R22=6.877
C13/C10=2.916

The value for R23 should contain the source resistance (499Ohm?) for the calculation. One of the Components can be choosen independently.

Note that the values in the pearl article at passdiy.com are not 100% consistent with the above formulas as standard components are used.

joe