Replacing electrolytic caps with film in PS

[Jamier]

When replacing electrolytic caps with film or film/oil in PS should you duplicate the values or can the uF rating of the new film cap be reduced?

[braubeat]

this program will give you a good feeling for how changing cap values affects the quality of the filter

http://www.duncanamps.com/psud2/

Michael

[Tom-s]

Is there anything similar for Mac users?

[Doc B.]

It's a pretty simple program. You might try running it under Wine.

[Paul Joppa]

Don't reduce the cap values in the Stereomour or Stereomour II. In general, cap values are chosen the same whatever the type. In almost all of our designs, we do not use more capacitance than necessary to get the performance we want (hum in this case).

People often try smaller capacitors in the hopes that the designer used a capacitor larger than necessary. This is called "wishful thinking". The alternative is to analyze the design yourself to see if a different value will work - hence the suggestion to use the PSUD software. This is a lot of work!

[braubeat]

one thing you can look at if the film caps are too expensive or unobtainable is when you add a choke to the filter the improvement can be dramatic

michael

[Jamier]

Where would a choke be best placed in the Stereomour II PS circuit?

[ALL212]

this program will give you a good feeling for how changing cap values affects the quality of the filter

http://www.duncanamps.com/psud2/

Michael

When using this program...

What values should I use for the transformer and load?
Defaults are T1 = 333 RMS v  @ 31ohm Source resistance and a 5k ohm load.

[ZacharyP]

When using this program...

What values should I use for the transformer and load?
Defaults are T1 = 333 RMS v  @ 31ohm Source resistance and a 5k ohm load.

Interested in this too.

[Paul Birkeland]

What values should I use for the transformer and load?
Defaults are T1 = 333 RMS v  @ 31ohm Source resistance and a 5k ohm load.

The short answer on the transformer voltage is that it's about 160V.  I tend to prefer to change the resistive load to a constant current load, and the current drawn through the amp will be pretty constant with the Speedball upgrade, and can easily be measured and calculated on a stock amp (for the most accurate results).  The simulation will never agree with the measured results perfectly.

The longer answer on the transformer is to hit the [...] box by each attribute in the Edit Transformer Properties window to provide the program with additional data to predict transformer behavior.

If you are simply using PSUD to model power supply ripple, the specifics of the transformer are a bit less important (IE - you can start with the stock Crack power supply, see what that looks like, then mess around with alternatives in an attempt to match or exceed the original specifications).

-PB