Filter Cap Question

[Jman]

I am getting ready to build a 5e3. Anyone have any thoughts about using larger Filter Caps? The original layout calls for three 16uf filter caps. If so, what benefit would it have and would it effect the tone of the amp? Thanks for your help.

[Chuck H]

You could go larger IME. There are some here that would tell you that the rectifier tube will fail if the filter is too large. And they're right. But the data for rectifier tubes is very conservative in this area, again IMHE. You could use a 33 or 40uf with a tube rectifier or any value you like with a solid state or copper cap type tube rectifier. The copper cap rectifier plugs right in and simulates the sag of a tube rectifier. The only trouble with going higher on the uf value and using a copper cap is that the day may come when you or someone else decides to plug in an actual tube rectifier. Then, if the uf value of the main filter is too high, you could get smoke.

It's my (highly biased) opinion that the 5e3 benefits from more uf on the main filter. It seems to strengthen, tighten and otherwise improve bottom end performance and headroom.

Chuck

edit: It's been proposed here that you could also use the standard filter cap size (16uf) after the rectifier (to stay in spec) and then follow with a resistor (like 50 ohms) and a larger cap (like 80uf) and feed the OT center tap from the 80uf node. This amounts to a sort of lopsided Pi filter and probably works well. I do wonder if you could use a diode (or a pair in series) in place of the resistor to avoid the voltage drop. Maybe I'll start another post on this.

[tubeswell]

On the other hand IMHO you don't want a 5E3 to get too clean, otherwise it loses its basic charm. :-) So I vote for 16 to 20uF in all three filter positions. You still get a nice sounding amp with 3 x 20s

[Jman]

Thanks for your replies!