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Question About Capacitor Upgrade in Tube Amp

Hi,

I am preparing to do a coupling capacitor upgrade on a recently purchased tube integrated amp. The two 0.22uF on the preamp tubes are fairly straight forward. But I noticed another similar model 0.33uF cap on the large filter capacitor for the B+ supply that is installed across the hot lead to ground.

Does this cap on the B+ just block high frequency noise from the power supply or does it have any effect on the amp tone? Is there any reason to "upgrade" this cap?

I know it may be hard to tell exactly what is going on without a schematic.

Also any recommendations on a good cap to use in the upgrade of the coupling caps? I was looking at Mundorf SilverGoldOil for the quality at not too crazy a price. The amp already sounds good but lacks a little clarity that I think a coupling cap swap will help with. It is SET 300B amp.

Thank you!

 

calieng
terry9
2,243 posts
 

You ask, "Does anyone know how the power supply bypass capacitor effects high end frequency response?"

Maybe. The component may sound smoother, with a less etched treble if the power is cleaned up with such a capacitor. This etched treble is distortion which has been removed. Some who are used to digital may not like the effect.

terry9
2,243 posts
 

I would also suggest that Dielectric Absorption (DA) is the most important measure for modding, because the other measures should have been considered in the design phase. The properties you list are critical when using electrolytics, which are not (should not) be under consideration here.

calieng OP
144 posts
 

@terry9 

Thanks for the additional info.

I was just making the point that there are physical properties to capacitors that can alter the sonic characteristics - but the cut and paste text was more related to electrolytic yes.

Some people believe that a capacitor with a certain capacitance value must sound the same as another with the same capacitance value regardless of the type of construction. That goes against common sense for anyone with a basic understanding of science or materials.

 

charles1dad's avatar
charles1dad
10,236 posts
 

@calieng 

Some people believe that a capacitor with a certain capacitance value must sound the same as another with the same capacitance value regardless of the type of construction. That goes against common sense for anyone with a basic understanding of science or materials.

Goes against common sense.+1.

Charles 

ieales's avatar
ieales
1,201 posts
 

I would also suggest that Dielectric Absorption (DA) is the most important measure for modding, because the other measures should have been considered in the design phase.

Nope. DA is not the most important by a long shot.

Of properties mentioned this far, left out are:

  • Geometry, rolled or folded
  • Lead material, length and attachment methods
  • Foil material
  • Foil inner / outer connection direction for DC blocking
  • Microphonics
  • Age

The properties you list are critical when using electrolytics, which are not (should not) be under consideration here.

OH, yes they should. Trying to clean up a marginal supply with a magic bullet is silly and rarely effective. A better supply can transform an amplifier.

Capacitor technology has improved immensely in recent years. More capacitance in smaller packages with reduction in ESR, ESL.

 

 

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