Upgrading coupling caps - which ones first?


I have been experimenting with different coupling caps on the output of my amp.  I now want to try some more expensive caps (Vcap, etc), but cannot afford to replace every coupling capacitor in my system.  Therefore I want to place the best capacitors where they will make the most difference.

For each channel of my amp, I have one coupling cap between the driver and phase splitter stages, and a pair between the phase splitter and output tubes.  There are also output coupling caps on my DAC that feeds the amp which I am thinking about upgrading as well.  Which ones benefit the most from an upgrade that should be targeted first?
solman989

Showing 2 responses by solman989

The caps in the amp are .1 and .47 uF at 600V, and the output caps in the DAC are 3.3uF 200V. 

it is probably reasonable to expect that higher values of capacitance and voltage rating will tend to correlate with less ideal behavior of a capacitor.

My thoughts also.  Amp input impedance is about 70k which means I could get by with a much smaller ~1 uF cap on the DAC without any frequency rolloff.
So far I've been playing around with the .47uF output caps on the amp and right now I am trying to decide which ones are going in there permanently.  After that I will target the DAC.  So far I have tried Jupiter copper foils, Clarity MR, Mundorf Silver Oil, and of course the stock Nichicon polyester film caps. 

Surprisingly the stock Nichicons have a lot going for them.  They have a clear, wide open sound with the best bass of the bunch, and extended highs that seem tipped up and can be a bit thin sounding and on the shrill side at times.

The Mundorfs have an extremely smooth sound that is very musical, and are a tiny bit darker with a smaller soundstage in direct comparison with the Nichicon.

When I first installed the Jupiter, the imaging was what I noticed first.  It is more pinpoint but at the same time the sound was a bit closed in.  After a few days I reinstalled them for a second evaluation and they seemed to have opened up.  Their presentation is similar to Mundorf but not as smooth, and bass is not up to the levels of the Nichicon.

I am a big fan of Clarity TC caps in the power supply so I was eager to hear the MRs in coupling duty.  The first impression of these caps are that they are clear and have a big sound to them.  They don't quite have the smoothness of the Mundorf, they are instead more neutral and true to the source it seems.

These caps were all burned in for a week with a tuner on the speaker output of an old amp connected to a dummy load.  I'm not sure if they still need to be run in some more but I could swear that the Jupiters sound different now then when I had first installed them.

So what I've discovered is that all these caps do some things great but not everything.  Based on what I've heard so far, the ideal cap would have the bass slam and transparent open sound of the stock caps, combined with the smooth liquid highs of the Mundorfs.  Does such a cap exist?  We will see.  I can only imagine the can of worms I am opening up once I start with the DAC.  Why can't I leave well enough alone!?