Help me mod my tube amp

Byron, it’s been a few months now.  The caps should be well burned in.  How are they holding up and how are you enjoying the sound so far?  Is the sound stable with different temperature?  Do you wish the sound can still improve a bit in a certain way? 
 

I’ve had the Hovland caps in my Dialogue Two since 2007.  They’re still holding up and the amp sounds warm and spacious, and transparent with whatever tubes I roll into it.  I’ve settled on RFT Siemens EL34s, Tungsram 12au7, and a variety of Amperex Heerlen 12ax7, Tungsram 12ax7, Telefunken 12ax7, and Mullard box plate 12ax7 to roll with.  
 

Now I’m thinking it’s time to refresh the Hovlands with something more current.  I have short listed down to Duelund CAST PIO Pure Copper Foil or Tinned Copper Foil, Jupiter Copper Foil & Wax, Miflex Copper Foil PIO.  
 

My understanding of Prima Luna is that it will accept a wide range of output tube types.  You can start with trying different types and brands of both the small signal and output tubes.  If you plan to do a lot of swapping, get socket savers so you don’t wear out the amp’s sockets by making a lot of changes.

Beyond swapping tubes, you might need some help on changing components unless you go with identical values.  I would start with the coupling capacitors.  Many of the desirable types are vintage (e.g., “chocolate drops”) so you might have to research or experiment; many newer types are quite lean and detailed which you sound like you are trying to avoid.

Yes, the vintage Hovlands still sound quite musically in mine.  I am afraid that if I get greedy and ask for more with newer caps then I might get less in return.

I also understand that a better rated and more expensive cap doesn’t mean it’ll always sound better in a vintage amp.  

 

Hi baaach,

Thanks for asking for an update. I've been listening pretty much daily since the upgrade (2-3 hour per day), so the caps and NOS tubes (Amperex, Brimar) are nicely burned in. The sound is pleasing to my ears. I know it's an overused descriptor, but it sounds musical. Resolution is good, and backgrounds are black.

I have been thinking of some additional upgrades just for fun. I am thinking of upgrading the 22µF/450V Nichicon capacitor next to the 12AX7s with an Audio Note Kaisei elecrolytic cap. I am also thinking of upgrading the .47µF/630V Swellong bypass cap on the power supply with a V-Cap ODAM or possibly a Mundorf supreme or a Dueland JDM. Open to suggestions.

Also, in spite of someone's reassure in this thread that the resistors in the amp are Takman, I asked Gemini and it told me that the resistors in the PL Dialogue 4 are NOT Takman. My amp is not the PL Dialogue Premium, which is apparently when PL started using Takman resistors. If my resistors are in fact some generic industrial grade stuff, I am considering upgrading some/all of those as well. Again, open to input if anyone has recommendations.

Thanks all,

Bryon

Hovland caps are terrific sounding and they continue to hold up with no sign of going bad.  Audio Note parts are also terrific new choices.  Resistors can be a bit tricky.  A builder I know who makes ultra high end gear uses old carbon composition resistors where they matter to the sound because he likes the thicker sound they deliver.  He knows that they don’t don’t hold their values and can become noisy sooner than modern resistors but he thinks it is worth it.

I would spend money experimenting with vintage small signal tubes—many are much better than modern versions and last much longer.  Vintage power tubes can be good too, but many are quite expensive, and because they don’t last as long, you get less value for the money.