• Item: Tube Headphone amp  
  • Type: retro-thermionic - "Priory"  
  • Posted: 6 September 2021  
  • Builder: mwhouston  
  • Country: Australia  
  • Comments: 0  

Tube HP amp

From the COVID lockdown last year I made a real push to use as many parts I had on hand as I could to build them into working pieces of sonic art as possible. Not just cheap passive parts but expensive tubes and transformers. I had two Hammond low power high voltage trannies, a Svetlana 6AS7 and cheapy 12AU7 plus a beautiful base and most other parts to build either a preamp or a tube headphone (HP) amp. Take a look at what I decided.

This is the seventh tube HP amp I have built. This includes three Bottlehead amps for others from kits. This excellent build includes;- A beautiful Cypress base, Hammond power tranni, Svetlana 6AS7, Alps Blue Velvet pot and 4oz gold plated knob, very low noise SS rectification and 330uf of storage capacitance plus a 5H Hammond choke. Not only is the double Pi PS choked but has Ultra fast/Soft recovery diodes. All components in the PS are fully snubbed with poly caps. The amp is super quiet.

Of course all point-2-point wiring and no shielded wire or PCBs. All signal wire is solid core Cat5 copper. WBT silver solder used throughout. Only one capacitor in the whole signal path as the 12AU7 driver tube and the power tube are directly connected. To get that extra deep "full" sound I used 1W carbon film resistors. Every time I have used carbon Rs in any build I always get a richer warmer sound. Its the same here.

This HP amp produces the most textural, deepest warm sound I have heard in my HP amps to date. Reverb just extends for ever. And to think the passive components are very basic. But there ae some tweaks - the 400uf output NP cap has a 0.1uf Russian PIO cap snubbing (or by-passing) it. Every electrolytic has a poly subbing it. The amp is dead quiet, only the music gets through.


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