"Shu" - CV-181-Z and Golden Dragon preamp

 

For quite a number of tube preamp builds of late I have been using SS rectification. Coming across a new Golden Dragon 5U4 rec tube and new Shuguang CV-181-Z (6SN7) dual triode in my stash changed all that. Most of my builds of late have been SRPP but I started with single stage tube preamps. Time to revisit that and time to revisit tube rectification. You have to have a power tranni which will support a 5V filament at sufficient current for the rec tube and also have sufficient high voltage current support. The Hammond tranni I had hand on hand for many years (and this includes how long I have had the tubes) will do the job easy. In a big push through these many lockdowns to use up expensive parts in "da lab" and even having the cast Al chassis I knew I should go ahead.

Epoxy enameled sprayed cast Al enclosure with Hammond power tranni and heavy rubber feet makes a good start. Ceramic tubes sockets, silver plate fine copper wire in the signal path and a Pi X 4 filtration PS make the basis for a great tube preamp. I could have used some stock metalised poly output caps but I ordered Mundorf EVO oils for the output. Glad I did. The PS is CRCRCRC with the final cap a 4uf PIO. All filter caps are snubbed. 

Two selectable inputs and one out. Silver soldered signal path with fine silver plated wire and all carbon film resistors plus the excellent 50 Year Treasure ceramic based and gold pinned tube (CV-181-Z) make for real good music. Rich, smooth and soulful. 

"Priory" - tube Headphone 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.