“Mundor/F5” - Pass F5 inspired with advanced boards

 

I was vey impressed with last F5 I built using Jim Audio boards. The amp sold before a I could start construction. The build was a big step up from the F5 before by upgrading the filter caps to 88,000uf of Mundorf MLytics and the toroid tranni upgrade from 160W to 300W. The total presentation of that amp was beguiling.

Here is my build based on what I thought maybe the best amp I have ever heard. Ounce more 88,000uf of Mundorf MLytics audio grade caps at over $300 for caps alone. Same upgraded Jims brds. and as before all Cat5 twisted pair hookup wire. This amp shines. Given the right music you are challenged to think something so compact and unassuming can generate such presentation. It’s a 25W Class A simple amp. Bass goes easy to 30Hz, mids are transparent and treble clean and controlled. Compact and astounding. 

“3D” - Three channel Class D amplifier

 

I completed a three channel Class D power amp for another SNA member. 1X 150W and 2X 180W Tripath amp modules, 500W PS with Mundorf MLytic caps - 2X 22,000uf and EVO oils on the input. I sent the amp off without taking any images and had to ask the new owner for a few picks.

"Shadow" - SRPP 12AX7WA Sovtek preamp

 

Just finished this compact tube preamp with Sovtek NOS NIB 7025 (12AX7WA). Again on a jiffy box - “Shadow” - this time is an ironstone epoxy enamel finish. All metal film Rs and PIO output caps with silver plated fine copper hookup wire. Two inputs. SRPP topology. External PS is a Radi0kit kit for 12V and  250V DC. The preamp is absolutely dead quiet. No snap, crackle or pop.

"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. 

"Cadence" - SRPP 6SN7 Preamp

 

After building yet another SRPP 6SN7 preamp for another, who had his onw tubes, I build this one to used the spare Psvane Grant Fidelity 6SN7 Spheres I had. A few changes from the previous one but similarities to others. Big difference is the colour - Hammertone Copper. Other preamps I have used the same colour but not with the Hammond Wood chassis. 

Similar to others with with the Danish Jensen copper paper and oil output caps. Before discontinued they were quite expensive. Other similarities are the final filter cap in the preamp which is a Russian PIO 4uf with a Russian 0.1uf snubber. Fine silver plated hookup wire and Alps Blue Velvet pot round it off with the 4oz solid brass gold plated knob. This time resin tube sockets and not the usual ceramic. Cheeks are treated with a high grade finishing oil which dries to a hard glossy wax finish while lifting the grain. Nice.

Using an earlier PS which is choked and relies on an external 24VAC 1A wall wart I found the sound quite a jump up from all other preamps built with the same tubes. Also in this build I used 1W carbon film resistors except the grid resistor which is metal film. There is only three resistors in each channel and the two main Rs in the signal path are the carbon film. Ck is a low ESR type. Is this the carbon Rs the secret to the better sound or is the expensive caps? Whatever bass has a whole new depth and texture, mids crazily engaging and textured and treble super smooth and sweet.

This preamp was built to sell and move on the spheres. Not sure that is going to happen any more.

"Essence" - 6SN7 Preamp

 

Not the first of the 6SN7 preamps I have built but his one is not for me. And not the first in this hammertone blue. This is a commission job and the future owner has his own, fine, Psvane 6SN7s. Pictured here with my Psvane Grant Fidelity Spheres (expensive) for testing (and a lot of enjoyable listening). Two selectable inputs selected from the front switch and two outputs. One output for an active sub woofer. 

Under the bonnet are standard metal film resistors, a 24 step stepper attenuator, low ESR cathode bypass cap and my fav. 0.47uf Russian Military paper-in-oil output caps. The knob is 4oz of brass and gold plated. Combined with the stepper has a good solid feel. The heavy weight knob also helps with resonance control in the attenuator and chassis. From past builds you will recognize the Hammond wood cheek chassis. Paint is epoxy enamel with an acid etch primer. Always comes up well when the primer is used. 

The sound is what I have come to expect from similar builds with these tubes - balanced, clean and clear with detailed and warm midrange. Different tubes will have slightly different listening results but should stay very much in the enjoyable zone. PS is external with electronically filtered HT and regulated filament voltage. The preamp is absolutely dead quiet. The new owner will love this preamp. He should like the colour, he picked it.