"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. 

"Essence" - Pass inspired Class A enhanced amplifier

 

Being very impressed with my earlier F5 build (see previous post) I made a second but this time spent a lot more on a better, cleaner, more robust power supply. Same Jim's Audio amp boards but now with Mundorf MLytic audio grade filter caps. The caps are larger providing a total of 88,000uf of filtering. Again the filter caps are snubbed to ensure a dead quiet PS and an extremely pure midrange and treble. Only twisted pairs of Cat5 solid core wire used throughout for all hookups. No shielded wire for the signal path.

To bolster the PS even more a 300VAC transformer was used. Bigger caps and bigger tranni made for a tight fit in, once more, a compact pro enclosure. The enclosures got lost in transit and when finally arrived the front panel was scratched and gouged. To hide what I couldn't sand out a hammertone copper finish was applied. This has a nice textured finish and looks excellent.

All the audio and sonic qualities of the previous build were even more enhanced in this build. Hearing deeper into acoustic instruments and texture in voice were far more evident. 25W in my system is more than enough and this build has impressed me so much I am making two more with the intention of keeping one and selling the other. Such a simple design and inexpensive to build, I have to have one for myself. 

"Dolce" - Pass inspired Class A amplifier

 

After building a very expensive F5 Turbo for another I thought I would build my own. Using Jim's Audio F5 boards, a cool looking 200 X 300 X 100 enclosure a local 160VAC tranni and  4 X 10,000uf caps I built this. Looks cool sounds even better. 

I didn't push the bias current so the amp just runs warm and the sound is the same - "warm". The name "Dolce" really says it all. The upper bass is rich and fills the lower mids giving male voice extra weight and chest. The woofers bloom a bit more and bass goes down to 30hZ in my system. I like it and so does the new owner. 

"Ironstone" - MM phono preamp

 

For a change in colour and always a great sounding tube MM phono preamp I put together this kit from Radi0kit. I had the chassis and a spare kit and after a total external colour change to our house had a spray can of Ironstone leftover. As with my other tube phono preamps I chose the premium version of the Radi0kit kit. 

This build also uses an external PS and again I'm using the Radi0kit tube PS. Using a four pin power plug to bring in the DC heater and HT voltages. The PS can also be used on my later tube preamps having 12V regulated DC and electronically smooth 250V HT. 

Not only a great sounding tube phono stage but this time a more unusual looking low sheen blue/grey coloured preamp. All other builds of this kit have sold with the new owners saying how much they like the look and sound. This one is also up for sale. 

"Quiet Strom (take II)" - `100W Class D Tripath amplifier

 

This amp has been put together from most parts on hand. The enclosure once held SS amp and has a good PS including 20,000uf of smoothing caps. The T4 module has a further 10,000uf Nichicon filter cap onboard. This amp module is a T4 Tripath module and with an appropriate tranni will deliver 180Wpc. The PS will deliver 100W and with even low efficiency speakers will play loud.

The smart looking two tone enclosure is steel and Al. The IEC socket also has a RFI/EMI power filter. It is fused (internal) and earthed. Silver plated wire-warp wire is used in the signal path. The amp is dead silent with music off and is highly detailed. Bass is deep and extended and very well controlled. Very good use of parts which have been unused for so long. 

"Cello" - TDA7293, chip based 100W amp

 

Chips for power amps are continually improving. The TDA7293 is capable for 120W in my configuration this amp will produce 100W. The kit comes with all components, PCB, heat sink etc. The PS is onboard and all that is required is a 30-0-30V tranni. I used a 300VAC toroid because I had it on hand. 

The enclosure is two tone steel and Al and is very solid.  Solid brass gold plated speaker binding posts with quality RCAs. Hookup wire is all Cat5 twisted pair with no shielded wire. Not required. The enclosure is earthed and fused. The sound is extremely balanced and very engaging to listen to. Bass is very extended and well controlled. At low to medium volumes THD is 0.001%  

The overall sound is very dynamic and challengers my more powerful amps which cost three times the price. The amp module kit is $A15 delivered. Hard to beat. Of course the main cost is the tranni and enclosure. Very impressed.

Mimic - Custom, chip based MM RIAA phono preamp

 

Yet another chip (OPA2134) based phono stage. Most parts were on hand and in this build I used Russian PIO 4uf (snubbed) caps on the output. Metal film resistors here where in other builds I have used carbon. Other caps are a mix of MKT - for accuracy - and Polyester. Once more there is no PCB but a very small piece of vero-board. Differential PS in on board and two 9V batteries power the unit. Silver plated hookup wire (wire wrap) and WBT silver based solder is used. With quality batteries 50 hours of play can be expected. 

The metal enclosure is deadened in the lid and under the bottom with bituminized heavy Al. This adds weight to an otherwise light metal (Al and steel) enclosure and also dampens any resonances. There is  an earthing point and an external battery test point. The overall sound is very neural and dynamics are outstanding. The preamp is dead quiet with good gain. Simple and over-achieving.