"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.

Altec/FaitalPro and Ploycone woofer speakers

 

Initially I was asked to make an amp to work with some speakers. It turned out I made a whole system for the customer;- tube preamp, 300/500W SS amp, Xover and speakers. Boxes were supplied along with woofers (polycones) I recommended. Boxes are 170ltr, Dacron lined. The woofers are 95db efficient and the Faital compression drivers 109. I had to pad down the horns (Altec 511B) 14db. Xover at 1100hz and 3rd order on the horns and 2nd on the woofer. Owner to paint boxes.

The sound is a little forward but pleasantly so and the woofers are flat to 30Hz. Fs for this inexpensive efficient woofer is 25Hz. Bass is tight but with the speakers closer to the wall bass will lift a bit and sound even fuller. Very transparent sound driven by the Holton based amp. 

"La Ruse" - Gold Lion ECC83 SRPP preamp in a plastic jiffy box

 

"La Ruse" as the name suggest is hiding something. Its under the paint work and similar to "Illusion", its chassis is a plastic jiffy box. This time spray with Ocean Blue hammertone. Mach that with a large gold knob, looks the part. The tubes I've had for years and are Genelex Gold Lions ECC83 gold pin (similar to 12AX7) which have high gain. About time I finally put these premium tubes to work.

All resistors are 1/4W carbon. I like carbon because it appears to produce great musical flow and combined with the high gain tubes produces a big bold sound. No cost cutting with the attenuator which is my favorite Alps Blue velvet and it is on the output. With the pot on the output you are not throwing away precious raw signal by attenuating the input then trying to amplify what remains producing more noise. 

Once more Russian Military paper-in-oil caps are on the output, they always sound good. There are two inputs selected by the small switch at the front. The external PS produces 12V regulated and 250VHT electronically smoothed. All hookup wire in the audio path is silver plated fine copper wire. There is no PCB. Wiring is a combination of  component-2-component and point-2-point. The preamp is dead quiet. La Ruse not only looks good but sounds great and very grounded. 

"Noir" - SRPP Psvane 12AU7 TII preamp

 

A new preamp all completed in record time. Should be I've probably made eight like this. Sounds detailed, laid back and smooth with the Psvane 12AU7 TIIs. Worked at first on.

 

Voltages are;

HT = 247V

bias = 2.44V

current = 5mA.

 

I'm using a Radi0kit external PS kit. Regulated 12V and electronically smoothed HT. Turn it up and it’s dead quiet no hum, buzz, crackle, snap or pop. Looks and sound extremely good. 

 

Alps pot on the output, Russian PIO output caps and SRPP topology. Metal film resistors. Wood cheeks have been finished with a finishing oil. They really have lifted.  Epoxy enamel paint on top of etching primer.