Friday, January 15, 2021

“Sortilege” - enhanced Class D power amp

 



















Another 180W Class D amp based on the hifimediy T4 module. This time the input caps have been upgraded to Mundorf EVO oils and an additional 22,000uf of Mundorf MLytic audio grade capacitance has been added to the PS. Total caps with onboard Nichicon is 32,000uf. The filter caps are snubbed. Enclosure is attractive two tone, earthed and fused. A RFI/EMI power filter has been added and a ferrite choke on the power cord to block RFI. A 500VA tranni does the grunt work and the onboard Motorola ultrafast/soft recovery diodes for the rectifying. 

The amp sounds excellent, clean, clear and fast with optimum bass control. For the extra work replacing the input caps and adding the better filter cap the sound quality has improved. Other amp builders who have heard it agreed and its new own is very pleased. So am I.



 


Saturday, December 26, 2020

“Mantra” - kit tube MM phono preamp.

 












Another quality tube MM phono kit from Greek Radi0kit. This time in a Hammond wood cheek chassis and sprayed Indian Red. Also from Radi0kit the PS kit which employs regulated 12V for the filaments and electronically smoothed HT of better than 250V depending on load. 

As with all these kits they sound excellent with the standard JJ 12AX7S tubes. Parts are quality;- ceramic sockets, Visheys, Dale, Nichicon and Cornell Dunbilier. Mantra is dead quiet, looks smart and sounds really great. Happy with the build.




Wednesday, November 25, 2020

“Carbon” - chip based phono preamp

 















A mix of MKT, Polyester and low ESR electro caps. All carbon film Rs through. Differential PS onboard. Genuine OPA2134 from RS and machined milspec socket. Two 9V batteries for about 50 to 100 hours play depending on battery type. I often use eBay lithium’s first 100 hours.

 

Cast Al enclosure with bituminised heavy Al in the bottom for resonance and vibration control. Paint is Epoxy Enamel with an etching primer. The finish is gloss and tough. This one is also called “Carbon” for obvious reasons. 

 

Some don’t like carbon film resistors but I find they produce a very smooth sound but still let instruments shine in their own space. The preamp is new and requires about 50 hours to burn in. Listening to it with late model Rega P3 and Gerrott P77i cart. Very nice and to think it will improve

Monday, November 16, 2020

“Succinct II” - integrated 180W Class D amp with tube preamp

 









The original Succinct was built on commission and again it was a 180W Class D amp. The owner lost all in our latest bushfires. By accident I found this out and offered to replace the amp for cost of parts only. We added a tube preamp to make this a true integrated. 

It is all housed in a light weight 2U charcoal 19” rack mount. There are two inputs selected by a small front switch. The onboard PS with the hifimediy T4 module is used here and a Radi0kit 12V/250V PS is used to power the tube section. The tube is a Raytheon 12AU7 and the preamp is built on a small piece of Vera-brd. The tranni is 300VAC and connects direct to the amp module. The amp module has speaker crowbar protection. Twenty second delay on and immediate off. 

The sound, as usual from these T4 modules, is pristine, very detailed and with excellent bass drive down to 30hZ the limit of my speakers. For way under $AU1K this map has a stack of power (180W into 8ohms) and crystal clear with only a touch of tube warmth. 



 


Friday, October 30, 2020

180W Class D power amp

 











Yet another Class D compact 180W amp using the onboard PS. This means you only have to add a Tranni of the appropriate voltage and wattage to complete the amp. The enclosure is solid and in attractive two tone. It is fused and earthed. This one was built on commission. I‘m happy with the finish and sound. Extremely detail and excellent bass control.  

Sunday, October 4, 2020

“Illusion” - 6SN7 SRPP preamp in a plastic jiffy box

 

















Mostly from parts on hand in da lab this simple 6SN7 SRPP preamp was constructed. Having a universal PS makes making many preamps very inexpensive. Of course when it comes to sales the preamp and PS go and therefore I have to make another PS. Constructed in a large plastic jiffy or projects box this great looking preamp ("Illusion") was primed and top coated with copper hamertone epoxy enamel spray paint. A tough and cool looking finish.

The tubes are Ozzy Miniwatt 6SN7 GTAs. On the tube tester both tubes test "88" well into the good zone and closely matched. Under the bonnet is a turret brd. I have a bag of these and it is time to use them up. They come with heavy ceramic sockets and flashy gold plated hold downs. Illusion has two selectable inputs and one output and Al foil lines the inside and bottom of the preamp. 

A switch at the front selects between inputs. A standard pot is on the output so all of the input signal is amplified before volume level is set. Russian military PIO caps are on the output and there is no input caps. Never a problem. Input impedance is 300K. There is a mix of multi-stand and solid core copper wire and WBT silver solder used throughout. Metal film resistors are used.

The sound is solid, grounded and feels relaxed and natural with good drive and bass. It gives me great satisfaction to use primarily parts on hand (vintage tubes been in da lab for well over twenty years). To now have those inexpensive parts in a working great looking and excellent sounding preamp and so cheap to build, is gratifying.  An enjoyable building and listening experience.   

Wednesday, September 16, 2020

"retro-K465" portable headphone amp



 








Oatley released a headphone amp kit based on the OPA2134 - K465. A CMoy style simple HP amp based on the OPA2134. Oatley guarantees genuine OPA2134s and I have validated that. I received an early release which was assembled with pot and sockets on board. These were removed and the good input caps replaced with Russian PIO caps. 


A larger ABS enclosure was used than the last two HP amps to accommodate the cct. brd and two 9V lithium batteries. The batteries are converted to differential supply on board - +/- 9V. The enclosure is lined with Al foil top and bottom and is earthed. 


Once more my "safe on" wiring using the changeover switch on the input socket ensures the amp cannot accidentally be left on and drain batteries. The sound is good with excellent clarity, good volume and drive. The kit should be simple to assemble. The kit is complete with 9V battery clips and the ability to also use AA battery holders. You can see I am now spoiled for choice with three HP amps, one with the PT2308 chip and the others with OPA2134 chip.