"fiih-300" - Holton based 300W power amp

 

Once again a powerful 300W Holton based power amp using the upgraded 200W modules. These have the more powerful dual die power FETs installed to allow the modules to produce 300W into 8 ohms and 500 into 4. 80,000uf of 100V filter caps all snubbed and an RFI/EMI power filter.

An over size heatsink is used but still runs up to over 50C. Tranni is 500VAC but will be more than enough to drive the hardest loads to high volume. Once more excellent Holton bass depth and control. Clear, transparent mids. Allover an excellent sounding amp. 

“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 owner is very pleased. So am I.

 

“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.

“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

“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 amp has a stack of power (180W into 8ohms) and crystal clear with only a touch of tube warmth. 

 

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.  

“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.