Tuesday, July 7, 2015
This MM phono preamp is based around the Radi0Kit - RK318, premium parts, valve phono preamp kit. There are two grades to the kit, this one uses superior parts, WIMA, M-Cap, Dales and ceramic sockets. The PS is my own 240-24-240V design and uses a low profile 160W toroid. Over kill here but to fit this whole build into a 19" 1U rack mount enclosure required a special transformer. The oversize toroid provides excellent mains filtering. The mains is feed via an IEC socket on a short tail.
The PS is a C-L-C-R-C type. The choke is a 5H Hammond and combined with 247uf of filtering produces a dead black 280V HT. The 12V filament current is regulated and heavily filtered. JJ short plate low microphonic tubes come with the kit. WBT silver solder used throughout. With high quality components, a robust and clean PS and all housed in low profile, professional enclosure, "La Gitana" (Gypsy) looks as good as it sounds.
Sunday, April 26, 2015
This amp started as a low power Class A SS amp and therefore the 10mH 5A Hammond choke. I removed the power amp section and choke and replaced it with a 100W Sure Electronics Class D amp module. There are also 2 X 10,000uf caps in the PS.
Not quite the Sexy build of my other "Ds" but practical and a great use of a part of an amp which has not been used for many years. The PS is rated 100W and the amp uses a 100W Class D module which should drive 40W+ into 8ohms. So far the bass is excellent and the stereo imaging is huge which is what you would expect from Class D.
Thursday, April 16, 2015
Here is my 4th Class D amp in the last few months based on the hifimediy Eastern Audio Technologies T4 amp module. It is claimed to produce 180W pc into 8ohms at extremely low levels of THD. And is very Tripath. Where this module shines above the rest is crow-bar speaker protection built on the PCB, no fan (apart from me) high grade audiophile components (M-Caps, big chokes etc) and the glorious ability to accept DC or AC. Yes a full rectification network on board.
For me the way to squeeze the best out of the "Ds" is to feed them a big robust DC PS. I used an Altronics 500VA 30 + 30 toroid and capable of a 16A delivery. Through a rec bridge into a 15,000uf cap. Yes this time just one. But it is snubbed with a 10uf 100V poly which itself is snubbed by a 0.1uf 630V poly.
As usual with all my amps and most preamps I install a RFI\EMI power filter and choke the power cord. A Jaycar 2U 19" Black Stipple finish rack mount enclosure and the faint amber LED dress the device. Where I cut lose on this build is the super heavy, insulated speaker binding posts at the back. I wanted this to be an Audiophile strength build so the heavier binding posts. And to cement that desire I called this one "Audiophile" .
Only a few hours on the new baby so a way to go but good stereo imaging, great sound stage and excellent transparency. Good so far hoping to get even better in the next few months.
Tuesday, March 24, 2015
After building two other medium and high power Class D amps (see earlier posts) I thought I would like to hear what a IR (International Rectifiers) chip set base amp sounded like. This 250W module comes full assembled but, as with the others, you are required to make the PS etc.
I chose a 3U 19" rack mount enclosure. I required an enclosure this large because I wanted to use some very large and very expensive Mundorf M-Lytic capacitors I had. The PS can produce 420W and the capacitors are 2 X 47,000uf low ESR type. According to specs the caps can release several hundred amps. The usual RFI\EMI power filter fronts the 300VA transformer and gold plated brass speaker binding posts and RCAs grace the rear.
In other builds small fans are used to cool the power FETs but in this case a very thick Al block is used as a heatsink. For this reason this amp makes no noise where the others have a low fan noise. On a brief listen to the amp it sounds fine and more mellow and balanced than the other two. Further images will follow.
Note: I recently did some up grades to PS and amp module not performed originally. The inside image shows the latest changes; I have upgraded the PS adding some 10uf polies across the storage caps. I believe this improves mids and highs. Also the input 22uf electros have been replaced with some high quality Russian audio caps.
Sunday, February 22, 2015
My good friend Bill has some crazy expensive hifi gear. He has also bought some of my home grown goodies to supplement his gorgeous high-end stuff. Also he travels to NZ regularly and has some very classy high-end ear buds. BUT the plane's audio system fails to drive them to their best. CMoy to the rescue!
Bill gave me one solid, immovable mandate in two parts: Small and light. When checking out the specs of most OPAMP chips; LM833 and OPA2134 (my fav.) I discovered they will work down to +/- 2.5V. I'm running this fledgling on a single 9V battery with a differential resistive and capacitive network to give me +/-4.5V. OK not a lot of headroom but I'm working under tough conditions here.
A small Jaycar ABS enclosure houses all parts and battery required. I use prototype brds. I bought from Stiff Dick many years ago. When on the LED just glows to show some one is home. At 152gm with battery and being a little larger than the palm of your hand I think I have met all mandates. Not only that it sounds excellent.
As you can see I work in 3D when it comes to cct. bds. The whole shebang is silver soldered and solid core fine copper wire hooks it all up. The two tone ABS enclosure is lined with bitumanised heavy Al foil for screening and resonance control. It will carry a "retro-thermionic" decal and will be delivered in a black velvet slim fitting bag. What a spoil!
Friday, February 13, 2015
After completing a 100W Class D amp and enjoying the sound thought I would try a more powerful one. What I did find with the 100W version is when called on to go loud, on my medium efficiency speakers, the amp sounded harsh. This is not the case with this new amp. It will play extremely loud with no strain or harshness. The 500W Sure Electronics module will produce 200W into an 8ohm load.
In this build I have used 2 X 300W power transformers and 40,000uf of storage capacitance. The power supply can deliver 16A! The enclosure is a 2U 19" rack mount and the amp weighs 10kg. This is the most detailed amp I have ever built heard or built and produces the sharpest imaging imaginable. Decay and reverb go on forever and bass and treble are extremely well delivered.
Thursday, November 20, 2014
It is one thing building power amps and preamps etc. as SS or valve based devices. It is so easy to slip into that very well known and well excepted mold. I have done so many times. But what about something a little more out of your comfort zone. And what about trusting an $AU32, 100Wpc pre-built amp module from the far east. Well? Well I did but only after a friend had already bought and built based on the same module.
Sure Electronics will ship a tiny (hand size) Class D amp module for the price of two fine beers. What you need to supply is 30VDC @ about 6 to 8A and something to put it in. My build is in a Jaycar 2U 19” rack enclosure which houses a 18V, 9A toroidal, rectifying and filter board and little else. There are two selectable gold plated quality RCAs on the back and 4oz solid brass knob at the front. One input allows direct connection to the module the other via attenuator. This way the amp can be used as a power amp or have the ability to control volume levels. The sound is very crisp, bright and detailed. It grows on you.