Bottlehead headphone amp with Speedball

I was asked by a fellow Stereo Net Australia (SNA) member to assemble a bottlehead headphone amp named Crack.  But I didn’t know that I was also going to have to paint the top plate and prep and finish the blond base. But wait, there is more. The member had also purchased the Speedball upgrade which consisted of three cct. brds. which work as a constant current source. Fortunately the member realised the amount of work involved and rewarded my efforts. Thanks.

The instructions which come with the it are detailed bit I would not advise this kit for a first timer, The cct. brds. are compact and require careful soldering. The rest is easy but still a fair bit of work. The amp came up well, sounds excellent. I would recommend the kits and upgrade Speedball. The amp worked well with my 32ohm DT770s but I feel may work even better with 250ohm or higher cans.  

EL84 SE UL power amp with attenuator

This is a Decware inspired EL84 power with attenuator. My twist was to make it an EL84 SE UL (not a triode amp}. Also I upgraded the PS. One PS tweak was to use a Russian PIO 4uf cap as the first cap. Larger electros than specified were used and a 10H choke as part of the dual section PS filtering. All larger electros were snubbed.

The inter-stage caps are Audio Note Tin foil paper and oil. This amp is called "Tamarisk". There are a number of small creeks which wind through this part of of southern Victoria and one is called Tamarisk. I just like how it sounds. The finished amp looks cool and not too heavy.The sound is a big step-up from my 6V6 SE UL. With live classical music the sound appears to unfold in layers. Decay and reverb also appear to occupy their own layer. The bottom images shows the Sophia Princes 274B as the new rectifier tube for the amp.

"Salix" - MC stage with Audio Note Tin foil caps

This build is very similar to the previous post in as much as construction is identical except Audio Note Tin foil caps are used in place of the AN Silver foils.

The AN caps are Tin foil with an Al clad outer. The leads are silver wire and the caps better priced compared with the Silver foil version. Once more Vishay resistor, Nichion electrolytic caps, solid copper high-end RCAs and a Hammond enclosure were used. All hook-up wire is silver plated fine copper and solder is WBT silver solder. The sliding lid is lined with bitumanised heavy Al foil to control resonance and vibration.

Construction is on Veri-board, there is a battery test point at the front and a soft blue "ON" led. Salix and Tengu have a Masonic relationship in the higher degrees.

"Tengu"- extreme MC phono stage

After building the Boozhound Labs MM and dedicated MC stage featuring the Russian PIO caps, I was inspired to build an extreme version of the MC stage. I was very impressed with the performance of the MC stage built from a kit. Having at hand some ultra expensive Audio Note (AN) caps, I thought what better use.

The AN are silver foil and clad in a pure copper outer. The leads are fine silver wire and the caps currently sell for AU$427 each! To further ensure this was going to be a "killer" build I added Vishay resistor, Nichion electrolytic caps, solid copper high-end RCAs and a Hammond enclosure. All hook-up wire is silver plated fine copper and solder is WBT silver solder. The sliding lid is lined with bitumanised heavy Al foil to control resonance and vibration.

Construction is on Veri-board, there is a battery test point at the front and a soft blue "ON" led. On an initial listen the bottom end appears a little richer and the sound stage more defined. But early days. The cost of parts is over AU$1000! "Tengu" are Japanese mystical creatures let's hope this has a mystical sound to compliment the price.

"Mimic - SE" MM phono preamp

See previous posts for the original "Mimic" which is Bruce Heron's (Oddwatt) OPAMP based MM phono preamp. What makes this a Special Edition (SE)? From the images above you will see Solen (French) caps which are on the output replacing cheaper NP electrolytics and from the rear high quality gold plated RCAs now replace the lighter versions. Once more WBT silver based solder has been used and silver plated fine copper wire for hook-up. This is consistent with the "Bourbon" build matching hook-up wire and solder employed. A battery test point is provided at the front.

The enclosure is the same as before and now matches perfectly the Boozhound Labs based MC preamp. As usual the enclosure is bitumanised heavy Al lined. I matched the exterior look of both phono preamps to make them appear as a matched pair. I am now taking orders!!.

"Bourbon" - Boozhound Labs MC stage kit.

I received a Boozhound Labs MC kit for assembly and review some years back. I promptly assemble the cct. brd. but thats where it stopped. Finally it is complete and I'm extremely impressed with the overall sound. The kit comes with the usual Boozhound Russian PIO caps and some high quality Muse electros. Silver solder was used and fine copper wire with silver plate is used for hookup. A battery test point is provided at the front.

My Ortofon Rondo Blue MC cart is hailed as very dynamic with excellent balance from deep bass to extended treble. Now I know what they mean. It feels like I have a brand new cartridge installed. I thought my other MC stages were good but this one stands on it its own. Extremely impressive performer.

"La Gitana" - MM valve premium component phono preamp

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.

"Quiet Storm" - 100W Class D in re-cycled enclosure and PS

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.

180W Tripath Class D power amp - Audiophile strength

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, Panasonic, Wima 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 filter cap and 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 and also solid copper premium RCAs. The amp has two selectable inputs. I wanted this to be an Audiophile strength build so the heavier binding posts and to cement that desire I called this one "Audiophile". There is also a 28 step, step attenuator and 4oz solid brass knob.

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.

250W IR Class D amplifier

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.

CMoy knock-off for a Kiwi friend

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!

"ROBUSTO" - 500W Class D power amp

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.