Wednesday, December 30, 2015

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.  

Friday, November 13, 2015

EL84 SE UL power amp with attenuator


















This is a Decware inspired EL84 power with attenuator. My twits was to make it an EL84 SE UL (not 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 layer. The bottom images shows the Sophia Princes 274B as the new rectifier tube for the amp.

Friday, October 23, 2015

"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.



Monday, September 21, 2015

"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.


Friday, August 28, 2015

"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!!.

Thursday, August 27, 2015

"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.

Tuesday, July 7, 2015

"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.