Friday, July 22, 2016

"Mimic - S" - custom built phono preamp

















"Mimic - S" combines a lot of the SE upgrades with better RCAs and better internal poly caps. As usual silver plated copper wire is used for hookup and WBT silver solder. For this custom build the customer wanted two inputs and the ability to switch from MM to MC on the fly. This build does all of that. The top switch selects the different inputs and the bottom MM/MC.

Once more this simple OPAMP based phono stage sounds very good. It sounded especially good with my direct drive TT and MM Garrett Brothers K2 cart. Running on 3 X 9V batteries ensures dead quiet operation with about 100hours operation between charges.








Wednesday, July 6, 2016

Crackatwoa - Bottle Heads Grand headphone amp!


Once more I have assembled a Bottlehead headphone amp for someone else. I really don't mind, no outlay only my time. This has to be the top of the range. Others I have assembled are of smaller kits. Two big cct. brds. and two valve regulators.  The overall sound is absolutely excellent. If you intend to purchase a Bottlehead amp, get this one.

Crackatowoa - Bottle Heads Grand headphone amp!


Once more I have assembled a Bottlehead headphone amp for someone else. I really don't mind, no outlay only my time. This has to be the top of the range. Others I have assembled are of a smaller kits. Two big cct. brds. and two valve regulators.  The overall sound is absolutely excellent. If you intend to purchase a Bottlehead amp, get this one.

Friday, June 17, 2016

Bottlehead tube headphone amplifier #2




































Yet another Bottlehead headphone amp for someone else. I'm not complaining it helps support my hobby. Apart from stronger colours than I usually work with this was a standard build. On request of the owner I added a few small poly caps to improve top end and reduce noise in the PS. It does have the Speedball upgrade.

The colours are a copper top plate and a dark timber stain base. The base has also had four coats of polyurethane. The amp sounds great and the owner was very pleased with the work.




Tuesday, March 1, 2016

"VoXGrandious" - Beyma, High efficiency, 15" speakers





























































The specification of the 15" drivers promised much deeper bass then the 12" versions, and that's what I got. In 170ltr braced enclosures these large speakers produce effective bass down to 31Hz. The bass is very tuneful and transparent, not something I have heard in other speakers.

With just a little more efficiency at 99db\m\w my flea power amps really roar. I have also teamed these speakers up with power Class D amps with excellent results. The woofer section is crossed at 1600Hz and the 2" titanium tweeter is padded down by 6db. The woofer is on a 2nd order roll-off where the tweeter is a 3rd order roll-off.

The completed speakers weigh 40kg and are well dampened inside with two 14cm X 8cm long ports on the rear. Crossovers are external with separate woofer and tweeter brass binding posts on the rear for flexibility.The finish has been rolled on and teased out to produce an acoustically dead and soft stippled finish. An expensive but very pleasing build.


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.