robmid Posted November 22, 2022 Posted November 22, 2022 (edited) My build of the 2022 Direct StereoCoffee kit from Chis Daly is up and running. I'm over the moon and my marriage is saved too. Why? Because, for the first time in 60 years of DIY audio I have lost the perpetual DIYer urge to constantly fiddle with my equipment to try and improve performance... just because I can. My wife is delighted, because we can enjoy our music together without me leaping out of the seat and moving a speaker or unplugging things and heading to the work bench. In my opinion the StereoCoffee has become an adult and is no longer a prototype. This is probably my final S/C build. I can't truly articulate the way my whole system has tightened up and become more focused on musical detail and atmosphere because of the way almost invisible background detail has become and integral part of the music. My collection of favourite tracks that I thought I knew inside out, sound very different. Bass and sub bass has more impact and greater detail. The LDR/passive character is still there but with impactful, undistorted dynamics that encourage non fatiguing, high volume listening. Interestingly, low level listening doesn't diminish the enjoyment and it isn't necessary to go full bore for satisfaction. NOTE: If you are in QLD and can get to Caloundra, I'm happy to demo it, especially if you are a cynic of LDR Preamps. * I don't sell them so please don't ask. INTERCONNECTS AND STUFF NOTE: After experimenting with DIY silver, copper foil, litz configuration and various speaker cables, the only ones that didn't colour the signal in any way are from Geoff at Aurealis. They didn't just sound a bit better, they were vastly superior and the price isn't out of reach. Tip: Make sure you clean interconnect pins thoroughly every time you move them. The difference IS audible. Despite being 75mm in length, the signal wire material DOES make an audible difference. Silver has a nasal character, thin copper foil adds a slight but audible ringing. I have replaced the copper foil in the picture with strands of inexpensive quad core Mogami microphone cable from Creek Industries in the ACT. RCA sockets also make a difference. Genuine Neutrik sockets produce a predictable bright, dynamic sound for about $8/pair and Eichmann/ETI do the same thing but provide much more fine detail combined with more 3D imaging and impactful bass, but they are around $90 per pair. My compromise has been to use Neutrik for the output and Eichmann for the highest quality source. The other two inputs use Neutrik. My theory is that the S/C source should be as pure as possible to take full advantage of it's potential. THE NEW KIT BOARDS The S/C kit now requires 2 x 12v ac power sources to provide optimised current to the shunt anodes and series LDR anodes as required. A low current toroidal transformer is recommended and will cost less than two wall plug packs. A new single power/control main board replaces dual boards in the previous build making wiring simpler Improved ripple reduction has been assisted by asynchronous rectification and the complete switching of thyristors. IC relay input switching of LDRs is available as an option that will allow more switching options. External Start position and Final bass ratio adjustment potentiometers are standard feature. My CONSTRUCTION Because this will be my final build, I decided to have a crack at some woodwork as I had a router on hand. I wasn't confident with my routing skills due to my car being damaged by a flying piece of timber. I was planning on using Huon Pine but my lack of confidence and the price pointed my to Tassie Oak from Bunnings which only cost about $30. Two grooves were routed along the full length of the timber to allow a countersunk base and a perspex lid that could be slid into position from the rear. The timber was then cut into four lengths at 45 degrees for the mitred corners. A router template was made and the front and rear panels were routed out about 3mm to accept the front and rear perspex inlays. After routing the front and back they were still 16mm thick. The front was too thick for the switch so I duplicated the cutout on the rear of the front panel to about 10mm which was just enough for the nut to be tightened. The rear panel needed to be about 3mm thick to allow the RCA sockets to be mounted and that was impossible with the router so I cut out the hole and screwed a 3mm perspex plate on the outside. The benefit is that the LDR board can be removed via the cutout complete with the RCA sockets to access the underneath of the LDR board. To allow grounding, an aluminium plate from Jaycar was cut and screwed to the base of the case. WIRING TIPS I used heavy hookup wire from Jaycar, but it can be difficult to insert in the screw blocks and takes some patience. Use it flat and don't twist it because it's not copper and doesn't twist well. It's CRITICAL that all the screw connections are firm and the wire thick enough, otherwise you can get all sorts of unexpected results. Another solution is to use some resistor legs as wire and fold them back like a paper clip to make a double width wire and squeeze them tight. Solder them to the end of the wire and cover with shrink tube. These wires are easier to insert in the blocks and guarantee excellent contact. You could use different coloured heat shrink to make it easier to trace your wiring. StereoCoffee 2022 DIRECT wiring diagram START Adjustment (Initial setup) Disconnect all signal interconnects Turn VOLUME CONTROL to 12:00 SWITCH ON and measure the resistance between LEFT OUTPUT and the selected LEFT INPUT Turn the START external adjustment VERY SLOWLY until the initial resistance measures 43k. NOTE: SQ will vary slightly depending with different resistances. I have found that HIGHER resistance makes SQ sharper and LOWER produces richer SQ. FINISH Adjustment Plug in your interconnects and select a track with good bass and detail and adjust the volume to your preferred listening level and play for about 30 minutes to allow the power supply to warm up. * Some Hans Zimmer live tracks are good. If you are reasonably satisfied with the initial SQ at your preferred listening volume it's time to adjust the FINISH (Bass integration) using the external potentiometer. Rotate the FINISH potentiometer to position 5 (half way) and listen for slightly muddiness. Adjust the FINISH position very slowly in either direction until you hear a more clarity together with 'subterranean bass'. Final fine tuning can be done over time, as you become aware of the purity and depth of sound stage that is still available. MAKE NOTE of the START & FINISH positions in case you lose the sweet spot. NOTE: It is easy to bump the Start and Finish knobs, so mount them in a protected position if possible. --------------------------------------- Start and Finish (*extract from supplied documentation) Start and Finish are both adjustments on the StereoCoffee that take advantage of LDR's ability as an optocoupler, so there is no touching of signal lead pure audio paths. Likewise input switching is achieved using a contactless method by switching on/off power to each input instead of the audio signal. INSTALLING START & FINISH in your kit carries the ability for outboard adjustment, where a control dial is supplied, suitable for installation on your front rear or side panel. (See photo) Start has the ability to silence volume at zero and allow adjustment for volume commencement where you require it. Start allows audio systems that, for example, are less sensitive to easily adjust volume to just where it is needed. Start can also be used to adjust fine volume setting in tandem with Finish. Finish has the ability to allow adjustment for less resistance loading, mainly on the source component, and to a degree your amplifiers fixed resistance, than would normally be available. Finish has the ability to preserve your source components true audio ability. Lesser volume controls provide no adjustment, and can restrict or adversely load the source impedance. Stereo coffee overcomes this easily, and provides up to 5 times more or less loading - the effect is ability for your audio system to reproduce the dynamics of your source component effortlessly. Finish with similarity to Start is contactless and does not involve any touching of components across pure signal paths. --------------------------------------- Start and Finish external adjustment (New) NOTE: The foil grounds have been replaced with Mogami Message me if you need help setting of the Start/Finish calibration which can be tricky for the first time. Cheers, Rob Upgraded prototype kit boards tested over last 12 months Early Passive Preamp builds during my search. My first 2013 StereoCoffee with the original control board upgrade. Clone Note (white) and 24 position Resistor Attenuator with silver wiring and was a slight improvement over an ALPS Blue potentiometer, but annoying to use. Edited November 30, 2022 by robmid Additional Adjustment Information 3 1
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