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About jamesmking

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    Limited Edition Bronze Participant


  • Headphones
    stax sr007a
  • Headphone Amps
    DIY T2, DIY joamat mini t2, DIY single box blue hawaii se, megatron, DIY hi-amp alpha centauri
  • Sources
    garrard 401, loricraft psu+plinth, hadcock 242 se, ortofon cadenza bronze, leema agena, mf v90 dac + golden reference LV psu + synchronous rectifier
  • Other Audio Gear
    quad esl 2805, leema hydra, townshend allegri, dcs 905 adc, ps audio p3, van den hul first cables, cardas golden reference mains cables, cardas golden reference speaker cable

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  1. the smd version is at https://www.head-case.org/forums/topic/12733-balanced-to-unbalanced-board/page/2/ intermixed with the balanced to unbalanced board discussion. It looks like it is based on the 2017 through hole and does not have adjustment pots for dc offset. The 2018 through hole version has extra circuitry for controlling the dc offset and adjustments pots. I built the through hole version 2018 and found that with a 10K tkd pot on the input it had some high frequency instability with the volume control almost all the way up. I also got some dc offset with varied as the buffere
  2. rather than create an adapter I soldered clip leads onto the pcb and ran the leads through the existing holes in the plastic case: I disordered the existing clips that had about as much grip as tin foil. The clips also allow me to use adapters for sot23 etc etc. (the same adapters I also use with my peak dca75 transistor tester and identifier)
  3. I agree a lot comes down to how much you are going to build and your budget... however sometimes solderwick cant cut it. I once soldered an octal socket on the wrong side of a 2mm 2oz copper board.... solderwick that out ðŸ˜ą desoldering station to the rescue, board and socket survived. the socket was ptfe round pin with tight pcb holes. 😎
  4. good soldering technique and understanding what is going on when you solder: (a little wordy, somewhat dated and slow paced but the latter part of the video has lots of useful info). I heartily agree a good quality temperature adjustable soldering iron is essential and it will make soldering easier, more consistent and you will get better joints. Something along the lines of the hakko fx888d (although the use interface is horrible) that has descent power and is reliable and has repeatable temperatures. also good quality solder and good quality flux
  5. GR78xx and gr79xx are surface mount versions of the golden reference LV without the input or output smoothing capacitors. In general the golden reference LV come in dual (both positive and negative supplies on one pcb) or separate plus and minus pcbs. The gerbers can be found at: https://drive.google.com/drive/folders/0B_iJFfZStuVhSE5nOHBVdTByR1k the latest dual golden reference that I know about is goldenreference6D.zip this is marked on the pcb as version 0.45: the dual output board has provision for 25mm diameter input smoothing cap and optional output on led.
  6. the fresh led has a sharper curve than the used ones, I am zoomed in on the curve, If we look at the full curve the LtL-4221nlc is sharper compared to the HLMP-1700. The TLLR4401 looks promising but is also not quite as sharp. I almost feel like putting 2 pin sockets in the D24 position and trying different les to discover which sound best 🙂 Xicon 273 series. Although discoloured they are not burnt. The drift from new was less 140.5K -> 141.5K so not actually that significant. I did place them on the underside of the pcb. This time I'm placing on the top side and I thin
  7. the style of that 6 in the 2sk216 seems a lot different from mine. But maybe they changed font... perhaps its a 7s2sk216 (7 2sk216 is series. in a single package)... ðŸĪŠ I just tested a few of mine. Setup on the DY294 : selected NPN gate and source connected to the emitter on the dy294 drain connected to collector on the dy294 and I get around 230V breakdown. spec sheet says 200V.... ----------------------------------------------------------------------- My peak dca75 in identify mode says the following: N-Ch Enhancement mode MOSFET Vgs(on)=0.557
  8. I think it might well be thermal. About a month ago I replaced the groove tube el34s with modern production branded mullards and the bases of these run far hotter than the groove tubes so that could also have contributed more heat conduction to the leds... I did match all 6 leds in the amp by curve tracing on a peak dca75. The other 4 leds still work well and have very similar voltage drops meanwhile both the D24 leds (which are positioned close to the El34s) degraded. I did not raise any of the leds off the pcb and I think there was excessive heat conduction from the pcb into the underside of
  9. testing breakdown voltages would be a good idea. Fingers crossed you have a real ones. Here is some high resolution photos of a known good one from a reliable source- and its brothers are working my T2... Markings are printed not etched and are a greyish cream colour not white. (photo has been colour balanced). Ends of legs are fairly sharp. close up of the circular area in the middle. Lighting adjusted to make the text in the dimple more readable at the expense of the printed markings. Text in the dimple is raised. The starting angle relative to the top of the transistor for t
  10. happy birthday Kevin, thank you for bringing so many diy projects to life and for you advice and troubleshooting help.
  11. Longish term modern DIY T2 reliability. I estimate its been used around 8+ hours (and more often than not 12 hours) a day almost every day since I built it. yesterday I took it apart for cleaning. I noticed all four 140K resistor strings connected to the voltage reference in the virtual batteries where somewhat discoloured.... hmmm... on further testing I found the D24 led on both channels did not light up at all not even dimly. :-(. but the amp seemed to work and sounded good. (on the left is a brand new resistor from the same pack as the 140Ks I removed from the virtual
  12. water cooled data centre means you can overclock the cpu(s) more....
  13. fantastic. I was about to lose all hope. thank you to everyone involved in getting head-case back online
  14. My megaslow build. Thank you JoaMat for supplying the 3 mosfets I needed for the golden reference psu. The megatron is workingish. This build was a little perplexing. I used groove tube 12ax7, electroharmonix 12au7 (gold pin) and groove tube el34s. I implemented the 12ax7 increased current modification form the outset. I found that I could only get about 220Vrms output before clipping. The clipping was not symmetrical and it was the bottom of the wave on the +O that was clipping only. I started to probe with a scope and found that the voltage drop at the
  15. it seems like at the moment the only thing in stock is out of stock notices.... 😞 check the height of the 1000uF cap... at 105mm tall its a beast which will not fit into a 2u case. (around 65mm depending upon the height of the standoffs for the pcb is about as tall as you can go for a 2U (80mm tall case)... are you going 120mm tall 3U case? the issues with very large capacitance input caps is that they will create a very large inrush current on switch on so you may need a larger value fuse than you would otherwise. Also the larger the cap the more diode switching noise it will cause
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