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About rumina

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  • Birthday 07/04/1970

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    Zürich Switzerland
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  • Location
    Zürich Switzerland

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  1. it's a BRZHIFI BZ2607 case from aliex..., size is 260*311*70mm. i have to many silver boxes so i like compact sizes even if the layout isn't perfekt. the trafo is a 100va /24volt from triad magnetic VPT24-4170 (mouser), with a bias of 200ma the amp needs only around 40va so a lot of reserve here, next time i would chose one that is a bit smaler.
  2. finished today my cfa2, was a trouble free build beside that i like small case (think is a tetris disorder i caught in my teenage years ;-). once again, these trafo covers look nice but the shielding effect is near zero, to get ride of a small hum i needed to add some grain oriented bands. heatsinkt of the case seems a bit overdesingned, gets only a bit warm. offset without servos was surprising low at around 10-15mv, could use nice matched mje15030/15031 from my previous dynahi project. the amps sounds very nice, one of the few amps that are neural and speedy that i like, really a "
  3. my pcbs arrived today here in switzerland, thanks for the work 🙂
  4. i go for partial assembled boards, thanks for your work 🙂
  5. these cover are mostly cosmetic but i like to use them, the only shield a tad vs grain orientated metal or mu metal. place the trafo near the big transistors with heatsink and you have a silent amp like in this pic (the 3th i made). my first version had some inducted hum because the trafo was on the other side near the small transistors. good luck with your build :-).
  6. nice to see your success, it's the amp i like a lot with my power hungry magentoplanar headphones. after the that340 i tested the trendsetter lsk489/ls689 but at the end i enjoyed the 2sc3381/2sa1349 the most, quite shure that with the 2SK170/2SJ74 this amp performs superb. let us see the amp when it in its chase ;-). well done
  7. superb that are some nice amps :-), well done
  8. great please add me with: 2x grhv, 4x grlv78xx, 4x grlv79xx, 1 main board, 1 mini t2 thanks
  9. if the case is high enough you can try to mount the transformer standing up, base parallel to the back plate (or mount it direct to the back plate). i would remove the screw of the trafo, turn it up whitout fix mounting to test if the hum is less (if less thats a least one part of the problem).
  10. this is the case i used: https://de.aliexpress.com/item/143-40-4-180mm-WxH-D-aluminium-elektronik-pcb-geh-use-6063-extrusion-fall/32857644347.html?aff_platform=api&cpt=1549182007927&sk=ZVxRRvI&aff_trace_key=807df99551d348b39035d168c5f73204-1549182007927-05033-ZVxRRvI&terminal_id=1183572cd19e4eb0be580194ccaeaa77 the pcb slides in the grooves (some tap around the edge for isolation). but you need make some place for the top cinch connector (grind the topcase a bit with a dremel or similar tool, shorten the silver latch). then do the same thing for t
  11. my two smd amps with bivar leds running at 20 volts and led vf 1.71 volt, i also would go down a tad with the bias to around 15ma. second one (the one in your list) with 16.5 ma / 81c max after 2 hours - ok but on the edge. so i would use next time r14/29 around 210 ohm for bivar leds and 402 ohm r1/r3. this is my second one, a lot of holes top and bottom, printed front and rear, whitout potentiometer, additional 4.4mm output. i use this one for travel together with a dap: my first amp only with small heatsink in the group buy case (with r14/29 240 ohm) was around 100c max and
  12. may i ask i someone has a Song Huei 10k quad pot 2142 left from the group buy. i have a older smd dnynalo pcb that i whant to use, thanks far a short pm ?
  13. @pars some measurements for my finished second smy dynalo - found a good combination for the bivar leds. amp gets stable after 30 min (with heatsink mounted), hottest parts are the small transistors at ~81 c, the regulators are ~75 c. heres the data: D1 / D2s = Bivar SM0805HCL R14 / R29 = 226 ohm R1 / R3 = 402 ohm 330mv / 16.5 ma hot 205mv / 10 ma cold my first dynalo has R14 / R29 = 240 ohm and was running to hot, could bring the heat down with some heatpipes attached from the heatsinks to the case (power consumption stable at 25-26 watt). the second one runs at
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