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The Multi Amp aka Dynalo Mk2

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This is so interesting. The full-size Dynalos I built are the coolest-running amps I have. Really surprised at how much hotter all the smaller parts end up. I want to make a mini, but the heat issue worries me. 

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My full size SS Dynalo (thru hole MPSW parts) runs fairly warm at 17-19mA bias, but nothing like mini warm. I haven't cased it yet (this winter), so I'll see what it is like when cased.

Here is the link to the spreadsheet I created for tracking what users are using for bias and what kind of heat they are seeing:

https://docs.google.com/spreadsheets/d/1D5LDuRdupZRoWR-GfAd03fkFSBAMY4-E_VcYfCAI1Z0/edit?usp=sharing

I don't know if HC allows sigs or not, as I thought if they did I would put the link there so it didn't keep getting buried.

Edited by Pars
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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:

smd_dynalo_2.thumb.jpg.242320b6bf63faf256d08fc4b77381fa.jpg

my first amp only with small heatsink in the group buy case  (with r14/29 240 ohm) was around 100c max and even discolored the pcb a bit. more holes  (best over 4mm diameter) and a heatsink lowered the temp to around 80c. if they get hot the bias rise quite fast even when the start bias is relative ok or low.

but i love them, like the sound better then my big dynalo, i now use on both  from trendsetter - linear integrated systems matched lsk489 lsj689 jfets.

Edited by rumina
typo
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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

smd_dynalo_2b.jpg.7adfb7ec3b5057a56bbdb0f623c68ed8.jpg

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 the two caps underneat he pcb, they need 2 mm more space on the side of the pcb. now you can slide in the pcb from the top (not sliding the pcb in) in the groove opposite the caps underneat, push down and the pcb holds in place.

for the topcase to fit you need to grind down the ac socket a bit, easy done with a dremel.

due the case is a tad longer then the pcb i printed two case holder plates that hold the pcb in place, so you can also use the orginal alluminum plates, sadly the topplate is realy thick and i was to lazy and printed the two top plates also.

i attache the freecad files and stl files so everyone can use them (missing are the holes for the pot/4.4mm plug and vents if you need them, easy to add).

the case is thight but works fine with some work and patience, take care of the heat, venting is not easy for this case.

 

 

smd_dynalo_roundcase_front_back_v2.zip

Edited by rumina
update link for the case / corrected 3d files use v2
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