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Cheap Raal Direct Drive Amp


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On 8/8/2020 at 8:42 PM, kevin gilmore said:

wired in series for +/-24v and then connected to each channel

Kevin two UHP-350-24 connected in series is +/-48V.
Should we be using two UHP-350-12 in series for +/-24V?

I’ve ordered UHP-350-24....

 

Edited by johnwmclean
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27 minutes ago, johnwmclean said:

Kevin two UHP-350-24 connected in series is +/-48V.

How are you figuring to get 96V out of two 24V power supplies?

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I think he meant to put them in series and take the gnd from the connection between the two, -24 from the negative free end, and +24 from the positive free end.

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On 8/6/2020 at 5:24 PM, themystical said:

If somebody is going to get these PCB's fabricated, I would be interested in a couple. Please PM me so that we can share costs?

I have ordered some of these PCB’s ( 2mm copper) so if somebody is interested please PM me. Probably makes more sense in the UK or EU because of shipping costs I suspect.🙂

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7 hours ago, n_maher said:

Sweet!  You up for giving it a shot driving speakers instead of ear speakers?

can try but it will be limited by voltage swing. 25W/8-ohm and 50W/4-ohm

as of right now here is where the difficult work actually starts, and the time consuming work. I'd be interested if anyone wanted to finish it up before putting in the $$/cost on their own unit. 

for future board revisions:

- make the jumper over the bass boost 3x 0.1" pins so a push-on jumper can be used + have a place to store it and/or add small signal DPDT 24v relay to switch it (add a 2nd value with moar boost?)

- don't block the heatsinked part mounting screws with the electrolytic caps

- holes for wires too small to accommodate 16awg, used 20awg instead

- caddock resistors need to be bent in an L, move them closer to edge of pcb if possible

- 2nd output hole for wiring another output

Edited by justin
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Posted (edited)

the jumper was supposed to be .1    newest software loves to keep switching to metric (fixed)

forgot about the size of the caps, can always put them on the bottom.

i had thought that 18awg was enough. size increased to 60th

not going to be able to move the caddock resistors much. only 25th. then runs into the output wire

Edited by kevin gilmore
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I received a suggestion that the grounds for the L/R output, which in this case is the 4-pin XLR but would also be the negative posts on the speaker terminals, be wired back to each L/R channel board rather to the star ground at the switching PSUs

open for debate on that

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16 hours ago, themystical said:

Seems to be working really well!! 
Any comments/initial reaction on SQ with and without base boost?

How warm is the heat sink getting?  Could it be much smaller?

keep in mind the thermal transfer for this package is not great, with a good insulator the IC will be 3C/W hotter than the heatsink. so you do need to keep the heatsink cool. temperature in this case with the RAAL is dependent on music and how loud you're listening. My guess is in most uses the heatsink will not exceed 40C. with no audio it will be room temp.

so if the heatsink reaches 40C w/ an average of 15W per IC then the IC temp will be around 85C

There is also the TO-3 package @ $150 ea. and Apex has parts of a similar price

Edited by justin
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