USSA-5 Build with Review

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Joined 2016
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Doh! Can't find my BD550C's. I know I bought them because I checked the order sheet. Have to see if I used them on something else?! Got the BD560s OK.

Still not all is lost because in the process of looking for them I took the time to inventory all my parts - a job that has been waiting too long - now I can just look at my spreadsheet knowing that finally it reflects what I have inside my boxes.
 

fab

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Joined 2004
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Hi nikosokey
You can use the 5.6 A but I have tested with 7A ripple current. Maybe other builders have tested with lower ripple current:rolleyes: it would work with much less ripple current but it is a matter on how good you want your psu....;)
For the first cap of the CRC you can use lower ESR and ripple current than the second cap.

Fab
 
meanie,

As far as I know Antek have ready stock of 2 x 22V toroidal transformers. They will probably ship from the US which will result in some shipping/postage cost - however their transformer prices are lower vs others in most cases, so total cash outlay from your side might end up being close.
 

fab

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Joined 2004
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Hi nikosokey
I had written a long response but waited too long and it expired so I lost everything:mad:

. With 1.25A bias current at about +/-24vdc you get in theory 25Wrms class A in 8 ohms and half of that power in class A in 4 ohms. But you get more power in class AB because of your 4 ohms (50Wrms) provided that your psu is capable of delivering it, thus maybe more 40wrms.
With 93db and 4 ohms I would use the same psu parts rating as indicated in the manual but you can reduce psu voltage and increase bias current accordingly to get same heatsink power dissipation. This way you get less max power in class AB (which you probably do not need) but more power in class A.:)
Having said that the power in class A is more than indicated in reality because of the square law effect of the output mosfet which is increased because of the very low degeneration.

For example with +/- 20 vdc and 1.5A bias you get same heatsink dissipation as with +/-24vdc and 1.25A bias. This gives 18wrms in class A (theory) but probably 25Wrms class A because of previous explanation.

Fab
 
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