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-   -   The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB (https://www.diyaudio.com/forums/group-buys/336479-slb-smooth-butter-active-rect-crc-cap-mx-class-power-supply-gb.html)

xrk971 30th October 2019 06:05 PM

A member asked me if the SLB could be used to provide 7A current at 22Vdc output at the load. Jhofland ran the sims and it appears that everything is still within design limits as long as we are using it at the lower voltage and that there is limited adjustment of the output voltage with the pot. It should be used to adjust the cap Mx to “eat” about 1v of AC ripple at the second cap. So this is about 3Vdc drop. But do not use for higher voltages than 22v at 7A. This is almost at the limit of the ripple current rating on the first cap.

You may know what Class A amp uses 7A at +/-22v.

The BJT pass transistors need plenty of heatsink though at 21W each.

Also, you should probably parallel the big power resistors, say two 0.22R side by side or use a 10W however you can fit them as they will get hot.

pinnocchio 31st October 2019 01:51 PM

Received my set of PCBs along with the speaker protection. Thanks X!

xrk971 31st October 2019 02:02 PM

Well that was pretty quick delivery to Canada. Let me know how the packaging for the SSR’s faired.

pinnocchio 31st October 2019 03:37 PM

The SSR seem to be in perfect shape! Will be testing them shorlty since I have three amps to try. Thanks!!!!

aljordan 1st November 2019 05:47 PM

Does the green color of LEDs D1 and D2 play any role in the circuit or can I sub them out for another color?

Thanks

Shawnstium 1st November 2019 05:59 PM

They are just for indication. Only time the color matters is if you need a certain voltage drop, like when LEDs are used for cathode biasing of a tube.

aljordan 1st November 2019 08:33 PM

Quote:

Originally Posted by Shawnstium (https://www.diyaudio.com/forums/group-buys/336479-slb-smooth-butter-active-rect-crc-cap-mx-class-power-supply-gb-post5962150.html#post5962150)
They are just for indication. Only time the color matters is if you need a certain voltage drop, like when LEDs are used for cathode biasing of a tube.

Thanks for the info!

Harry3 8th November 2019 12:48 AM

Quote:

Originally Posted by xrk971 (https://www.diyaudio.com/forums/group-buys/336479-slb-smooth-butter-active-rect-crc-cap-mx-class-power-supply-gb-post5758641.html#post5758641)
The idea was to have those positions available in case we see oscillation - but will initially leave unpopulated. As I said, our earlier tests with the CFP cap Mx had issues with oscillation. We will redo the simulation though to make sure performance is not too negatively impacted.

Just to confirm - do you populate both C24 (47pF) and C17 (1000uF) or do you leave C24 out if the SLB does not oscillate?

xrk971 8th November 2019 01:54 AM

The 1000uF cap is the cap that is being “multiplied” so you need that. The 47pF cap is good insurance. I would install it just in case. More important are R17 and R18, don’t make them any lower than 2.2R. 10R is very safe, 4.7R is good moderate value. It sets the gain of the ripple reduction.

Harry3 8th November 2019 05:52 AM

Thanks for the explanation - understand about the cap (1000uF) that's being multiplied.


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