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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)

Vunce 4th April 2020 07:11 PM

You still need a “softstart” for the inrush of current hitting the primary side of the transformer. The SLB doesn’t help that.

xrk971 4th April 2020 07:44 PM

Like this one:
Soft as a Feather Pillow (SFP) SSR Soft Start Circuit GB

454Casull 4th April 2020 08:37 PM

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-post6147947.html#post6147947)
You still need a soft start to prevent current in rush to charge the trafo when you power up. I don’t think I said anywhere that a soft start would not be needed. That’s why we came up with the soft as a feather pillow SFP soft start circuit. It uses SSR’s so nothing to wear out compared to mechanical relays.

Post #1 in this thread:

Quote:

Originally Posted by xrk971
7. As icing on the cake, the SLB provides a smooth slow ramp up to prevent mains current overload and tripping fuses, plus, it eliminates turn on speaker pop.


454Casull 4th April 2020 08:38 PM

Quote:

Originally Posted by Vunce (https://www.diyaudio.com/forums/group-buys/336479-slb-smooth-butter-active-rect-crc-cap-mx-class-power-supply-gb-post6147952.html#post6147952)
You still need a “softstart” for the inrush of current hitting the primary side of the transformer. The SLB doesn’t help that.

Alright, well, if the transformer is not that big I'd be OK with that. Especially since the total capacitance would typically be relatively small due to the cap multiplier.

xrk971 4th April 2020 09:30 PM

Yes, sorry about the mixed message - the cap mulitplier provides a softer ramp up voltage to the amp, and in some cases, this slower rise can prevent speaker thump at turn on. However, it doesn't do anything for the surge created by the large transformer in rush current. I will edit post 1 to make that more clear. To really stop turn on thump, the RTR SSR speaker protection with turn on delay is the best way to take care of that.

andyr 5th April 2020 11:31 PM

Quote:

Originally Posted by Vunce (https://www.diyaudio.com/forums/group-buys/336479-slb-smooth-butter-active-rect-crc-cap-mx-class-power-supply-gb-post6147952.html#post6147952)
You still need a “softstart” for the inrush of current hitting the primary side of the transformer. The SLB doesn’t help that.

But surely the 8D-20 in series with the active input to the power traffo does that, V?

Andy

Vunce 6th April 2020 12:06 AM

Yes, if your not utilizing a softstart module, the NTC (8D-20) in series with the trafo primary winding will soften the hit. The downside to that option is heat and sacrificing a couple of AC volts.

andyr 6th April 2020 12:24 AM

Quote:

Originally Posted by Vunce (https://www.diyaudio.com/forums/group-buys/336479-slb-smooth-butter-active-rect-crc-cap-mx-class-power-supply-gb-post6149795.html#post6149795)
Yes, if your not utilizing a softstart module, the NTC (8D-20) in series with the trafo primary winding will soften the hit. The downside to that option is heat and sacrificing a couple of AC volts.

Aah, I didn't know that it reduced the voltage going into the traffo when it had warmed up.

But that's absolutely what I need - as I was getting 22v out from the SLBs when I tested them (without an 8D-20 in place). As my 4R ANs will be driving 3.2 ohm Maggie mid panels and 2 ohm Maggie ribbons - ie. below the nominal 4 ohm spec - I was not keen on upping the DC rails from 20v to 22v.

So it looks like the 8D-20s will do what I need! :)

Andy

Vunce 6th April 2020 12:30 AM

Right on Andy! :)

KevinHeem 19th April 2020 09:18 PM

1 Attachment(s)
Oh Sh*t, I was soldering in some spades and totally smoked C23 by carelessly resting the iron on it. Unfortunately I have no spares :mad:

Attachment 835742


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