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The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB

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sp33ls

sp33ls

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Joined 2018
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xrk971 said:
So for the typical 25w Class A amp, use dual 200VA 22v trafos one per channel. Note that some brands like Antek sag more than others so step up one more notch to 24v. But maybe a Talema or Toroidy is fine at 22V. Yes, dual secondaries not center tapped. One more thing, it never hurts to go up one more notch in VA rating either so dual 300VA would assure you of even better performance.
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Does anyone know how the medical grade Triad trafos perform under load? Hoping that 250VA 24V donut per channel should work nicely here for Firstwatt-based amps (+/-24V), and not too much excessive voltage.
 
Vunce

Vunce

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Joined 2014
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sp33ls said:
Does anyone know how the medical grade Triad trafos perform under load? Hoping that 250VA 24V donut per channel should work nicely here for Firstwatt-based amps (+/-24V), and not too much excessive voltage.
Click to expand...
Just so happens that I have the exact configuration you’re asking about, I’ll connect a load to the SLB and check voltage. Unloaded output is +/-32.5VDC.
 

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plus9paradox

Member
Joined 2016
Vunce said:
Yeah, the Wago 221 connectors ROCK!! I found a Wago mounting bracket that holds 2, 3 and 5 sized connectors. Makes the wiring very neat.

WAGO 221 Lever-Nuts 75pc Wire Connector Assortment Pack with Case https://a.co/d/dNY51vY

https://www.wago.com/us/rail-chassis-terminal-blocks/mounting-carrier-221-series-24-12-awg/p/221-501
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Vunce,

WAGO connectors do rock ! Love the execution. Really wanted to build those into my boards in lieu of faston's but darn if my BOM cost didn't skyrocket. Looking forward to getting many many free samples from WAGO @ IMTS this year.
 
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sp33ls

sp33ls

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Joined 2018
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xrk971 said:
When did you all hear about these Triad medical grade 24v trafos? A big sale I missed perhaps?

24v is probably good for 27vdc under load with an SLB. Perfect for something like Alpha Nirvana or LuFo or SuSyLu.
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Nah, no large sale. Just happened to find another forum member selling a pair. :)

Sounds like ~27VDC shouldn't be a problem for a SissySIT build. I'm guessing the MOSFET may run a bit warm, but I've also read that it's not horrible to err on higher voltage as opposed to lower -- so long as it's sufficiently heatsinked?
 
sp33ls

sp33ls

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Turns out I'd have to lower bias current after all if I were to end up with 27VDC+ rails.

I'd like to get closer to get closer to your standard Firstwatt-based PSU (which is 23VDC I think), so I think many shoot for 24V.

Thoughts on going with this 22VAC from Toroid? They have an omega bracket for easy mounting (and shielding?) which is cool. However, these seem to be 117V primaries and my current apartment hovers around 119~120, so that may bump up just a hair?

Or, should I just go with 300VA Antek 20V if I'm trying to minimize excess voltage?
 
KevinHeem

KevinHeem

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Joined 2007
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aljordan said:
I am trying the SLB on my Aleph J mono amps and am getting a large spike into the speakers when I shut the amps down. This doesn't happen when I power the Aleph J with the standard First Watt power supply, nor when I power my F6 boards with the SLB. Any idea why this happens with the Aleph J, and is there any way to alleviate it short of installing speaker protection boards?

Thanks,
Alan
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Hi Alan,
I'm having the same turn-off spike in my recently completed SLB->Aleph J amplifier. For now, I connect speakers after amp is on and disconnect before shut-down. Wondering If you ended up installing speaker protection?
 
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aljordan

Member
Joined 2006
home.maine.rr.com/aljordan
KevinHeem said:
Hi Alan,
I'm having the same turn-off spike in my recently completed SLB->Aleph J amplifier. For now, I connect speakers after amp is on and disconnect before shut-down. Wondering If you ended up installing speaker protection?
Click to expand...
No, I didn't. I am going to try to back down the rails to ~24 volts. If that doesn't mitigation the issue, I'll go back to the standard first watt power supply that I was previously using.
 
Vunce

Vunce

Member
Joined 2014
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I’ve been thinking about your Aleph J/SLB turn-off spike noise, I wonder if you added some capacitance at the SLB output it would slow the power rails down at turn-off similar to a standard First Watt CRC psu.
Before you lower the voltage, add a 10000uF cap across each power rail. As built per schematic the output caps are 220uF, add the new caps in parallel to these.
 
xrk971

xrk971

Founder of XSA-Labs
Joined 2012
etsy.com/shop/XRKAudio
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This asymmetry in the bleed down was what I suspected as the source of the turn off thump. If we ask ourselves why the asymmetry is not there when it is on, it would indicate that the input stage swings positive when no more power is supplied. It might be that increasing the bulk capacitance above the positive input stage rail may help. Maybe increase the value of C4?
https://www.diyaudio.com/community/attachments/aj-skema-bw-png.330720/
1660702112255.jpeg
 
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