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SMPS for Pass A3
SMPS for Pass A3
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Old 30th December 2017, 12:40 AM   #1
tribute is offline tribute  Australia
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Question SMPS for Pass A3

Hi, I am thinking of building a pair of Pass A3 board. To keep things simple as I already have it, can I used the below SMPS to run the unit. (26VDC 350W) It has 3 power outlets on it and can be adjusted down if required, but am not sure how low.

Input 110/220VAC Output 36VDC 9.7A 350W S-350-36 Regulate Switching Power Supply | eBay

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Old 30th December 2017, 01:05 AM   #2
globalplayer is offline globalplayer  Germany
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I think the Pass A3 needs + and - 25 V DC.
Your psu has just a single +36 V DC output.

Also I doubt you can adjust it as low as 25 volts and even then you will need 2 of them to get the + and the - voltage and then I would go for the Mean Well LRS-350-36 instead which isn't really more expensive and is a quality component.

Even better would be 2 of the Mean Well LRS-350-24 which are 24 volts and should easily reach 25 volts.

Just connect + of one psu to - of the other and use as ground.
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Old 30th December 2017, 01:10 AM   #3
Zen Mod is offline Zen Mod  Serbia
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SMPS for Pass A3
1. you decided how to establish bipolar supply from it ? you can use so called Quad trick , but with somewhat more powerful transistors

2. be sure that power rails are floating , ref. to case of switcher , then connect (new) audio gnd to chassis via CL60 or similar NTC
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Old 30th December 2017, 01:29 AM   #4
globalplayer is offline globalplayer  Germany
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^Forget what I said.
From the Mean Well LRS psu schematic it seems that - (GND) output is connected to input ground and case.
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Old 31st December 2017, 10:44 PM   #5
tribute is offline tribute  Australia
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Hi Guys, Thanks for your replies. I though the A3 could operate at over 25 VDC provided it had adequate heat sinks.
Not sure how to check Power rails are floating, please advise.

Cheers & Happy New Year to all.
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Old 1st January 2018, 05:24 PM   #6
Nelson Pass is offline Nelson Pass  United States
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SMPS for Pass A3
I don't recall what an A3 is. Would someone care to remind me?

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Old 1st January 2018, 05:35 PM   #7
Zen Mod is offline Zen Mod  Serbia
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SMPS for Pass A3
most certainly OP meant Aleph 3 , 30, Volksamp (30)
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Old 1st January 2018, 05:37 PM   #8
vdi_nenna is offline vdi_nenna  United States
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Old 1st January 2018, 05:51 PM   #9
Aatto is offline Aatto  United States
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i built preamps (class A, AB ... ) with SMPS also almost all my headamps running on smps, and just tried my FH9 with two smps is series, dead silent ! let me tell you this i ll never go back to big heavy expensive transformers no more, you need a good filter (CRC possibly CRCRC .. ) and maybe a cap multiplier, also of course a good smps to start with, i suggest laptop power supply with a dc boos board, i m also building my pass alpha 3 ( hello mr. Pass sir ), already bought the laptop supplies and dc boost boards for it, to connect laptop power supplies in series you have to remove one of the ground connections ( do it on your own risk ! ) otherwise it would short and one of them will turn off.

i didn't like the idea of smps specially for pre and headamps since there are a lot of mixed ideas n reviews out there, but mr X (XRK971) suggested it and it was one the best advice i had here.

Last edited by Aatto; 1st January 2018 at 05:57 PM.
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Old 1st January 2018, 05:54 PM   #10
Aatto is offline Aatto  United States
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check this out, gonna try this next :
500W Amplifier SMPS board
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