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Powering an NC400 with the power supply from an old amp

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#1
Hi All,

Been lurking on these forums for a while but finally have a question to ask!

The DIY amp reviewed here:
https://www.audiosciencereview.com/...and-measurements-of-hypex-nc400-diy-amp.5907/

Really caught my eye, I love the idea of a transparent amp and I love a good diy project!

As I went through the comments one issue which came up was that the parts suggested on the https://www.diyclassd.com/ may not provide sufficient power and I was wondering if I could cannibalise an older amp for the power supply?

Maybe case and inputs too!

I am aware that the quality of a power supply affects the performance but the nitty gritty of what specs and how to match them are a little beyond me.

I was wondering if you could help me figure some of this stuff out.

Thanks

Will
 

Doodski

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#2
Hi All,

Been lurking on these forums for a while but finally have a question to ask!

The DIY amp reviewed here:
https://www.audiosciencereview.com/...and-measurements-of-hypex-nc400-diy-amp.5907/

Really caught my eye, I love the idea of a transparent amp and I love a good diy project!

As I went through the comments one issue which came up was that the parts suggested on the https://www.diyclassd.com/ may not provide sufficient power and I was wondering if I could cannibalise an older amp for the power supply?

Maybe case and inputs too!

I am aware that the quality of a power supply affects the performance but the nitty gritty of what specs and how to match them are a little beyond me.

I was wondering if you could help me figure some of this stuff out.

Thanks

Will
Do you have a specific amp in mind? Do you have a service manual?
 
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#3
No my plan was to grab something off ebay etc, once I had worked out what I should be looking for, hopefully something broken but with a working power supply.
 

Doodski

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#4
I'm not the resident expert on Class D amplification. Wait around for one of them to come before you jump in. I was just gonna get you ready for one of them who will probably ask what amp you have. ;)
 
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#5
Thanks for the heads up :)

This idea is in the very nascent stages, just trying to figure out feasibility at the moment.
 

Fred Jacquot

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#6
Hi All,

Been lurking on these forums for a while but finally have a question to ask!

The DIY amp reviewed here:
https://www.audiosciencereview.com/...and-measurements-of-hypex-nc400-diy-amp.5907/

Really caught my eye, I love the idea of a transparent amp and I love a good diy project!

As I went through the comments one issue which came up was that the parts suggested on the https://www.diyclassd.com/ may not provide sufficient power and I was wondering if I could cannibalise an older amp for the power supply?

Maybe case and inputs too!
If you believe that the SMPS600N400 is not enough, 2 solutions:
1. The relatively easy way: take a SMPS1200A400.
2. Your way: find transformer(s), sync rectifier(s), reservoir caps in old amplifiers. Basically you need two rails @+/-65V 25A after rectification/filtering. @restorer-john may help. You will also need a soft start.

I have my doubts that 2 will be cheaper than 1 but I am not an ebay expert.

I am aware that the quality of a power supply affects the performance but the nitty gritty of what specs and how to match them are a little beyond me.
Now let me ruin the party (seems I like it). It's not only mains current that can be lethal. DC 65V 25A is also dangerous. Are you sure you want to take risks playing with something you don't really master?
 
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#7
I'm fine with the electrical dangers, have built and hacked things using high voltage and I will do my due dil before sticking my hands in anything, part of why I am here!

I have no firm beliefs yet, would you say the SMPS1200A400 is sufficient?

I'm hoping to build something relatively future proof as I start getting into the higher end audio world.
 

Doodski

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#8
There it is... Using Prms = [Vpeak(0.707)]^2/Rload you need a ~240-265 watt RMS into 8 ohms / channel amp with massive storage capacitance. Amps like that are rare and expensive. It would be better to buy a new PWM power supply that's designed to mate with the amp module(s) and much safer for you too. You don't want to take a hit from a 65 V DC high capacitance power supply you'll look like a heart attack victim being zapped and can even break bones doing it. Been there done it and it's shocking >@^_*@<
 
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#10
Haha to be fair I have no interest in dying doing this!

That's a handy calculator thanks.

Seems the SMPS1200A400 is the smart move.

I suppose I can always up the power later with it all being modular.
 
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#11
I'm planning to use a blown Urei 6250 (http://www.jblproservice.com/navigation/Vintage JBL-UREI Electronics.html) that I bought on ebay for $50. The Urei has a massive transformer and good heat sinks. The original AB amp had +/-63V rails. Also, the back panel has XLRs and nice speaker binding posts. The 19" rack chassis is good with plenty of room for the NC400s. I intend to use new main caps and new rectifiers. I also will use a new speaker relay PCB. I'll keep you posted on progress.
 

restorer-john

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#12
I'm planning to use a blown Urei 6250 (http://www.jblproservice.com/navigation/Vintage JBL-UREI Electronics.html) that I bought on ebay for $50. The Urei has a massive transformer and good heat sinks. The original AB amp had +/-63V rails. Also, the back panel has XLRs and nice speaker binding posts. The 19" rack chassis is good with plenty of room for the NC400s. I intend to use new main caps and new rectifiers. I also will use a new speaker relay PCB. I'll keep you posted on progress.
I think that will be an awesome supply and a great basis to build your Class D amplifier. $50, what a steal!
 

Xulonn

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#14
I think that will be an awesome supply and a great basis to build your Class D amplifier. $50, what a steal!
Wow! I haven't seen a manual done with a typewriter (or daisywheel printer) in a very long time...

JBL6250 Manual.jpg
 
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