Finished my class D build. Sounds AMAZING

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Spiritg

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Joined 2023
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So we have:

300va toroidal with 2x 25v secondary

Soft start board with momentarily switch support

HTPC case, solid aluminium

Dual mono TPA3255 boards - fully balanced. XLR input only.

For context I also have a Musical Fidelity X200r and a Technics A900s. Both well regarded Class A amps costing 2 or 3 times what it cost me to build this.

It blows the Musical Fidelity out of the water, no contest. It's slightly better than the Technics, with a more relaxed sound and better separation.

I was dubious about Class D. Not any more.
 
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Puffin

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Joined 2006
I have put together several Class D amps having been one of the first modders of the Sonic Impact plastic throwaway amp that started a frenzy to get hold of one. The magic inside was the Tripath TA2024 which gave out a max of between 5 - 8w but in my opinion the advances in Class D have left the Tripath behind. Of course Tripath folded some years ago. I also had a TA 2020 but I blew it up somehow (not the classic touching together of speaker outs whilst powered up)

I have 2 TPA 3116s which I like, an IRS2092 and a couple of TA2024s....somewhere and recently a TPA 3255. I had intended to go the DIY route for one of these, but an offer on Aliexpress for a commercial offering from Sure/Wondom with case etc, but no power supply for silly money was too good to refuse. I have tons of stuff lying around and made up an adjustable PS with a tranny around 200va. I have tried 24v, 32v, 42v and have settled on 46v (it can take 48vdc) Sounds really good compared with some recent Amp Camp Amps I built.
 
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gcsa

Member
Joined 2023
@Spiritg That's a lovely build, nicely done. I'm near the end of my first class D build, however not quite to the same standard as yours. I've built several amps over the years, mostly for fun to be honest, however I'm yet to master the craft of making them look great like yours. Although they sound exactly how I want them to, the interiors generally look like dustbins. And the exterior, well, like a smart dustbin. I'm sure my wife sighs every time she looks at them.
So, what's that HTPC case you have there? I'd never thought of using one of those before, and yours has heatsink fins on the sides which would suit another class AB project I have in mind.
Also the soft start module interests me... where did this come from, and how does it work power wise (is there a low voltage transformer winding needed to power it from standby?).
 
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Spiritg

Member
Joined 2023
@gcsa - kind words thank you :) case is a streacom, build quality is impressive. Discontinued now I think, mine was an eBay find. Soft start is an eBay job - wolfzone I think is the seller. No low power feed required. It lives inline between the power socket and the transformer.

@ErikdeBest that's the very one(s) although I bought through AliExpress. I went for the balanced version. I wasn't expecting anything special, but all credit to the designers. Sounds fantastic! One thing I wasn't happy with was the brutal heatsink mounting. PCB pinched. I used spacers and thermal pads to fix this.
 
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Karlsonate

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Joined 2023
ZeroZone (or whatever OEM it is, there're many incarnations over the years) is a pretty good designer/producer of audio amplifiers.
They even made a IRS2092-based monoblock amp, which is a rarity (AFAIK, the IRS2092 mainly comes in usually dubious "500W amp", fan-slapped-on-top form factors). Here's the review for said product.
 
Alie-nSoundSystems

Alie-nSoundSystems

Member
Joined 2023
@Spiritg Yes it'd be a good upgrade, but on AD's website they write that OP270 is not really recommended for new design. However, I'd personally use the newest professional audio opamp by TI called OPA1633, I haven't tried it yet, but it looks quite promising. (I also know that you need to modify the board to use that ic, but it maybe worth it!) If you decide to try it, I'm waiting for your feedback!;)
Have a nice day!
 
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Spiritg

Member
Joined 2023
Couple of new pics. Changed speaker wiring from QED profile 72 strand to QED Silver Micro as I had some on hand and found a iffy solder joint on the terminals.

Also added an insulating board under the soft start board (ABS plastic not carbon fibre) just in case!
 

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Karlsonate

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Spiritg said:
Thanks guys.

I'm really looking for a drop in socket upgrade. So no SMD or extra caps ideally (I don't trust my soldering skills when dealing with things that small!)

Appreciate the information though :) are there any other solid options?
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You can (usually) never go wrong with TI OPA selections, OPA 1612/1656/1622... as long as they are dual op-amps. Some feel that these op-amps have a "V-shape" audio signature.
If you lean towards neutrality, LM4562/49720 is a good start.
"Tube warmth", bass, OPA2604.
Just won a lottery? Burson or Sparkos :)
 
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Spiritg

Member
Joined 2023
Thanks again guys.
jean-paul said:
A very nice build, congratulations! Class D is maturing and it is here to stay which not all DIYers of other topologies will appreciate but ...change is good!

Just don't solder 230V mains wiring to PCBs.
Click to expand...
Thank you :)

Kinda had no choice sadly based on the soft start board design. Input is solder only, (dual) outputs are spade compatible. Is the concern here a poorly executed solder joint or is there more to worry about? Pad ripping off?

@Karlsonate thank you. Lots to digest there. I certainly haven't won the lottery so I will see what's available cheaply on eBay :)
 
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