Class D Amp Photo Gallery

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#1,622
I think they are still being offered. He may need to restock his store. I didn't see the amp board, but thought the site would still be useful. I'm not sure, but he may be doing another group buy in the thread first to evaluate interest before restocking.
 
#1,627
Hi Redjr,

Is this board able to drive subwoofer?

I will need ~400W per sub (02 channel).

Does XRK sell populated PCB?

Thank you.


redjr said:
Hi all,

I'd like to present my latest class D amp build. At the core, this project was based on member xrk971's newest class D amp board. This board is based on the TI TPA3255 chipamp. The specifics of this amp can be found over at this link. The amp board is available as a bare PCB, or as completed PCB in his Esty store.

The Hardware --

The TPA3255 chip itself is mounted upside down on the underside of the board to make mounting to a chassis a good option. Of course, there are other options to raise the board, traditional heatsink, fan, etc. could be used for cooling as well. What worked well for me was to use a 130mm x 44mm x 6mm piece of aluminum stock, bolted to the chip via the PCB using thermal pad/tape to the bottom of the enclosure. The whole amp assembly secured with 6mm brass standoffs. Note: The heatsink MUST BE electrically isolated from the chassis.

For the PSU I used a Connex SMPS600RS. This is 48VDC single rail SMPS with available auxiliary voltage of +12V. The 12v was necessary for 2 additional boards I used in my build - explained next. I have excellent success using the Connex line of SMPS' over the years in several projects. Highly recommended.

The blue PCB shown attached to the back panel with XLR connectors in the upper right, is the SE to Balanced board since the amp operates natively in BTL (Bridge Tied Load) mode. This allows both balanced and unbalanced (RCA) input connectors. I recently upgraded my heavily modded ES90938Q2M DAC with Balanced outputs, so wanted that capability.

After testing on my bench, I found that the SMPS600 and the amp did not play nice together due to excessive amount of inrush current from the SMPS to the amp. A different kind of soft-start was required, since the SMPS already had a soft-start built-in. What was needed was an inrush current limiter circuit between the SMPS and amp. I contacted xrk971, and with his help, an inrush current limiter PCB was born. It will be offered in his Esty store in the future. The prototype I tested worked fine and I was able to complete the project build. Note: This appears to only be an issue with some models of SMPS' and the amp. So if you're building this amp, please try your intended SMPS first, as it may work fine. xrk971 confirmed it worked with a different model of SMPS from Connex he used for testing. So this simply may be a one-off obscure occurrence. In fact, it worked with a lower voltage/power SMPS I tried as well - without the inrush current limiter circuit being necessary. The Inrush Current Limiter circuit is powered by the SMSP auxiliary 12v output.

The Sound --

I have to say that I have build a number of class D amps, and by far this is the best sounding DIY solution I have found. The first thing I immediately noticed was how quiet this amp is. There is nothing but silence when it's turned on. Then when the music starts.... wow! While class D amps may have a 'bright' overall sound, in my listening to it over the past several weeks, I never found this amp harsh, or fatiguing to listen to in any way. Instead, the sound is smooth, full-bodied yet very articulate in executing the music with clarity and detail. With plenty of wonderful and warm sounding mids, and solid bass when called upon.

While I primarily listen to digital streaming from my home media server(roon), I also listen to LPs. One of the best, more recent LPs in my collection that is an absolute pleasure to listen to, is James Taylor's 'America Standard' Limited Edition, double 180gram, Audiophile 45RPM LP set. This is one of the best mastered LPs I've ever owned. All sides were click and pop free while being played back on my vintage turntable; JVC QL-7 using a Denon DL-103 MC cartridge. The cartridge is paired with a Puffin DSP phono preamp. The dynamics of this LP set were stunning, easily rivaling many digital tracks. James' voice is simply transformed in such a magical, and very easy to listen to way.

I continue to be amazed at how well this amp sounds and the technical execution of the music. And, did I say I haven't even tested a full balanced signal chain from my DAC to amp yet? 🙂 Next up.

A few more pictures of my amp along it's build journey.
Click to expand...
 
#1,631
The group buy #2 for the completed, Ready-to-Run (RTR), class D TPA3255 amp is now active in the following thread;

XRK RTR TPA3255 Reference class D Amp GB2
Click to expand...

Thanks =)
Keep in mind guys : this board is designed for the Automotive world. This means that you will buy it @ a fair price only if you intend to use it in a suitable environment.

I discussed with xrk971 a few weeks ago and he was very honest about it. The price of this card is clearly justified if your use is oriented towards the automotive world since the card is designed to resist vibrations and automotive stress conditions... consider this point carefully before your purchase 🙂
 
#1,636
I discussed with xrk971 a few weeks ago and he was very honest about it. The price of this card is clearly justified if your use is oriented towards the automotive world since the card is designed to resist vibrations and automotive stress conditions... consider this point carefully before your purchase
Click to expand...

Actually, it was designed not for automative but for professional audio - tour rigs and such. Lots of knocking about and bumps etc. But I did not want to sacrifice on sound quality or performance with regards to noise or distortion. It would indeed work fine in a car or any other high vibration environment (boom box), active speakers, motorcycles, boats, airplanes, boats, submarines, spacecraft, etc. 🙂

Secure Molex Minifit connectors are also used in all my other latest "home audio" amps (Alpha Nirvana and FH9HVX, and soon the Aurum-X) for the purposes of providing a quick and secure way to connect active power MOSFETs/BJTs to heatsinks, independent of the amp PCB. Lets you remove and service or swap out an amp board in minutes.
 
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#1,637
@orchardaudio The SMPS modules in this amp look very compact. Do you know who makes / sells them?
 

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#1,639
xrk971 said:
Actually, it was designed not for automative but for professional audio - tour rigs and such. Lots of knocking about and bumps etc. But I did not want to sacrifice on sound quality or performance with regards to noise or distortion. It would indeed work fine in a car or any other high vibration environment (boom box), active speakers, motorcycles, boats, airplanes, boats, submarines, spacecraft, etc. 🙂

Secure Molex Minifit connectors are also used in all my other latest "home audio" amps (Alpha Nirvana and FH9HVX, and soon the Aurum-X) for the purposes of providing a quick and secure way to connect active power MOSFETs/BJTs to heatsinks, independent of the amp PCB. Lets you remove and service or swap out an amp board in minutes.
Click to expand...

Thanks. It would be a nice idea to propose a new version for "domestic" use. I would imagine a version at a more interesting price without including the options related to the conditions required for the automotive world but the same sound quality.
I mean an alternative to 3E Audio for example ):cheerful:

By the way : Would you be able to make a new GaN Amplifier board ? I'm sure you will have lots of fans for this project)
in september I should sponsor DrMordor to start producing Gan amps )
 
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