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Old 9th August 2020, 09:11 PM   #1611
daniboun is offline daniboun  France
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Thanks for the feedback )

Sure it is a great amp as per review !
You should try the TPA3255 based on 360 Customs design, it blew me away as well

Someone tried the Evaluation Infineon Merus / Gan Modules ? : I found it @ $500 shipped !

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Last edited by daniboun; 9th August 2020 at 09:22 PM.
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Old 10th August 2020, 06:09 AM   #1612
daniboun is offline daniboun  France
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Other question :

I saw you are using some AC/DC power converters (4x60W / 24VDC / 2.5A output) in this version VS SMPS PSU on the other one.
I imagine it's to make the product more accessible in terms of price?

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Old 10th August 2020, 11:53 AM   #1613
poseidonsvoice is offline poseidonsvoice  United States
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No, it's because I had it in stock. I had purchased a few of those boards a while back and I am putting it to good use. Moreover the Neurochrome SMPS-86 (discontinued) has:

*Integrated Softstart (once the output voltage of the power supply has reached 75% of the nominal output voltage, a relay trips and shorts out the thermistor. This allows the thermistor to cool, allowing the soft-start to work even during a short power outage).
*Surge capacity to 320J.
*Pi filter on output so AC ripple is 5.6mv RMS (measured).
*50mohms output impedance

In addition it has all the positive attributes of a MeanWell supply, i.e. less than 1% regulation, built in mains filters, galvanic isolation from input to output, the ability to handle a wide set of worldwide voltages on the primary, overload protection, overcurrent protection, etc...

Most SMPS supplies have a ton of ripple on the output, like 100-300mV RMS. This supply is not noisy at all. An equivalent linear supply would need very large capacitance numbers in the supply, along with a pi filter or two or capacitance multiplier circuit, along with being heavy.

That being said, it probably makes little difference since the PSRR of Leo's circuit is phenomenal and my lead lengths are very short. It's a testament to the design of the BOSC/Starkrimson circuit.

Best,
Anand.
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Last edited by poseidonsvoice; 10th August 2020 at 12:04 PM.
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Old 10th August 2020, 11:59 AM   #1614
daniboun is offline daniboun  France
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Ok thanks 👍 I do understand now.
Nice boards Indeed
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Old 10th August 2020, 12:02 PM   #1615
orchardaudio is offline orchardaudio  United States
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Yes the amps have very good PSRR thanks to their fully balanced design from input to output.

The power supply that I use to do all my measurements is CUI / SDI250-56-U-P219. This power supply has 560mV of ripple on the output.

Anand will be sending me his amp to do measurements on, we will see if the lower ripple power supply has any effect.
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Old 10th August 2020, 12:48 PM   #1616
drMordor is offline drMordor  Russian Federation
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Quote:
Originally Posted by daniboun View Post

Someone tried the Evaluation Infineon Merus / Gan Modules ? : I found it @ $500 shipped !
Bad gate driver))) Need special driver.
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Old 10th August 2020, 01:48 PM   #1617
daniboun is offline daniboun  France
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Thanks Bro ��
Waiting for your Gan modules ��
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Old 10th August 2020, 08:56 PM   #1618
Pygmy is offline Pygmy  Netherlands
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Quote:
Originally Posted by daniboun View Post
Hi,

Check out, you can find here the XRK Audio for instance, based on high end design :

RTR TPA3255 Amplificateur de reference classe D | Etsy

They are expansive that's true ! but they are far away better than any Chinese TPA32XX amp

360 Customs do not sell their finished amps.
Xrk seems not to have any finished boards for sale anymore..

So I guess I'm out of luck trying to buy a decent quality finished board.

Does anyone have a suggestion for a *semi*-decent finished TPA32XX board?
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Old 10th August 2020, 09:44 PM   #1619
redjr is offline redjr  United States
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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.
Attached Images
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File Type: jpg P1020283.jpg (838.1 KB, 100 views)
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Old 10th August 2020, 09:45 PM   #1620
daniboun is offline daniboun  France
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Best "chinese" board = 3E Audio or Aiyima 3251 (Tilear PCB) with OPA1656
Another alternative (but non PFFB enabled) :

jlelectronicsph on eBay

✅ Transient voltage protection (SCR + TVS + Fuse)
✅ Oversized Zobel Network
✅ Linear post regulator
✅ Voltage supervisor (no startup/shutdown pops)
✅ Nichicon muse input caps
✅ OPA1656

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Last edited by daniboun; 10th August 2020 at 09:49 PM.
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