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TPA3255 Reference Design Class D Amp GB
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Old 14th February 2020, 09:59 AM   #391
wineds is offline wineds  Australia
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Quote:
Originally Posted by zdr View Post
Read the thread. There are very favorable comparisons.
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Old 14th February 2020, 11:00 AM   #392
xrk971 is offline xrk971  United States
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TPA3255 Reference Design Class D Amp GB
Quote:
Originally Posted by zdr View Post
That board has errors on it that prevent it from being a practical amp. I bought two from different vendors and one was on Amazon. Still same problem because same layout.

1. The error lights for fault and OTW are always on when operating normally. How useful is that?

2. The amp has no remote reset capability, so if your input RCA has a glitch, the amp goes onto protect error mode and shuts down. The only way to reset is to unplug the power input. That is every inconvenient as the errors can happen with something like hot plugging in the RCA to a source.

3. I was unable to get more than 48Vpp out of it with a 51v PSU. I believe the hardwire soldered or layout based setup mode jumpers were incorrect and so it is not working in BTL mode which should give a swing of close to 2x48v minus MOSFET dropout on each end or 96v-8v or +/-78v theoretical max or 27.6Vrms for 190w into 4ohms.

4. It has an LM2575T-12 switching step down regulator for make 12v. That’s only good for 40V max input. It needs the LM2575HV-12 version which can go to 60v input. So I suppose the regulator must be sort of working because it makes music with a 48v to 51v supply, but who knows what the regulator is doing in terms of regulation.

5. The measured harmonic distortion profiles were not close to the specified levels of the TI reference design.

Basically, I can’t believe they went into production of tens of thousands of these boards without anyone catching these glaring errors.
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Old 14th February 2020, 11:04 AM   #393
Kay Pirinha is offline Kay Pirinha  Germany
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The discussion appears to be coincident that the only board that can compete with the TI reference is the 3e Audio board, though being not as versatile. And most probably this GB one . Most of the other ones are lacking of quality especially of the output inductors, 'lytics etc.
Best regards!
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Old 14th February 2020, 11:27 AM   #394
Yatsushiro is offline Yatsushiro  France
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Quote:
Originally Posted by xrk971 View Post
That board has errors on it that prevent it from being a practical amp. I bought two from different vendors and one was on Amazon. Still same problem because same layout.

1. The error lights for fault and OTW are always on when operating normally. How useful is that?

2. The amp has no remote reset capability, so if your input RCA has a glitch, the amp goes onto protect error mode and shuts down. The only way to reset is to unplug the power input. That is every inconvenient as the errors can happen with something like hot plugging in the RCA to a source.

3. I was unable to get more than 48Vpp out of it with a 51v PSU. I believe the hardwire soldered or layout based setup mode jumpers were incorrect and so it is not working in BTL mode which should give a swing of close to 2x48v minus MOSFET dropout on each end or 96v-8v or +/-78v theoretical max or 27.6Vrms for 190w into 4ohms.

4. It has an LM2575T-12 switching step down regulator for make 12v. That’s only good for 40V max input. It needs the LM2575HV-12 version which can go to 60v input. So I suppose the regulator must be sort of working because it makes music with a 48v to 51v supply, but who knows what the regulator is doing in terms of regulation.

5. The measured harmonic distortion profiles were not close to the specified levels of the TI reference design.

Basically, I can’t believe they went into production of tens of thousands of these boards without anyone catching these glaring errors.
Hi X

This AliExpress link is to the 3e Audio boards, not the run of the mil AliE boards to which you attribute certain errors!

TPA3251 / TPA3255 Digital Power Amplifier Board 1/2/4 Channel 135W / 175W / 315W / 600W on AliExpress
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Old 14th February 2020, 12:07 PM   #395
xrk971 is offline xrk971  United States
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Sorry, my mistake - as I did not know they were on AliExpress (thought was only eBay before) but I did say “Blue” boards that look like this:
What is wrong with TPA3255?-chinese-tpa3255-errors-jpg

The 3e boards don’t have any of these issues although differences probably more in output inductor and quality of PCB (2mm thick, 2oz copper, and layout with via stitching by JPS64). But one feature not on 3e board is Post Filter Feedback (PFFB) which gives the best performance in terms of distortion.
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Last edited by xrk971; 14th February 2020 at 12:10 PM.
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Old 14th February 2020, 02:19 PM   #396
zdr is offline zdr  Belgium
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Quote:
Originally Posted by xrk971 View Post
Sorry, my mistake - as I did not know they were on AliExpress (thought was only eBay before) but I did say “Blue” boards that look like this:
Click the image to open in full size.

The 3e boards don’t have any of these issues although differences probably more in output inductor and quality of PCB (2mm thick, 2oz copper, and layout with via stitching by JPS64). But one feature not on 3e board is Post Filter Feedback (PFFB) which gives the best performance in terms of distortion.
Did you mean to say 1oz (2oz is recommended in data sheet, so that should be good thing).
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Old 14th February 2020, 02:34 PM   #397
zdr is offline zdr  Belgium
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Is pcb layout open source? I need to adjust it to my needs. If not, I will just design it from scratch.
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Old 14th February 2020, 05:33 PM   #398
xrk971 is offline xrk971  United States
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My boards are 2oz copper - extra thick. No, the layout is not open source. The PCBs are available bare for $38. You would save yourself a lot of effort as it has been tested and verified to work. It also sounds great.

The PCBs are here:
TPA3255 Reference Class D amplifier PCB | Etsy

A fully assembled and ready to run board with genuine Mouser-sourced BOM and assembled in the USA amp board is also available for $227 here:
RTR TPA3255 Reference Class D amplifier | Etsy
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Last edited by xrk971; 14th February 2020 at 05:37 PM.
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Old 14th February 2020, 06:01 PM   #399
xrk971 is offline xrk971  United States
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I did a full power test to see where clipping occurs. 51v DC-DC from 12v battery as power source for 51vdc. Driving with 1kHz sine wave from a pocket DAP and headphone amp through THAT1646 SE to Balanced line drivers Amp connected to EBG 300w 10ohm resistor cooled with CPU cooler. I got 32.1Vrms from a Fluke 116 True RMS DMM, that's about 90.1Vpp. The Oscope showed closer to 100Vpp. If this were driving 4ohms, it would be about 190w, maybe 200w.

Click the image to open in full size.

Here is Oscope screenshot - this is right at onset of clipping, so starting to get a little ragged at the peaks:
Click the image to open in full size.

Into 10ohms, this is 103Wrms. This amp can definitely make some power.
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Last edited by xrk971; 14th February 2020 at 06:03 PM.
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