Hi,
I highly doubt you get the black PCB with ELNA caps as shown by Dani.
The new version already with Green PCB with 2200uF ARC audio caps and Blue ELNA fake signal caps, Which i received in July.
Let's see your luck.All the best!
Could I please get a little advice from you guys. I have just finished building a music streamer with a raspberry pi running volumio to Khadas Tone Board DAC to 3e TPA3255 amp board. I am powering the amp with the Meanwell 48V 350W SMPS and the rpi and DAC from a separate 5V SMPS. Last night after testing it for a couple of hours I had a problem which I think is software related. Still troubleshooting that. What I did notice though is that the amp heatsink sits at anywhere from 48 - 55 deg C at idle. This really surprised me as I thought this was where Class D amps really shone. Power efficiency I mean. I was planning on leaving my streamer on most of the time but now am wondering if that is a good idea. Surely this amount of heat dissipation represents a reasonable amount of lost energy. This is without the chassis cover on by the way. I didn't built in any ventilation because I didn't think it would be necessary but now rethinking that.
Is this a normal operating temp for these amp boards?
If so I might have to drill a few holes...
Is this a normal operating temp for these amp boards?
If so I might have to drill a few holes...
Last edited:
Hi Gilera,
It may be normal for the 3e board, but not necessary the case for a TPA3255-based amp:
I'm running the TI EVM board and I could say that when idle (even if for hours, hidden into my Hi-Fi wooden furniture), it should be about 35°C or so...As an indicator: 45-50°C would not allow you to keep your hand steady on it for more than 20-30s without feeling you're burning your fingers...
Kal.
It may be normal for the 3e board, but not necessary the case for a TPA3255-based amp:
I'm running the TI EVM board and I could say that when idle (even if for hours, hidden into my Hi-Fi wooden furniture), it should be about 35°C or so...As an indicator: 45-50°C would not allow you to keep your hand steady on it for more than 20-30s without feeling you're burning your fingers...
Kal.
Thanks. You would think that 3e would make this recommendation better known. I'm sure the output would be fine for my application and I could have bought a 36V PSU with similar power output to my 48V supply. I bought the 48V because I had read several posts where people had claimed that is was better to run the amp up near the top of the input voltage range. I'll be a bit annoyed at 3e if I have to buy another PSU for this reason alone.
I'm still monitoring it (a digital meat thermometer!) but it definitately was 55deg C without any music playing yesterday. It because uncomfortable to keep your finger on it after a few seconds. I unplugged the amp from the DAC just to make sure nothing is getting through at idle - surely there should be no load on the amp if no music playing. I also have a 10k DACT type stepped attenuator between the DAC and the amp for volume control.
Later in the day I measure 48degrees at idle with very little change in ambient temp (around 20-24degrees here at the moment) so not sure why there would be such fluctuation. I would be interested to hook up a power meter to see what idle usage of the whole setup is. DAC + RPI should be low idge usage.
Do most people have ventilation in thir chassis? I'm assuming the temp with the cover on will be higher and am wondering at what point I should worry about the longevity of the components.
Another option might be some kind of signal activated power switch for the V+ wire from the SMPS to the amp. Rod Elliott has a circuit shown on his webpage for this purpose.
Project 38
I don't like the idea of playing around with the signal path unless absolutely necessary.
the worst amp I've seenBut TPA325x forgives a lot of mistakes
I know eh!
Dudes, digital placement is supposed to be toight!
toight!, toight!!, toight!?
...google, YES just a few down, from 2013, at another place ...
DIYHiFi.org • View topic - Old School! Ultracurve8024 DAC upgrade, trans out, USB ctrl
"I was able to get 805 sm caps on the pins of the bigger CS8412 Rx but man those DAC pins are 'toight' (Austin Powers). Would sm 605 fit?"
.
.
.
If a layout looks all symmetrical and nicely lined up ... well, it's layed out for LOOKS not performance. All parts should be as close as possible to the chips, the chips should be as close as possible, the parts should be tiny and the whole thing should fit on a playing card. NOT DIYfriendly!
...oh and do placement 1st, THEN figure out how you're gonna put a heatsink on the chip ...
...and don't forget
this good advice (especially thermal, sounds like this guy's PRO):
The last few pages of this thread have been a funny summary of my overall feelings with the TPA3255. I've been using a TI EVM for the past 2 years to drive my subs, and have finally grown tired of:
1. Heatsink on the wrong side of the board
2. Heatsink too small for continuous duty
3. No PFFB
4. Poor PBTL implementation
5. Crummy AFE
6. limited inductor choice
7. Zero EMI/EMC considerations
8. Irrational insistence on 2L PCB for an amp that really needs 4L
I figured I'd fix the above issues by doing up my own board and going full commit on the PBTL arrangement with proper PFFB and a good AFE. A bottom mount heat pipe implementation for cooling, and provisions for a heatsink large enough for continuous duty at full power output. I'm using the best inductors you can get (Coilcraft AGP4233 / Codaca CPQ4228) and the best caps (parallel NPO SMD). There's room for 8 x 1800uF 80V bypass caps (18mm diameter) with the closest caps sitting only 5.3mm away from the chip pins, and the inductors sitting only 12mm away from the outputs. The latter two items are also courtesy of mounting the TPA IC on the bottom and the caps/inductors on the top instead of trying to make room for a heatsink where you really need the PSU caps and output filter.
It's a 4L PCB so all EMI sensitive traces are buried with proper via shields around the perimeter. The output filter is optimized for low distortion and low EMI. If you mounted on this a heatsink and copper taped the perimeter, you'd pass EMI cert with no enclosure at all.
The AFE uses a pair of OPA1632 op-amps with a complete TI PFFB arrangement. The bi-polar 12V power supplies are generated from a single supply input using Linear Tech's LTC3265 low noise bi-polar supply charge pump. Both the GVDD and VDD supplies for the TPA have dedicated low noise 12V linear regs from a 15V buck supply. You provide between 36-54VDC and the board does the rest.
Attached are some pictures of the preliminary layout and overall arrangement. I will be doing complete measurements on the APx555 and they will be provided here. Thermal measurements will also be provided. PCB's or complete boards will be available in the future once all testing is complete
Regards,
Owen
Last edited:
I placed a thermocouple in the trough area of the finned heatsink of my 3e board and measured 38-40C when using the 36V SMPS but 50-52C when using the 48V SMPS. I could place my finger over the openings to the inductors when using the 36V PS and, as daniboun has already stated, they are not uncomfortable to the touch. When using the 48V PS it felt like my skin would burn.
Cheers, Pete
I was a bit surprised at the heat of my 3255 at 48V. I have a adjustable PS so set it at 40V and it runs cool. The inductors are fairly cool at 48V.
I may still run 48V in the long run with a larger heat sink but I need to see if the sound is better at the higher voltage. On my 3116 it sounds better at 19V than 12V by a good amount.
I may still run 48V in the long run with a larger heat sink but I need to see if the sound is better at the higher voltage. On my 3116 it sounds better at 19V than 12V by a good amount.
Is the TI EVM heatsink a higher rating? Anyone found a larger heatsink that suits the 3e board? Cheaper than buying a new PSU. After more testing I can say that my 3e board's heatsink definitely sits around 50 deg C at 48V at idle. Are other people measuring at idle or normal usage? Surely you would expect much higher power dissipation if pushing the amp. I do not have suitable speakers or place to test this out currently. The high temps do seem like normal behaviour according to other responses though.
Idle current is seems high enough for 10 - 12V extra to make a significant difference so you would think this would be problematic at high output.
Idle current is seems high enough for 10 - 12V extra to make a significant difference so you would think this would be problematic at high output.
