So I found myself wanting a couple channels of amplification for some subwoofers in a medium sized room. I was intrigued by the promised performance/$ of these TPA3255 boards. I am not building from scratch or anything, just going to play with the Lego pieces that are out there. That being said, I was hoping someone could talk some sense in to me about my possible configurations.
I am looking at the boards put together by 3e-audio and power supplies from connex electronic . . . as these seem to be decently well respected. All other parts being the same, I am just comparing the two components.
The board offerings are either a BTL ($70) or 2x PBTL (2x $65).
The supplies are the SMPS600RS ($89) or 2x SMPS300RS (2x $65)
The possible configurations are as follows:
1. SMPS600RS + BTL = $159 (Base)
2. SMPS600RS + 2x PBTL = $219 (Base + $60)
3. 2x SMPS300RS + 2x PBTL = $260 (Base + $101)
Thoughts:
Assume 4 ohm speakers for now . . .
1. Plenty of supply, 4 ohm stable . . . perhaps cooling becomes an issue? Cheap.
2. Plenty of supply, 2 ohm stable, twice the onboard capacitance . . . twice the cooling as base. Not as cheap
3. Discrete power supplies, 2 ohm stable, twice the onboard capacitance, twice the cooling as base. Approaching what it would cost just to buy an off the shelf Crown XLS 1002, albeit without getting to play with Lego.
Is there any true benefit in going to the higher cost configurations?
Links:
BTL
PBTL
SMPS300RS
SMPS600RS
I am looking at the boards put together by 3e-audio and power supplies from connex electronic . . . as these seem to be decently well respected. All other parts being the same, I am just comparing the two components.
The board offerings are either a BTL ($70) or 2x PBTL (2x $65).
The supplies are the SMPS600RS ($89) or 2x SMPS300RS (2x $65)
The possible configurations are as follows:
1. SMPS600RS + BTL = $159 (Base)
2. SMPS600RS + 2x PBTL = $219 (Base + $60)
3. 2x SMPS300RS + 2x PBTL = $260 (Base + $101)
Thoughts:
Assume 4 ohm speakers for now . . .
1. Plenty of supply, 4 ohm stable . . . perhaps cooling becomes an issue? Cheap.
2. Plenty of supply, 2 ohm stable, twice the onboard capacitance . . . twice the cooling as base. Not as cheap
3. Discrete power supplies, 2 ohm stable, twice the onboard capacitance, twice the cooling as base. Approaching what it would cost just to buy an off the shelf Crown XLS 1002, albeit without getting to play with Lego.
Is there any true benefit in going to the higher cost configurations?
Links:
BTL
PBTL
SMPS300RS
SMPS600RS
You might want to look into Micro-Audio SMPS’s. I use them on my TPA3255 and they offer superior performance compared to most other SMPS out there. They are quiet first and foremost. No hiss or hum issues. I have measured the noise floor down to -130dB with them and they are made using a unique topology that doesn’t mind adding a large cap bank after the SMPS to provide additional protection from bus pumping. The owner, Sami (Cresnet) is also super helpful and customer service oriented. Plus features like always on auxiliary power, regulated +/-auxiliary power for opamps and remote turn on with delay are also super useful to have. The SMPS630_SO is a great choice for TPA3255.
SMPS630-SO – MicroAudio
Background noise measurement from my TPA3255 with SMPS630_SO PSU into a 10ohm load:
Test setup:
SMPS630-SO – MicroAudio
Background noise measurement from my TPA3255 with SMPS630_SO PSU into a 10ohm load:
Test setup:
Last edited:
Thanks for the PSU recommendation, are there any published specs for these units? I did not see available product manuals/specs, compared to Connex.
Do you have any insight on a single BTL board vs dual PBTL configuration? I have seen a number of TPA3255 somewhat underperforming, probably because they were using laptop type PSU. With a proper PSU, can a single board put out decent wattage, or is it better to spread out the demand across multiple units?
Do you have any insight on a single BTL board vs dual PBTL configuration? I have seen a number of TPA3255 somewhat underperforming, probably because they were using laptop type PSU. With a proper PSU, can a single board put out decent wattage, or is it better to spread out the demand across multiple units?
You might want to contact Micro-Audio directly for datasheet and manual. He has it - just not easy to find on the website. Email is info@micro-audio.com
PBTL is parallel bridge tied load and allows the amp to drive 2ohm loads. If your driver is 4ohms or higher, there is no benefit for higher power with PBTL. You do need a proper 52v PSU to achieve the higher power. Also, the TPA3255 needs a preamp capable of driving a 22dB gain amp to reach max power. The quoted power is at 10% THD and at top of the “wall” of distortion. I would not operate there and so realistically, the max power is about 1/2 of what is quoted as max power if you want reasonable distortion levels.
If employing PFFB, the gain is reduced to 15dB and the max power is also reduced since the amp’s input opamps cannot put out more than 12vpp due to the on board 12v buck converter.
PBTL is parallel bridge tied load and allows the amp to drive 2ohm loads. If your driver is 4ohms or higher, there is no benefit for higher power with PBTL. You do need a proper 52v PSU to achieve the higher power. Also, the TPA3255 needs a preamp capable of driving a 22dB gain amp to reach max power. The quoted power is at 10% THD and at top of the “wall” of distortion. I would not operate there and so realistically, the max power is about 1/2 of what is quoted as max power if you want reasonable distortion levels.
If employing PFFB, the gain is reduced to 15dB and the max power is also reduced since the amp’s input opamps cannot put out more than 12vpp due to the on board 12v buck converter.
Last edited:
When thinking about whether the TPA3255 would work, I was really only considering the 1% thd numbers or where the "knee" was on TI posted data sheets.
As far as preamps go, I figured I would pick up one of 3e-audio's ADAU1701 implementations. Not only would it provide DSP to the AVR's sub out, but it converts single ended input to balanced going into the TPA3255. I don't know a whole lot about gain in amplifiers, so based on what you said it is concerning to see the ADAU1701 board list 10dB gain . . . though this is would be after whatever gain is provided by the AVR, correct? The ADAU board spec says it will output 3V at 1% THD with input voltage of 1.1 Vrms. Would this mean I am more likely to see ~2V output with an typical AVR sub preout @ 0.7V (haven't measured)
No idea about PFFB, nothing is mentioned in the amp's specs
As far as preamps go, I figured I would pick up one of 3e-audio's ADAU1701 implementations. Not only would it provide DSP to the AVR's sub out, but it converts single ended input to balanced going into the TPA3255. I don't know a whole lot about gain in amplifiers, so based on what you said it is concerning to see the ADAU1701 board list 10dB gain . . . though this is would be after whatever gain is provided by the AVR, correct? The ADAU board spec says it will output 3V at 1% THD with input voltage of 1.1 Vrms. Would this mean I am more likely to see ~2V output with an typical AVR sub preout @ 0.7V (haven't measured)
No idea about PFFB, nothing is mentioned in the amp's specs