My TPA3251D2 based Class-D Amp

Wharfedale Diamond 12.1 & 12.2 Speakers
jls001 said:
May be I'll wait till PBTLs make their appearance in the market. I'm keen on sampling a higher powered amp. As it is I have to complete my PeeCeeBee v4:)
Click to expand...
TPA3255 Class D is a practical way of experiencing high power amplifiers. 255Wpc into 4ohms 1% distortion class A will be a huge monster.

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SanjeevM said:
TPA3255 Class D is a practical way of experiencing high power amplifiers. 255Wpc into 4ohms 1% distortion class A will be a huge monster.

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Click to expand...
Completely agree with you. I ordered two tpa3255 boards. I connected it with 48v 350watt SMPS and it surprised me with its sound quality.
If anyone interested to try tpa3255, I have put my second board for sale here.

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jls001 said:
Right! I am already debating if I should use one transformer, or two:)
Click to expand...
I am using the 3e-audio TPA3251 board right now. Its wonderful, and you must try it out too. Or better directly try out the TI Eval board of 3255. The SMPS PSU + board will be around $200. Very straightforward to build.

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SanjeevM said:
Dear FMs,

Enthused by the performance of the TPA3116D2 Class-D chip, I ventured into the TPA3251 territory, and replaced the 3116 board in my player with the 3251D2 based board from 3eAudio.

The 3251 is a high performance amplifier chip which gives 140W stereo into 4ohm at 1% distortion. S/N ratio is 111dB, Distortion at 1W is 0.005%. I have connected it to my 6 ohm bookshelves, so I guess I am getting around 100W stereo.

I have bought a 24V 10A toroidal transformer, an Audio Grade 4700uF 63V X 8nos Dual Rail Power Supply board from Eight Audio and set the whole thing up. My RPi and Allo Boss DAC are the same, connected to them is the 7 inch LCD screen as before. The TPA3251 board now gets 36.6 volts DC. The recommended range is 24 to 38 VDC.

As the transformer is pretty big in size, I had to build a new cabinet. That took time.

I am currently running the RPi + DAC from a 10000 mAh mobile battery bank, just to give the RPi a very clean linear supply. The battery bank voltage sags a bit, at no load it gives 5.1V, but on load it falls to 4.6 volts and a low-voltage sign shows up on the display. The RPi still plays, though the screen becomes a tad unresponsive.

I have also built an adjustable regulated 5V 5A PS using LM338, but somehow the 338 is heating up considerably, going into thermal shutdown even at 1.5A current drawn by the RPi+DAC+LCD combo, so I am not using it right now. Perhaps the voltage drop is quite a lot from 9V to 5V at 1.5A.

The sound quality of this board is much better than what I got out of the 3116. Highs and lows are both clearer and resolved. The amp sings with an 'open throat'. Since the distortion and noise figures for this chip are markedly lower, the instruments sound more authentic and the background is black. You can hear even the faint sounds which got drowned out by noise in 3116.

I am very appreciative of the sound quality of this 3251 board. Perhaps it will outshine quite a few boxes and heaters :) I will strongly recommend it to all FMs.
Click to expand...
Try LT1083/84 regulators for rpi.

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I recently experimented powering the RPI by a battery.

I used the MI powerbank to give 5v DC power to the RPI + Boss DAC + 7In touchscreen combo. Used it for two weeks.

Then I switched back to the adapter which came with the RPI. It is a 5v 3A device which is supposed to be very good.

The audible result, corroborated by two discerning guests was::
-- Sound lacked bass when I used the adapter.
 
SanjeevM said:
I recently experimented powering the RPI by a battery.

I used the MI powerbank to give 5v DC power to the RPI + Boss DAC + 7In touchscreen combo. Used it for two weeks.

Then I switched back to the adapter which came with the RPI. It is a 5v 3A device which is supposed to be very good.

The audible result, corroborated by two discerning guests was::
-- Sound lacked bass when I used the adapter.
Click to expand...
Has any other FM also experienced the same?


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SanjeevM said:
Has any other FM also experienced the same?


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Click to expand...
Thanks Sanjeev for sharing this with us. You motivated me to try u regulated power supply with much tpa3255evm. I need suggestions from all the experts. What type of transformer should I order? 0-48 or 48-0-48? Thinking about ordering 300va.
I am thinking about getting one more board to use in Mono configuration. Two 300 VA transformers should be better to keep both channels totally isolated.
Tia.

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Since the TI TPA3255Board is a stereo board, it has only on pair of sockets for DC IN, so it needs one trafo.

You could use a 0-36 VAC Transformer with a 10Amps winding. The DC voltage after rectification on a bridge rectifier will be 36 x 1.4v - 1.4v = 49 volts DC.

You should use a capacitor bank sufficiently large after the rectifiers to reduce ripple. I am experimenting myself on the size of the bank. I tried the EightAudio PS module which has a 4700uf x 4 (per channel) capacitor bank. This board failed after some time, so I have to make a new one now. If you use too large capacitors, you will have to use a soft start module to reduce the starting current.

If you want separation of channels, you can use a trafo with a bifilar winding of 0-36 volts, so you get two 0-36 coils with the same primary. Two trafos will take up too much space.
 
SanjeevM said:
Since the TI TPA3255Board is a stereo board, it has only on pair of sockets for DC IN, so it needs one trafo.

You could use a 0-36 VAC Transformer with a 10Amps winding. The DC voltage after rectification on a bridge rectifier will be 36 x 1.4v - 1.4v = 49 volts DC.

You should use a capacitor bank sufficiently large after the rectifiers to reduce ripple. I am experimenting myself on the size of the bank. I tried the EightAudio PS module which has a 4700uf x 4 (per channel) capacitor bank. This board failed after some time, so I have to make a new one now. If you use too large capacitors, you will have to use a soft start module to reduce the starting current.

If you want separation of channels, you can use a trafo with a bifilar winding of 0-36 volts, so you get two 0-36 coils with the same primary. Two trafos will take up too much space.
Click to expand...
PS:
By separation of channels, I mean two boards in mono.
 
SanjeevM said:
Since the TI TPA3255Board is a stereo board, it has only on pair of sockets for DC IN, so it needs one trafo.

You could use a 0-36 VAC Transformer with a 10Amps winding. The DC voltage after rectification on a bridge rectifier will be 36 x 1.4v - 1.4v = 49 volts DC.

You should use a capacitor bank sufficiently large after the rectifiers to reduce ripple. I am experimenting myself on the size of the bank. I tried the EightAudio PS module which has a 4700uf x 4 (per channel) capacitor bank. This board failed after some time, so I have to make a new one now. If you use too large capacitors, you will have to use a soft start module to reduce the starting current.

If you want separation of channels, you can use a trafo with a bifilar winding of 0-36 volts, so you get two 0-36 coils with the same primary. Two trafos will take up too much space.
Click to expand...

Thanks, Sanjeev for valuable inputs.
Can you please explain capacitor board module failure?

Regarding having two 0-36 binding (10A + 10A) instead of two Trafo - How much increase in size would be expected?

Which diodes should I order for Audio performance?
TIA

PS: I am planning to order Toroid Transformers from ToroTrans. They quoted 1560/- + GST for 0-48 300VA. I will request them to send me qoute for 0-36V 10Ax2.
 
Last edited:
The size of the trade does not increase much. The cost of 2x36v could be 2k or so, but that will serve you well.

I am not very sure what caused the failure of the PSU board. I had a psu board which had 4 diodes and 2 banks of 4x2700uf caps. On switch on, the trafo used to make a buzz sound. One day it just started to blow fuses. Perhaps it was because of high initial current that the board conked off.

I am planning to put a soft start circuit on the primary side and to use a 20,000 uf cap bank per channel.

You could order any 10A rating diodes for this PSU.

On other boards people have used the Meanwell 48v 350vs switching power supply and they report good results. This SMPS has to be brought from abroad.
 
stefan said:
Those meanwell 350-48 can be bought from within India, if you have a GST no. 1850+tax (28%) I had an invoice sent a couple of days back, I had already bought it for 2900 delivered from industry buying Inc tax and delivery.
Click to expand...
How was your experience with this PSU? Did you find it quieter than a linear PSU?

I was using a battery for the RPi + Allo boss dad combo. When I switched to the Allo adapter, I found that bass depth got reduced.


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