I will try to develop and build a multi channel amp for a large 3-way active speaker build.
I have been considering Hypex solutions but before going that path I would like to see what I can create myself. I enjoy the process of learning new things. Have built a couple of active speakers based on ADAU1401/1701 and pretty cheap Class D amps before that I am satisfied with.
The plan is to:
Arylic HD DAC Streamer -> I2S -> ADAU1467 (DSP) -> I2S -> AK4468 DAC -> Differential signal 2V RMS -> OPA1632 -> Differential signal 2.5V RMS -> TPA3255
I have bought 3x2 channels of TPA 3255. (https://www.aliexpress.com/item/100....order_list.order_list_main.60.76611802JUlLBt). They use one TPA3255 chip per channel in PBTL mode. On the input signal path, one TL072 opamp per channel is used. Input connector is single-ended so I assume the TL072 acts as a buffer and inverter to create a differnetial signal for amplification, need to double check that. It says is also has a post feedback loop.
The plan is to develop a PCB with AK4468 and pre amp stage to take the differential signal to 2.5V to get the most out of the TPA3255. If I do so I will also the skip the TL072 op amps on the board and pass the signal straight into the TPA3255 in order to not toch the signal more than needed and to ensure 2.5V RMS.
Is it to overcomplicate things and instead go the extra way into a single-ended signal and keep the TPA3255 pretty much as-is?
Any advice in this conceptual phase of the project?
I have been considering Hypex solutions but before going that path I would like to see what I can create myself. I enjoy the process of learning new things. Have built a couple of active speakers based on ADAU1401/1701 and pretty cheap Class D amps before that I am satisfied with.
The plan is to:
Arylic HD DAC Streamer -> I2S -> ADAU1467 (DSP) -> I2S -> AK4468 DAC -> Differential signal 2V RMS -> OPA1632 -> Differential signal 2.5V RMS -> TPA3255
I have bought 3x2 channels of TPA 3255. (https://www.aliexpress.com/item/100....order_list.order_list_main.60.76611802JUlLBt). They use one TPA3255 chip per channel in PBTL mode. On the input signal path, one TL072 opamp per channel is used. Input connector is single-ended so I assume the TL072 acts as a buffer and inverter to create a differnetial signal for amplification, need to double check that. It says is also has a post feedback loop.
The plan is to develop a PCB with AK4468 and pre amp stage to take the differential signal to 2.5V to get the most out of the TPA3255. If I do so I will also the skip the TL072 op amps on the board and pass the signal straight into the TPA3255 in order to not toch the signal more than needed and to ensure 2.5V RMS.
Is it to overcomplicate things and instead go the extra way into a single-ended signal and keep the TPA3255 pretty much as-is?
Any advice in this conceptual phase of the project?
The best solution is to use the TPA3255 amplifier in combination with a dual ±15V low-noise, low-distortion op-amp stage, powered by an ultra-low noise, high-PSRR linear regulator.
While the ADAU1467 is a good option for DSP-based processing, I now prefer an analog signal path to preserve the DSD output from high-performance DACs like the ES9038PRO or AK4499.
Additionally, I have tested multiple TPA3255 boards from Aliexpress, but none of them met my expectations in terms of quality and performance.
I designed the TPA3255 with PFFB myself. Unfortunately, the TPA3255 operates with a single supply, which means that each input signal pin requires a DC blocking capacitor. Therefore, it is important to allocate space for high-quality film capacitors, such as MKP types, which are typically quite large.
It can be observed that all TPA32xx products from Chinese manufacturers are designed with cost efficiency in mind. They often use basic switching and linear regulators that cannot effectively handle switching noise. Additionally, their designs make the op-amps operate in a single-supply configuration, requiring a bypass capacitor from the +input pin to ground and a blocking capacitor in series with a resistor to the -input pin.
If you aim for high sound quality, you will need a large number of high-capacitance components. A dual-supply power configuration is a much better solution in this case.
The LC filter component is also an important aspect to consider.
If the TPA32xx is designed properly, it can deliver excellent sound quality.
If the amplifier we build fails, we can repair it ourselves.
While the ADAU1467 is a good option for DSP-based processing, I now prefer an analog signal path to preserve the DSD output from high-performance DACs like the ES9038PRO or AK4499.
Additionally, I have tested multiple TPA3255 boards from Aliexpress, but none of them met my expectations in terms of quality and performance.
I designed the TPA3255 with PFFB myself. Unfortunately, the TPA3255 operates with a single supply, which means that each input signal pin requires a DC blocking capacitor. Therefore, it is important to allocate space for high-quality film capacitors, such as MKP types, which are typically quite large.
It can be observed that all TPA32xx products from Chinese manufacturers are designed with cost efficiency in mind. They often use basic switching and linear regulators that cannot effectively handle switching noise. Additionally, their designs make the op-amps operate in a single-supply configuration, requiring a bypass capacitor from the +input pin to ground and a blocking capacitor in series with a resistor to the -input pin.
If you aim for high sound quality, you will need a large number of high-capacitance components. A dual-supply power configuration is a much better solution in this case.
The LC filter component is also an important aspect to consider.
If the TPA32xx is designed properly, it can deliver excellent sound quality.
If the amplifier we build fails, we can repair it ourselves.
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Thank you @Moddang! Will reflect and research based on your input. I think I will stick to the DSP option. It will however be a jump in complexity compared to what I have done in the past. Think I will use that version of the TPA3255 as starting point as well and potentially replace certain components based on measurements. Will buy myself an oscilloscope as well to be able to learn more on what impacts the signal quality. Will keep you posted.