Group Buy for: The Journey of DIY No-Feedback Class D Amplifier (1)Subtitle: The Motivation and Story Behind It

[S.Huang]

To power the amplifier, I prefer to use two 48V switching power modules with PFC, each capable of a maximum output of 350W. Any comments?

 

[flmhhh]

I think it is great power supply, suggest adding an EMC filter to the AC power input.

 

[S.Huang]

@flmhhh Yes, EMI filter can reduce noise and protect the device.

 

[S.Huang]

@flmhhh , thanks! And I want to add a volume pot. Found a rack to DIY a stepped attenuator. Need to calculate resistor values for different levels. Would u pls to check the input impedance?

 

[flmhhh]

That is cool, the input impedance is 22kΩ at 13dB gain and 5kΩ at 26dB gain.

 

[flmhhh]

The PCBA has been stuck in LA customs since April 10th, still not sure when it will be released. 🙁

 

[S.Huang]

The result of using 92 high-precision thin-film resistors is a 23-step stepped attenuator. Both left and right channels have balanced inputs, with a matching 5K ohm input impedance.

 

[CreazyTuba]

I'd love to sign up, if there are still two units available — planning to build a stereo class d amplifier.
Really looking forward to this!

 

[uptownsquash]

@CreazyTuba if there isn’t an extra you could take my spot. Just lmk!

 

[flmhhh]

@CreazyTuba I have 2 extra units available for you. Thanks!

 

[flmhhh]

After paying a 45% tax, the PCBA was finally delivered today.

Will solder on these expensive thin-film coupling capacitors, bring up the system, and run tests.

 

[flmhhh]

Folks, the test results have been posted in the original thread. The results are quite good, and the subjective listening experience is very impressive (even better than first version I think)

 

[flmhhh]

All remaining boards have been brought up and are functional, with an operating frequency between 3.68 and 3.71 MHz. Will assembly and perform the final testing. the module will be ready to ship in one or two weeks.

 

[CreazyTuba]

Sweet, I’m really looking forward to it!

 

[flmhhh]

All the boards have been tested, and the performance remains quite consistent, so I don’t think it need pairing. I’ll proceed with assembly in a couple of days.