I got a spare PCB for Burson BANG amplifier and started to change it from driving speakers to drive headphones instead. This should probably make it the cheapest good quality amp able to drive Hifiman HE-5 (too bad I don't have one to test it).
What I did:
- Added two Pentium 3 blue heatsinks, one for each LM3886TF chip.
- Added 4 x WIMA 220pF for decoupling (not necessary, but I felt like I need to do this).
- Removed and bypassed the input opamp to lower the gain and reduce the noise.
- Replaced the 2 gain resistors (20K with 10K) to lower the gain from 20X to 10X (about 5W/50-Ohms, enough for all planars, even for Hifiman HE-5); it outputs about 15-16V RMS.
- Connected XLR plug instead of speakers plug (for use with powerful balanced headphones) via shielded wires.
- Did a small external resistive adapter to divide the output power to match sensitive cans like IEM’s (similar with lowering output gain to about 2.4X) and connected to a standard 6.3 mm jack; it outputs a bit less than 5V RMS. Thanks to Frans (aka solderdude) for that: https://diyaudioheaven.wordpress.com/tutorials/power-amp-adapter/.
Now it looks like that:
And the outputs:
It measures very well, there is no background noise on the jack plug (about 5V RMS) and very little noise on the XLR plug (about 15V RMS).
What I did:
- Added two Pentium 3 blue heatsinks, one for each LM3886TF chip.
- Added 4 x WIMA 220pF for decoupling (not necessary, but I felt like I need to do this).
- Removed and bypassed the input opamp to lower the gain and reduce the noise.
- Replaced the 2 gain resistors (20K with 10K) to lower the gain from 20X to 10X (about 5W/50-Ohms, enough for all planars, even for Hifiman HE-5); it outputs about 15-16V RMS.
- Connected XLR plug instead of speakers plug (for use with powerful balanced headphones) via shielded wires.
- Did a small external resistive adapter to divide the output power to match sensitive cans like IEM’s (similar with lowering output gain to about 2.4X) and connected to a standard 6.3 mm jack; it outputs a bit less than 5V RMS. Thanks to Frans (aka solderdude) for that: https://diyaudioheaven.wordpress.com/tutorials/power-amp-adapter/.
Now it looks like that:
And the outputs:
It measures very well, there is no background noise on the jack plug (about 5V RMS) and very little noise on the XLR plug (about 15V RMS).
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