A dedicated page for reverse-engineering the Douk Audio U3 headphone amp.
original top view
desoldered top view
| ID | Type |
|---|---|
| C3 | 47uF 25V electrolytic (Jwco PET) |
| C13 | 470uF 35V electrolytic (Jwco VENT) |
| C12 | 47uF 25V electrolytic (Jwco PET) |
| C15 | 470uF 25V electrolytic (Jwco VENT) |
| C18 | 470uF 25V electrolytic (Jwco VENT) |
| C10 | 470uF 35V electrolytic (Jwco VENT) |
| C17 | 470uF 35V electrolytic (Jwco VENT) |
| C4 | 470uF 35V electrolytic (Jwco VENT) |
| C8 | 470uF 35V electrolytic (Jwco VENT) |
| ID | Type |
|---|---|
| Q1 | NPN hFE=278, Vbe=0.68V, Ic=7.4mA |
| Q2 | PNP hFE=313, Vbe=0.75V, Ic=2.7mA |
| Q3 | NPN hFE=289, Vbe=0.68V, Ic=7.4mA |
| Q4 | PNP hFE=315, Vbe=0.74V, Ic=2.7mA |
All transistors were measured by their flat side facing downwards.
Q1
Q2
Q3
Q4
Using LM4562 OP-AMP as a replacement of the original TI-NE5532 (datasheet).
| ID | Type |
|---|---|
| C3 | 47uF 63V LOW ESR electrolytic (Panasonic) |
| C13 | 470uF 35V LOW ESR, low impedance electrolytic (Panasonic) |
| C12 | 47uF 63V LOW ESR electrolytic (Panasonic) |
| C15 | 1000uF 25V LOW ESR, low impedance electrolytic (SAMXON) |
| C18 | 470uF 35V LOW ESR, low impedance electrolytic (Panasonic) |
| C10 | 470uF 35V LOW ESR, low impedance electrolytic (Panasonic) |
| C17 | 470uF 35V LOW ESR, low impedance electrolytic (Panasonic) |
| C4 | 330uF 35V low impedance polymer (Panasonic SEK) |
| C8 | 330uF 35V low impedance polymer (Panasonic SEK) |
The higher capacitors don't fit into the old case, so I decided to cut of the top of the case and repliace it with plexiglass. You can 3D print the top case extension and use it as a template to drill threaded holes to fasten the plexiglass sheet.
Using 2N3904 NPN and 2N3906 PNP transistors respectively. With the same pinout as the original transistors.
| ID | Type |
|---|---|
| Q1 | 2N3904 NPN - hFE=229, Vbe=0.73V, Ic=7.4mA |
| Q2 | 2N3906 PNP - hFE=249, Vbe=0.77V, Ic=2.2mA |
| Q1 | 2N3904 NPN - hFE=229, Vbe=0.73V, Ic=7.4mA |
| Q2 | 2N3906 PNP - hFE=249, Vbe=0.77V, Ic=2.2mA |
- https://yama-audiolab-0910e.blog.jp/archives/18373911.html
- https://yama-audiolab-0910e.blog.jp/archives/18514568.html
- https://yama-audiolab-0910e.blog.jp/archives/18852685.html
- https://www.superbestaudiofriends.org/index.php?threads/douk-audio-u3-review-the-douk-of-wishful-thinking.13953/
- https://www.head-fi.org/threads/douk-u3-mini-headphone-amp-question-on-power-supply-voltage-amp-rating.953409/
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