{"id":2941,"date":"2022-11-16T17:22:58","date_gmt":"2022-11-16T17:22:58","guid":{"rendered":"https:\/\/maffez.com\/?page_id=2941"},"modified":"2023-01-02T10:31:29","modified_gmt":"2023-01-02T10:31:29","slug":"donner-b1-tech-info-modifications","status":"publish","type":"page","link":"https:\/\/maffez.com\/?page_id=2941","title":{"rendered":"Donner B1 tech info\/ modifications"},"content":{"rendered":"\n

Please reference me when reposting images from this page. Thx<\/p>\n\n\n\n

This is all very preliminary and a tad frantic as I’m pretty busy otherwise, but more concise info will follow soon. In brief: partly super close to TD3 in terms of IC choice and VCF\/VCA setup. VCO tuning, however, seems to be done per MCU scheme (trimmers not populated!), and generally, this has a very tidy layout and partly more selective choice of parts. 4580 is the dominant op amp (with LM358 for v\/oct and TL072 for distortion being exceptions). The general sound engine character is closer to the TD3 than to the TT303MK2 or the TB-EFA module I am familiar with. Especially the resonance character is pretty TD3 style (that\u2019s the matched transistor pairs in the filter for you). As for the VCA, once more the OML discrete Ba662 clown<\/a> has been honoured by being used, as far as I can tell. While I can’t say how this reflects on Donner, I think this speaks for guest’s accomplishment and the quality of what they did there!<\/p>\n\n\n

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VCF and VCA section\u2026<\/figcaption><\/figure>\n<\/div>\n\n\n

What else? CPU: ARM GD32F<\/a>, distortion is your usual Boss clone (better than on td3, need to trace that first though), delay, yasss! uses a PT2399 chip – these are fun to mod!<\/p>\n\n\n\n

Disassembly <\/strong><\/h2>\n\n\n\n

Disassembly of the unit is super easy and in places some modifications are practically almost already implemented – the VCF audio input and the VCA control input for instance, sports a bridged jumper, which you can hijack for using potentiometers or input jack or other stuff – nice!<\/p>\n\n\n

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simply unscrew these six and pull knobs of the pots on the front, the gently pry open<\/figcaption><\/figure>\n<\/div>\n\n
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voila, the jack PCB and the sound PCB and control PCB<\/figcaption><\/figure>\n<\/div>\n\n\n

The only thing with which you need to be a tad careful is the ziff connection between the smaller sound PCBon top and the larger PCB underneath. Best lift the smaller one up and turn it slowly and carefully. After unclipping the larger connector leading to the jack board, you can then focus on the little ziff. <\/p>\n\n\n

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pry black ziff brace up first, then gently pull awm ribbon<\/figcaption><\/figure>\n<\/div>\n\n\n

Layout <\/strong><\/h2>\n\n\n
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Sound engine PCB<\/figcaption><\/figure>\n<\/div>\n\n\n

You find more detailed pictures below, but this should suit for a general overview. PSU I need to look at in more detail, but there’s the voltage generation bit per op-amp and we can do a PSU starve like on the TD3 by changing one resistor. Trimmers for OSC scale and offset are not populated, so I guess the software takes care of that. The mini IC left of the waveform switch is a headphones amp and the rest (transistor selection, use of caps, etc.) largely as per Behringer clone. Accent is switched per 4066IC, and, if I’m not tripping, slide is done per software here. Thankfully, the Donner has manual accent trigger and manual slide trigger as features and you can also set gate length, which goes a long way in terms of finding some grove. Sooner or later I will of course mess with the circuits… <\/p>\n\n\n\n

More pics at the bottom of this page. <\/p>\n\n\n\n

Modifications<\/strong><\/h2>\n\n\n\n

Most of these I hastily tested for an hour yesterday, so treat this more as a shopping list and preliminary inventory. Completely untested stuff is in italics<\/em>. Moe pics and mostly also sound soon!<\/p>\n\n\n\n

Unmodded Donner BS1 for initial impressions<\/strong><\/p>\n\n\n\n