This project was started in March 2020, while the first covid 19 lockdown was in place, its goal – to offer a diy version of the 208, that everybody, even a beginner, can build to create vintage (or upgraded!) style buchla 208!
To this end –
All the pcbs have been designed with the original schematics, and the almost all of the original layout.
The pcb has ground plane, parts numbers in the silk screen, and the built is fast and easy. Some parts like even have many layout options on the pcb, to match your local store parts.
No shortcuts have been made in prototyping – the first 4 logic cards are now exceptionally electronically stable and the uA726,the tracking is spot on.
The calibration sequence is accurate, easy, and fast.
The sound is, of course, always fat, with shiny highs and those vintages analogs vibes!
The 208 X can be built as a vintage buchla 208, using the same Bom and panel as the original
As an upgrade, with 9 additional functions that can be added as desired!
(the choice is entirely up to the constructor – the pcb fully supports either build!)
Additional option functions –
- seq 2 step
- seq reset via cv or a momentary switch
- Env loop retrigged
- Mo hi range
- WF X a second preset ,for the timbre,for more metallic ,agressive sound
- a new card 12 ,new reverb driver,a new phone amp(works with a 8 Ohms speaker too). A new audio routine is possible to separate the MO and the CO
- reverb level mix control cv input
- fx pre/post mono send /stereo return
- white and pink noises
For those interested in detail, some notes on the cards below –
Card 1 – coupling capacitors added ,step 2 with switch on the paneladded, seq reset circuit by CV and / or a momentary switch.
Card 3 and Card 4 – bleed resistor added.
Card 5 – AM progressive index up to 100% .
Card 6 – hi range audio with switch on the panel,calibration by multi turn for 2 octaves J112 transistor layout added for the analog switch.
Card 7 – Wfx 2 presets for the timbre,with switch added on the panel, J112 layout added for the analog switch.
Card 9 – it is now possible to swap the rare and expensive DTL mc846 to the standard 74LS03.
Card 12 – A new card 12, with HQ driver reverb, phone / speaker amplifier, MO-CO custom audio routine possible. Pre reverb audio out available.
A reverb mix level cv input ,added with a control led (if desired)
A HQ psu 208Xmicro PCB :
400mA for each -15V+15V rail, 1.2A for the 5V and the external 12v (brick)is filtered by inductance pcb with isolated rails voltages and it can be installed under the seq space for a standalone standard 78 mm high,4u boat 208 solution(or the easel solution 218/208)
A mono send with a gain control pot,pre (pre reverb )/or post Master volume ,stereo returns with a gain stéréo control pot . One switch pre reverb/Main level and post is implanted. 2 fines levels noise sources on tiny jacks x2, white /pink from Electricdruid .
Some rares expensives parts like the DTL can be swapped to a cheaper circuit, for example, the mc846 to 74ls03 ,thanks to Dave Brown
The rare and expensive Jfet transistor 2N4341 in card 6 /card 7 is a simple switch,can be replaced by a j112, making the build cheaper with no change in the sound .
- PCBs are supplied bare (other components must be sourced)
- No warrenty is given nor implied