Updated mouser basket 11 March 2021
https://www.mouser.com/ProjectManager/P ... 47f1a5ba4e
First ,thanks to all the pioneers (like me) builders who have spent time and shared their experiences since 5 years now,especially Roman F,Dave brown ,
Vediscapes,beautyof decay,Djangosfire,Dunnington audio,Captanapalm, xpander ,special thanks to Phildao for his 208 parts layout cards work ,etc
Im a musician since 42 years now,i ve always listened the electronics parts,like film capacitors,mustard without memory,MKP caps, LCC resistors ceramic carbon composition 1 % without noise, CTS 13 caps ,etc i know the most important in a circuit is the original design ,then layout and the choice of parts which is important for the character of the instrument .(vintage coloration or neutral,frequency,spectre...)
Don Buchla was a genius designer,in 70s the parts he used in the card 12 of the 208 ,the 4136 is acceptable but here the lm 380 was far to be good to drive a spring reverb tank ,and the phone amplifier is .....then
i build my last 208 (i’ve built 17),trying to use selected parts ,in the audio path like the original,the addition of each steps parts quality at the end give me a incredible sound ,imho more fat organic and present ,the logic stable .We ‘ve (Boops Ed. Team) designed a new card 12 as an option with a new audio bus,real reverb driver with one filter option,a 2W ,4 ohms phone out .and the Mo dry audio out can be separate,if you want it.Bye bye the Lm 380n
pic of the original card 12 ,with only the main audio parts ,aop resitors input ,aop ceramic compensation caps ,one quad aop,handy for the diy builders to test the first cards.
October 2021
Use the original card 12 schematic ,check the I/O .
Here the mod for the Mo alone dry and the Mo+Co wet
I use a resistor on the pot ,like daveB at modular synthesis to change the curve of the reverb pot .
And :For more reverb gain R13x2 =470k and C12:2 47pf
aout 2020
Important info
Dont forget to short N and Q grounds pin 15 /pin16 on molex card 12 .
march 2020
Finally,i dont keep the 10k mod on the mother board,for more reverb level.THEN NO MOD NEEDED ON THE MOTHER BOARD 1/1 swap !!!!
03 /05
A reverb mix level CV circuit (vactrol based) PCB is ready ,pm
09/04
Monsieur davebr page at Modularsynthesis
https://modularsynthesis.com/roman/boop ... card12.htm
Many thanks
20/03 Captannapalm audio test a few posts below (thanks) and his mouser bom
Here is a Mouser BOM. This does not include a quad op amp U2, IC sockets, or the J2 & J3 headers/plugs for reverb cables. I built mine with this BOM and everything works great. I only changed C7/C8 after I built mine because the form factor was big. C13 is also big but there’s room for it, and Mouser didn’t have a smaller one for that value.
https://www.mouser.com/ProjectManager/P ... 46bb3779c5
13 03 2019 :reverb connection added
11 03 2019:Card pcb/heatsink built infos +mother board little mod
05 03 2019 :Bom available below
04 03 2019 price is 40 eu /reverb pot mix level pcb +bracket is 15eu
28 02 2019
the final test is better than expected ,all is ok
i ve installed the RC filter for the reverb,and keep it .
video :Phones test with a 8 ohm guitar cabinet,camera mic ,the level is really loud,i will test it with a real monitor with a tweeter ,later.
price for the pcb 40 eu pm
https://soundcloud.com/boops95/buchla-2 ... b-internal
https://soundcloud.com/boops95/buchla-2 ... 12-upgrade
https://soundcloud.com/boops95/buchla-2 ... 2-mo-alone
Phone test
https://soundcloud.com/boops95/buchla-2 ... b-internal
https://soundcloud.com/boops95/buchla-2 ... 12-upgrade
https://soundcloud.com/boops95/buchla-2 ... 2-mo-alone
BUILT INFOS
first notes
Check 5 times ,solder one time
-the right jack socket is the direct audio out MO by default (or the CO if you choose it),it has a Level 100% ,no reverb
BOM
RE resitors ,PE pots are already on the 208 motherboard
The value of these pots is a plus for better impedance (optional)
1-4 is for 1/4 W resistors
mods
If you want your 208 more punchy change
R19-R42 was 150k by 330k
If you want more reverb level
Change R13 was 220k by 470k
capacitors 100pf/220pf are ceramic single layer SLCC
others are film,polyester MKT/polypropylène MKP see pics
c4 MKP or MKT axial cap 17,8/ 6 6 hight 17,8 mm width
Q1Q2 check for shortcut ,its tight!
Q3 Q4 Q5 Q6 need a SINGLE heatsink for thermal coupling and have to be isolated ,i use silicone ,only Q6 is not isolated
heatsink built
use a 1mm or 1,5mm aluminium around 40mm x15 mm
the holess are 3,2mm
print the pdf or the fpd if you want order it
see pics for the right installation
CHECK 5 TIMES SOLDER 1 TIME
U1 U2 U3 in the bom ,modern ones are used,(the dip ic become obsolete thought)but you can use a lot of others refs,
and following your ears keep the right one.
just check the datasheet for pinout
example for the quad aop ,a tlo74 should work,,the 4136 NO
u2 /u3 available at mouser
TLC081 is not TLO81 !
tlc081
OPA134
Reverb connections:
use Idc male and female connector x2 for J2/J3
the red pin on the pic is the hot /Signal point the other the ground of your shielded cable
Tip: use your master ,big red knob at a good level 8/9/10 then you can have a great mix of vcos/reverb
Begin with flat parts
R1 1k
R43 470R
R41 33k
R24 10k
The 4 x diodes check the polarity
IC sockets two 4x2 :8 pins and one 2x7 :14 pins for the experimentations later
C18/C19 solder them on the top ,check the polarity before.
MOTHERBOARD little mod,you dont need to move the panel! YOU DONT NEED THIS MOD MARS 2020!
Just put solder on each side of R73 /10k (RE2 on the schema) push it ,with a resistor leg to take it off.
Solder a new 10k resistor ,protect the legs if needed .Check pics and the schema
you can have the CO alone ,see pic
LISTEN a few posts BELOW the audio test of Captanapalm
