This thread is for builds of the 1184 Quad VCA mixer. info here
Hey Sam, which pots do I need for these?
Ignore that… I just realised the BOM has gone up
cool! and for the dual I am doing the BOM right this second
So, which is it, 1183 or 1184?
its a bit of both. on the pictured one its 1183, however after realising 1184 would work better with a quad vca. so lets meet in the middle and go 1183.5 :P. some will have 1183’s on them. the first batch!!! haha.
Oooooh, limited edition!
hahaha exactly! I figured whats the harm! nothing like a convoluted backstory to things!!!
I posted the BOM for easy gathering over here
I have a question regarding the BZX55C2V0, because I have trouble finding it (here in Germany). How important is the exact voltage, can I also use a 2.4V zener? I have looked in the datasheet and there I can not find anything on limiting the input voltage. The only thing I found in the datasheet was a limit on the CV: -2V to 2.5V.
Can anyone explain this a bit more to me?
Not sure where that 2 V comes from – the 3360’s inputs and outputs are current driven with a ±400 uA max range. The input stage matches the datasheet, with an added inverting buffer followed by the datasheet’s 47k that maps ±10 V (20 Vpp) to ±200 uA, which is within range. I don’t see what the diode is doing there; seems to me you could just leave it out…
The output is also a little bit odd – output is a ±200 uA current at max gain (1.0×), so you’d expect there to either be a resistor to ground (datasheet uses a 47k to shift back to ±10 V) followed by an inverting buffer, or a straight I-to-V stage (signal directly into an opamp with a 47k feedback resistor), but I guess the two 100k resistors have the same effect? You could probably replace that with a piece of wire and
a 47k one 100k if you’re a bit adventurous
EDIT: You’d have keep the 100k feedback to get the same output voltage. The first 100k doesn’t really do anything, what I can tell (after turning on some more braincells), since the current doesn’t have anywhere else to go but through it. You could probably use any value there. Or a 0 ohm link.
just got mine built and it nearly works!
LED 2 doesnt seem very happy and its not turning on, not quite sure where to look on the schematic, they still dont make much sense to me
im wondering if anyone has a concise way of explaining how its meant to work, becasue im getting nothing from the main out, but i am getting outputs from each specific vca
are they all normalled into each otheras a chain , because if i plug into 1, i get no output from 2/3/4, which feels like its wrong considering the module is a mixer?
also switching the inv when there is no cv would just cause the channel to go dead right?
many questions! im gonna look at thtat schematic more and try and work out where i went wrong on that LED
No, nothing’s normalled. They mix at the output. That is, for instance, channel 1 output goes to the output jack and if nothing is plugged in there it connects to the mixer section. If something is plugged in there, it doesn’t.
The LED is driven by the input CV. For LED 2 look at Q2, R30, R40.
hey! good to see it is sort of working!
yeah so all of the VCA’s mix into the mix output. but are switched like analogoutput said, so when you plug the output of VCA 1 in, it removes it from the mix bus. (There is an easy mod if you dont want that to happen! and I can get to that later today! ill take some photos). the idea was if you wanted to use the first VCA in invert mode where you can use it as a side chain, then plug the output of it into the second via, only the second VCA would be in the mix.
now in order for the mix bus to work the audio travels through the switch on the jack, so when there is a jack in it the switch in the jack is broken.
so also look at the jack socket ands see if all of the points have been soldered.
if you have put none switched jacks in place dont fear!!! it’s fine. with the mod I have explained above which I will do later, it will make the mix bus function
as for the LED! I think that is probably down to either a dry joint somewhere. like analogoutput said, check that aspect of the circuit, also check the soldering on the pcb connector terminals. and also! check you have the LED the right way round. you can do this by looking at the metal bits in the actual LED and see if they match the working ones.
Ah ok nice, yeah that’s a nice way for it to work, I was only checking to see if what I have here is functioning as it should.
So switched out the LED and it works now! But LED 1 went down Haha, i notice if i pull the second board( with the switches and the pots) off slightly from the pin headers it works, but when I push it on snug it doesnt
So all 4 channels are working fine (haven’t checked cv yet) but I’m getting nothing from my mix out
Built mine over the weekend, that was a lot of 100k resistors. Took a bit of back and forth joining the 2 sections together, but nice not having any wires. Its a solid brick for sure.
ok!!! good news except the header socket thats annoying!. im not sure what to suggest, maybe figure out which socket the LED connects, and plump a tiny tiny ting bit of tin foil in that hole???
when I do the modification later on. ill just check where you should check out to see why the mix out wouldn’t work.
Is that with nothing plugged into the individual outs?
yeah nothing in any of the outs
ok ace! appreciate the time to reply!
so i went to check the header socket and the pin for the LED soldering was slightly dodgy
heated it up and now works a dream, surprised to see how such a small discrepency in soldering can cause a failure!
Mixer is U7, R69 through R72. From there it goes to the daughterboard via J5 to be attenuated at RV5, then back to the main board via J4 to be sent to the output jack. You could check if there’s a signal after R72, before and after RV5, and before the jack to narrow it down.