DIY rotary DJ mixer

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efinque

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Jan 3, 2018
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I think the 10K resistors in the summing might be too much.. I'll test with lower resistor values later.

I also came up with an idea of an adjustable summing bus (vertical trimmers mounted so that there's a flat rod going through them) but I think it's bit of an overkill for a mixer of this type.. maybe for prototyping.

EDIT : switched the summing resistors to 220ohms..
 

efinque

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Aight, here's the revised version of the schematic..

t_Cad1r1.png


EDIT : added a few notes and cleaned up the schematic..

EDIT 2 : minor fixes..
 

efinque

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Untitled_56.jpg


Here's a rather artsy front shot of the finished build... let me know what you think!

I used a no. 2 brush and silver paint instead of the planned decal work.. it turned out ok I guess.

EDIT : it's still not fully functional though.. the phono channels are dead and the HP amp/cue section needs to be reworked..
 

efinque

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Here's another, a smaller one I made from the leftovers just for fun..

mixer1.jpg


It's missing knobs though, and I think I blew the LED when testing it, but other than that it works, although it's a bit distorted.
 

home_listening

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Hi,

I released a Bozak CMA-10-2DL Clone project a few years ago and open sourced(ish) the project once I was out of PCBs. If you wanted to have a look the files are available for download here:

https://fabricastronautblog.wordpress.com/2017/09/26/pathos-mixer-the-end/

Please be very careful with transformers, Wiring the 15V lines in reverse generate something like 3500V. Never plug your projects into the wall without a fuse. Ever.

Good Luck!
 

efinque

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Jan 3, 2018
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Sorry for reviving an old thread but I've been thinking whether to ground the inputs/preamps to the summing or output?

EDIT : I'm short on wire atm which is why I'm asking.. another idea was to use a very large resistor at the output ground.

EDIT 2 : nevermind, just tested (1MOhm) with the small mixer.. I've been sleeping on this, whilst scheming a programmable step sequencer synth using an Arduino
 

efinque

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Petrag said:
Hello everybody, why is the schematic of the rotary no more visible?

It's because postimg routinely removes files.. I can re-upload the schematic if you want.

EDIT : here 'tis, a little messy but you get the idea

t_Cad1r1.png

 

efinque

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Meanwhile I've been plotting a 2-way crossover for a sound system..

xover.png


I've been doing some tests with the filters..

IMG_20180920_233731_235.jpg


Here's the HPF.. it works to some extent although is very quiet. I was thinking of aping the synth filter for the lows.

I also rolled a few PIO caps for fun (and a very rough transformer) The trafo doesn't work though..

IMG_20180922_194816.jpg


I tested the caps in the HPF but they didn't cut any lows so for now I'm sticking to the Nichicons.. I guess they'd have to be sealed somehow too.

EDIT : I've been trying to troubleshoot the mixer too and build other projects. I think I should've posted this in a new thread.. lazy me. The caps are thin cardboard, gun cleaning felt and tin foil soaked in car lock oil and coated with stearine from both ends&surface. One I made hit a spark when powered with 12V. In the picture is my try at a "matched" pair.. I think they're not for heavy use as the legs can come off due to the way they're attached. They hold little to no power afaik, I did some tests with different materials.
 

efinque

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Jarno said:
That is a nifty way of mounting components to audition them!  :D

Thanks!

I used to have a breadboard with springs (to attach components) when I was like 10.. got the idea one night to test the filter like that, those springs are from a ballpoint pen though.
 

efinque

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I just auditioned the xover.. it's ok I guess for a first try. The lows are very distorted though.

Here's a front panel shot (I had the frequency curves the wrong way around, also added knobs from an old Alesis Nanoverb)

IMG_20180925_125757.jpg


I finished the grounding with a screw terminal and did some small housekeeping. (edit : it's missing the knobs and the top panel among a few other things.. the case is a top cover from an old reel to reel deck.. it's hard to tell the exact cap values since they're homebrew, luckily I made spares for future use. If I win the lottery I'll try with Amp Ohms or some other esoteric caps)

EDIT : I may add a full range mid too in the future and put the LPF resistor pot around the back since it really serves no purpose..
 

efinque

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I made this small filter module on a cardboard.. I was thinking of putting it in the crossover to see if it helps with the low end.

IMG_20180926_124841.jpg


One idea was to use it as a business card.

EDIT : not that I do electronics for a living.. but it'd be something original and special.
 

efinque

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I put 1MOhm resistors to all mixer grounds  (booth, master and HP), I'll see if it works..

EDIT : wired the phono preamp too, and labeled the connectors around the back

EDIT 2 : I may also wire the thing all over again. I think the headphone amp is busted too.. oh well, back to the bench. I've burnt a bunch of LED's too. I noticed it picks up RF noise, could it be the SMPS? Anyway, I'm just repeating myself here... but I think the crossover was a great success.
 

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