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Bozak DJ Mixer Clone - Opened up
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Bozak DJ Mixer Clone - Opened up
home_listening
Hello All,

I was selling pcb and front panel sets for a Bozak DJ mixer clone earlier in the year. These are all gone now and I'm not planning on doing another run so rather than let it languish on my harddrive, I thought I'd put all the files up for people to download/look at/build perhaps if they want to.

https://fabricastronautblog.wordpress.com/2017/09/26/pathos-mixer-the- end/
flts
Thank you, this piqued my interest earlier when you posted about it, but as I didn't really have a need for mixer like that I resisted ordering a set. Might get back to this idea now, and build a "cheapo version" (cheapo as in, handmade panel and box from leftover materials, not cheaping out on parts) for myself just for fun.
tobb
wow,thank you!
fluffymuff
Hi,

thanks for posting about this and open sourcing your project. I have been looking for exactly this kind of project for years now and wish I'd found you sooner but I'm certainly not complaining, this looks fantastic. The documentation looks great as well.

I've got a huge backlog at the moment but I certainly intend to give this a go at some point soon. My only concern is with the power supply, I think i'll need to find someone locally who can help with that, unless there are off the shelf supplies I could use?
flts
fluffymuff wrote:
I've got a huge backlog at the moment but I certainly intend to give this a go at some point soon. My only concern is with the power supply, I think i'll need to find someone locally who can help with that, unless there are off the shelf supplies I could use?


Yeah, if you don't have experience of building mains supplies (and are reluctant to learn due to safety issues / other reasons) then it's probably best to enlist someone to help, eg to build an external LM317HV based supply like the designer has done. High quality prebuilt +40VDC @ 1A linear supplies are quite few and they're expensive.
flts
home_listening wrote:
I thought I'd put all the files up for people to download/look at/build perhaps if they want to.


Just a quick q: based on the link it appears you've had good experience fabbing boards from those specific Gerbers at DirtyPCBs? It looks like the preview doesn't "get" the non-rectangular board outline quite correctly, but I assume the end result from them is still OK?

We thought about ordering a couple of sets together with local DIYer friends, and DirtyPCBs is what I most often use these days as well. So would be an easy option if they have handled the outline (and the two milled holes?) correctly so far.
home_listening
flts wrote:
home_listening wrote:
I thought I'd put all the files up for people to download/look at/build perhaps if they want to.


Just a quick q: based on the link it appears you've had good experience fabbing boards from those specific Gerbers at DirtyPCBs? It looks like the preview doesn't "get" the non-rectangular board outline quite correctly, but I assume the end result from them is still OK?

We thought about ordering a couple of sets together with local DIYer friends, and DirtyPCBs is what I most often use these days as well. So would be an easy option if they have handled the outline (and the two milled holes?) correctly so far.


Hi,

I used these exact gerbers with DirtyPCBs for my production run, so should be no trouble at all. They do say something to the effect of don't worry about the gerber viewer as it is just for loose reference.

You're quite right about the power supply, I used a very conventional topology with the LM317HVT. An alternative is the TL783. It isn't difficult at all to improve on the original which was a very basic discrete regulator. The mixer draws about 250mA/10W.

Thanks all for the kind words!
flts
home_listening wrote:
I used these exact gerbers with DirtyPCBs for my production run, so should be no trouble at all. They do say something to the effect of don't worry about the gerber viewer as it is just for loose reference.


Great, thanks for both the design and the help / clarification! We'll see if we'll manage to order a small set of boards in the very near future...
fluffymuff
Thanks for the advice guys.

fits - i would definitely prefer to learn how to build one myself so i've done a bit of googling and found this article

https://makezine.com/projects/0-24-volt-2-amp-bench-top-power-supply/

If i substitute the LM317 for the LM317HVT and use a 220v transformer like this one http://www.mouser.com/ds/2/410/media-1067702.pdf am i getting close to what I need to power the Bozak?

Cheers
home_listening
Changes to that schematic:

    Use a 10K trimpot for setting the voltage (actual resistance wanted is 7440R)
    Use a 240R resistor between Output pin and Adjust pin
    More capacitance on the input
    More Capacitance on the output (for a bench supply less is better as it responds to changes faster but in this case use 1000uF or more)
    Transformer with 36V secondary (or 18V + 18V)

And yeah, use the HVT designated part.
flts
Even better (and this is completely optional), aside the other changes above, maybe substitute that 5K trimpot with a resistor + trimpot in series instead of the 10K trimmer. Choose the values so that the adjustable total value of the "adj pin to 0v" resistor always keeps relatively close to the target (7.44K) - and yet gives enough adjustment range to dial the correct voltage output.

Eg. if you use a 6.8K resistor and a 2K trimmer in series, that gives you an adjustment range of 6.8K to 8.8K.

That way you can dial a pretty accurate +40V easily, but even if you accidentally turn the trimmer to zero or max, you won't throw serious over- or undervoltage to the circuit. Plus if the trimmer decides to break down mechanically and short (which isn't common with proper quality trimmers, but not unheard of either), you're still left with a voltage that's in the correct ballpark due to the fixed resistor.
fluffymuff
Hey, thanks for all the info... really helpful, i'll try and give this a go at some point and report back whatever happens... good or bad!
roglok
thank you! that is very generous. i've been ogling your pages for a while now, planning a simplified version of the Bozak and i might just use your PCBs to build it up...
w00t
Willzyx
Just ordered a set of 10 via PCB way. I will have a few spares $30usd worldwide shipping included. PM if interested

I don't plan on doing any panels maybe somebody in europe can do some?
I/Ø
Thanks for sharing!
I was recently talking with a friend about the Bozak Isolators, which seems pretty hard to find...and we found your website, great work!

Some years ago we just found the Pioneer SF850 crossover / discrete isolator schematic

We might finish building some of Mr Eliot´s design ideas:
http://sound.whsites.net/project153.htm
http://sound.whsites.net/articles/eq.htm#s6

dsf
Sheeeet, how did i missed this :( been looking into something like it for quite long cry
flts
dsf wrote:
Sheeeet, how did i missed this :( been looking into something like it for quite long cry


Hi! Worry not.

I ordered a batch of 10 PCB sets for myself and local DIYers, I think 2 sets are still not spoken for and the order should arrive to me the coming week.

Willzyx is also offering his spare sets (see one of the messages above in the thread) for $30 if there are still any available.

My extras will cost slightly more, probably something like 45-50 euros with shipping included, as I ordered with ENIG plating from DirtyPCBs and have to pay Finnish VAT. I don't intend to make a profit as it's home_listening's design but I need to check the final DHL bill and shipping prices for exact sum.

Anyway, you can probably get a set from one of us if you're quick enough smile You'll just have to source the case + panel + power supply + parts yourself.

FWIW I plan on drilling the panel myself "ghetto style" so won't be of much help with the panel side.
dsf
I'll get a set from you !! Thanks smile
flts
dsf wrote:
I'll get a set from you !! Thanks smile


OK! I'll send you a PM once the boards are here and I've figured out the final cost so you can check if it's OK for you.
flts
Hi dsf, sent you a PM during the weekend, check your messages smile

Also, to anyone else, due to one of the group buyers canceling his participation, I have at least one if not two extra sets available for pretty much what I paid for them plus shipping.

They are ENIG plated green PCBs (4x input, 1x prgm, 1x cue), one set costs 45 euros including EU wide shipping.
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