DIY DJ mixer

[Mote]

That is the theory but in practice?

[pern]

Simple example:


In CH 1 - Left
--------------

- Input buffer
- Pre Fader EQ
- Ch volume fader
- Buffer
- LP, BP, HP filter. No volume put but Xfader connected to CH 2 - Left
- Filter Summing amp
- Mixer Summing Amp
- Output Gain/ Buffer.

[RAWDATA1]

I would like to tune my behringer djx700, thought about, to take out the internal PS, ad an fx button and separate fx channels (internal/external) what would give me the posibility to put 2 fx at each channel.
Power supply ripping should result in a better noise ratio and less heat inside.
Anybody know what to do to improve the EQ sound quality, maybe also ajusting the frequencies?
Also Some extra gain and output level would be very welcome...

On the other hand, maybe digital mixing would make it even more interesting...

[pern]

Without an schematic it's hard to give any advice.

It also depends on how you want the FX functionality to work. Anything added before inputs and after outputs should be easy to fix.
But doing mods directly on the PCB on such a complicated mixer could be hard.

[cr0wl3y]

Rawdata1:

Not sure it's worth spending money and time on this. Taking out the PSU could in theory improve things but I cannot imagine it will transform a budget mixer to a wonder machine and it will create other hassles for you (you need to make a housing for the PSU, install a socket onto the mixer to connect it etc). It will also completely obliterate the resale value of the mixer - even though you see it as an improvement, potential buyers are likely to see it as a liability.

As for more substantial improvements, I have not seen schematics and layout for any behringer mixers, but tend to agree with pern that mass market commercial units, particularly those packed with functions and DSPs, will be a pain to reverse engineer. For example, to add simple switch-able sends and returns to each channel you probably have to do some pretty awkward tweaks to the pcb (break connections and add jumper cables to other boards and so on), not to mention find space on the top for the toggle switches and at the back for the send/returns. "Improving the EQ sound quality" sounds difficult to define and even more difficult to implement. You can probably change the cross-over frequencies by tweaking some of the components, on the assumption that the design is analogue and simple enough to get you hear around and you can physically do the soldering work.

The gain may be very easy to tweak: many commercial mixers have small jumper switches inside that let you chose different levels of input sensitivity. Check the manual/online to see if yours does too. You can probably also further beef up the gain by tweaking the pre-amp sections. But if you are thinking about taking the PSU out to "improve on noise", are you sure this is something you want to do?

Having owned cheap and mid-range mixers, my advice to you would be to not bother with any of this, if it is better sound you want to achieve. If you want to improve quality at the expense of functionality, there are a few commercial and DIY options around that are great and well within your mixer's price range. If you need all the fancy on-board FX, EQ-kills, cross-over curves and BPM counters, stick with the stock Behringer until you can afford something better and then upgrade and sell it on to partly fund the new purchase.

If on the other hand you want to do this for fun and education, I suggest you get a simpler mixer as a "barebones" base and start playing with that.

Good luck.
Nikos