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Old 10th April 2013, 11:29 PM   #1
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Default Building a DJ mixer

Hello everyone,

I wasn't exactly sure which section to post this in, so I hope moderators can move it if it's in the wrong place.

I'm looking to start the planning to build a simple DJ mixer. I know that DJ mixers can be had for quite reasonable prices these days, but I figure if I'm going to be paying upwards of $1k for a mixer, I might as well build one myself and use good components, and strip it of some of the extra features I wouldn't need myself.

I have a pretty basic understanding of electronics; I've built a few amplifiers (Tube, solid state) as well as many guitar effects and other gadgets before, thus I don't think it's too ambitious of a project.

It would essentially be a two channel mixer with a crossfader to fade between the two turntable inputs, maybe an AUX input and a microphone input.

It would be RCA inputs into a phono preamp (also want to make this switchable between line in and phono in)-->EQ section-->crossfader-->master outputs

Do y'all have any links to good examples or schematics of those different blocks? e.g. phono preamp schematic, great EQ schematics.

I've got all the schematics from Rane and am trying to piece this together bit by bit and plan the design of this. Any help would be greatly appreciated.
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Old 10th April 2013, 11:38 PM   #2
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Save the trouble and buy one.
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Old 11th April 2013, 01:35 AM   #3
Zero D is online now Zero D  United Kingdom
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Hi, it all depends on what you want/need to include.

If you just require what you stated, then it won't be too complicated

If you require any or all of the following, then it'll get progressively more indepth etc.

Tone controls

Headphone

Metering

I applaud your desire to do it, so i'll help you. Let me know EXACTLY what you want.
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Old 11th April 2013, 02:25 AM   #4
Enzo is offline Enzo  United States
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REally. A simple DJ mixer like that won't cost you anywhere near $1000.

Here is one for under $100, meets your specs too.
Numark M2 DJ Mixer | Musician's Friend

SOmething to consider too if you are actually DJ-ing. More and more offer USB ports. My DJs now carry their music in a computer. A port connects the mixer to the computer. Also some guys keep tunes in an iPod, and they make basicx DJ mixers with iPod jacks too.
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Old 15th April 2013, 08:09 PM   #5
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Let me reiterate that I'm not looking for suggestions on buying a mixer. I understand there are plenty of mixers out there that have 99% of what I stated I'm looking for, but I'm looking to build one. "Save the trouble..." No, it's absolutely no trouble at all for me, actually.

What I want is to build a relatively simple DJ mixer with high quality components because I am a big audio geek (I'm sure most of us on this forum probably are anyways, so I hope I'm amongst friends).

@Enzo, there are audio interfaces that can serve that function, so it's all good on that aspect. Thanks for bringing it up though.

@Zero D: I'm looking to build a two channel mixer. Each channel will have a phono input and if possible, a line in (switchable). Each channel will have 3 band EQ, with EQ kill per band, and a gain control (pre EQ). One volume control per channel (post EQ). Crossfader between the two channels (it would be cool to learn how to implement other stuff to the crossfader like reverse crossfader or crossfader curvers, but I suppose that can come after). Ability to cue each channel (e.g. have a cue switch that will send the signal to the headphone when engaged, regardles of what the volume fader is set at for the channel).

Two sets of stereo outputs, one for monitors, one as master output. Balanced, if possible. Headphone output that can switch between what's being cue'd and the master mix.

Sound simple enough? I think it would be, it's just a matter of putting together the blocks for each section.

Any help would be greatly appreciated. I think it's definitely doable.
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Old 15th April 2013, 09:59 PM   #6
Zero D is online now Zero D  United Kingdom
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Lightbulb Doable

Hi, OK now i know what you require. Also i'm pleased to hear you will be using Vinyl too

I would suggest having a GOOD look at the various projects in here ESP Projects Pages - DIY Audio and Electronics

Decide which you think is right for you, & then post back with the Project Numbers so i can check them. If you're not sure which you think are best etc, just say so & i'll offer my suggestions & guidance

I built a Crossfader to add on to a mixer years ago, so that's not a problem for me to design in.

Are you going to design the PCB's for All/Any of these, and/or make the PCB's, or get them made ?

Or build on for eg Veroboard ?

Or hoping to buy kits of each block, or just the PCB's for them & use better components, & possibly upgrade the circuits ?

And of course you will need to Neatly drill out a suitable case for all the controls etc, & legend with something. Unless you are going to have the case professionaly made to your requirements ?

You didn't mention anything about metering, either PreFade or PostFade and/or output ? If so, i expect you want an LED type ?

Do you want an internal Power Supply, or external ?

Sure it's going to be a LOT of time/work, for everyone involved, but i presume you already understand/appreciate that.

Years ago i built a 4 channel stereo mixer with Bass/Treble on each input. 2 x Phono 1 x Jingle Machine 1 x Mic. Headphone monitoring on each channel. LED Metering. That was using a mix of transistors & IC's ! and it worked/sounded fine. These days i would use all quality IC's
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Old 15th April 2013, 10:10 PM   #7
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I got a Behringer 4 channel mixer second hand (ex-BBC) off ebay for 20.

It works fine with no scratchy pots.

They are only 40 ish new.

I have built my own too, I made a ECC82 valve mixer with 2 stereo channels and a couple of mic inputs.

You don't need numerous channels just 2 stereo channels for cd/vinyl and a mic channel.
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Old 15th April 2013, 10:21 PM   #8
JZatopa is offline JZatopa  United States
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I used to DJ and considered building my own rotory mixer a while ago. The reason i wanted to build one was because nobody was building a really high end mixer. There are many ways to approach this. I would recommend you start looking for DIY projects that fit what you need and piecing it together. When I was considering this I wanted to use aleph ono preamps for the turntable input and possible an aleph 1.7 for the preamp. Personally I was going to use rotory faders as I liked long smooth transitions in my mixes. I was going to skip the EQ as I was looking for the best SQ possible, you could always add an effects loop with an external EQ later.

I would like to point out you could make a regular mixer and use outboard phono preamps. Might make your lifer simpler.

After thinking about it for a long time I decided to mod the mixer I had to a rotary and call it a day. I don't DJ anymore professionally but I do play around with traktor and a vci-100.
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Old 15th April 2013, 10:26 PM   #9
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Quote:
Originally Posted by DJNUBZ View Post
I used to DJ and considered building my own rotory mixer a while ago.
I much prefer rotary pots.
I found the linear pots would collect dust and become scratchy quite quickly.
The rotary pots are enclosed and so dont catch as much dust.

On my Maplin disco I put the phono pre amp in the record decks, I needed power for the record decks so another mains connection for the pre amp was no problem.

I would be wary of using long leads from a phono pick up.
It really needs to be as short as possible to avoid picking up noise.

The Behringer mixer I mentioned really is top quality, they are broadcast quality.


BEHRINGER XENYX 502 ex- BBC 5 channel AUDIO MIXER + power supply.
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Old 16th April 2013, 01:46 PM   #10
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Behringer and Numark don't give away schematics, and the market here is flooded with them that have bad pots. Having seen pictures, Numark has flat cable and surface mount parts inside, which is not suitable for modification IMHO.
I'd say look around for a Peavey disco mixer (has RIAA) or the jewel I found for $15 the Herald Electronics RA-88. The latter has hissy 4558 op amps and a stupid hummy power supply and power switch right next to the op amps (stupid), but the faceplate is beautiful stainless steel, the pots are outstanding, and the IC's are dip package so you can put in sockets and change them. (it needs bypass caps, too, I drilled holes in the pwb) The RA-88 is in a steel box too, so if you move to a wall transformer and delete the power switch you can get the hum out. I put toroid chokes on the power supply and caps to ground on the inputs, so the steel box excludes the noisy ******le CBer that beeps out Dixie as he drives by and lamp dimmer hash too. You could gut the whole PWB and just use the box, pots and faceplate for $15 and still be way ahead.
The disco version Peavey is rare but the common Unity mixer I have from them (no riaa) uses NJM4560's which are much less noisy than NJR4558 IMHO. Lots of rotary pots on a Unity line mixer. If you can't find a Herald or a Peavy disco mixer, you could take a Peavey Unity and change the gain on a couple of channels and insert some RIAA rolloff parts. Lot more fun than drilling D shaped holes in a faceplate.
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Last edited by indianajo; 16th April 2013 at 01:54 PM.
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