RLA-inspired 3-band DJ crossover

[efinque]

Sup GDIY,

here's a build that's close to being finished, so far it's missing labeling. Afaik the original RLA units had RCA in/out, 24db/oct filters and a fullrange mid band. They were operated from the DJ booth. My take on this has 6,3mm jacks and 6db/oct filters.

The crossover points are 400Hz LF and 800Hz HF.

The preamp section is built from kits, I've yet to test them though. I jumped them with alligator clips to check the freq bands; the filters sounded sweet.

I'll try to post a schematic once I get an EDA software.

Any thoughts?

-ef

 

[efinque]

Here's a pic of the front panel labeled.

EDIT : more labeling

 

[PermO]

Cool unit.

How is this in use ?
You have this on the mix output of DJ mixer to cut high or low ?
What does the "full" knob do ?

I'd say you'll need more than one filter

 

[scott2000]

hmm..is it a clone of this? Seems full would be just that....
https://reverb.com/item/33445931-richard-long-and-associates-x3000a-crossover-w-box-and-manual

 

[efinque]

Cool unit.

How is this in use ?
You have this on the mix output of DJ mixer to cut high or low ?
What does the "full" knob do ?

I'd say you'll need more than one filter

Thanks!

Yes it's to control the output to separate amplifiers/speakers in a 3-way system. The full knob adjusts the fullrange band which would be a set of fullrange/mid-high speakers in many cases.

It has a first order LPF in the sub band and HPF on the HF band.. I was thinking of upgrading them to 2nd order.

To scott2000 : yes I was going after the RLA X3000A crossover (I saw one going for ~7,2k EUR, a collectors item these days I guess)

 

[efinque]

Here's the schematic I did on my smartphone :

Fairly simple design, the only hindrance is that when the sub freq is turned down the HF goes up (and vice versa)..

Most modern amplifiers have limiters and overload protection in them anyway.

 

[efinque]

Checked the unit yesterday, the left sub ch didn't work.

Troubleshooted with a DMM, it was a faulty potentiometer.. now, I can't be bothered to order a new pot so I just jumped the left and right jacks with pieces of wire.

I've yet to test the preamps, in one of my builds they worked a charm.

 

[efinque]

I got bored so I did a datasheet with frequency response plots etc :

I just ran white noise through the filters and recorded it in Audacity.

I did another one for a mixer build too :

I'm not much of a graphics designer though but I think they turned out ok.

Great for future use If I get around to making and selling these.

 

[efinque]

Tried my hand at writing a user manual for the xover:

Link to Dropbox

It's missing THD specs though as I have no means of measuring them.

What do you think?

 

[efinque]

Tried measuring THD for the mixer, first I generated 30secs of 1kHz sinewave in Audacity.

Then, using my smartphone, I played the test tone into the mixer and recorded that in Audacity via an USB soundcard.

Here's what I got. As you can see it has those upper harmonics right from the fundamental frequency, in this case the red line (1kHz).

I also recorded a "clean" signal (slightly attenuated, to compensate for the mixer internal resistance) without the mixer (to subtract from the signal with the mixer intact)

First, I calculated the square roots of the upper harmonics in dB, divided them with the fundamental frequency and did the subtraction.

Like (√1dB..+ndB)÷100dB and so on.

I got a THD of roughly <5,16%, is this normal for a passive mixer? I've installed power amplifiers doing <0,1%.

This is how I was planning to measure the xover in the future (and to revise the manual), which is why I'm asking.

 

[MidnightArrakis]

Sup GDIY,

here's a build that's close to being finished, so far it's missing labeling. Afaik the original RLA units had RCA in/out, 24db/oct filters and a full-range mid band.

I'll try to post a schematic once I get an EDA software.

Any thoughts?

>> That's a lot of empty enclosure space for a product that has next to no circuitry within it!!! You could probably fit at least 16-channels of your circuit in the amount of space your current rack-mount chassis has!!!

Should you send me your schematics of your circuitry, I could design the entire thing on a single PCB, including the front-panel controls, you there would essentially be -- NO WIRING -- involved whatsoever!!! That's the type of product designs that I am involved with doing. Not only THAT!!!, but.....I could also design for you a 1U rack-chassis that would only be as large as necessary to fit your circuitry, front-panel controls and rear-panel connectors all in one set of a nifty all-inclusive PCB within a 1U rack-chassis!!! Whaddya think???

Here are some somewhat similar examples that I have personally designed:














>> Manufactured $20,000 finished product of the above 12U Rack-Mount Card-Cage Chassis design:


Now.....I completely and fully understand that my mechanical and PCB-design expertise -- MAY NOT -- meet your exacting and specific high-level of design engineering skills that your proposed new product may require, but.....I would still like to have a chance to give it a shot!!! If you believe that I am not skilled enough, just let me know, OK??? THANKS!!!

/

 

[efinque]

>> That's a lot of empty enclosure space for a product that has next to no circuitry within it!!! You could probably fit at least 16-channels of your circuit in the amount of space your current rack-mount chassis has!!!

Should you send me your schematics of your circuitry, I could design the entire thing on a single PCB, including the front-panel controls, you there would essentially be -- NO WIRING -- involved whatsoever!!! That's the type of product designs that I am involved with doing. Not only THAT!!!, but.....I could also design for you a 1U rack-chassis that would only be as large as necessary to fit your circuitry, front-panel controls and rear-panel connectors all in one set of a nifty all-inclusive PCB within a 1U rack-chassis!!! Whaddya think???

Here are some somewhat similar examples that I have personally designed:

View attachment 125373
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View attachment 125382
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>> Manufactured $20,000 finished product of the above 12U Rack-Mount Card-Cage Chassis design:
View attachment 125389

Now.....I completely and fully understand that my mechanical and PCB-design expertise -- MAY NOT -- meet your exacting and specific high-level of design engineering skills that your proposed new product may require, but.....I would still like to have a chance to give it a shot!!! If you believe that I am not skilled enough, just let me know, OK??? THANKS!!!

/

Thanks for chiming in, your 3D models look amazing! Are they CAD drawn by any chance? Can you add dimensions in them?

I'd love to have a 3D CAD model in one of my manuals some day.

Unfortunately I'm don't have much money to invest in manufacturing and I'll keep this thing "boutique", as in handcrafting every unit myself for now.

I did think of simplifying the unit so that the filters would be placed on PCBs for easy recapping.

The space issue is one thing I've been mentioned on djforums, it's a shame but at least it's rack-compatible design.

 

[PermO]

To improve the looks of your mixer... instead of a sharpie.

Design your layout in software (I use Paint.net for that, it's free and has cool fonts) and simply print it on adhesive paper and stick it on.

I go to a print shop for that as I don't have a fancy printer like they do, bring my design on USB stick and pay 2 euro and I have a sticker.

 

[efinque]

To improve the looks of your mixer... instead of a sharpie.

Design your layout in software (I use Paint.net for that, it's free and has cool fonts) and simply print it on adhesive paper and stick it on.

I go to a print shop for that as I don't have a fancy printer like they do, bring my design on USB stick and pay 2 euro and I have a sticker.

Yeah, or use a Dymo like I did in the crossover build.

I did see printable decals for sale too.. I think they're similar to scale model decals.

 

[MidnightArrakis]

Thanks for chiming in, your 3D models look amazing! Are they CAD drawn by any chance? Can you add dimensions in them?

I'd love to have a 3D CAD model in one of my manuals some day.

Unfortunately I'm don't have much money to invest in manufacturing and I'll keep this thing "boutique", as in handcrafting every unit myself for now.

I did think of simplifying the unit so that the filters would be placed on PCBs for easy recapping.

The space issue is one thing I've been mentioned on djforums, it's a shame but at least it's rack-compatible design.

[your 3D models look amazing!] -- THANK YOU!!! I sincerely appreciate the comment.

[Are they CAD drawn by any chance?] -- All of my above images are "CAD-drawn", except of course, the equipment shown in the photographs!!! I used the "SolidWorks Premium" 3D Mechanical Design CAD-Modeling program to design all of the chassis shown up above.

[Can you add dimensions in them?] -- Yes, and.....I have already created complete "Mechanical Detail Fabrication Drawings" for all of the above chassis and PCB-designs.







[I'd love to have a 3D CAD model in one of my manuals some day] -- It can be done!!! You will see!!!

[handcrafting every unit myself for now] -- Yeah, but.....but.....but.....there's all of that unnecessary and labor-intensive manual hard-wiring that could be -- COMPLETELY ELIMINATED -- by just >> KNOWING -- HOW -- TO DESIGN YOUR PRODUCT << to begin with!!! How much "wiring" do you see in the above chassis designs and just look at how much circuitry and connectors there are!!! HUH???

[I did think of simplifying the unit so that the filters would be placed on PCBs for easy recapping] -- Even by keeping the same 1U rack-chassis that you are currently using, your circuitry can -- STILL -- be put onto a PCB, including the front-panel controls, audio connectors and (I'm assuming) a DC-input connector. Start off doing this.....

1) Provide me with the Manufacturer's Name and chassis Part Number. I can look things up with that information from there.

2) Send me a clear and "sensible" schematic of whatever it is that your circuitry consists of. It can even be drawn on a napkin.....>> IF IT IS LEGIBLE AND EASILY READ!!! << You can PM me to send everything.

3) A -- BOM / Parts List -- consisting of the capacitors, resistors, inductors, etc. that you use to construct your circuit. This will include each different components' "Manufacturer" and "Manufacturer Part Number". This information is needed in order to correctly specify each part to a specific and correct PCB footprint.

How everything can play out "could" be like this:

Get your circuitry transferred over to a PCB, even if the PCB is on the "large" size. Your assembly effort and time will be significantly reduced because all that you will be doing is placing the parts onto a PCB and soldering them. THERE WILL BE NO MORE WIRING!!!

Because you are now able to more quickly create your new product, you can easily make a bunch and have them all available for sale. As you sell your new product, you take a certain amount of money from each sale and set it aside into a "Savings Account" and let it build up. Once you have a fair amount of money saved up in your account, then you will be able to afford to have a much smaller 1U rack-chassis and PCB-design created. Once you have a whole new chassis designed and ready-for-market, you will be able to announce a >> NEW & IMPROVED << chassis for sale and your fans from all over the "DJ World" will be beating down your door to buy your newest product offering.

THAT'S CAPITALISM FOR YA!!!

/

 

[efinque]

[your 3D models look amazing!] -- THANK YOU!!! I sincerely appreciate the comment.
[Are they CAD drawn by any chance?] -- All of my above images are "CAD-drawn", except of course, the equipment shown in the photographs!!! I used the "SolidWorks Premium" 3D Mechanical Design CAD-Modeling program to design all of the chassis shown up above.
[Can you add dimensions in them?] -- Yes, and.....I have already created complete "Mechanical Detail Fabrication Drawings" for all of the above chassis and PCB-designs.
View attachment 125415
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View attachment 125422

[I'd love to have a 3D CAD model in one of my manuals some day] -- It can be done!!! You will see!!!

[handcrafting every unit myself for now] -- Yeah, but.....but.....but.....there's all of that unnecessary and labor-intensive manual hard-wiring that could be -- COMPLETELY ELIMINATED -- by just >> KNOWING -- HOW -- TO DESIGN YOUR PRODUCT << to begin with!!! How much "wiring" do you see in the above chassis designs and just look at how much circuitry and connectors there are!!! HUH???

[I did think of simplifying the unit so that the filters would be placed on PCBs for easy recapping] -- Even by keeping the same 1U rack-chassis that you are currently using, your circuitry can -- STILL -- be put onto a PCB, including the front-panel controls, audio connectors and (I'm assuming) a DC-input connector. Start off doing this.....

1) Provide me with the Manufacturer's Name and chassis Part Number. I can look things up with that information from there.

2) Send me a clear and "sensible" schematic of whatever it is that your circuitry consists of. It can even be drawn on a napkin.....>> IF IT IS LEGIBLE AND EASILY READ!!! << You can PM me to send everything.

3) A -- BOM / Parts List -- consisting of the capacitors, resistors, inductors, etc. that you use to construct your circuit. This will include each different components' "Manufacturer" and "Manufacturer Part Number". This information is needed in order to correctly specify each part to a specific and correct PCB footprint.

How everything can play out "could" be like this:

Get your circuitry transferred over to a PCB, even if the PCB is on the "large" size. Your assembly effort and time will be significantly reduced because all that you will be doing is placing the parts onto a PCB and soldering them. THERE WILL BE NO MORE WIRING!!!

Because you are now able to more quickly create your new product, you can easily make a bunch and have them all available for sale. As you sell your new product, you take a certain amount of money from each sale and set it aside into a "Savings Account" and let it build up. Once you have a fair amount of money saved up in your account, then you will be able to afford to have a much smaller 1U rack-chassis and PCB-design created. Once you have a whole new chassis designed and ready-for-market, you will be able to announce a >> NEW & IMPROVED << chassis for sale and your fans from all over the "DJ World" will be beating down your door to buy your newest product offering.

THAT'S CAPITALISM FOR YA!!!

/

Unfortunately the xover uses kits which are for educational and experimental use only so I'd have to start off by breadboarding components into preamps and doing my own PCBs.

The rest is off the shelf, mainly from one supplier.

 

[MidnightArrakis]

Unfortunately the xover uses kits which are for educational and experimental use only so I'd have to start off by breadboarding components into preamps and doing my own PCBs.

The rest is off the shelf, mainly from one supplier.

[the xover uses kits] -- Then, "Reverse-Engineer" them and change/modify/update as is necessary just to make them "different" enough from the originals. Once you have your own schematics, you should be "Good To Go"!!!.....

/

 

[efinque]

[the xover uses kits] -- Then, "Reverse-Engineer" them and change/modify/update as is necessary just to make them "different" enough from the originals. Once you have your own schematics, you should be "Good To Go"!!!.....

/

I tried breadboarding a transistor preamplifier today with no luck.. (edit : or I did hear a small crackle when connecting the sound source into the transistor input)

I need some opamps I guess. Opamp datasheets usually come with instructions on how to turn them into functional circuits.

EDIT : I did try switching the transistor with a 3V CR battery.. it worked but unfortunately it doesn't pass audio.

 

[efinque]

Aight I breadboarded my own preamp. It's rather simple and distorted though but I bought some opamps too for experimenting.

Link to thread

I also ordered a spare pot for this xover build (the LF which had a NC taper), it should be here next week. I'll keep you guys updated.