Compact desktop line mixer?

[Brian Roth]

90% of my gear is DIY. If there’s an affordable commercially-available product, I wouldn’t say no to it though.

But if DIY, then the trick is to determine the best path forward. I could definitely repurpose an existing mixer of some kind, but then I’d have to match the control set (or at least, the holes and labels) that already exist. Building fully from-scratch could be fun from a circuit-design perspective, but I hate metalwork.

Re. hating metalwork. Perhaps because I began DIY in Jr. High Screwel I'm not that adverse to it. Simple projects in the electronic magazines required some sort of enclosure. So, I worked in my parents garage with an electric Craftsman drill and some bits, butchering <g> Bud aluminum project boxes sold at the local supply houses, or from mail order. I also learned to prefer the "bakelite" boxes....lol.

I even sold Roth Fuzz stompboxes to guitarist friends in High Screwel, I learned how to silk screen the panel legends. A huge hit in the marketplace....perhaps six sold. <G!>

Anyway, it's not that difficult if working with flat aluminum panels (like rack). A drill press helps a lot, along with Greenlee punches for larger holes (like XLR) . I select components that mount in round holes. For odd things like fader slots, large rectangles, I outsourced that to a shop which has a vertical milling machine. Nowadays, FPE looks good for anything requiring non-round holes.

Bri

 

[kags]

Thanks, Ian....that clears up a lot for me. Doing web searches for "7RU Eurorack" only came up with the synth versions...two rows of 3u and one row of 1RU with multiple mounting rails going from left to right. That design "breaks up" the possibility of a single 7U module. The one you linked in post #36 has that configuration.

Now I can focus on DIN-standard Euroracks <g>. How much does an empty 7RU frame typically cost? Here in the Colonies <g>, I am unfamiliar with the format or who sells the frames. More searching coming up.....

Best,

Bri

https://www.perfectcircuit.com/tipt...5&indexName=magento2_live245_default_products

Only 6u, but just a quick search result

 

[Brian Roth]

Further Brain Pharting....

Ian's approach is excellent. He has obviously put a bunch of thought into it. As I mentioned somewhere in this thread, I am a modular Fan Boy!

I've been thinking about a hillbilly design. Mechanical basis is a stock rack box from places like Par Metal, Collective Cases, etc. Examples:

http://www.par-metal.com/product-rmc-12series.php

https://collectivecases.com/?product=3ru-basic-cases

The height of the box depends on what the builder desires. Need only rotary level pots and pans? Select a 2RU box and drill the chassis yourself. Need 100mm slidewire faders, aux sends, etc....select a taller chassis and have FPE make the front plate.

Or build it in an army surplus ammo box!!! lol

Want to use "a dollar a dozen" pots from Alibooboo....great. Want to pay the price and use Alps Blue Velvet or stepped attenuators? Fine...space out the front panel as needed. Slidewire level pot...great....just a taller front panel.

Inside the box I see smallish PC boards that each handle four(?) inputs. Each card has the input stage for balanced or unbalanced sources, fader buffer, bus lines and whatever else. The cards daisy chain the buses from left to right. The cards connect to the front panel controls and rear panel I/O with readily available wire assemblies like this EXAMPLE:

https://www.mouser.com/ProductDetail/Molex/217797-1031?qs=QNEnbhJQKvayQViE7n1aoA==#mz-expanded-view-489214318323

Those come in a large variety of pin counts, connector types, and lengths. On each of the channel cards, mating connectors on the PCB tie into the wire assemblies to/from the panel devices. Thus, you can wire the front and back panels separately, then stab the connectors onto the PCB.

I kinda settled on 4 channels per PCB. Allows a lot a variables. Need only 8 channels? 2 PCBs. Need 24 channels? 6 PCBs. etc etc

Each PCB would have all the "stuff" for the maximum possibility of control configurations (with likely some on-panel jumpers for the controls/switches). Short load the PCB if a feature(s) isn't required,

Proposed "maximum loaded" front panel controls:

1. Level trim
2, Level control (slidewire or rotary)
3. Pan
4. Two aux sends...(pre post switches or PCB jumpers??)
5. Mute
6. Stereo solo
Maybe solo in place? Would be combined with mute.

Finally, a master card would do summing, etc.

Folks....just a half-baked idea from an Olde Hippie solder-slinger!

Bri

 

[Brian Roth]

https://www.perfectcircuit.com/tipt...5&indexName=magento2_live245_default_products

Only 6u, but just a quick search result

Nope, not a DIN Eurorack as Ian discussed in post #37, but rather a synth Eurorack. That had me totally confused for a bit.

Bri

 

[kags]

Nope, not a DIN Eurorack as Ian discussed in post #37, but rather a synth Eurorack. That had me totally confused for a bit.

Bri

Gotcha - I think the same store has the DIN versions, too. I believe even SSLs use 3U euro racks for the cards inside the center section

 

[Brian Roth]

Gotcha - I think the same store has the DIN versions, too. I believe even SSLs use 3U euro racks for the cards inside the center section

From what I've deduced, the DIN Euroracks are sold through totally different sales channels (industrial) than the "Doepfer" synth versions.

It's been nearly 10 years since I was in the center of a SSL and pulled up that 200000 pound <g> center section and prayed the glides and latches functioned! Seriously, I had gotten to the point of it being a 2 man project. But, I never thought much about the internal rack design.

Bri

 

[kags]

My SSL 651 sections don’t have latches - much more strategy involved!

 

[ale47p]

for those who have CAD compatibility problems I suggest to check them with FreeCAD to see what's really in those files.
you don't need to learn it, just import the files and see how they are!

 

[13engrsapper]

@Brian Roth would an old ScampRack format work perhaps?