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?

 

[Brian Roth]

@Brian Roth would an old ScampRack format work perhaps?

IIRC, those were built around some existing European rack format. The module spacing was very slender. I don't know if that format rack is still sold, or would be correct for this project.

I know (knew?) those racks well! In the early 1980's I worked for the ad agency which handled Audio+Design's USA marketing. We did some "trade out" for gear I installed at our studio. Below is a scan of an ad we placed in the trades (RE/P, etc,). I was the copywriter for their ads. Also a couple of pix of a later version of one of our outboard racks just before the entire analog system was yanked out to be replaced by an Avid ProTools setup. You can see we had a lot of Audio+Design gear in that particular rack!

Bri

 

[ruffrecords]

[here is the fpd file] -- THANKS!!! I'll check it out.

[with the extension changed to txt] -- There's actually -- another way -- to rename a file for attachment to this forum!!! YA-A-AY!!! And, it actually has a very slight advantage over the conventional manner that is being used on here.

Instead of -- changing -- the filename extension to something else.....you just -- add it onto -- the existing filename extension, like this (as an example):

>> BasePanel7U40mm.fpd ..... becomes: BasePanel7U40mm.fpd.pdf

The "advantage" of renaming a file this way, is that whomever is downloading this file can easily still see what the original extension is. To rename an attached file done like this, all ya gotta do is delete the second extension, hit "Enter" and yer GOOD-TO-GO!!!

TRY IT!!!

Excellent idea with built in error checking! I will use it from now on.

>> By the way.....is it possible for you to attach/send along a -- STP -- file of your front-panel? And, maybe you could try the renaming trick above as well!!!

/

Unfortunately not. It was designed in fpd

Cheers

Ian

 

[ruffrecords]

[Anyway, here is the fpd file] -- OK!!!.....So, I downloaded your -- .txt -- file, renamed it to -- .fpd -- and it loaded right into FPD!!! LOOKS GOOD!!! (Sort of!!!) Then, now that I had your file into FPD as it is supposed to be, I went ahead and exported it as an -- STP -- file and then imported that into my SolidWorks program. Surprisingly, the end result was only "kind of" OK and I was quite surprised!!!

I did not know you can do that in fpd. I will have to try that. Could e ideal for 3D printing

Interestingly, your graphical "zeros" (i.e., -20, -10, etc.) somehow ended up becoming a "cut extrude" feature in SolidWorks. It also then made me think if the same type of thing might/would happen when this file is being 3D-printed. Here is how the STP version of your FPD file imported into SolidWorks:

Conversion from one program's format to another is always fraught with difficulties. Just look at word processors and there definitely seem to e some oddities with exporting from fpd.

>> The "0" in your graphics became an
oblong slot in the sheet-metal:

Strange

[the outline is definitely rectangular] -- YES, INDEED.....THEY ARE!!! (Sort of). Your front-panel had very crisp 90-degree edge-angles in FPD, but they all had a radius in SolidWorks:

I hate it when a program takes it upon itself to alter my design, especially if done without explanation.

Cheers

Ian

 

[ruffrecords]

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

Unfortunately 7U frames are not standard frame sizes. 6U and 9U are. But it does not matter. All we really need are the extrusions. The sides we can make ourselves either out of wood or sheet metal

On your side of the pond Schroff would be my go to supplier for DIN standard Eurorack parts.

Cheers

Ian

 

[Brian Roth]

Unfortunately 7U frames are not standard frame sizes. 6U and 9U are. But it does not matter. All we really need are the extrusions. The sides we can make ourselves either out of wood or sheet metal

On your side of the pond Schroff would be my go to supplier for DIN standard Eurorack parts.

Cheers

Ian

Thanks Ian. I now have a starting point to educate myself. A project for later in the day after I grab some sleep. I am still snowbound in my little house, so plenty of time on my hands!

Is there an easily available and comprehensive document for the DIN Eurorack standard?

Thanks again!

Bri