Compact desktop line mixer?

[OneRoomStudio]

While the feature set is being tweaked, I decided to look around at fader options. Of course I thought of P&G, but they are no longer being made and would be a budget-buster.

Next I thought of TKD. I've seen them on various consoles, like the Neotek Elan at a studio here in town. They've always seemed quite reliable and "feel good".

https://www.tkd-corp.com/en/product.html#manualfader

I did a little bit of searching and found this:

https://wheatstone-store.ecwid.com/TKD-CPA-9101-UNC-Fader-p195011493

Yippee! 421 in stock for $30.00 each. Uh-oh! Linear taper.

TKD does not appear to have have stocking distributors so I guess they would be factory ordered with a minimum quantity.

I decided to look around at Mouser. Only filter was 100mm and audio taper. So it will include special order.

https://www.mouser.com/c/passive-components/potentiometers-trimmers-rheostats/slide-potentiometers/?taper=Audio&travel=100 mm

Not a lot of choices. I seem to recall these nice ones:

https://www.mouser.com/ProductDetail/Alps-Alpine/RSA0K12A1013?qs=YMSFtX0bdJDDCro05rKppg==

...but that one is stereo. I attached an Alps catalog sheet and plan on "assembling" part numbers with a reasonable selection of Ohms value options and do web searching.

The remainder are PCB mounts from BI (conductive plastic tracks ) and Bourns (carbon). Mouser seems to have the BI faders in both mono and stereo. I will assemble parts numbers for alternate resistance values and do web searching.

Digikey doesn't list tapers (!!) on their selection page nor on a few random part numbers I opened to read specs.

I need to do a deeper dive into Alps choices.

I am not a fan of the little cheap sliders. They usually feel wobbly and rough and seem to break easily. But, next Mouser order I place I may add a fader or two just to see.

As I mentioned, the PC mount choices will require a PCB behind the front panel. My instinct is to have a "strip" board for each fader vs one giant card.

IMHO the mono and stereo faders should be from the same manufacturer and "series". That way the handle height (and fitted knob) are the same, and they will all "feel" the same.

Enough searching for me tonight....the floor is open for discussion!

Bri

PS, I looked at Alibaba...lots of "Ten for a Dollar" type crap. <g>

I believe a lot of modern compact mixers are using the Alps board-mount faders (i.e., this mono model, and this stereo model). The price is certainly right, and the form factor would make a single PCB/single panel for the faders easy and economical. @MidnightArrakis - I think ribbon cables from the “fader PCB” to the channel PCBs would be the simplest method.

Caveat - I have not had these faders “in hand,” so I can’t speak to the feel/quality.

 

[MidnightArrakis]

I believe a lot of modern compact mixers are using the Alps board-mount faders (i.e., this mono model, and this stereo model). The price is certainly right, and the form factor would make a single PCB/single panel for the faders easy and economical. @MidnightArrakis - I think ribbon cables from the “fader PCB” to the channel PCBs would be the simplest method.

Caveat - I have not had these faders “in hand,” so I can’t speak to the feel/quality.

[ribbon cables from the “fader PCB” to the channel PCBs would be the simplest method] -- While they may be the "simplest" to implement, they also constitute an additional cost. Everything has a trade-off, one way or another.

/

 

[OneRoomStudio]

[ribbon cables from the “fader PCB” to the channel PCBs would be the simplest method] -- While they may be the "simplest" to implement, they also constitute an additional cost. Everything has a trade-off, one way or another.

/

True. Ribbons aren't strictly necessary though. A simple 3-pin header per channel would do the trick and would only be tens of dollars over all.

I succumbed to @Brian Roth's thinking and added a stereo Tape Ret input (and fixed the post-fader sends so they're post mute/solo). I also made it so you could send the Tape Ret to the mix bus, which would enable someone like me (who doesn't need to monitor post tape) to use them as an additional stereo input on mix-down. In fact, if you're not using the aux sends, you'd now have a 15x2 mixer in a pretty compact format! The way I would use it (only using one mono and one stereo return for FX), I'd have 12 inputs for mix down (but only 8 with faders). Pretty handy!

 

[MidnightArrakis]

True. Ribbons are strictly necessary though. A simple 3-pin header per channel would do the trick and would only be tens of dollars over all.

I succumbed to @Brian Roth's thinking and added a stereo Tape Ret input (and fixed the post-fader sends so they're post mute/solo). I also made it so you could send the Tape Ret to the mix bus, which would enable someone like me (who doesn't need to monitor post tape) to use them as an additional stereo input on mix-down. In fact, if you're not using the aux sends, you'd now have a 15x2 mixer in a pretty compact format! The way I would use it (only using one mono and one stereo return for FX), I'd have 12 inputs for mix down (but only 8 with faders). Pretty handy!
View attachment 143964

>> Has a "mechanical form factor" been determined for this "GroupDIY" mixer yet? If so, what are the dimensions and the overall profile and shape of this thing? Can you enlighten me? THANKS!!!

Anything like this??? (Minus the VU-meters):



/

 

[ruffrecords]

Hi Ian. How did we end up with 13 faders? All the block diagrams posted by @OneRoomStudio have 8 mono faders for the inputs and 1 stereo fader for the master 2-mix bus. IIRC, that is one more than the SSL x-desk.

I'm obviously missing something! But the "one panel for faders" makes a lot of sense.

Bri

To be honest I did not bother to count how many faders we need. If the channel module were 8HP wide then you would get 10 in a standard 84HP width with half a module width gap at the end. I have seen designs where this space is used for PSU indicators for instance but not getting an exact number of modules in a standard space annoys my sense of order and neatness. In my own mark 2 tube mixer design the modules are just 7HP wide so in 84HP you get exactly 12 modules.

I don't think we have decided on the channel width yet but I ASSumed we wou;d probably use the synth boys 8HP standard width. They often use 104HP extrusions which gives exactly 13 modules of 8HP so that it what I went with.

Bottom line I was only trying to illustrate the advantage of combining several faders on one panel. We could probably have one panel for the 8 channel faders and another for the stereo master and some misc stuff which is what I did in my last mixer build:

https://lh6.googleusercontent.com/u...pBWp3CzQDiq0n8D-7cdjPpQ8uFvi7KEBTGfUPJg=w1280

Cheers

Ian

 

[ruffrecords]

>> Has a "mechanical form factor" been determined for this "GroupDIY" mixer yet? If so, what are the dimensions and the overall profile and shape of this thing? Can you enlighten me? THANKS!!!

I think it is still up in the air.

Cheers

Ian

 

[OneRoomStudio]

Bottom line I was only trying to illustrate the advantage of combining several faders on one panel. We could probably have one panel for the 8 channel faders and another for the stereo master and some misc stuff which is what I did in my last mixer build:

That's exactly what I was thinking. Plus, if it was a single panel for 8 faders, with a separate (smaller) panel for the master fader (and maybe monitor/headphone controls), it would be easy for folks to use the same metalwork/pcbs to to build 8/16/24 channel versions if they wanted to.

The most economical way to build this would be one panel for 8 channel faders, one panel for 8 channel controls (a pcb-per-channel behind the panel would ensure ease of maintenance, but one big panel is a lot cheaper than 8 smaller panels), one panel for the "master section" (i.e., Aux masters, FX returns, master fader insert, etc), and one panel for the master fader and other controls. The monitor and headphone controls could either go on the master control panel or the master fader panel.

That would only require 4 panels for an 8-channel board (or 5, if there's a panel for meters).

Edit - I suppose there would have to be a rear panel too for the connections.

As for pcbs, you could do one 8-channel fader board, 8 individual channel boards, one board for the aux sends/fx returns, one board for the master section (summing amps, master inserts, etc), and one board for the monitor selections/headphone controls. Those last two or three could potentially be combined. Maybe one more for the meters if we keep those.

Sort of a "semi-modular" approach, to keep costs under control, but allow for easy of building/maintaining.

 

[Brian Roth]

Bottom line I was only trying to illustrate the advantage of combining several faders on one panel. We could probably have one panel for the 8 channel faders and another for the stereo master and some misc stuff which is what I did in my last mixer build:

https://lh6.googleusercontent.com/u...pBWp3CzQDiq0n8D-7cdjPpQ8uFvi7KEBTGfUPJg=w1280

Cheers

Ian

I received this:
-------------------------------------
403. That’s an error.

Your client does not have permission to get URL /uzPSwAXIba95FV1F5MclROPMDZ2X-9DYeXClokmkMaoqSMKwa76Va3nWqPcUYwNNU0fOJwWVhaSggkzBM2_wT8TD8hipBWp3CzQDiq0n8D-7cdjPpQ8uFvi7KEBTGfUPJg=w1280 from this server. (Client IP address blah-blah-blah says Brian...lol)

Forbidden That’s all we know.
---------------------------------------------

Bri

 

[Brian Roth]

I believe a lot of modern compact mixers are using the Alps board-mount faders (i.e., this mono model, and this stereo model). The price is certainly right, and the form factor would make a single PCB/single panel for the faders easy and economical. @MidnightArrakis - I think ribbon cables from the “fader PCB” to the channel PCBs would be the simplest method.

Caveat - I have not had these faders “in hand,” so I can’t speak to the feel/quality.

Odd....the Mouser lookup I did in post 179 only revealed a linear taper Alps choice (besides that nice big fancy one).

Bri

 

[ruffrecords]

That's exactly what I was thinking. Plus, if it was a single panel for 8 faders, with a separate (smaller) panel for the master fader (and maybe monitor/headphone controls), it would be easy for folks to use the same metalwork/pcbs to to build 8/16/24 channel versions if they wanted to.

That is pretty much what I did.

The most economical way to build this would be one panel for 8 channel faders, one panel for 8 channel controls (a pcb-per-channel behind the panel would ensure ease of maintenance, but one big panel is a lot cheaper than 8 smaller panels), one panel for the "master section" (i.e., Aux masters, FX returns, master fader insert, etc), and one panel for the master fader and other controls. The monitor and headphone controls could either go on the master control panel or the master fader panel.

That would only require 4 panels for an 8-channel board (or 5, if there's a panel for meters).

Edit - I suppose there would have to be a rear panel too for the connections.

That sounds reasonably cost effective.

As for pcbs, you could do one 8-channel fader board,

You can probably get away with this because there are relatively few components on the panel so removing the PCB from the panel for servicing should be not too difficult

8 individual channel boards, one board for the aux sends/fx returns, one board for the master section (summing amps, master inserts, etc), and one board for the monitor selections/headphone controls. Those last two or three could potentially be combined. Maybe one more for the meters if we keep those.

Edit: And don't forget the backplane/motherboard that carries the power and buses to/from every channel module and the other PCBs

Sort of a "semi-modular" approach, to keep costs under control, but allow for easy of building/maintaining.

Yes, the complex parts of the circuit with many controls (i.e the channels) you make as modules, the simpler parts can be on PCBs attached to panels. You just need to watch the cabling to and from the boards. The monitor section can all too easily end up having a serious cable harness. In fact it is difficult to overemphasize the importance of minimising cabling as anyone who has built a mixer will tell you

Cheers

Ian

 

[OneRoomStudio]

Edit: And don't forget the backplane/motherboard that carries the power and buses to/from every channel module and the other PCBs

This is an interesting point, and one I hadn't thought of too much. On my old Soundcraft 200B, this was accomplished with ribbon cables (more info on that here from my friend, Eddie Ciletti). What are the advantages of using a board/backplane for this?

 

[ruffrecords]

This is an interesting point, and one I hadn't thought of too much. On my old Soundcraft 200B, this was accomplished with ribbon cables (more info on that here from my friend, Eddie Ciletti). What are the advantages of using a board/backplane for this?

You can pretty much make a ribbon do anything a backplane can if you have enough ways but a backplane will generally have lower impedance power tracking. I seem to remember seeing quite a few posts about modding 200Bs to improve noise by reducing power wiring impedance.

If you think about the synth boys system there is still a ribbon cable from every board to the backplane so some of the backplane advantage is lost. On the other hand, if any part of the 200B style daisy chain ribbon system fails you may end up replacing the entire ribbon assembly. With the synth boys method you just replace one ribbon.

I have never built a mixer with ribbon interconnect between modules. I prefer modules that plug in directly to a backplane (but that is just me). There is more than enough cabling inside a mixer without adding to it by using a ribbon cable backplane.

Cheers

Ian

 

[MidnightArrakis]

To be honest I did not bother to count how many faders we need. If the channel module were 8HP wide then you would get 10 in a standard 84HP width with half a module width gap at the end. I have seen designs where this space is used for PSU indicators for instance but not getting an exact number of modules in a standard space annoys my sense of order and neatness. In my own mark 2 tube mixer design the modules are just 7HP wide so in 84HP you get exactly 12 modules.

I don't think we have decided on the channel width yet but I ASSumed we wou;d probably use the synth boys 8HP standard width. They often use 104HP extrusions which gives exactly 13 modules of 8HP so that it what I went with.

Bottom line I was only trying to illustrate the advantage of combining several faders on one panel. We could probably have one panel for the 8 channel faders and another for the stereo master and some misc stuff which is what I did in my last mixer build:

https://lh6.googleusercontent.com/u...pBWp3CzQDiq0n8D-7cdjPpQ8uFvi7KEBTGfUPJg=w1280

Cheers

Ian

This is the message I received when I clicked on the link you provided in your reply:

/

 

[Brian Roth]

I agree that DSubs are the way to go, but I also would love at least 1 or 2 pairs of TRS inputs for convenience. Sometimes you have a floater piece of gear or a visitor wants to plug their device in, so some TRS connections that override the Dsub on, say, channels 1-4 would be welcome.

I understand the expense of dsub cables turns some people off, but they are ubiquitous these days. I also agree it’s difficult to hand cut a db25 hole in a chassis. I trace the cutout from a middle Atlantic panel and use a Dremel to cut and smooth and it works fine and takes about 10 minutes.

Another idea that I employ is to simply cut a rectangle and mount a Middle Atlantic db25 plate to the chassis of a device with screw or rivets . This creates a nice finished look. This is what it looks like.

Catching up on a lot of messages,,,

I didn't see any plates like that at Legrand/Middle Atlantic's kinda goofy website, Looks useful! Part number? Thanks!

Bri

 

[Brian Roth]

True. Ribbons aren't strictly necessary though. A simple 3-pin header per channel would do the trick and would only be tens of dollars over all.

I succumbed to @Brian Roth's thinking and added a stereo Tape Ret input (and fixed the post-fader sends so they're post mute/solo). I also made it so you could send the Tape Ret to the mix bus, which would enable someone like me (who doesn't need to monitor post tape) to use them as an additional stereo input on mix-down. In fact, if you're not using the aux sends, you'd now have a 15x2 mixer in a pretty compact format! The way I would use it (only using one mono and one stereo return for FX), I'd have 12 inputs for mix down (but only 8 with faders). Pretty handy!
View attachment 143964

As mentioned...just catching up....will print out and gander at it..."News film at 11" lol

Bri

 

[Brian Roth]

I believe a lot of modern compact mixers are using the Alps board-mount faders (i.e., this mono model, and this stereo model). The price is certainly right, and the form factor would make a single PCB/single panel for the faders easy and economical. @MidnightArrakis - I think ribbon cables from the “fader PCB” to the channel PCBs would be the simplest method.

Caveat - I have not had these faders “in hand,” so I can’t speak to the feel/quality.

Looking at those Alps faders....look promising. But odd:

1. The simple search I did last night didn't find them...shrug

2. Must be a custom ordered part for Mouser. Using the linked Alps data sheet and filling the blanks on the "build a part number with all the options" section, the Mouser part number doesn't exist.

Single sourced parts kinda bug me.

Bri

PS...later I'll copy/paste the Mouser numbers into a search.

 

[cavedata]

I didn't see any plates like that at Legrand/Middle Atlantic's kinda goofy website, Looks useful! Part number? Thanks!

Another possibility -
https://www.redco.com/Redco-DSUB-UCP-Module.html

 

[Brian Roth]

OK...packaging thoughts.

One big-ass front panel for the faders and/or channels is somewhat reasonable, but NOT one big-ass PCB for either/both. We are not Behringer (or SSL, etc) who can afford the money and time to get everything all mechanically lined up by doing multiple prototype iterations. "Damn....faders 1-4 work kinda OK but things drifted and faders 5-8 are dragging on the front panel slots." etc etc

That's why I suggested individual little "strip boards" for each fader that is mounted on a PCB. The TKD "style" faders directly mounted to the plate would be a similar thing.

Similar thing for the input pots and switches if directly soldered to the PC boards. If someone (@MidnightArrakis or others ??) wants to layout the panels and PCBs, pay to order prototype metal work and PC boards and front panel controls and assemble the mess and PRAY everything lines up (lather/rinse/repeat if wrong)...then go for it! It's not my money and time. lol

FWIW, the pots on the SSL 4K desk's input strips used wire jumpers to the corresponding PC boards...no alignment problems there!

I am just trying to reduce the design complexity (and eliminate the requirement of single-sourced parts to make everything fit together). Not as much of an issue for a one-off, but we are effectively doing a production run.

More comments in a "minute" <g>

Bri

 

[Brian Roth]

Another possibility -
https://www.redco.com/Redco-DSUB-UCP-Module.html

Yeah, I've used similar plates. They are designed to screw into boxes that electricians use for switches and outlets. Very handy!

Trident 80-C module "mini sidecars" I built with breakout cables:

Bri

 

[Brian Roth]

More Metal Musings <g>......

The Eurorack format has come up. I see all kinds of possibilities here.

I vaguely knew about it, from the synth stuff and the DIN industrial "computer room" rack applications. Thanks to Ian's suggestions and links to vendors, I am more than intrigued.

Ian's mockup really stirred my aging brain cells:

https://groupdiy.com/threads/poor-mans-tube-mixer.73216/page-8#post-953411

A LOT of the metal work design elements are are easily available as catalog items. For instance:

https://schroff.nvent.com/en-gb/products/enc34560-084

Slide in the metal strip with all the mounting holes:

https://schroff.nvent.com/en-gb/products/enc34561-384

There's a bunch of other "Erector Set" Eurorack metal components available.

For those who weren't a child tinkerer...

https://en.wikipedia.org/wiki/Erector_Set

Side cheeks for this mixer project could be 1/4" aluminum cut into an irregular trapezoid or pentagon (hexagon.....yada) to define the profile. The extrusions act to hold the chassis together in the 3D world while also providing mounting points for the front panels.

The standard DIN rails max out at 84 HP length, but Ian mentioned the "Doepher" synth format allows longer rails...Need to research on what is available.

Only downside (?) is the module mounting holes are in 0.2" increments, 500 series modules won't work nicely.

Onto panels....The FPE panels are shockingly expensive. In other threads on this forum, panels designed for and made by PC board fab houses are discussed. Recently:

https://groupdiy.com/threads/metal-work-for-500-series.89714/post-1185499

https://groupdiy.com/threads/metal-work-for-500-series.89714/post-1185733

Chinese PC board houses are also offering aluminum "boards". One vendor even listed options up to 0.25" inches thick.

Don't know if the PCB front panels would be usable for full-width Jumbo panels. I lean towards individual panels for each fader and audio channel...regardless....if the price can be kept under control.

I'm just slinging spaghetti against the wall to see if it sticks! LOL

Bri (who also has a lot of experience trying to nail Jello to the wall as well)