Compact desktop line mixer?

[Potato Cakes]

The X-Desk is an absolutely great desk, especially when considering all of the routing options and price point. I mixed this entire project on an X-Desk that I borrowed while I was working on modding my Scorpion:



The only thing that I could not use was the talkback. When you pressed the button, the loud click in headphones rattled your brain, so I had to use a separate mic to talk to performers. But for everything else, I would strongly recommend one if building a mixing setup with limited budget.

It would be awesome to have a DIY version of this size that handled mixing duties. You could even include a discrete transformer based summing bus option. Metal work wouldn't be terrible. A folded top cover and a bottom with sides folded up. Make it a little bigger to use 100mm faders.

I also do not enjoy metal work. Mostly because want I want it to look like and what it actually does look like are very different things.

Thanks!

Paul

 

[OneRoomStudio]

That sounds great, and yes, the X-Desk does seem very close to what I'm looking for. Used prices are still fairly high though.

It would be really cool to have a DIY option with similar functionality and a similar compact layout, in a modular setup (and maybe a nicer mix bus). Speaking of functionality, it can probably be simplified further from my initial post. I guess we really don't need an input trim, since we're just feeding pots/faders to set gain anyway. I also agree that HPF can be done in the box. Considering that, here's a basic schematic of an "input channel." I could be swayed to go with either the "Cheap version" or the "Fancy version." If going the cheap route, U3 could be an IC opamp as well, and the rails could be +/- 16V instead of 24V.

 

[MidnightArrakis]

Metal work wouldn't be terrible. A folded top cover and a bottom with sides folded up. Make it a little bigger to use 100mm faders.

I also do not enjoy metal work. Mostly because want I want it to look like and what it actually does look like are very different things.

>> Your mix sounds terrific and her music is also emotionally touching as well. NICE CONCERT!!! -- Makes me wish that I was younger again when I used to mix and record concerts. I really do miss being a part of all of that activity way back then!!!

>> Here's a little something that I had recorded back around 1973 with basically "NO" equipment that in a rather broad sense is "somewhat similar" to Shannon's style of music!!! I built the microphone mixer from a kit that was available at the time and the mixed audio was recorded onto a CROWN "SX-722" reel-to-reel tape-recorder:

https://app.box.com/s/katttpc90byxtkvcovc38a896h467s40

>> Here's something else that I had recorded back in 1978 that was also simulcast on a local FM-station (and, by "local" I mean to where the venue was located and not where I lived, as I lived in the next state over west from where this concert took place). This was a "nightmare" situation, as the simulcast mixing console was located in the -- BASEMENT -- of the concert venue with NO visual stage monitors or anything!!! I had to "guess" who was singing and doing solo's in order to ride the faders. Back then, we didn't have readily available compressors, video cameras and monitors or much of anything. So, what you hear here is just me "winging it" while mixing to an audience of over 100,000+ FM-radio listeners in 2 countries!!! PRESSURE MUCH???..... This was also recorded onto my CROWN "SX-722" tape-recorder and the signal was from an FM-tuner that I had taken along with me. I had a choice of either taking a "Direct Out" from the mixing-console or a "Line-Out" from the FM-tuner. I chose the FM-tuner audio because I thought at-the-time that having the radio-station audio included would be pretty neat. In hindsight, however, I have regretted doing things this way because -- ANYBODY -- could have recorded this concert off-the-radio and say that "they had mixed it". On the other hand, essentially -- ONLY -- the person who HAD mixed the show and had recorded it directly from the mixing-console itself could actually say that they had mixed it and also have the tapes to prove it. So.....there's that!!!.....

https://app.box.com/s/irt04zmy4bh8trkhaljlnhq5obv31obn

[I also do not enjoy metal work. Mostly because want I want it to look like and what it actually does look like are very different things] -- NO BIGGIE!!! Just sketch out what you would like to have and maybe I could design all of the metal-work for you as you -- WANT -- it to be!!! That's what I do now. (See attached PDF file).

Here's a beginning of something that I am currently messing around with now. This is all rather bare and raw because I have JUST started to work on this and figure everything out:



>> In addition, go back to my Post #78 in this thread to view my sheet-metal "Reverse-Engineering" of a 200B channel-strip:

https://groupdiy.com/threads/compact-desktop-line-mixer.89576/post-1184097

/

 

[Potato Cakes]

That sounds great, and yes, the X-Desk does seem very close to what I'm looking for. Used prices are still fairly high though.

It would be really cool to have a DIY option with similar functionality and a similar compact layout, in a modular setup (and maybe a nicer mix bus). Speaking of functionality, it can probably be simplified further from my initial post. I guess we really don't need an input trim, since we're just feeding pots/faders to set gain anyway. I also agree that HPF can be done in the box. Considering that, here's a basic schematic of an "input channel." I could be swayed to go with either the "Cheap version" or the "Fancy version." If going the cheap route, U3 could be an IC opamp as well, and the rails could be +/- 16V instead of 24V.

View attachment 143249

I am currently using AM10 style op amps in my TAC scorpion which are line level only and use no transformers for the balanced input. It was a project from Eli Audio a while back. We could do something along those lines and then use transformers for the master fader and output. 2-4 aux sends and some stereo returns and this might be a very cool project that could fit in about an X-Desk sized footprint.

Although going the IC route makes a little more sense. If you wanted fancy you could use TLE2072 for the unbalancing/routing. I think the biggest difference will be a great sounding circuit with quality transformers in the mix bus section.

Thanks!

Paul

 

[Brian Roth]

That sounds great, and yes, the X-Desk does seem very close to what I'm looking for. Used prices are still fairly high though.

It would be really cool to have a DIY option with similar functionality and a similar compact layout, in a modular setup (and maybe a nicer mix bus). Speaking of functionality, it can probably be simplified further from my initial post. I guess we really don't need an input trim, since we're just feeding pots/faders to set gain anyway. I also agree that HPF can be done in the box. Considering that, here's a basic schematic of an "input channel." I could be swayed to go with either the "Cheap version" or the "Fancy version." If going the cheap route, U3 could be an IC opamp as well, and the rails could be +/- 16V instead of 24V.

View attachment 143249

Looking good! Here are a few comments.

1. I attached a RothCAD <g> scribble of the basics for an alternate input stage. I found the idea decades ago in Jung's Opamp Cookbook and have used it many times since. Easy gain tweakability. Back Then we didn't have the nice THAT chips, so a common dual opamp worked well.

2. FWIW, I prefer the dual gang pan pot circuit vs. the single gang with wiper grounded. Years ago, an article in (maybe?) R/EP by (maybe?) Paul Buff discussed how to optimally tweak the single gang version.

3. Speaking of pan pots, the R values of the one hanging from the Aux 3 level pot will load down the wiper and affect the taper of the level pot.

4, Just an random idea for the pre/post Aux switches....maybe a center-off switch for muting that aux?

5. Maybe same idea for the PFL switch: AFL/off/PFL.

6. If the "Mix Bus" switch is replaced by relay contacts, it could provide both muting and solo-in-place.

I may be over-thinking this!

"A camel is a horse designed by a committee."

Bri

 

[Potato Cakes]

>> Your mix sounds terrific and her music is also emotionally touching as well. NICE CONCERT!!! -- Makes me wish that I was younger again when I used to mix and record concerts. I really do miss being a part of all of that activity way back then!!!

>> Here's a little something that I had recorded back around 1973 with basically "NO" equipment that in a rather broad sense is "somewhat similar" to Shannon's style of music!!! I built the microphone mixer from a kit that was available at the time and the mixed audio was recorded onto a CROWN "SX-722" reel-to-reel tape-recorder:

https://app.box.com/s/katttpc90byxtkvcovc38a896h467s40

>> Here's something else that I had recorded back in 1978 that was also simulcast on a local FM-station (and, by "local" I mean to where the venue was located and not where I lived, as I lived in the next state over west from where this concert took place). This was a "nightmare" situation, as the simulcast mixing console was located in the -- BASEMENT -- of the concert venue with NO visual stage monitors or anything!!! I had to "guess" who was singing and doing solo's in order to ride the faders. Back then, we didn't have readily available compressors, video cameras and monitors or much of anything. So, what you hear here is just me "winging it" while mixing to an audience of over 100,000+ FM-radio listeners in 2 countries!!! PRESSURE MUCH???..... This was also recorded onto my CROWN "SX-722" tape-recorder and the signal was from an FM-tuner that I had taken along with me. I had a choice of either taking a "Direct Out" from the mixing-console or a "Line-Out" from the FM-tuner. I chose the FM-tuner audio because I thought at-the-time that having the radio-station audio included would be pretty neat. In hindsight, however, I have regretted doing things this way because -- ANYBODY -- could have recorded this concert off-the-radio and say that "they had mixed it". On the other hand, essentially -- ONLY -- the person who HAD mixed the show and had recorded it directly from the mixing-console itself could actually say that they had mixed it and also have the tapes to prove it. So.....there's that!!!.....

https://app.box.com/s/irt04zmy4bh8trkhaljlnhq5obv31obn

[I also do not enjoy metal work. Mostly because want I want it to look like and what it actually does look like are very different things] -- NO BIGGIE!!! Just sketch out what you would like to have and maybe I could design all of the metal-work for you as you -- WANT -- it to be!!! That's what I do now. (See attached PDF file).

Here's a beginning of something that I am currently messing around with now. This is all rather bare and raw because I have JUST started to work on this and figure everything out:

View attachment 143254

>> In addition, go back to my Post #78 in this thread to view my sheet-metal "Reverse-Engineering" of a 200B channel-strip:

https://groupdiy.com/threads/compact-desktop-line-mixer.89576/post-1184097

/

I suggest you should do a full metal work design that are about the same dimensions of the X-Desk with corresponding PCBs, present your work here on this thread and ask for input/suggestions on feature set, and then offer a group buy for boards and chassis. Or you can just order the all the parts and then setup a White Market account and sell them there. If you are going to be offering your services as available for hire you need to post them in the Available for Hire section of this forum.

Thanks!

Paul

 

[Newmarket]

That sounds great, and yes, the X-Desk does seem very close to what I'm looking for. Used prices are still fairly high though.

It would be really cool to have a DIY option with similar functionality and a similar compact layout, in a modular setup (and maybe a nicer mix bus). Speaking of functionality, it can probably be simplified further from my initial post. I guess we really don't need an input trim, since we're just feeding pots/faders to set gain anyway. I also agree that HPF can be done in the box. Considering that, here's a basic schematic of an "input channel." I could be swayed to go with either the "Cheap version" or the "Fancy version." If going the cheap route, U3 could be an IC opamp as well, and the rails could be +/- 16V instead of 24V.

View attachment 143249

What are the perceived benefits of the "Fancy Version" ?

 

[ruffrecords]

I suggest you should do a full metal work design that are about the same dimensions of the X-Desk with corresponding PCBs, present your work here on this thread and ask for input/suggestions on feature set, and then offer a group buy for boards and chassis. Or you can just order the all the parts and then setup a White Market account and sell them there. If you are going to be offering your services as available for hire you need to post them in the Available for Hire section of this forum.

Thanks!

Paul

To the best of my knowledge, @MidnightArrakis is retired and has always offered his services for free.

Cheers

Ian

 

[darth fader]

>> Your mix sounds terrific and her music is also emotionally touching as well. NICE CONCERT!!! -- Makes me wish that I was younger again when I used to mix and record concerts. I really do miss being a part of all of that activity way back then!!!

>> Here's a little something that I had recorded back around 1973 with basically "NO" equipment that in a rather broad sense is "somewhat similar" to Shannon's style of music!!! I built the microphone mixer from a kit that was available at the time and the mixed audio was recorded onto a CROWN "SX-722" reel-to-reel tape-recorder:

https://app.box.com/s/katttpc90byxtkvcovc38a896h467s40

>> Here's something else that I had recorded back in 1978 that was also simulcast on a local FM-station (and, by "local" I mean to where the venue was located and not where I lived, as I lived in the next state over west from where this concert took place). This was a "nightmare" situation, as the simulcast mixing console was located in the -- BASEMENT -- of the concert venue with NO visual stage monitors or anything!!! I had to "guess" who was singing and doing solo's in order to ride the faders. Back then, we didn't have readily available compressors, video cameras and monitors or much of anything. So, what you hear here is just me "winging it" while mixing to an audience of over 100,000+ FM-radio listeners in 2 countries!!! PRESSURE MUCH???..... This was also recorded onto my CROWN "SX-722" tape-recorder and the signal was from an FM-tuner that I had taken along with me. I had a choice of either taking a "Direct Out" from the mixing-console or a "Line-Out" from the FM-tuner. I chose the FM-tuner audio because I thought at-the-time that having the radio-station audio included would be pretty neat. In hindsight, however, I have regretted doing things this way because -- ANYBODY -- could have recorded this concert off-the-radio and say that "they had mixed it". On the other hand, essentially -- ONLY -- the person who HAD mixed the show and had recorded it directly from the mixing-console itself could actually say that they had mixed it and also have the tapes to prove it. So.....there's that!!!.....

https://app.box.com/s/irt04zmy4bh8trkhaljlnhq5obv31obn

[I also do not enjoy metal work. Mostly because want I want it to look like and what it actually does look like are very different things] -- NO BIGGIE!!! Just sketch out what you would like to have and maybe I could design all of the metal-work for you as you -- WANT -- it to be!!! That's what I do now. (See attached PDF file).

Here's a beginning of something that I am currently messing around with now. This is all rather bare and raw because I have JUST started to work on this and figure everything out:

View attachment 143254

>> In addition, go back to my Post #78 in this thread to view my sheet-metal "Reverse-Engineering" of a 200B channel-strip:

https://groupdiy.com/threads/compact-desktop-line-mixer.89576/post-1184097

/

I would build this enclosure, supply all materials minus the meters,and ship it for free just to see this project completed. If you design it.

 

[OneRoomStudio]

What are the perceived benefits of the "Fancy Version" ?

Higher headroom, theoretically better CMMR, street cred. In use…probably not too much. I agree with @Potato Cakes that the DOA’s and transformers are probably best left to the summing and output amps.

@Brian Roth good feedback! I like the THAT input, and it’s cheap enough and high-performance enough that it seems like it’s worth using. We could easily use 5534’s elsewhere. I’ll have to dig into the pan pot circuit. My goal was to avoid hard-to-find, and often poorly-matched dual gang pots.

@MidnightArrakis LED meters are cheaper, smaller, and easier to drive

Also, for reference, the X-Desk is 19” wide and 12.25” deep, which makes it perfect for both desktop use and rack-mounting for those who like rack-mounted mixers.

 

[k brown]

X-Desk: Wow, three grand used, for that little guy (not including whatever D-Sub fanouts one would need)!

One could DIY a helluva mixer for that amount of money.

 

[Brian Roth]

@Brian Roth good feedback! I like the THAT input, and it’s cheap enough and high-performance enough that it seems like it’s worth using. We could easily use 5534’s elsewhere. I’ll have to dig into the pan pot circuit. My goal was to avoid hard-to-find, and often poorly-matched dual gang pots.

My only reason for suggesting the Walt Jung balanced input design was the ease of adding a trim control and the lower price of a dual opamp vs. a THAT chip. Call me Budget Brian! lol The audio performance is excellent.

The dual gang pan pot design is regularly used in just about every pro desk ever made. It has a bit lower signal loss, easy to establish the "how many dB at center". It uses a dual gang LINEAR pot so section tracking isn't a big deal. Downside.....more space behind the front panel (and violating Budget Brian's approach it is more expensive).

Bri

 

[Brian Roth]

This Camel <g> is taking on a life of it's own! Ian and I were originally venturing in directions using off the shelf rack boxes or DIN Eurorack subracks. Now we're discussing totally custom metal work and the feature set keeps expanding!

For some reason, I was having problems accessing the SSL website the past few days. Tonight, I can get there to study the X-desk specs.

A couple random thoughts after a quick look.

1. It sure seems like the X-desk offered solo-in-place as well as stereo AFL.....but no PFL.

2. Each channel has two selectable line inputs. Hmm....

3. Nearly all I/O connections are on DB-25's.

4. It has channel inserts and direct outs.

Then we get into the master section with talkback, external playback inputs, alternate speaker selects, etc.

What feature set do we need?

Ask ten engineers, we will get forty answers! <g> This seems far beyond my original minimalist OTB ideas....like that Speck mixer with a few added features, But, as a once-upon-a-time desk builder I quite am interested in this project.

The feature set on my desk (two were built) was from two engineers at the client's studio with my input. Not bragging, just sayin'......

http://brianroth.com/projects/m77/m77.html

Bri

 

[OneRoomStudio]

This Camel <g> is taking on a life of it's own! Ian and I were originally venturing in directions using off the shelf rack boxes or DIN Eurorack subracks. Now we're discussing totally custom metal work and the feature set keeps expanding!

For some reason, I was having problems accessing the SSL website the past few days. Tonight, I can get there to study the X-desk specs.

A couple random thoughts after a quick look.

1. It sure seems like the X-desk offered solo-in-place as well as stereo AFL.....but no PFL.

2. Each channel has two selectable line inputs. Hmm....

3. Nearly all I/O connections are on DB-25's.

4. It has channel inserts and direct outs.

Then we get into the master section with talkback, external playback inputs, alternate speaker selects, etc.

What feature set do we need?

Ask ten engineers, we will get forty answers! <g> This seems far beyond my original minimalist OTB ideas....like that Speck mixer with a few added features, But, as a once-upon-a-time desk builder I quite am interested in this project.

The feature set on my desk (two were built) was from two engineers at the client's studio with my input. Not bragging, just sayin'......

http://brianroth.com/projects/m77/m77.html

Bri

Haha, true, this could expand far beyond my original concept, but for me personally, none of the items you mentioned would be needed.

-Either AFL or PFL would be fine as the only solo.
-No need to go crazy with multiple inputs (unless we make a stereo channel module).
-DB25 is fine, but so it TRS
-I can’t see the need for direct outs, and while bypassable inserts are cool, you can just insert outboard between the interface and the mixer.

I think the “K.I.S.S.” philosophy is a good approach. The thing that appealed to me about the X-Desk was the form factor. Summing, auxes, and faders. Would it be nice to have some rudimentary monitoring controls in the master section? Sure. Would it be nice to have basic metering (which the X-Desk didn’t have)? Yup! The mix bus could have a little more “guts” (DOAs and transformer outs). Other than that, I don’t think the features should creep too much - at least, that’s my two cents.

 

[Brian Roth]

Haha, true, this could expand far beyond my original concept, but for me personally, none of the items you mentioned would be needed.

-Either AFL or PFL would be fine as the only solo.
-No need to go crazy with multiple inputs (unless we make a stereo channel module).
-DB25 is fine, but so it TRS
-I can’t see the need for direct outs, and while bypassable inserts are cool, you can just insert outboard between the interface and the mixer.

I think the “K.I.S.S.” philosophy is a good approach. The thing that appealed to me about the X-Desk was the form factor. Summing, auxes, and faders. Would it be nice to have some rudimentary monitoring controls in the master section? Sure. Would it be nice to have basic metering (which the X-Desk didn’t have)? Yup! The mix bus could have a little more “guts” (DOAs and transformer outs). Other than that, I don’t think the features should creep too much - at least, that’s my two cents.

There has to be some "master" features like bus summing, but then any solo (besides "solo-in place") must somehow interact with the monitor system in the control room. How do we interface with the Mackie Big Knob (or whatever) along with a DAW?

DB25 I/O offers great "density" but seems to eliminate the possibility of "home construction" of the metal work. That would mean the chassis construction can be only be done by a metal fab shop. OTOH, that WILL completely lock in the feature set which may be a good thing?.

I don't have any brilliant ideas for some of this....just spit-balling!

Bri

 

[MidnightArrakis]

I suggest you should do a full metal work design that are about the same dimensions of the X-Desk with corresponding PCBs, present your work here on this thread and ask for input/suggestions on feature set, and then offer a group buy for boards and chassis. Or you can just order the all the parts and then setup a White Market account and sell them there. If you are going to be offering your services as available for hire you need to post them in the Available for Hire section of this forum.

Thanks!

Paul

[I suggest you should do a full metal work design that are about the same dimensions of the X-Desk] -- "THANK YOU!!", I appreciate your comments!!! However, while I will certainly tackle a "full metal-work design" for my own personal projects, I would only bother to create a comprehensive and detailed set of metal-work designs based upon what a "GroupDIY Committee" here has finalized upon. In other words, provide me with a bunch of sketches and written detailed notes and I will go through the interpretation of said information and transform them into the necessary and required 3D mechanical design CAD-models to have a project become manufacturable. The same goes for the PCBs. Come up with a set of schematic sketches, BOMs and mechanical details pertaining to the PCBs and then I will design the PCBs to fit all of my mechanical design requirements. But, for me to create a set of mechanical designs and then have a "GroupDIY Committee" come up with a list of "change this, change that, move this over there, make this bigger, make that smaller, etc., etc., etc.".....NO!!! I deal enough with that kind of stuff everyday.....anyway!!!

[with corresponding PCBs] -- Designing a PCB and then becoming involved with a near continuous-loop of changes and modifications isn't something I particularly enjoy doing. I have also done that enough times with the defense contractors and other engineering firms that I have worked with. In other words, once the "GroupDIY Committee" has completed, finalized and verified the schematics of whatever circuitry they have "group-decided" upon, then those schematics can be passed onto me and I can begin the PCB design process from there. I prefer to focus on circuits that are "completed and verified" as being -- DONE -- before I go and jump-in to turn those schematics into a PCB. That's just me.....

[MidnightArrakis is retired] -- "THANK YOU!!" ..... While I "should" be retired, I'm not!!! I am 3-months away from becoming 76-years old and I am now presently employed by a huge and well-known U.S. defense contractor working as a "Design Consultant" on a "100% FULLY-REMOTE" 40-hour workweek work-at-home basis. At present, the project I have been assigned to involves having me designing all-new test equipment for the testing of U.S. missiles being shipped to all of the various war zones around-the-world. I have been working on creating a rather large schematic that contains around 20 relays since this past September and I am unable to complete my schematic due to two engineers who cannot agree upon how or where to connect two different "GROUND" nets to any one of the >> 10 OTHER DIFFERENT GROUND NETS << that are in this schematic!!! So, do you see my reluctance here???.....

>> So.....let me know what y'all finally workout and then you can send me your sketches, details, written information, etc., etc., etc. and I'll take it from there. Sound like a plan???

>> FYI: -- Back in 1984, and somewhat similar to the mixing-console project performed by -- Brian Roth --, I had designed a -- 40-input X 12- X 4- X 2-output -- monitor mixing console for the concert sound-reinforcement company I was working with at the time. Whereas basically all "regular" console channel-strips are fabricated sheet-metal pieces that are bent-over to create "flanges" for mounting and strength purposes, the channel-strips on my monitor-mixing console design were made from narrow aluminum extrusions. These were inherently stronger than standard sheet-metal pieces while also, surprisingly, less expensive. Of course, they still had to be fabricated with all of the control, switches and LED cutouts, but..... MAN!!! ..... were they ever ROBUST!!!

/