Compact desktop line mixer?

[OneRoomStudio]

>> Here is what your LED-bargraphs look like "BEFORE" and "AFTER" by having one of the slots enlarged by 0.040" or 0.020" on each side of the LED-bargraph itself. On the left is how you currently have things fitting together by using a small hammer to force the LED-bargraph into the panel-slot. On the right, this shows a 0.020" tolerance gap all around the LED-bargraph, allowing it to easily fit through the slot and end up becoming flush with the top of the panel. For reference.....0.020" is about the standard thickness of 3 sheets of standard notebook paper pressed together, with each sheet being approximately 0.007" in thickness.

View attachment 145270

>> This image shows the LED-bargraph corner-edges and the tolerance gap clearance to the panel slot radii in each corner:
View attachment 145271

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Thank you! I wouldn't have caught that. I'll update my file.

BTW, were you ever able to able to convert the enclosure to a 3D STL? I'd love to mess around with trying to figure out how I could fit things on the backplane PCB, so if you could share that, I'd really appreciate it.

 

[MidnightArrakis]

Thank you! I wouldn't have caught that. I'll update my file.

BTW, were you ever able to able to convert the enclosure to a 3D STL? I'd love to mess around with trying to figure out how I could fit things on the backplane PCB, so if you could share that, I'd really appreciate it.

[were you ever able to able to convert the enclosure to a 3D STL?] -- As a single enclosure file? Or.....as individual pieces???.....

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[rh001]

Rather bizarre post tbh. There is still a choice of standard desktop mixers. The original question was about dedicated line input mixers. The reason lies in the evolution of audio tech.
Not bizarrely due to "population growth".
fwiw Population growth may be required to support an increasingly older non-wealth creating demographic.

It's ok to disagree but it's also ok to be polite. Why not just pretend you're Japanese. They say national hero and figure skating champ Yuzuru Hanyu is exceedingly polite...it works for him. Age: 30yrs Estimated networth $30 to $50 million.

 

[OneRoomStudio]

[were you ever able to able to convert the enclosure to a 3D STL?] -- As a single enclosure file? Or.....as individual pieces???.....

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Ideally, as an explodable/ungroupable group of pieces (not sure if either of those are words).

 

[MidnightArrakis]

One interesting aspect of Schaeffer's front panel service is that they can use customer provided material so, rather than buy a complete enclosure like the Takachi and have to replace some of its panels with custom ones you can send the blank panels to Schaeffer for them to use on your design.

Cheers

Ian

[One interesting aspect of Schaeffer's front panel service] -- And.....speaking of "Front-Panel Services", check-out this website:

https://www.lcsc.com/front-panel

>> @OneRoomStudio may also thoroughly enjoy this website as well!!!.....

https://www.lcsc.com/front-panel/about-products

>> HAVE FUN!!! BROWSING AROUND THE WEBPAGES ON THIS WEBSITE!!!.....

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[OneRoomStudio]

Ok, back to the channel circuit. I made some updates. I decided to use @JohnRoberts bicolor LED signal/peak light circuit (hopefully I implemented it correctly). I still need to determine the right mixing resistors and finalize the panning circuits.

 

[JohnRoberts]

I started to respond to this last night but saw enough differences between the circuit I designed 3+ decades ago to pause.


Here's the schematic I shared from the AMR Production series years ago.

I used a two lead bicolor LED connected between APK+ and APK-. For modest low audio signals the green LED direction starts conducting. This green direction is modulated brighter by increasing signal level until reaching the peak threshold established by resistor divider feeding the + input. When the peak direction snaps positive a simple peak hold circuit keeps the red LED illuminated long enough to easily see narrow transients.

SMPLA is the common input for multiple sampling diodes. Sampling diodes can detect for overload at multiple nodes in the channel strip. Preferably at least one sample from each polarity to detect asymmetrical waveforms. These sample diodes have their cathodes facing the SMPLA node. These sample diodes need to be DC connected to low impedance op amp outputs.

Not through two capacitors in series. I would use at least one sample diode from the input THAT chip, and another from the post fader 5534 output. Note: the 5534 is stable for gains >10 dB so the 22pF compensation cap is not necessary with that much gain. Most post fader gain stages use +10dB (3x).

JR

PS: Back when accepted consulting gigs I charged $100 hr... Now I would be more expensive and I am not looking for work.

 

[OneRoomStudio]

I started to respond to this last night but saw enough differences between the circuit I designed 3+ decades ago to pause.

View attachment 145407
Here's the schematic I shared from the AMR Production series years ago.

I used a two lead bicolor LED connected between APK+ and APK-. For modest low audio signals the green LED direction starts conducting. This green direction is modulated brighter by increasing signal level until reaching the peak threshold established by resistor divider feeding the + input. When the peak direction snaps positive a simple peak hold circuit keeps the red LED illuminated long enough to easily see narrow transients.

SMPLA is the common input for multiple sampling diodes. Sampling diodes can detect for overload at multiple nodes in the channel strip. Preferably at least one sample from each polarity to detect asymmetrical waveforms. These sample diodes have their cathodes facing the SMPLA node. These sample diodes need to be DC connected to low impedance op amp outputs.

Not through two capacitors in series. I would use at least one sample diode from the input THAT chip, and another from the post fader 5534 output. Note: the 5534 is stable for gains >10 dB so the 22pF compensation cap is not necessary with that much gain. Most post fader gain stages use +10dB (3x).

JR

PS: Back when accepted consulting gigs I charged $100 hr... Now I would be more expensive and I am not looking for work.

Thank you for that thorough explanation, John! I clearly misunderstood the input to the circuit, and this helps a lot. I will rework it. I also appreciate the free advice, and I hope that by having a discussion of the circuit here, it will help others too. Your time and knowledge are very valuable. The same can be said for the tips and advice from @Brian Roth, @ruffrecords, and @MidnightArrakis!

The magic of this place is being able to get insight into DIY projects from experienced and knowledgeable folks.

 

[JohnRoberts]

Here's another TMI anecdote that explains why I sample for clipping at multiple points inside each channel strip.

Back when I was in the trenches competing with Mackie mixers (who actually advertised their SKUs). I had one of my sales reps share an encounter he experienced when visiting one of his dealers. The dealer had a popular 4 bus Mackie sound reinforcement mixer set up with its output feeding Peavey amps and speakers on demo. When my rep walked into the store he heard obvious clipping distortion. The dealer said that the Mackie's output was so strong it was blowing away the input of the Peavey amps that couldn't handle it. Obvious BS that reveals the power of advertising to influences customer expectation bias. Apparently even that Peavey dealer was drinking the Mackie koolaid.

It turns out that that particular Mackie mixer was not sampling at multiple points of each channel strip so it was possible to adjust the channel gain structure such that it could clip internally without firing the peak LED. IIRC they only sampled for clipping after the post fader gain stage, so it was possible to pull down the fader gain low enough while clipping the mic preamp front end without ever triggering the peak LED. I actually started demonstrating that example at Peavey dealer seminars to inform and amuse Peavey dealers and salespeople in attendance. Clipping is most audible on bass, so while speaking into a handheld mic I could easily make an impressive clipping demo, without waking up the peak LED just by talking.

Ironically (perhaps?) Mackie advertised about how much headroom they had, while not accurately indicating actual clipping. Caveat Emptor.

JR