![](https://s3images.coroflot.com/user_files/individual_files/613050_pa_cwces3ccbejoiafoa2lzgf.jpg)
I have modified Ken Stone's schematic to suit my own needs. I have omitted those features that I will not have room for on my panel. My build will be for a 4 input mixer with pan and volume pots for each of 4 inputs. There will be 2 stereo outputs and 2 inverted stereo outputs as well. I will also need to revise this schematic so that the mixer is AC coupled. I will not be using this for DC signals, so it is best to AC couple the circuit so as not to introduce any DC offset during usage.
![](https://s3images.coroflot.com/user_files/individual_files/613050_xagwg7yze_jaywrbzezhpib47.jpg)
Bill of Materials. I plan to build this on a perf board. I've also included the AC coupling components.
![](https://s3images.coroflot.com/user_files/individual_files/613050_6dwmofy9bwgclopxuisf7vjn9.jpg)
This is the initial breadboard build. I had to place an order for 4 x 50k log and 4 x 50k linear pots. I'm also awaiting a shipment of 47pf capacitors. When these arrive in the mail, I'll place them and I should be able to debug very quickly.
![](https://s3images.coroflot.com/user_files/individual_files/613050_shtbbbs29lxpumwkym53yqbac.jpg)
Top view. on the top of the breadboard there will be a row of eight 50k pots. Four will serve as volume control, and four will serve as stereo pan control. I have AC coupled the four inputs and the two outputs as well.
![](https://s3images.coroflot.com/user_files/individual_files/613050_2ltyxxdg8tx6lvixej7pzqh3b.jpg)
Pots have arrived. All ducks are in a row. 4 x logarithmic pots are used for the volume control, as human hearing tends toward a logarithmic curve. 4 x pan pots are linear in that I want the pan control from left to right to be linear and likewise, even. I'm still waiting for a shipment of capacitors and then I'll be ready to test the unit against my modular system.
![](https://s3images.coroflot.com/user_files/individual_files/613050_lxhie3mzw0nkmb5x5gv8e9jyi.jpg)
All components have arrived to complete the breadboard build. Upon initial testing the outputs were mute. Tracing through the circuit with an oscilloscope probe revealed that I neglected to ground each of the TL072 op amps at pins 3 and 5. With the non-inverting inputs to each op amp grounded, functionality meets expectation. With my solder iron heating up, its time to move this circuit onto a perfboard.
![](https://s3images.coroflot.com/user_files/individual_files/613050_mkmidaoqnj2p3nurkzpyyo6eg.jpg)
Top view of perfboard. I have tested the 1st input and non-inverting stereo outputs and all is working great.
![](https://s3images.coroflot.com/user_files/individual_files/613050_yyuvoastakmo8vzwzbmsnjmjg.jpg)
Rear view of perfboard. I still have a lot of pots and jacks to wire up before placing the board into the face panel.
![](https://s3images.coroflot.com/user_files/individual_files/613050_jemly00sdgedoxdaye5pyqnme.jpg)
I have modified a YuSynth panel template to serve my needs with this module. There are L and R non-inverting outputs as well as L and R inverted outputs.
![](https://s3images.coroflot.com/user_files/individual_files/613050_tehxucgvxb47tnscizrbn5aou.jpg)
Here I have used masking tape to fix the template onto the blank panel. Next I will drill holes in the the locations which are accurately marked.
![](https://s3images.coroflot.com/user_files/individual_files/613050_hbhhywfpobqv7vqrcts2_a5g0.jpg)
Using a drill press I have forged holes for the pots and jacks to fill.
![](https://s3images.coroflot.com/user_files/individual_files/613050_ne6ioxqwa9vcw88fevprmb2oz.jpg)
Mixers have a lot of jacks and pots to deal with.
![](https://s3images.coroflot.com/user_files/individual_files/613050_wku50klk24pixvgf9un7jacnc.jpg)
I have mounted the perboard to 2" brass standoffs. Cable ties are used to keep the all those twisted pairs nice and neat.
![](https://s3images.coroflot.com/user_files/individual_files/613050_gfaclctegiraacubmyz__z8uk.jpg)
Side view.
![](https://s3images.coroflot.com/user_files/individual_files/613050_pmzy6zyb7elgbrdlqyngoxhun.jpg)
Alternate side view.
![](https://s3images.coroflot.com/user_files/individual_files/613050_g6veuycacgusdxumvctdwmfzm.jpg)
All done. I have tested the module and everything is working as expected. Performance in linear and there is no noise introduced. I am very pleased with this mixer. Next I'm going to try to add text to the face plate with label maker.
![](https://s3images.coroflot.com/user_files/individual_files/613050_fjp_06dss8ukplewowoau9blw.jpg)
My label maker arrived. I'm using white on black 3/8" tape. The tape has a slight reflective glare to it, but overall I'm happy with the results. It looks better than the paint marker and I should I ever get a mill, I can still remove the labels. I find that the bold face font works best for viewing. I plan on using the label maker on future face plates as well as on my previous paint marker panels. The paint marker wipes away with lighter fluid, so I can pretty all my DIY modules as well as this one.
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