Texar Prism Multiband Processor clone

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Stratofox71

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Mar 11, 2021
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New to the forum and wanted to post a recent project I have been working on. I already own a pair of Texar Prisms that I casually use and having studied the inner workings of it I decided to try an attempt at a modern spin without resorting to DSP and with reduced complexity.  The result is a PWM based design with a handful of components in a small SMD footprint to achieve the functionality of the more complex Texar M101 board. A microcontroller is the heart of the digital control and display function and emulates what was a mostly analog design on the original with some digital ICs for control.

At this point I have optimized the code to track alongside my original analog units and they perform much better than I originally anticipated for taking a simplistic approach to the design. What you see is the proof-of-concept prototype but if there is any interest I may proceed further and look at packaging the design into a more DIY friendly approach.

 

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JMan

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Very cool first post! 

I wasn't actually familiar with these, so I did a quick Google search and read a little.  Seems like they are a fairly particular unit (at least from what I found).  I guess they were intended as broadcast equipment, and I see a lot of chat about pairing them with an Optimod 8100 in that context.

How are you using them?  Do you like them as a standalone tracking/mixing compressor?

It's always great to see people working on new and interesting projects! 
 

Stratofox71

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Mar 11, 2021
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Yes the Texar/Optimod pair was pretty much a standard in the 80s up through the 90s. The station I worked at had a pair of them along with a Mod Sciences Stereomaxx and our modulation monitor needle barely moved just below 100% during program. It was a combo that could create loudness without being unbearable or with the density reduced it made for fuller content.

My analog pair is aged out of spec so I dont use them extensively. The Vactrols age and drift so renewing them and running a calibration procedure is required to bring them back to their 80s glory. If you spot a pair on eBay they usually go fast so theres still a user base out there.

Here is the history of the Prism  https://www.thebdr.net/wp-content/uploads/PDF/Audio/Processing/the-audio-prism-story.pdf

 

Stratofox71

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Mar 11, 2021
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Its been a few months and I revived this project to a more DIY friendly approach. I have built it into a fully functional project that works better than the 80s analog counterpart. If there is interest in this I can work on a plan to make boards available along with parts lists and the build guide. There are 2 main boards, one for each channel and two main display boards, along with an IO board for bal-unbal-bal conversion. The form factor is flexible but I will make the front panel express file and CAD available to customize.

Jeff
 

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fragletrollet

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I'm new to the design, but does this unit allow for external sidechain input on each band for frequency specific work (bass ducking and de-essing)?
 

Stratofox71

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Mar 11, 2021
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Since it was modeled to replicate the Texar Prism there is no sidechain input, but the design could be modified for various options.
 

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BGA

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As an owner of both Texar and Gentner Prisms I am very impressed with your work and would most definitely be one of the first to build a new pair. Well Done
 

Stratofox71

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Mar 11, 2021
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Thanks everyone for the kind words. This is really been more of a quest to see if I can do it but has turned out to be more than I envisioned. I honestly never expected to get the concept to work but I proved myself wrong. I'm still waiting on boards and a few parts to arrive and am working on documentation and a site to make these available. I ordered enough boards to build 5 whole units, and 2 of those sets I have pre-commitments for, so if the additional 3 sets go fast I will order more as fast as possible. I may be able to supply kits but the chip shortage and ever changing parts availability has made this interesting.

One feature I decided to add is the ability to control the gate, density, slow agc and quiescent point to each band individually via serial port commands. This is a big departure from the analog Texar in that you can make adjustments under-the-hood. The plan is to write software where you can adjust settings and store presets as session files.

Between full time work and some college classes I'm trying to squeeze this in as much as possible to get it out there. Stay tuned.
 

Stratofox71

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Mar 11, 2021
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PC Boards are on the way. This week Ill be working finishing documents and putting some pricing in place for the boards. Keep in mind the boards will have some SMD parts supplied and placed. Over the weekend I updated the firmware in the box and wrote some software to adjust individual parameters. This makes it very flexible. It also has the ability to save settings to the unit as well as save configuration settings to session files that can be recalled.
 

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Stratofox71

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So this will now turn into the support thread.

First batch of PCBs have arrived. I ordered enough for an initial 5 units but already pre-sold some so I have enough for 2 left. That being said, I need to know who is interested in boards so I can start supplying what is left and/or order another batch. The other issue is I need to order enough parts for these now for the demand since I place the SMD components and some of them are dwindling fast in distribution. Given the chip shortage this could grind this to a halt. Just PM me if you want to be on the list and I will get a count so I know how to proceed.

Pricing will be over in Black Market. Texar Prism Clone PCB thread

Build guides for the boards are attached with include BOMs. Ill upload more as I complete them. At least you can see what is involved and overall parts costs.
 

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