Hello, I’m getting ready to X-Y hack my Vectrex in preparation for Chromagnon and I’m wondering if it’s best to add 3.5 mm jacks or RCA jacks for pairing with Chromag?
Any other useful retrofits that will help it pair better?
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It would be best to use 3.5mm jacks, since Chromagnon’s XY outputs are also 3.5mm.
I don’t know enough about Vectrex hacking to advise on other modifications.
It’s going to be really exciting to see Chromagnon’s vector applications in action!
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Make sure to add 3x switching jacks to tap the Vectrex’s XYZ cartridge signals for processing. I’m excited for Minestorm regurgitated by Chromagnon. 
You might also consider adding the spot killer mod on a switch which can help with displaying lower frequency content. I have left this off of the ones I’ve modded as it increases the chance of burning the phosphor if you’re not careful.
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As @Z0NK0UT mentions, 3.5mm jacks is the way to go.
Current LZX gear outputs 0-1v which is much lower than Eurorack and too weak to drive the Vectrex and fill the whole screen. Unless the Chromagnon can scale the output voltage up to eurorack levels which I doubt, you’ll want to bring those levels up with either the LZX Bridge utility or the LZX Cadet V DIY module edit: NEVERMIND @Z0NK0UT confirms that it will scale up! I’d go with the Cadet V unit since it has 4 channels vs two on the Bridge and the Vectrex has three inputs, xyz. I also find the LZX Passage (or three Cadet VII Processors) very useful at adjusting positioning and mixing the signals going into the Vectrex.
While waiting for the Chromag, if you have any eurorack hardware, the Vectrex will work great with it. You can connect VCO and CV right into it. Something as simple as the Behringer Neutron will provide tons of fun. Easy patch: Send the LFO to the OSC Shape and then patch each VCO outputs to X and Y of the Vectrex and will get you very cool animations that match the sound waves being played.
One thing to note with the Vectrex is that it doesn’t sca as fast and can’t keep up with video signals like an oscilloscope can so things like Rutt Etra may not be possible. In my attempts at this the image tends to roll over itself horizontally. It would be neat if the Chromag had a way of adjusting the horizontal refresh rate but my understanding of the subject is not sufficient to know if that’s even possible.
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As it stands, even with a Bridge or Cadet Scaler, LZX output will not take on the full spectrum of a Vectrex, only a small portion. However, any old oscilloscope will be just fine.
If perhaps the Chromag has some signal boost on top, I’m not sure how compatible the two may be.
In all my browsing I haven’t seen the “nominal” input range for a modded Vextrex - is it safe to assume +/-5V or perhaps higher to get FSD?
I guess one approach could be to use an LZX Cadet Scaler to go from +1V to +/-5V, then another Euro module (ie, my favourite - Befaco AxB+C) for the final gain adjustment?
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This is exactly what I use with my Vectrex.
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Ahh, great to know!
Have you measured the voltages required to drive the Vextrex, otherwise what gain are you using on the AxB+C?
Back to the original question - I’d go with switched jacks as suggested above.
When I finally get around to modding my Vectrex, I might even use 6.5mm switched jacks - it’s easy to get a 3.5mm to 6.5mm adapters, and I have a lot more 6.5mm cables in longer lengths than I do 3.5mm…
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Chromagnon will have onboard scaling for the XYZ outputs, since we know they are destined for inputs requiring more than the 1V LZX standard.
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“I’d go with switched jacks as suggested above.
When I finally get around to modding my Vectrex, I might even use 6.5mm switched jacks”
Rik_bS
That’s how I’ve modified my Vectrexes https://youtu.be/q3sKZA2r7qk
Did you follow a specific ‘Hack Tutorial’ for the switchable jacks? I’m a bit of an electrical noob and have only seen Duff’s (very great but) basic tutorial .pdf
if you get Switchcraft 12A jacks it’s not too hard to see how to wire them up. if I come across one, I can take a picture and label the tabs you connect to
i’d really appreciate that, thank you!