DIY Questions:)

Hi there folks, hope you are all good out there! So I am looking to build a 4U little LZX system. I already have a 104HP rack. Basically I am looking to add into the 1U row of an Intellijel Case hopefully x8 of the 4HP DIY modules from LZX (Probably x4 of the Castle Module, x2 RGB Encoders and x2 Luma Amplifiers). I have never done DIY before and certainly not using the 1U of an Intellijel case. Has anyone done this before? Anything like this? Will they fit into a 1U row horizontally? Thanks for your input on this:) Cheers!

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You could probably fit two or three 4hp modules horizontally. Make your own panel to fit them in there. The castle and Cadet stuff is made to be flexible. There are mounting holes in the corners and all the jacks have easy access solder pads for alternate types of jacks.

Hi there Philip,

Thanks for getting back to me. Yeah that sounds good. I am basically only getting into the Castle Modules because I love your artwork, it is really interesting and inspiring. I basically only have room for 4 of the Castle modules. Right now in my system I have Cortex, Polar, Marbles, Shapechanger, x2 Bridge and an Arch. Which four modules would you say would make a good addition to this little system? Many thanks!

I’m not Phil - but I would say that I have one of each of the Castle modules - with the exception of the Clock VCO of which I have four. So take from that what you will.

I’d say:
ADC, DAC, and some others.
those 2 Castle modules are vital and very fun!

And to riff on this, with an ADC and DAC you can explore (at least) this kind of patch:

and if you add flipflop and clock vco:

There is probably not a bad combo, though, depending on your interests.

So I’m having some problem with the Cadet IX -
Not clear as to what does “R43 may be a 2K TempCo resistor”.
Also couldn’t find J3 & J5 in the BOM… are they DNP?
Thanks!!! :upside_down_face:

R43 can be a 2k 3300ppm temperature compensation resistor, preferably mounted in thermal contact with the expco transistors, or it can just be a boring, regular 2k resistor.
The former makes the osc less sensitive to temperature changes as the synth warms up or the room around it warms or cools.
This is very important in audio synths, as the ear easily detects very small shifts in frequency, but depending on use might be less so for your video synth.
I mounted the regular resistors on mine and i have yet to regret that decision, but that might of course change with your usage and obsessiveness.

J3 and J5 are optional connectors/solderpoints for modding/expanding your osccilator. They can safely be left off.


indeed. I also used a normal 2k resistor there, with my 7 oscillators that i’ve build.

j3 is the squarewave output, which is a very useful mod!

I grabbed the 2K 3500 ppm tempco resistors off Thonk. I wasn’t sure which ones until reading this thread. Do you think those will work fine? Also could I get away with using 1N4148 150 mA diodes or do I need the 1N4148 200mA diodes that are listed in the BOM for the VCO. Good to know about the J3 sqaurewave output. transistorcat, what do you mean by the expco transistors? Thanks guys.

Usually we use feedback techniques and temperature invariant components to rid ourselves of temperature effects in electronics. None of these exist or work (at least not completely) for exponentiation, since the PN juctions in the transistors are the controlling factors.
In classic synth design (and modern DIY) we get the temperature dependence under control by introducing a temperature compensating factor (a “TempCo”).
How well this works depends on how close our compensating mechanism can match the temperature dependence in the transistors, and on how closely we can track the temperature.
In IX osc the transistors in question are Q2 A and B. If the tempco is thermally far away from the transistors, we will be compensating for the room temperature, but not for the self-heating of the transistors and the circuit around it. I don’t have my board in front of me so i don’t remember how the tempco footprint is placed, but on an audio osc the transistors in question and the tempco will usually be placed such that they can be placed up against each other and glued together with thermal paste.
As a side note, temperature compensation is futile if Q2A and Q2B are not well matched, so that’s where i’d put my attention.

Thanks for the response. The Tempco would need jumpers to be glued together with thermal paste. I have matched the transistors VBE to a difference of 1mV to 2mV. What if I glued with thermal paste a piece of metal between the transistors?

As i and reverselandfill have stated, anything will work.
for the temperature stability, all i can say is that the better the thermal contact between the transistors and the resistor, the better the matching will be.