#61

I bought a second hand Kweiwen Benjolin the other day for cheap. It has a mod where each oscillator modulates the other when there’s no CV connected. It’s fun, but almost completely uncontrollable, and it seems to get stuck in glitchy loops very fast. Is removing the mod as simple as removing the black wires? I’m told that’s the mod.

I’d like to be able to get some more control from it!

benjolin%20mod
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#62

fat tip / thin solder is the way to go.

#63

Have a look here
https://github.com/kweiwen/benjolin/wiki/2.-troubleshooting-&-more-mods…

Looks like there are three wires on your benjolin. Kweiwen talks about two wires. I guess the third wire is the same idea but attached to the filter

Anyway. Just desolder the three wires and see what happens. You can always solder them back again

#64

And yes I would say the three wires is the mod

#65

Yeah, I saw that too and wondered why the filter (presumably) had been modded. It’s fun, just a bit one dimensional!

#66

Any tips for putting a BOM together? I’m finding component websites (inc. Octopart) really confusing. Looking to build a couple of NLC modules, e.g. dual VCO - any help? I’m lost :slight_smile:

#67

where are you at? do you have a board in hand?

#68

Mouser (and other similar like Arrow, I think) have a BOM import page, although you’d have to copy & paste into excel format.

Or, I think most NLC modules are designed so that components can be bought from Tayda. It doesn’t have a bom import application, but is (fairly) clear to navigate. Twice a month there’s a discount code (announced on their FB or in the DIY section of MW forum).

Not sure if Tayda has tempco’s — Thonk used to carry I think.

1 Like
#69

Thanks! Thonk do still have a handful of tempcos, including the 1k on that VCO BOM.

@alanza, no board yet, but I have the BOM, and Thonk have this handy almost high-res photo:

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#70

There are a few teensy projects on the forum which have the midi code already set up explaining how to modify ect. I will look for one.

#71

A lot of great suggestions here!

I’m in the process of building the PreenFM 2. It’s a desktop multimbral, polyphonic FM synth:

http://ixox.fr/preenfm2/

The build seems pretty straightforward, but I’ll touch base to let you know how it turns out!

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#72

Revisiting my post about BOMs, can someone lend a hand? I’d like to build some NLC thru-hole stuff as mentioned previously. Take the Dual LFO as an example.

If we look at the 1k resistor, how do I work out what I need? As in, what material, what power rating etc?

1 Like
#73

For through-hole I always go for 1% Metal Film 1/4W.

Typically 1/4W are used in a lot of DIY through-hole projects (e.g. Music Thing Modular). Some even use 1/8W which means a smaller pad spacing (but lower power rating) e.g Bastl.

If special resistors (tempco, higher power rating etc.) are required then it should be noted on a BOM.

Here’s what I would order from Farnell for your 1K: http://uk.farnell.com/multicomp/mf25-1k/resistor-1k-0-25w-1/dp/9341102?st=1k%20resistor&MER=mktBestSellerA

2 Likes
#74

Thanks! Are there any similar things to note for other components? Diodes, capacitors etc. I’m struggling to find a plain English explanation for putting together a BOM.

#75

No problem. It is a bit of minefield to start with; so much to take in!

I started with pedals which are a lot easier in terms of inventory/BOM requirements (they typically use a lot of the same components and values).

For Diode’s and IC’s (Opamps, voltage regulators etc.) the BOM/schematic should state what value. If not then that is not a very clear schematic.

For through hole capacitors you are typically looking at 2.5mm or 5mm spacing.

Traditionally film capacitors were used in audio signal paths, but Multi Layer Ceramic Capacitors (MLCC’s) are being used more and more and should do the job fine (don’t tell the audiophiles though!).

As a very general rule for capacitors (for use in audio applications) from what I have learned:

Below 1nF = Typically use a ceramic capacitor (typically 2.5mm spacing).
1nF-1uF = Typically use a film capacitor (typically 5mm spacing).
Above 1uF = Typically use an electrolytic capacitor (spacing dependent on voltage rating).

Be careful with voltage ratings for capacitors (especially electrolytics). As a very general rule go for a voltage rating near enough double that of your supply voltage.

E.g. I would go for 25V rated Electrolytic caps for Eurorack projects.

If you are in the UK, Rapid Online (https://www.rapidonline.com/) is a lot easier to navigate and find standard parts than Farnell. Thonk is a very good resource for pots and the more obscure stuff.

I would also look at the Music Thing project. Many are through hole, and are very well documented and have clear schematics, BOM’s etc.

Hope this helps!

10 Likes
#76

very helpful, thanks! :slight_smile:

#77

I spent the weekend at a Casper Electronics workshop and now I’m excited to mess around with CMOS and build a small Lunetta synth onto some blank Eurorack panels. I’m wondering about Banana jacks, though. If they’re single pin, how do you ground them?

3 Likes
#78

on my banana synths there is a banana jack specifically for ground so that way you can connect systems together

or if you have an audio output on a regular 1/8 or 1/4 jack you should be fine when plugging into an external mixer

this is just my experience with ciat lonbarde gear

2 Likes
#79

You don’t. They just carry the signal.

If you want to patch separate devices that use banana jacks together then you do need to connect their grounds otherwise things will not operate as expected if at all. Usually as @wednesdayayay has said this is achieved by having a ground banana jack. This can be either on the synth/case or on the power supply.

1 Like
#80

So, one banana jack that you connect to ground, then that can be used to the ground jack of other synths?