Crimping JST-XH connectors--a Quick How-To

 It's a beautiful Spring day, instead of going out and enjoying it, I am teaching myself how to crimp and create JST-XH connectors.

I based this post on the video here; also instructions on the back of the crimping tool...I am writing all of this down because in 3 or so days I will forget all of this.

WHAT TO BUY

I got generic made-in-China JST-XH females pins from Amazon, they came in a pretty big reel.  

I also needed the "shells" (not sure what to call them) into which you shove the pins:

...the crimping tool:

I couldn't get the exact tool in the video, but these Engineer Precision Connector Crimping Pliers were Amazon's choice, looked just like what is in the video, and worked great. Hope the link here still works....

And of course, hook up wire (I used 24 gauge but I imagine 20 to maybe 26 will work) as well as some decent wire strippers.

MEASURING THE PINS

I pushed the rear fan on the pins until the were parallel and then measured their distance. Came to 1.85mm, that meant I had to use the 1.9mm slot in the tool.

The female pins themselves are really small, I didn't wear magnification to do this work, but probably should have.

The pin (this is a female version, the video shows males and females) have metal at the back that needed to be cut away. 

Cut off the flat dookie at the right with some good diagonal pliers.

Next I stripped the hookup wire, exposing about 1.5mm. This has to be done with a fair degree of accuracy. This was described well in the video at about :20.

Then I used needle nose pliers to gently affix the cable into the pin, otherwise the kept falling out of the tool before I could crimp.  I found I didn't want to overdo things here, just a bit of pressure, to keep the pin in place, was most effective:

Then I oriented the pin with the tool--the orientation needed was not self evident!  It goes with the open end of the tabs into the larger slot of the tool:

Then inserted the pin and wire and crimped.  Sorry, no photo....

When i was done, I could not pull the crimped end off the wire--it was really on there--all good.

Finally I shoved the pin into the shell.  When it worked, I got a nice little click.

Repeated ad nauseum for my entire project. 

The world is a happy place!  See you next time.

AS3364 Experimenter's Board--low parts count quad linear VCA's!

Readers: If you'd like to build the project featured in today's post, please go to PCBWAY's Community pages--gerber file; KiCAD 9 project/pcb/schematic/library files, a B.O.M., and more are here.  

You can also help out this site immensely by checking out PCBWAY using the link here. Thanks!

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When you put your Voltage Controlled Amplifier in series with a traditional ADSR you want the VCA to respond in a linear fashion, otherwise things can sound, well, crappy. 

The Irwin dual VCA from this previous post used 2 VCA's in series to get reliable linear response. 

Mike Irwin's design--I've built it many, many times now--sounds great, but always required 2 VCA's in series for every audio or control signal I wanted to amplify or attenuate.

But what about a quad VCA IC with linear response out of the box? And is affordable? 

That's the Alfa RPAR AS3364.

I built a simple experimenter's board for this IC, with buffered and clamped inputs for CV, so I could hear what it sounded like and avoid the terrible breadboard experience.

Works!

  

DESIGN

The secret weapon present in the AS3364 is the log to linear converters, seen in its datasheet, one per VCA:

The AS3364 datasheet recommends 0-2V for control voltages, which is not commonly found in modular synthesizers....but getting my 5V control voltage signals to this level was easy--I used a voltage divider and MCP6004 op amp configured as a unity gain non-inverting buffer:

One of four buffers  

To power the MCP6004 op amp I used a simple 78L05 voltage regulator with a diode drop to give me about 4.3V DC:

This got 0-5V control voltages into a useful range for each VCA. The MCP6004 clamped incoming CV a little bit higher than its supply rails; I got a nice buffer to boot. 

I stole this clamping/buffering idea from Mutable (open source schematics here--take a look, highly recommended) who uses variations of this same circuit fragment in some of her designs.

THIS BLOG'S SPONSOR!

Before I continue, got to put in a quick word for this blog's patient and always helpful sponsor, PCBWAY. Once I get my circuit idea, I turn it into a .sch/.pcb and gerber file and send it off to PCBWAY.  They get it back to me super fast....PCBWAY fabricates at low prices (5x 2 layer boards 99mm x 99mm PCB's for about $5 US.....). 

PCBWAY provides a lot of other cool services as well: 3D printing and assembly, for instance.

Hats off to them, I am extremely grateful for their sponsorship of this blog. They do great work!

THE BUILD

The project was really easy. I used all through-hole because I had a bunch of 20K 1% resistors around; the BOM shows 30K but anything from 10K-47K would have worked as long as I used the same resistors for all but R9.

Piece of cake.

Happiness is always getting new bubble wrapped PCB's from this blog's patient and friendly sponsor, PCBWAY.

Will it WFT (work first time?)

Only one way to find out--build it...

tested with +/- 12V to see if I have shorts/magic smoke--nope. 

Bench fu....

Ha!  Worked and sounded great!

WHAT NEXT?

Alfa RPAR, the guys who make the AS3364, have a bunch of other interesting chips, the AS3365 (panner), the AS3363 (ring modulator and other functions) and lotsa other chip dookie.  

I would like to test all of those IC's out, but in the meantime the AS3364 might find its way into future designs due to its extreme simplicity. For instance, the EFM LFO2  (build is here) uses LM13700's as in-circuit VCA's, it would have been easier to have used an AS3364 IC.

Overall, an interesting chip for what we do. VCF's? Panners? Ring Mod? Sure. Lots of things I haven't thought up, yet, but, "you can never have too many plain-old VCA's." 

See ya next time--Don't breathe the fumes.

Stereo Panner using the Irwin dual VCA

Hidee Ho boys and girls! 

Last time I laid out an Irwin Dual VCA, this time I wanted to put it to work.

I designed and built a stereo panner in Frac Format....

.....to replace a similar build from 2004 (?) which of course I didn't document.

Right one looks better?

The old panner was broken--the bias offset adjustment switches no longer worked making the audio agt output cut in and out in some applications. 

Could I fix this 20+ year old module? 

Not easily--when I inspected the old design I found that the add-on board for bias adjustment was wire wrapped--I did this?

....and in general the old module was built with (as my tech boss in the film business used to say) duct tape and snot.

I figured it would be easier to get new boards from this blog's faithful and ever-patient sponsor, PCBWAY, instead of reverse engineering then repairing my 20+ year old build--they always provide fantastic parts, and can assist in all your DIY needs, from 3D printing to assembly to metalwork and beyond.

You can greatly help this blog by checking them out: use the link here.

 

Back fast! 

In the shipment I got a "jacks and pots" board.....

                                         

.... and a small PCB for 2x dual concentric pots--a personal favorite component for saving front panel space....

....as well as a front panel:

.....I reused the Irwin Dual VCA from last time:

I figured I would use 4x40 standoff hardware to make modifications and fixes easier at this early stage of prototyping:

Construction

During the pandemic I found using 1206 SMD components was easiest for super-fast prototyping. 

I often found myself wanting to change out parts and through-hole swaps were time consuming and occasionally destroyed pads on the PCB.  

A previous post about my journey into SMD DIY is here. 

I have also standardized (somewhat) on JST-XH connectors and hook-up wiring for building nascent prototypes. Skiff designs at an early stage of development leads to frustrating and hard-to-fix shortcomings, like pots needing to be turned counter-clockwise to increase volume. Nice to be able to rewire things!

The initial build went fast, fast, fast. 

I laid out the jacks-n-pots board in less than 45 minutes:

From here it was smooth sailing--like building a kit.

Since the dual concentric pots mount at 90 degrees they needed their own PCB.

initial tests....

WFT?

So did it work first time (WFT)?  Yes, but soon quit (BSQ).

After taking an evening off--which counterintuitively speeds up troubleshooting, I came back to discover the problem was easily diagnosed: some of the 24 gauge wires I had soldered between boards were broken. As I tried to fix them, more broke, then fixing those, more broke. 

Arrg!

To ameliorate I came up with a simple bodge--using 100 mil edge connectors and shrink tubing:

..............which ended up looking like this:

It would have been more elegant to crimp JST-XH 100 mil connects to both sides of the jumper cables but at this early prototyping stage this workaround was good enough.

WHAT NEXT?

The 3 PCB's specifically for the project--jacks board, front panel, and concentric pots board--could be improved in terms of layout; also I had a few ideas for making modulation bias adjustment--needed in some cases for a nice smooth stereo pan at audio out--easier to tweak. 

So....I will create revisions of the 3 PCB's, rebuild this in the coming weeks, and, if there is love, post it all on PCBWAY's community site. 

I already have the "version 2" boards laid out. 

I figure they will WFT? We will see. Stay tuned!

 

Irwin Dual VCA: 20+ Years Later

Readers: If you'd like to build the project featured in today's post, please go to PCBWAY's Community pages--gerber file (main board); KiCAD project/PCB/schematic/library files, and a B.O.M. are here for a socketed SSM2164 version or clone and here for an SOIC IC build.

You can also help out this site immensely by checking out PCBWAY using the link here. Thanks!

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One of my first DiWHY projects from 2002 was Mike Irwin's dual VCA I found in an EDN article (copy of Mr. Irwin's original is posted here).  

Around 2004 I fabricated a bespoke PCB around Mr. Irwin's design and sold several dual-VCA's PCB's.

I needed a simple dual linear VCA for a stereo panner project (details in a future post).

Unfortunately the 2002 era PCB's are long gone....but....Easy! Using Kicad and help from my friends at PCBWAY I made more.

 

SSM2164 Quad VCA. I have a few tubes of New Old Stock (NOS) SSM 2164 IC's but you probably don't....fortunately, 20 plus years later you can get 2164 clones, e.g. here.

FABRICATION 

My 2002 design was through-hole, but nowadays, for quick prototyping, I think using SMD, a stencil, solder paste, and a hotplate are the way to go (fabrication in this manner is described in the high pass filter post here). 

 

getting ready to stencil....

I am always a bit surprised that solder paste, in spite of its name, is not very pasty. I carefully lifted the populated board onto the hot plate after hand-placing the SMD components so they wouldn't slide off.

Bake-o-rama....baked to 215 degrees C for a few minutes then let it cool to 150C, worked great.

Quick power test...power tested OK, no shorts.

Testing the completed VCA....

Did it work first time (WFT?)  Nope. Power draw from the board was about 20mA with all IC's installed...about right....but no sound, anywhere, no matter what.  

Instead of spending hours troubleshooting I did something both difficult and unusual for me: I walked away. 

That night I sprang up from a deep sleep--eureka! I knew why it didn't work. 

The board has 2 power terminals, one for large format (right), one for Euro (left top).  On the bench I used the Frac power header, but the latter Euro power connector SV1 had accommodations for ferrite beads, FB2 and FB1.  

On the bench I left the beads out, thinking: if I was not using the Euro header, why use ferrite beads?  

Doh! The power traces went from frac power header through the Euro power header to some of the rest of the circuit so yes, the beads were needed. 

I soldered in jumpers instead of ferrite beads and the board worked.

PCBWAY--This Blog's Sponsor

If you want to build your own dual VCA--I posted the THT and SOIC versions on PCBWAY's community site. 

Many thanks to PCBWAY for sponsoring this blog and for all the help they've provided over the years.  You can help out this blog immensely by checking out PCBWAY, here.  

A build option: setting the bias offset of the VCA's op amp buffers to something other than ground is possible.  

If you want to do that, leave the 0 ohm resistors off and put present a DC voltage to the OFFSET JST pins. 

OK, getting to the end of this quick post. this VCA will show up in some future designs. The boards I posted on the PCBWAY community site have a few minor improvements to things like silk screened legends, other than that, it's all Irwin, baby.