EFM Diode Filter: Where have you gone Tom Gambalio?

UPDATE: sound clip for this VCF is posted  here.

OK let's turn the dial back to 2004.

That year, a big batch of inexpensive, low parts count synth kits showed up at my door after a long wait.

They were from an outfit called "Electronics for Music" or "EFM".

From the wayback website: EFM was an outfit run by a dude named Tom Gamble. Out of Houston Texas in the good old USA, I am guessing Tom ran the whole thing: circuit design, PCB layout, parts picking, bundling up kits, documentation, mailing out them kits rawhide, maintaining the website, taking orders, and responding to users--sometimes--who complained when their kits didn't arrive or even worse, didn't work.

If Tom had someone helping him I've never read about it.

My own take on the EFM diode filter, finished, tests working.

Yep, I built some his kits; Tom's website clearly indicated his kits were for experienced builders which of course I wasn't. I bought 'em anyway.

Some of  the EFM kits I built are long gone, some of them are still in my to-be-built box, and a few I still use: his LFO5A, and the dual ADSR Deg2A for instance.

My only EFM unbuilt kit that still has the all the parts....NOS in bag, circa 2004!

Still have sommore EFM, over 15 years old, unbuilt.  I imagine others out there do as well.

The best EFM module, that I built anyway, was Tom's VCF6C diode filter.

About the filter: Based loosely (I think) on the EMS Putney VCS3 filter the VCF6c is a simple and effective design. The VCS3 filter is discreet while Tom's uses a hard to find 13600 OTA. But Tom still cops the basic idea.

UPDATE: 5-28-20 13600 OTAs are becoming unobtainium, I tried out a 13700 OTA, much easier to find and it worked--I can't hear any difference.  13700 and clones can be had from places like Druid.

I think the VCF6C sounds pretty good. Maybe sounds really good! It's been my go-to filter for traditional subtractive synthesis in my modular for years now.

The EFM diode filter kit I built in 2004 is kind of wearing out: traces have corroded and have had to be replaced with bus wires, things like that. I wanted to make sure I kept this sound alive in my modular, so using the PDFs from this site and forum pdf capture I fabbed up another board.

No decals yet, but the filter works

My 2 cent soapbox take on EFM: Tom's work was always a bit--rushed? His kits were missing parts at times; there were frustrating IC-frying errors in the PCB traces, schemos and BOMS (but then again, who am I to throw stones?). Maybe EFM was a bit like a microscopically tiny version of Howard Dumble, i.e., he'd take your money then get you the goods--when he gets around to it--at some point in the future.

Customers tore Tom a new one in the audio forums, for his mistakes and long shipping delays and general indolence. It was horrible!

Now looking back, I feel sorry for the guy and feel really stupid for being a dick...I was out what, $15 USD for some kit I was trying to build without a decent DVM or scope?

Tom is (or was? I really, really hope he's still with us!) undeniably talented, produced a heck of a lot of designs and kits and I'm sure worked hard to keep the ideas and kits flowing. I can see him trying to stay afloat in his sweltering garage in Texas in July, gathering up parts, purchasing more caps from surplus places, having to dump out the bag to count the damn things again, while his wife yelled at him for not watering plants and letting their dumb dog pee on their shag carpet.

Right???

Tom must have loved audio DIY and electronics, why else would he be so prolific?  But perhaps his passion drove him crazy. One day I remember his kits just vanished, his site was gone, it's like he just gave up.

Now 15 whatever years later I have never been able to find anyone who knows what happened to EFM or Tom Gamble. I've talked to fellow synth geeks, college electronic music professors, audio electronics mensches, and asked the moderators on DIY forums. Many remember EFM and a few even built Tom's kits, but no one knows where he went.

I am curious: where did Tom study electronics--he knew his way around--did he go to a university or was he self taught?  Did anyone help him with any aspect of his work? Did he really have to wrap up all those kits by himself?

Well, Tom, regardless: thanks! I know the work may have been too much, and we, the nascent audio forum trolls were hard to deal with, but I can say with certainty you did a damn great job on your take of the EMS diode filter. I am happy to report that after 2 evenings sorting out my own trace errors and getting around to putting in the right parts, I got it my redux of your VCF6C working, it's in my rack now and it's sounding good.

About the board: Speaking of crazy, if anyone other than me does build this, you will need a big butt-load o' diodes (this is covered in the aforementioned VCF6c forum capture). Then get out your diode meter and measure each voltage drop across each diode without touching it. You want to match to a thousandth of a volt drop across the diode, so, .6132V matches  .6138 for instance. Put those up in each "horizontal pair" of diodes, which perhaps makes sense if you look at the schematic:

I have posted Eagle/schem/ blah blah for this VCF on my website: here.

If you don't do this the filter won't sound good; I was sloppy at first and had to pull all the diodes and replace with matched.

My buttload-o-4148-diodes. I have no idea where these came from but I have had this lifetime supply forever

There are also 4 .1uF caps between the diodes, get out a capacitance meter and match those too. I bought a bunch of 5% mylar .1uF and matched them to about .5%. Seems to have worked, the filter sounds better after the match.

There is one mistake in my PCB: the left side of R8 goes to ground but instead needs to go to -15V.  It took me about an evening to figure that dumb mistake out but once found: easily fixed.....a corrected version is available on my website.

UPDATE 1-22-20: I don't think I included how I wired up the VC rez pot in any of the docs here or on my site.  Might have been omitted from the EFM site as well? It's a 50K linear pot, wired like the PNG you see below.  There are lots of ways to do this; you can just use a pot if you want, so tie 5V to the "top leg" of the pot and omit the jack....but VC rez is a cool feature found in Tom's design so here it is.

Tom, if you're out there still, reach out to one of us sometime. I don't know about the others, but I feel for you, am grateful for your hard work, and want to know you're doing well.

Saving OTAs--One Chip at a Time--a Simple Hack

Quick background: what the heck is an OTA anyway?

It's a type of IC. For audio and especially synthDIY you see Operational Transconductance Amplifiers (OTA) all over. These chips form the heart of some good audio VCOs, VCF's and a lot of VCA designs for instance.

The idea: It's like an op amp, but current goes out, not voltage; and, there is a "BIAS" pin to determine how much current goes out. A resistor can be used to turn this output current back into a voltage. So: simply put, if you can work within their operating range, OTA chips are good for voltage control of whatever.

The problem with OTAs: These chips are fragile!  If you put too much current into the bias control pin you fry the chip. No warning, no buzz, no hum--the chip is dead!

The upper limit is 2ma. You probably want to stay well below that.

Blowing up a CA3080's or LM13700s, which are still pretty easy to find, is frustrating, but may not be game over--especially now that Coolaudio is making OTAs again. However, for something harder to find, like a LM13600, you really don't want this! The chip is becoming too rare.....

OK how to make sure your OTA is OT-A-OK in your new DIY audio creation?  You can get a current meter and test pins before dropping the chip into your circuit. But I'm too lazy.  Here's a simpler method:

First, build one or two of these:

So you are soldering a medium size LED to a diode in series. For this example I am using a red LED but any medium sized normal LED will do.

OK that took about 5 seconds.....

My finished doodad looks like this:

Next build your entire circuit, up to the point of dropping in the OTA chip.

Solder a socket in where your OTA goes (so: to the PCB, stripboard, perfboard, whatever) and shove in your 2 part masterpiece in like this:

For 13600-13700 you want to test both bias pins. The test rig goes between bias in and V--

Different OTAs have different pinouts, but 3080-13700-13600 is most common so that's what you get here....

OK now sweep your CV (from a voltage generator?  From another module?)  Whatever.

For me, 0V cv should look like this: LED is off!

'
As you sweep up the control voltage the LED turns on until, until!! at 5V, it glows faintly:

If the LED doesn't lite at all, you probably have something wrong with your control circuitry.  You won't blow your OTA IC up, but it's a fair bet your circuit won't work.

If the LED glows bright blazing red, you are probably going to blow up your OTA. Don't put your OTA chip into the socket yet! Instead put a current meter where the LED was and check--but my bet is that it will read more than 2mA. Bummer, but at least your expensive Ebay 13600 IC that took 4 weeks to arrive from Latvia lives to fight another day.

Fix your circuit until the meter reads 1.5mA or less.

I use this trick to test any OTA circuit I've been building, modding, or repairing; I have saved quite a few chips!

OK That's it. OTAs live! yeh baby!

UPDATE 5-28-20: E-M user a.dighera has posted a vid (here!) showing an OTA test LED at work, specifically to make sure a precious 13600 OTA doesn't get blown up while testing a VCF6C filter (blog post for 6C is here).  From my experience, the brightness of this LED looks about right. A lot brighter and you should check your buiild with a DVM first. Many thanks a. for making this vid. 

Balanced Modulator Part II: Nothing like a good B-M!

Potty humor aside, I finished the Electronotes AD533 based ring modulator last week, and I am happy with how it turned out.

Front Panel is from Front Panel Express, post on that here

I was after a balanced modulator where the X and Y signals didn't leak into the output, like the good old PAIA 1492 based design I grew up with. The Electronotes "Preferred Circuits" design seemed like it would get the job done.

Good news: it does! This is a quiet, clear sounding module. Not much (if any) cross talk, cross-tweeze, bleed, high end roll off, low end humpty-humps and the other things that make some B-M's sound, pun intended: crappy.

I am yet to go wrong with any EN Preferred Circuits--the ones I've built are winners. If you are into reading about how the old stuff works, the publication is recommended--USD $39 for tons of great circuits is definitely worth the dough; get it here.

You can read part I of this post here where I build the reasonably stable and possibly unnecessary +/- 10V reference for this balanced modulator.

And--sound clip warning!!--hear the finished module here. For your listening pleasure (?) I tried to capture all the usual BM stuff: birds chirping, laser scifi sounds, gongs, bells, dumb Dr Who aliens, even a balanced modulated redux of a previous audiodiwhy sound clip.

You can get the Eagle files, PDFs, BOMs etc. from my website, if you want to make your own or modify this one.  Update 12-27-21 Get the Eagle LBR file, a library that contains the AD533 in the H10 can footprint, from my Github site, here.


ABOUT THE BOARD:

Here is the PCB, it's small....

The hard to get part is the AD533, which hasn't been made for a few years, but I found them for sale in China via Ebay. The cans I bought ($2 each USD--cheap!) took a long time to get shipped to the US, but once here they worked fine. The AD533 isn't unobtanium yet--if you find them for a lot more dough keep looking.

Building both the reference board and the B-M itself was pretty easy, no trace cuts or whatever needed. Got 'em right the first time.

Nothing like a good sounding B-M using a can.....

I had to create a modified Eagle Linear library to accommodate this part; I modified the Eagle10 pin can for this application, and I figure I got it right--it worked.

For the .0001% of the readers out there who might want an Eagle lbr file for an AD533 I can help.....If you want a copy of the lbr comment below and I'll get you one.

Frac me up Scotty! As usual I had to mess with the boards to get them to sit behind a 1U Frak. The solution: the BM board is located behind the 10V reference on 1/4" 4-40 standoffs.

If you want to save more space the 3x op amp IC's could be combined into a surface mount TL084.

Can the trim: The preferred notes went through a couple of paragraphs re: how to trim out the AD533 balanced modulator, but not feeling like digging out the book and reading it again I put a 2K sine wave through X and trimmed the Y trimmer until I couldn't hear the tone at output, then did the same for Y and X.  I am not sure what DCTRIM does, so I put it at midnight and ignored it. Ha! Worked fine--no bleed. I am happy.

Another way to simplify this is to use a currently stocked 10V reference like the LT1012. You'd have to figure out a way to derive -10V from the 10V but that shouldn't be too hard.

OK another one in the bag!  Good to have a good sounding traditional balanced modulator in my rig.  I'm ready for scifi sound design!

One day I'd like to recreate the original PAIA build and see if it sounds as good as I remember, but, on to other things.

Next up: working on an old Tom Gamble diode filter.  Got it to work once; try 2 (new PCB) was a complete failure.  Working on try #3 with PCB #3 now.  Update: got it to work!  Dumb mistake on the PCB! Post is here.

Until then don't breathe the fumes!

Building a Low Cost 10V reference for Audio

UPDATE: The Balanced Modular referred to in this post is now done and working!  For Part II please go here.

===============

I've been back at this audioDIY for a few years now and I am still looking for a really good balanced modulator.

A strange sentence right?

This is partially sentimental, my brother and I built a 1492 based PAIA 4710 Balanced modulator when we were very young indeed (12 and 14?).

Long Live PAIA!

I clearly remember how much I liked that module. The damn thing sounded frigging great! Metal klangs! Space gun laser sounds! Weird robot voices! Impress your friends! Baffle the girls!

Looking back, many of the modules in the PAIA 2700-4700 series sounded--well, bad, but not this one. Maybe my mind is playing tricks on me but the 4710 sounded better than anything I have in my rig now.  I have to admit it: I'd like a good, clean B-M.

So just rip off the 4710 schematic? Maybe...but 1492 IC's are hard to come by and hard to design around I think. The power (+18V, +/- 9V) isn't close to what I use in my DIY modular. Whatever.

I've tried recreating the good old days with AD633's as well as a Thomas Henry designed 3080 RM from his 3080 book but neither sound all that good. Also I fabbed up this Korg MS20 style RingMod which is cool but is pretty choosy about the incoming wave forms (ramp works best? Pulse?).  You can see my ring mod webpage here.

Hunting around more I found a AD533 based Balanced Modulator in Electronotes Preferred Circuits and thought this one might sound good!!

A lot of energy for the EN circuit is spent getting rid of "bleed through" which is the stumbling block of the latest B-M's I've tried to create. I'm not sure I use the right audio term for that. Crosstalk?  Here's what happens: The X or Y audio input can be heard, unadulterated, at output.  The digital (VST) BM's I use with Ableton never have that problem.

At output, I want pure, robotic, squeaky clean B-M sound. Looks like this circuit makes it happen.

For better or worse, the EN circuit requires an Analog devices 10V reference IC which is no longer made.  But! wait a minute, I already put together a working +/- 10V reference for a log converter I built several months ago. You can see that here. I will use that.

10V Precision Reference, finished, tests working

The ref circuit is simple.  It uses an LM397 zener at its core. The idea: you can heat up the 397 zener and nevertheless it stays pretty close to spec. So we have e-z super simple temperature compensation here, always a tough part, in my experience, of a good voltage reference design. Plug the Zener into the ADJ of a 317 and 337 v-reg, some glue trimmers and resistors, and the requisite coupling caps, and ahoy, you get a decently, pretty temperature independent steady voltage source.....

Here's a link to the datasheet for the LM329s.  I got some surplus for next to nothing, they are still out there. Can you make a more stable reference, put your circuit under a heat gun and have V++ stay steadier?  I'm sure you can.  But for a 1980's era Balance Modulator, I figure this design is good enough.

More next time: when I actually see if I can hook this to the EN Balanced modulator and make some sound. (update: works! here.) Until then, don't breathe the fumes.

Korg MS20 Filter--the Why in AudioDIWHY.....

OK this one drove me crazy. 

This should have been easy, we know that Rene Schmitz stuff sounds good (I have already built his "FEITW" ADSR) and I thought, let's try his MS20 filter.

So: Did the Eagle design based on what's on Rene's site, put together a board layout, and sent off for fab. 

This is a pretty simple circuit and from a good looking schematic, from a smart synth DIY maven, why wouldn't it sound good?

You know how I sometimes post: worked first time?  This one most definitely didn't work first time. Neither filter worked for beans for at least 3 evenings--and the second one took me more like 5 evenings to get working. This got me to wonder, why not just buy someone else's filter design? Does a kit qualify as DIY (of course it does....but it's not enough torture for me?)

I used a 2x dual concentric pot PCB for filter #2 which I cut down from this PCB.

OK I built two and at first both builds passed audio but both filters sounded--wimpy. Almost like a cheap stereo tone control, not that nice fat MS20 sound with dirt when you crank up the "Peak". I know Rene's designs are high quality, and a skinny sounding filter must be on me.

Building Filter #2....

After probing around a lot with my scope I ended up tracing this to a stupid mistake: I copied the schematic wrong into Eagle!  I drew up a critical voltage divider incorrectly, which was causing a journey to 6db cutoff, wimp ass sounding low pass land. But the 8-28-18 PCB is still useful, although you have to do a trace cut and some kludge wiring to get it sounding MS20-like.

But then again: what would DIY be without trace kludges?

With all that crappy advertising, you can get my PCB design (the one needing a trace cut, 8-28-18, and fixed yet untested version, 1-9-19) here.  My website includes BOM, wiring suggestions, and specifics about the trace fix.

MS20 filter #1 finished, no decals yet, (I think) it sounds Rene-errific

Great! we get that crunchy peak sound, fat lowpass and nice Korg growl!

Next I turned my attention to the second unit (two VCFs so I can HP + LP = band pass? Two on the original MS20 right?) But even with the trace fix, the second MS20 filter had a strange problem--when I cranked the CV up the audio output went completely dead.

Damn! It took me 2 more evenings of comparing the working VCF to the broken one to figure out problem! I suspected a parts placement error, but after checking twice, no, everything is OK.  Bad IC?  No; swapped everything and no change. Could I live with a VCF just not eating any CV above about 4V DC?  No, not really.  And besides, #1 worked, so #2 needs to work the same way.

Arrg!  Too much shotgunning! 

Ended up tracing this to a wiring problem with one of the grounds:

Filter #2, turns out, the normal is the fault--thanks to E-M GRUMBLE for the suggestion....

Goes like this: for an MS20 OTA filter: if you want high pass, stick audio into one end of a critical cap. If you want low pass, ground the same end of the same cap and put your signal into the circuit's main input:

Not having room for a switch in a 1U Frac, I used a normal to ground the cap, and the normal had a cold solder joint.  Yow! So when I put audio into the "LP" input, it would cut out at high CV.  If I put audio into the HP input, it wouldn't work at all. Not at all the way I would think this issue would manifest but there you go.

OK with all that sorted, I did a recorded the quickee demo, here.

Second MS20 filter works! Filter 2 has 2 mod inputs, I was going to use this as the primary filter of the two.

Five evening later, I have to wonder, was all of this worth it?  There are a ton of PCB's for MS20 filters already out there, did I really have to do my own PCB? I doubt it, really. Hell, I could have just bought one of those MS20 repops, and if it went south, bug Guitar Center for help right? Maybe not?

I think I just like to torture myself, building machines that I go crazy trying to fix over the course of 5-6 evenings. Welcome to the world of DIY.

Hey!  They work!

I realized something important: I hate, hate, hate haatteee it when things I build don't work. More than I should. So why DIY at all?  This is like being into sailing but hating water, right?

In my rack--panels redone using FPE

I'll have to ask my girlfriend, who is a mental health professional (really!) why this is, because really I have no idea. Was I dropped on my head at a young age?

Granted--too many fumes. I need a break.

ReneDSR: Fastest Envelope in the West, Finished; Sound file and Build Notes

Back Again!

I needed more ADSR's in my modular so I built some based on a very cool design from Rene Schmitz.....You may want to read part I of this post here., where I create the PCB, discuss what "Tau" means, show you useless bench build photos, and so on.

Left to right: finished modules: ReneDSR, Return of Son of ReneDSR, and Son of ReneDSR

Not just Decay....."Fastest Envelope in the West"--by adding a switchable "YA" cap the entire ADSR gits along, little doggies

Does capacitor size matter?  

That's the "rayson d'tre" for these builds, but?? From last time, the basic design of these sorts of ADSR's sends gate logic to an RC circuit.

Good news: 

OK we've already determined that the size of the resistor and cap (the resistor being a pot and/or a resistor network) determine attack, decay, and release speed. So, should we build these with large caps and small pots?  Small pots and large caps? I think the jury is still out, because to me it all feels and sounds good. You can mix and match caps and pots here and have fun; the sun will still come up the next day.  And, set up right, either combo can provide mix-cutting, DJ boogeying, MDA popping sweaty-bodies-dancing-w/-body-odor bodacious snappy synth decays.

I tried to create a very simple demo for these modules, and you can hear sound samples here.

About the sound sample--other than the WAV loops this is all my modular with ReneDSR:

00:00: multitracking 6 mono notes on a DAW (Ableton Live 10). Attack time is set to minimum; release is set to max; it's a very fast attack (I didn't measure it on a scope, but you can hear, IMO anyway, it's a reasonably fast attack) with 23 second decay for VCA, and same for VCF.  I put a lot of rez on the filter to make the sweep more noticeable. You're hearing a 10uF cap and 2.2M audio taper decay pot creating the ever import tau (see the last post).

From this I get an MiniMoog's long release (>20sec) or maybe a Prophet 5-ish sound. I am happy.

00:33: Dual Osc bass line, maybe a bit of a Stevie Wonder? I always like that; Stevie and the late great George Duke are my all time favorite synth bass players. I remain happy.

00:55: Sequencer patterns. This is 2 sequences overlapped, making heavy use of ReneDSR's fast decay, without which the moving patterns sound mushy. I am not a big Gorgio Moroder sequencer guy but I know a lot of synth freaks out there are and for this application the ReneDSR performs well.

01:44: Single Oscillator to VCF to VCA, with SonOfRene controlling the VCF and Return of Son of controlling the VCF cutoff.  In many mixes I find that a single OSC bass sounds sit better than dual or 3 osc basses. Maybe a bit Roland SH series sounding. Why not?

The Roland SH-5 has one of my all time favorite ADSRs.  From the shop manual, it's a pretty simple discreet design from those crazy and creative 70's Roland dudes, so a PCB maybe for a later build?

The Return of Son Of uses a 2.2uF cap and 3x dual gang 1M audio taper pots. Each switch selects very good control of a 1M audio taper pot; or, tap off the wiper of a 2M pot. This allows for a good fast attack and decay with a longer release as needed.

Return of Son Of RenayDSR Switch Wiring.

Another build idea: In any Rene 2.2MB pot build, you might want to put the 2.2uF cap on a DPDT switch with say 10uF cap for longer decays and releases.  Or for 1MB pots, a 4.7uF and a 22uF.  Experiment and have fun! You get the idea.

Front Panel didn't come out very well for ROSO, lumpy and bumpy, but it's good enough.

The other 2 units--ReneDSR and Son Of ReneDSR--are pretty much a straight builds of Rene's two design variations on his site.  The 1U device has 1MB audio taper pots for ADR and a 4.7 and 10uF cap on a DPDT switch with 100ohm resistors in series. The second unit was featured in this post, and uses 2.2MB Audio taper pots, which can be a bit hard to find.

One more tidbit: Rene's design calls for CMOS 555 timer chips, I bought about 10, and couldn't get a single one to work in the 3 circuits you see here.  A standard 555 worked every time. So they may be something wrong with my PCB, or maybe I got a bad run of CMOS chips. Whatever--gotta move on.

Overall, a fun build, and more good sounding ADSRs were very much needed in my rig.

So if you're looking around for an EZ ADSR that performs well, and is fun to build, this may be it. FDITW is highly recommended.

And as always, don't breathe the fumes!

Front Panels: The Technique So Far

Not only am I learning about electronics but also working with metal?

Here's a quick post about how I do this, hope I don't forget this in a couple of years. This technique (?) is good for drilling holes, reasonably accurately lined up, in flat metal prototype panels.

First: I get my aluminum blanks from PCBWAY in China ("Alubase PCB").  Personally I use FrakRac format for my Audiodiwhy craziness but this should work for 5U, Euro, a one-off front panel for a preamp, a 19" 2U panel for a power amp, or whatever.

Today I am building an modular synthesizer ADSR and need extra drills for SPDT switches and the PCB bracket's 4/40 screws....

Using Eagle (but any illustration program should work) I create a 1:1 drawing of the existing blank with existing holes, and add any extra holes that are needed.

Next I see if it all lines up--this one is getting close.

More alignment, but still not there.

Once aligned (or before) I can add pencil marks for anything else I want to drill. I am basically being lazy--it makes more sense to put this on the CAD drawing, but, oh well. Here, it's for the brackets to hold the PCB. A straightedge and ruler are friends for this.

In the words of my personal hero, Frank Zappa: here is the "crux of the biscuit": The glue on the left will attach the paper print out to the front of the panel, with enough stick to not come loose or tear during drilling. The solvent on the right will completely remove the paper template and any glue that doesn't come up when it's time to ditch the paper. Warning: the solvent stinks to high heaven, so wear gloves or whatever, work outdoors, and as a last resort, try not to breathe the fumes.

All can be purchased at amazon, craft stores, hobby stores and the like.

I use a very small hand drill to create the pilot holes. These can be found on line or in hobby shops--the model airplane folks apparently use them quite a bit for instance. I have found that punches and the like can distort the metal panel's shape.

I invested in a small drill press and put it in my garage. Highly recommended. But!! Caution: Use sharp bits, and always wear gloves and eye protection with this tool--seriously, I have had some close calls here.

Here's a mock up of how things ended up this time. Pretty good, but not perfect! The left hole for the PCB got screwed up; the drill press skittered because I didn't have the bit tightened down enough.  Damn! Glad I was wearing gloves!  This time, I am going against every fiber of my mild OCD; I am going to try to leave it as-is. It's good for me!

Final mock up. Not bad for a prototype, in spite of the screwed up goof on the left. Damn! Oh well. I need to finish the ADSR, and it's a 3 day weekend here in the US so maybe I will do some Lazertranning.

Moving on....happy drilling!