Friday, March 29, 2013

Gabotronics XMEGA Xminilab Review

So I know my last post was about oscilloscopes and I never like to post about the same thing twice, BUT I received an oscilloscope today, messed with it, and may as well blog about it since that's kinda what I do aside from Tweet and Post. I should put "compulsive tech/music/electronics blogger" on my resume...

So I decided to show my dad Gabotronics' line of oscilloscopes. Given its price and incredible functionality, he not only got me their Xminilab but also all its accessories: programming header, jumper leads, USB cable, and carrying case. Dare I say, it's one of the best oscilloscopes I've seen.
Before I go much further, I should point out that the USB cable is mainly for powering the unit, though it can be powered via +5V to one of its pins. It's not a USB-centric oscilloscope, however you can export data from the oscilloscope to your computer via USB.
So when I got it into my studio, I slowly unpacked it and pretty much basked in the fact that I finally had a working oscilloscope. Oh, and had Deadmau5 blasting at a decent volume (did I mention I recently sold some random gold and bought some KRK monitors? I didn't? Well there ya go.).
I opened the manual, and one of the first things I saw was the pinout. "Well," I said, "I may as well grab a breadboard to put this on." I then proceeded to use the jumpers to connect grounds to my PSU's ground and use them like permanent probes for the 2 analogue inputs, waveform generator output, and External input.
Without referencing the rest of the manual, I connected the first channel to the output of this simple oscillator circuit (which is indeed my simple op-amp based square wave oscillator with a 1Mohm pot for controlling frequency):
At the time I also had a couple filters after it, so I was messing with those as well. It has nearly all the functionality of more expensive units, including vast zoom capabilities, which is great for either reading idiosyncrasies of even high-frequency audio waveforms or watching LFO's operate (which is quite fun, if you've seen some of the LFO's I've created). This is the oscillator's output:
While playing with the various controls (which are laid out very much like an 80's button-job synthesizer), I noticed the manual stated there was an automatic setup feature. I had already set up the oscilloscope just using my mostly-basic knowledge of oscilloscopes, but because I was curious I tried it. Turn the 'scope on, patch the waveform generator to the channel input and hold K1 (the left-most tactile switch). The result was a super fast waveform scrolling by with no triggering. I reset it so I could actually see the waveform, and got rid of the second channel for clarity:
Nice screen, eh? And as you can probably tell, the screen is highly visible from almost any angle. Which is good, because I can't really take much of a top-down shot. Don't let the small screen scare you; it's very easy to read, and unless you're measuring the idiosyncrasies of noise, the relatively poor resolution is perfect.

Another good thing about this oscilloscope is how the controls are laid out. If you've ever used an 80's button-job synth, or just know how to push buttons in various sequences for a final output, then you will be familiar with using this oscilloscope. Would I prefer per-function knobs? Of course. But, Gabotronics was very smart in their menu layout, and everything is easy to access and figure out. They even have various diagrams of how menus work in the manual!
I've really only had a couple hours with this oscilloscope so far, but I can tell that it will be incredibly useful in making sure my designs work. Everything from voltage measurement, frequency counting, spectral analysis, outputting test waveforms, and of course being an oscilloscope, and I will probably use every single function multiple times a day.

I didn't go through everything it can do, mainly because Gabotronics laid that out better than I could:

So, for around $80 for the Xminilab, including all accessories, you can have all this amazing functionality in a rather small footprint (as you saw, I'm just using a small breadboard, but you could easily have it hanging off the side of a breadboard, or even make a little case for it).

In my opinion, it couldn't have been better.
PS: my apologies, my last computer crashed and now I have a new one (also courtesy of my loving father; damn I owe him a lot), but I don't have Photoshop on it yet so the pictures aren't all pretty n stuff. They looked fine on my camera's screen...

Thursday, March 21, 2013

Finding an Oscilloscope

One of the most important tools a synthesist (or synthesizer builder) can have is an oscilloscope. The only problem is that these are either costly or problematic - well, unless you do a bit o' interwebz searching.

If you don't know, a while back I got this Heathkit Oscilloscope from my dad, who got it from eBay.
The seller said it worked, and it had an image showing it working. As it turns out, all it does is power on (aka not explode when you turn it on). No display, no waveforms. I've checked it over, measuring resistances, capacitances, and so forth, and the only issue is that one of the tubes doesn't light up. Normally, this isn't an issue, except that tube just so happens to be a rare Russian tube that hasn't been made for like 50 years and now, if you can find one, will run you at least $60, which is more than the whole unit cost.

So, I certainly can't fix it, and don't want to find someone to see if they can fix it because they probably cost a lot as well, and can probably get a whole oscilloscope for the price of that one tube which may or may not repair this oscilloscope. Thus, I've done some research and found two things that are incredibly useful in my search: eBay, and Gabotronics.

Let's start with Gabotronics. Among other stuff, they make the world's smallest yet most powerful oscilloscopes. They have various models, but the two I like are the XMEGA Xprotolab and the XMEGA Xminilab. They are cheap ($60 and $80, respectfully), have way more functionality than I'll ever use, but are small and digital. Digital isn't so much a problem except that it means pixels, which means slightly less precise waveforms. Small really just means you'll be using the zoom functions a fair bit.

eBay, of course, is a good place to find cheap stuff. This is true also for oscilloscopes. I had to do a fair bit of filtering, but eventually found a bunch of oscilloscopes for less than $100. By this point you have to really look at the descriptions. Since I've had bad luck with the old Heathkit, I'm pretty much staying away from anything that remotely says it might not work. After that, I just add everything to my watch list and hope they stay affordable!

PC oscilloscope software obviously exists; in fact, I use Visual Analyser 2011 for looking at synth waveforms in my studio. My thing with software oscilloscopes is that you either need an interface or some kind of current and voltage limiting. Most computers don't like raw analogue synth outputs. There are many ways around this, sure, but then you have the problem where my computer is in a totally different room and I really can't move it much. Then, of course, name a computer that doesn't have noisy audio that's actually affordable. I pretty much stay away from using software 'scopes, as you can imagine.

Now, I just need to wait for an affordable oscilloscope to come around (or buy a Gabotronics one) and figure out what to do with my Heathkit. Maybe put it back on eBay. Or, maybe just sell various tubes from it. Or do nothing. I don't really know. I mean, it looks cool, but I'm not a huge fan of giant nonfunctional decor from the 50's.

All while trying to start a company. Where's this supposed "suitcase with $1M in it" I hear about sometimes? Could really use that.

Sunday, March 17, 2013

Stuff n' Stuff

Rapid fire updates, here we go!

I Wub Yew
So my debut album, I Wub Yew, is bound to go to international stores within the next few weeks. The album cover is 90% finished, I've actually added a new song to the tracklist (which I may have uploaded to Soundcloud and is being somewhat popular), and then I need to upload everything to my distributor and give them cash. After that, it's about 2 weeks until you see it in online stores all around the world, and physically through Amazon.

Xanu Modular
The Xanu modular is now stuck at revision 1, meaning that the panel designs and schematics are going to be considered 1st generation. It's in both 3U and 5U formats for now, but of course, custom work is no issue.
And, the good news is I may have a potential start to this whole thing with *drumroll* a sequencer:
No promises, of course, but it looks good.

I can't safely go this week or next without talking about Ultra. If you don't know, I'm talking about the Ultra Music Festival, a two-weekend electronic music event which stars all the biggest names in the industry for a giant rave in Miami, FL. Fking incredible event, really. I can't go, but thankfully they've been livestreaming the whole show on their YouTube page, so I get to see the show with degraded audio but better views!

And, of course, I really can't go much further without talking about the 2nd day closer show. Three words: Deadmau5, epic, and fireworks. Despite the 7 times he trainwrecked epically (that's DJ-talk for being out-of-time), it was an incredible show, both musically and visually. I mean, fireworks. Name a mouse who's had fireworks behind him. Exactly, you can't. Mainly because Deadmau5 is a human, but whatever.
Sadly, I'm only catching a few sets at a time, and today a bunch of acts played that I really wanted to see, but oddly enough reality has prevalence over being high off music. C'est la vie.

If you know me at all you know I'm big on gear. I have an idea to have a semi-public museum of synthesizers, guitars, orchestral instruments - a ton of neat stuff. Yesterday I got to play a really undervalued vintage synth, the Roland JX-8P. Analogue goodness with DCO's, it plays like a dream, sounds like a dream, and was a mere $200! I totally want it, even if it doesn't fully function (aftertouch and LFO bender don't seem to function):
Also, I'm still on the lookout for a pair of direct-drive turntables. Tomorrow I'll be going out to various thrift stores and such. I've only seen two turntables in places like that: one was a fancy cabinet model, and the other was pretty beat. I'm about as pre-addicted to turntablism as I am modular synthesis. Let's hope for the best!

I didn't grab a pic of it, but I finally got to play Casio's XW-P1. I was really hoping Casio had redeemed itself with this, but in fact it's just as bad as their standard "cheap keyboard" scheme. Don't get me wrong, it is musical and can sound good, but good GOD it's built like a piece of paper, has a pretty crappy interface, and it is literally the most digital-sounding synthesizer I have ever heard. What the actual fk, Casio. I was hoping I would want more from you than this little VL-Tone I have. I still want to have a few hours alone with it, but in the 20 minutes I spent with it, that's my verdict.

Ok, I think that's about it. I guess I'll see you next on iTunes, unless something else interesting pops up!

Saturday, March 2, 2013

First Xanu Module EVAR: The Xanu Delay

Before I get started, I'd like to quote an earlier post:
"Q: If you plan to turn this into a company, why do you post all of your schematics and explain how they work?
A: Why not? I mean, I technically own all of my designs, therefore I should be able to use them however I'd like. If you think about it, I'm just saving you time. You can go online and see the PCBs of any module, and you can look at the connections and build one yourself. I'm just saving you some time."

Ok, now, onwards to the subject.

I recently was talking about a module idea I had, a digital delay. Well, after figuring it out a bit and submitting the idea to Muff Wiggler, I'm ready to post a little more about it. It seems like it could be a rather successful delay.

First, general circuit design. What I can post isn't much because the actual delay circuit is rather large and I don't feel like drawing it, but you can get a general idea:
Click to make it larger. Something you may notice is how strangely the delay time is controlled. I used a FET in place of the actual time resistor, which means several things: VC is easy, delay time can be INSANELY long (given the FET is pushed to its limits), and it's really the only way I could have made it VC given the delay line I'm using (PT2399's). The problem with using FETs is that, to use them as resistors, you need to apply a negative voltage to the Gate (hence the inverter). Positively biasing them for a long time may make them melt, and it won't act as a resistor (well, technically when it melts it'll be a resistor of nearly infinite resistance and thus really long delay times, but whatever).

Enough technical stuff. Let's move on to ALL THOSE FREAKING ATTENUATORS WTF. Yeah, so there might be a few attenuators, but it's for a good reason. It means you can mix various signals very precisely and get a ton of different delays. And, given the somewhat high-gain output amp (gain of 11), there can be no volume loss by the end of the chain. You'll also note the input attenuator (the fixed resistors). That's useful because modular signals are typically pretty hot (high-ish voltage) and could probably very easily burn out the delay chip as well as clip through the output amp.

You also have the delay time manual control. This is actually just an attenuator lowering the voltage of the main power source to the FET. The delay time circuit also has a switched jack, so you can use manual delay time or control it via an external voltage. And, as a final note, You'll note that there is a Range rheostat on the same line as the FET. This isn't exactly necessary and could easily be replaced with just a 1k resistor (it needs some resistance), but including the Range control allows finer control on the delay time, which is good for manually syncing it with some kind of clock source. If I figure out how to automatically sync it with a clock, I'll let you know.

Now that that's generally explained, here's the front panel:
It's pretty basic, like most of my designs. But I did label this one and add lines on the knobs. Makes it more awesomer n stuff. The two outputs are exactly identical, I guess just because most people use Delays at the end of their signal chain and it makes it easy to interface with outbound gear. I may make it just mono, though, I dunno. I also grouped things: time controls on top, audio controls on bottom. I may move the Time-CV input to the bottom, though.

Input volume (input signal volume)
Output volume (total effect volume)
Feedback (literally feeds delay signal back through the delay)
Original (volume of input)
Delay (volume of delay, 0% bypasses delay circuit)
Time (delay time within range)
Range (sets max delay time)
CV amount (controls how much incoming CV controls delay Time)

CMOS-based with HQ AD and DA converters
less than -90dB noise
less than .5% THD
44kHz sample rate
Max delay time: ~2 seconds (guessing, will probably be more via the FET)
~15mm deep, will have to check when it's done
currently unknown current draw, but I doubt it's much.

Now, the bad part: everything works perfectly... except the actual delay circuit. It does delay, which is kinda expected, but for whatever reason you can hear the internal VCO and it has constant feedback. So basically it's a constant rhythmic noise source. I blame cats. But, this is more likely due to not having EXACTLY the right parts (digital circuits are so picky), so when I get/find the right parts I'll remake it and try again. I mean, who seriously just has 3900pF, 590pF, and .082uF caps on hand, let alone random resistor values? Though I did just get my Futurlec shipment in (finally), so maybe they're in there.
Now, bear in mind I can't make it or sell it RIGHT NOW, because I still need a few materials (12hp faceplate, jacks, knobs, etc.), but it generally works. I just need to fine-tune it a bit.

Neat fact: I'm literally only using this delay chip because Korg used it in their monotron Delay. And, I mean, it's made by Princeton Tech and has very few external parts compared to other delay lines. You really can't beat that. And before you ask, no, I'm not going to use BBDs and make it analogue, although the general principles can apply. I've never seen them have very long delay times (usually less than 1 second) and they cost a LOT more -- these were like $8 for 20 chips. BBDs are $8 for ONE.