Showing posts with label diy. Show all posts
Showing posts with label diy. Show all posts

Monday, June 7, 2010

x0xb0x SS#01: Finished

Better late than never! The finished x0xb0x, SS#01. I never did take the time to snap that last photo and wrap this up but here it is.

With all the experimenting one can do with a project like this, I have to admit that it was difficult to simply close it up and consider it done. Time and time again I would open it back up, try something new, and tweak it some more. Despite the long lag in posts here it has served my set up really well by being a go-between of all sorts. I've been using it practically daily since my last post. Midi in and thru has been used in full force, with Ableton Live serving as the Master to all the gear and the x0x slaving a Jupiter 6. The CV/ Gate has proven itself worthy controlling a modded MC-202. Finally DinSync, of course, has properly connected the 202 and a TR-606 to the whole rig. So , all in all, this is an extremely useful instrument and tool. The 303 cloning is perfect and the I/O it has on hand bridges the old gear with the new beautifully.

Did I meet my goals?

In one of my first posts I set out a plan for this project:

- Keep the hard costs as close to zero as possible,
- source as many of the parts locally and from within Canada,
- minimize (or at least be aware of) hidden costs,
- document time and cost.

Hard costs:
I'd say I came out ahead in some areas and lost out *a bit* on others. The grand total for *this instrument* came down to about $475.00 CDN when factoring in rare parts end to end (including a $50 BA662A), some custom features like the Korg EMX-1 TB-303 style silver knobs, puchasing from multiple sources, shipping from all of these sources, and duty fees in some cases, and hidden costs. In some cases it was only advantageous to make a larger quantity purchase to justify the shipping. This means building multiple x0xes to spread out the cost. I would say I embellished in some spots to get the sound just right and that increased the cost.

Parts from Canada:
If I only I knew then what I know now! Since the start of this project I have found other sources in Canada that significantly help control cost. I largely used sources based on the BOM that was provided by the x0xb0x community but I now know that many components can be had here for more or less the same price and I can cycle of drive to the store that sells them. My next project, as you'll soon find out, already begins utilizing these sources.

It's interesting to see how wildly prices fluctuate between suppliers. A basic component like a resistor costs $0.09 US each from Mouser. I can get the same carbon resistor locally for $0.02 and a 1% metal film resistor for $0.05. It doesn't seem like much but when you need hundreds of them and factor in shipping and duty this is a significant difference. One can rationalize this purchase by lumping it in with items like pots and encoders and what have you to justify a one supplier purchase, but if cost is important, as it was for me, it's worth watching carefully. My original pruchase from Futurelec helped tremendously. I picked up enough 1% metal film resistors (and other bits and bobs) from them for three units at a cost of $0.02 each.

Minimize hidden costs:
This is where one can bloat and kill a budget. Shipping here and there for this and that, duty (which you can't control), the odd trip for another part, and experiments with another component types. Before you know it you blew another $100. If you click-and-shipped your way through this maybe it's $150-$200. It's so easy to blow that extra cash and then marvel about how you got a 303 for $350. But did you? Nope. Not at all. Not even close. Look at the numbers and it'll tell a different story.

I think I did minimize these hidden costs to a degree. I didn't avoid them but I did minimize it as best as I could given that this was my first crack at it and I was aware that it was part of my goal. As I mentioned above I now know that I can do better in this area but I think I did okay.

Document time and cost:
Grand total: $475.00 for this unit and if I factored in my time at an hourly rate add on another $10,000.00 :D This is a very involved project. If I was in the business of electronics I suppose I could bang this out much faster but cine I was learning it took loads of time and preparation. The caveat with that $475.00 is that I've got enough components to build two more. If I don't pursue that (hint, hint) then the cost is significantly more.

What did I learn?

First of all I learned that I love the 303 more than I did before! This project is well worth going through, not only to have yourself a prefect 303 but to also learn about the inner-workings of a legendary intstrument like this. It's pretty cool to crack open a real 303 and understand what it's doing. For that reason alone I'd recommend it to anyone who's into synths and is prepared to open one up and look at it up close.

Secondly I've learned that I need to be patient. As soon as I got impatient I made mistakes, some of which cost me more money and time. Having said that, I may have been too patient in other areas of this project. A year and half to wrap up the synth and blog is too long. In reality it could have been completed in much less time, real life interruptions notwithstanding.

Finally I learned that I'm capable. I suppose it's like any area of interest, as soon as one gets a little bit knowledge in a new subject a whole world opens up and new possibilities become apparent. Despite the lag on this project's time line, I did make time to work on other synths in between since I had no fear of opening them up and seeing what was going on with them. The more vintage gear one has, the more it becomes a necessity to maintain it all. If you have deep pockets by all means take it to a pro. Quite often though the repair can be fairly simple, so projects like this x0xb0x begin to educate us gear heads.

Wednesday, September 2, 2009

x0xb0x SS#01:Tweaking

One of the things I noticed with my x0x was that it wasn't *quite* a 100% match to the 303 sound I knew. The resonance wasn't quite there and it had a slightly harsher sound to it. The forums cover this in great detail so I won't repeat it all here but I'll touch on a few points that affected my x0x.

The biggest, most immediate change I noticed was swapping Q11 from a 2SC536F to a 2SC945. This noticeably muffled the sound but warmed it up. The harshness everyone describes can be eliminated right away via this transistor. The muffling effect it produced could also be adjusted via TM3, the VCF trimpot, so the range could match an original 303 with the 945s in them. I trimmed this pot after the swap and was able to match it to the real 303.

Secondly, the resonance level needs to match. This is such a signature to the 303 that's it's a must have feature. If the betas are too low in Q8, Q9, and Q10 it doesn't "scream" enough. I have to admit that I found it lacking in mine too. I started by swapping out my 2SA733Ps to 2SA733APs. The APs are found in all original 303s. Unfortunately it didn't have any audible impact for my x0x. As such I dropped the Ps back in and left them. What *did* work was adjusting the resistance in r97. The stock version calls for 10K. I found the sweet spot on this unit at 9.2K. This produced a perfect match with resonance at about 90% and left 10% more for me that exceeded what my original 303 had here. Some people add an extra pot to make this variable but I don't see the need. This produced what I wanted and still kept my 733Ps in use without using "fancy" APs.

During this tweaking I ran A / B comparisons the whole time with matching patterns and I can say that it is SO close to a match now that it's scary. For most ears it's an inaudible difference and in real world use it won't be noticeable. I can hear very, very small differences but it doesn't affect the overall performance and cloning ability of the x0x. This unit is without a doubt a near perfect match to the real TB-303 on my desk here.

So, to round up, it's at least three key steps:
  • Q11: swap the transistor from a 2SC536F to a 2SC945
  • R97: Reduce the resistor value from 10K to 9.2K (though subsequent units, or your unit, may be a different value)
  • Adjust TM3 to match the cutoff setting to your preference. In my case my preference was the TB-303 I had here.

Sunday, August 30, 2009

x0xb0x SS#01:Testing & Tuning

All the parts were in place; I was soldering and building the x0x carefully; I certainly spent enough time on it. I couldn't figure out why the x0x wouldn't fire up. I compiled a list of all the tests and went through them once more as a matter of quality control. I completed a battery of tests and got support through the x0x forums and covered everything from my power supply to each IC in the digital section of the pcb. It turns out that my earlier envelope issue was still at the heart of the problem. It was still causing errors and wasn't sending the correct voltage to the amp. After about 2 hours of troubleshooting I was relieved to discover that 2SC536F in Q37 was faulty. I replaced it with another one and low and behold it was fully functional! LIGHTS AND SOUND! Relief & Joy. It wasn't my shoddy set of skills. It was a dead transistor.

Hours of jamming and more tests ensued. I had the x0x drive a TR-606 and vice versa, Ableton and ACID driving the x0x via MIDI, and even had a connection to the c0ntr0l software.

After a good week and a half or so of just enjoying the synth I finally sat down and tuned it as well. It's by no means a complicated step but it does require a bit of patience. The forums suggest setting the tempo to its lowest speed, setting up a low C and middle C, both with long slides and decays and using a tuner to match it all up. This method worked beautifully for me via Wavelab 6 and a free tuner VST.

I must say that I thought the x0x sounded amazing when I got it working but hearing it tuned properly really makes it sing. *Now* we have an instrument here!

Saturday, May 23, 2009

x0xb0x SS#01: VCA

The VCA was a reasonably painless step. It was really nice to see the BA662 IC get dropped into place. Seeing it on the pcb starts to give one the sense that the project is taking shape (despite upcoming steps being rather large).

Q31's hFE: 198
(again - based on my faulty meter)

Testing this section gave me some odd results. I was able get a change in sound behaviour but I couldn't say that it sounded like a note. I tested the resistors and got some odd figures here:

r127 (47K) : 39.4 K
r128 (220K): 52.5 K
r129 (2.2K): 20.25 K

The folks on the boards suggest that it's not entirely out of the ordinary and suggested I carry on to the sequencer to trigger notes properly, then troubleshoot again. I'll follow their advice on this one.

The parts for the headphone / mixer are set aside already. I'm looking forward to starting that.