0

Help tuning x0xb0x?
Moderators: altitude, adafruit_support_bill, adafruit, phono, hamburgers

Please be positive and constructive with your questions and comments.

Help tuning x0xb0x?

by MattB619 on Fri Jun 22, 2007 9:20 am

Hi, I am a total n00b and I need some help tuning up a used x0xb0x I recently bought. I'm wondering if anyone could be so kind as to help me?

Essentially, it is out of tune across octaves. I have a guitar tuner, and using the tuning knob, I tuned it up thinking I had the problem solved.

Oddly enough the tuning knob was at about 1:00 when I thought it was in tune.

When it plays higher notes or lower notes, it gets more and more out of tune, yet when I go back to the original note I tuned, that note is still in tune.

It seems to go flatter the higher I play.

I am not sure if it is the power supply not giving off the proper amount of voltage or if it is the VCO.

Does it sound like more of a power supply issue or a VCO issue? Is an oscilloscope necessary to fix this? THANKS!!!!!!!!!!!!!!!!
MattB619
 
Posts: 4
Joined: Fri Jun 22, 2007 9:18 am

by Localboy on Fri Jun 22, 2007 10:11 am

I'm afraid you'll have to open it up.

I used a oscilloscope but may work with a guitar tuner if multi-octave.

Set the 5.333V on pin 1 J4 using TM 6

Center the tune knob Vr2

Put resonance to zero

Measure off the wave switch (find the square waveform pin) if you have an oscilloscope (listen to output with guitar tuner? I guess haven't tried it)

Program normal C into the sequencer for 8 notes make them slides if using guitar tuner (I guess again) put C octave up for next 8 notes. End the slide between pitch changes.
Run this pattern, change tempo to suit.

It should switch between middle C and high C
Adjust Trimpot 5 (width) until the same note is played an octave apart. On the oscilloscope the end of the waveforms converge ie. 1 cycle middle C, two cycles high C. It does not matter which note. Maybe same note same offset on a tuner.

Check the tune knob again.

Now tune onto C with Trimpot 4 (tune) using the oscilloscope cursors, or your tuner. Width may change when you do this, so repeat. But on my Box width did not change at all.

Enter C low(1 cycle), C middle(2), C high(4), C higher( 8) ,on each beat, on the oscilloscope these should all fit exactly into 32.7Hz set on the cursors. Or on the tuner bring up the right notes.

I haven't tried with a guitar tuner, but it's worth a go if you have no easy access.
Localboy
 
Posts: 21
Joined: Mon Jan 08, 2007 5:08 am
Location: London

by rcl on Fri Jun 22, 2007 10:39 am

I tuned mine with a chromatic guitar tuner (software, at that). What you're describing is strictly a tuning issue, nothing wrong with your x0x. The phenomenon you're describing is that the "octave width" is not properly set. That creates sort of a domino effect, going from lowest C up an octave gets you to maybe A or B, then an octave up from there gets you to maybe F or G... so at the top of your scale you may be off by half an octave or more! (sucks)

To reiterate what localboy said, first calibrate to TM6 to 5.333 as best as you can (although I sure hope the guy who built it did this at least).

Next, set TM4 (tune) so that a given note (say a low C) is right on, then hit the C up an octave and adjust TM5 (width) until you actually get that C. Go between the low and high C until you are EXACTLY one octave apart. If it's slightly off, it will cause the same 'domino' problem you have now.

After the width is set, adjust TM4 again if necessary to tune the low C to exact pitch. Now test, and you should be pretty well in calibration.


Oh yeah, make sure your tune knob is centered for this! And make sure you don't tune an octave too low overall (i goofed and did this initially)


I'm very sorry to hear that this wasn't done by the person who sold you the x0x. This is extremely irresponsible and thoughtless, as tuning is one of the more irritating steps in building this thing. Hopefully you will take it in stride and not think any less of our community!!


Robert
rcl
 
Posts: 161
Joined: Wed Apr 19, 2006 7:30 pm
Location: Falls Church, VA

by MattB619 on Fri Jun 22, 2007 6:52 pm

THANK YOU SO MUCH!!!!!!!!!!!!!!!!!!

I have been looking for SOMEONE to respond to me for a while and thought I'd give these forums a try.

I will give this a go when I can get a chance and the proper tools in the near future and let you all know how it goes. I also hope to enlist one of my friends who is more experienced with electronics.

Thank you all again! Glad to hear it is strictly a tuning issue!!!!
MattB619
 
Posts: 4
Joined: Fri Jun 22, 2007 9:18 am

by MattB619 on Fri Jun 22, 2007 6:56 pm

The guy who sold me my x0x seems like a very decent fellow, and I get the impression he didn't really use it very much. Whereas I would use this thing every day :) Besides this issue, my x0x is in excellent condition. I have wanted a TB-303 for 10 years now and never could afford one. Now I have one :)

I will keep you all posted on the outcome. And I definitely don't think less of this community -- you all rock!!
MattB619
 
Posts: 4
Joined: Fri Jun 22, 2007 9:18 am

I DID IT!

by MattB619 on Sun Jun 24, 2007 4:47 pm

Just wanted to let you guys know that I did it!! All by myself no less!! Took me five hours yesterday, 2 trips to Sears and 1 trip to Home Depot to get the proper tools and such. I even got a multimeter and tweaked the power supply to 5.33v

I did not have access to an oscilloscope so I used a software guitar tuner, Chromatia tuner -- and played a middle C for 8 steps a high C for 8 steps going back and forth, back and forth.

I was surprised at how sensitive the trim potentiometers were! Felt like I was doing brain surgery. And how adjusting one changed the other. Kind of maddening!

While it is not PERFECTLY in tune, it's pretty damn good I think. When I tune C4, C6 is only about 15-20 cents sharp and C2 is only 15-20 cents flat. Which is as close as I could get it.

Before, C6 would actually play as a Eb7 and C2 would play as a Bb1 -- so I think it sounds much better than it before.

I just want to thank you guys a ton for your help. Could not have done it without you. Now I can get back to makin house music :)
MattB619
 
Posts: 4
Joined: Fri Jun 22, 2007 9:18 am

by rcl on Sun Jun 24, 2007 7:38 pm

Excellent! And you got to get your hands at least a little dirty with your x0xb0x too. Happy ending for everybody

Robert
rcl
 
Posts: 161
Joined: Wed Apr 19, 2006 7:30 pm
Location: Falls Church, VA

by rcl on Sun Jun 24, 2007 7:38 pm

Excellent! And you got to get your hands at least a little dirty with your x0xb0x too. Happy ending for everybody

Robert
rcl
 
Posts: 161
Joined: Wed Apr 19, 2006 7:30 pm
Location: Falls Church, VA

Please be positive and constructive with your questions and comments.