Joined: Feb 27, 2008 Posts: 156 Location: Roma, Italy - London, UK
Audio files: 15
Posted: Thu Jan 07, 2010 5:38 am Post subject:
Subject description: the spirit of tim servo?
Update!
So I fired up my TH 101 today for a second round of troubleshooting... and.. the Hum issue was gone.
same set up, same cables, same everything... but gone! Ghost in the machine indeed or perhaps the spirit of tim servo visited my oscillator last night
anyway.. the vco sound is very promising!
Now I'm puzzled by the difference on output volume of sine and saw (sine is much higher)... I thought it ought to be the opposite..
However the sine doesn't sound too much like a sine to me yet, perhaps I should really get on with the calibration
I'm posting a couple of samples here
Maybe I have to connect to a VCA first ... or just wait another night
Hi Aerograma, you can use the software oscilloscope. Maybe it can not reproduce the waves under 20hz depending on your soundcard, but you can calibrate it higher frequencies, actually in built notes says that around 1Khz it will be OK.
Well, Seems that the triangle output is completely distorted...
Check the values of R18 and R19. Are they correct?
R18=36KΩ and R19=120KΩ.
Also you should calibrate the triangle offset. If no real oscilloscope available, just put the multimeter to measure DC, tap the triangle output and adjust it to 0V
Using the software oscilloscope, we are not measuring directly the triangle output of the oscillator. Be careful in no distort the signal in the soundcard input.
I think you're getting pretty close. Couple of suggestions:
1) To properly view a VCO output on most soundcard based viewers, you're going to have to attenuate the signal quite a bit. The VCO output is about +5 to -5V (10V peak to peak), while soundcards are setup for a line level (about 1.7V peak to peak). This is going to be necessary with most any synth level signal.
2) Almost all sound cards have AC coupled inputs. This means that there is a capacitor in the soundcard input that removes any DC bias or offset from the signal. Because of this, you won't be able to see any DC bias that is present in the TH-101 output. Sound has the right method though - if you don't have an oscilloscope, use a multimeter and set it to DC. You should be able to see the DC level and adjust it to 0.
3) Get the Triangle DC bias adjusted first. The Sine and Saw are based on the Triangle, so that is important. You'll be able to see the Sine shape adjustments on your soundcard o-scope, although you'll need to resort to the multimeter again to get the symmetry adjustment right.
Like I say, sounds like you're slowly getting everything nailed down, but you do need to follow all those wave adjustments through. Hope this helps!
Good!
But if achieved the triangle you could achieve the sine in this way. without wait for the analogue oscilloscope.
What are u getting at the sine output?
Okay, you're getting closer! Remember that the sine adjustments interact with each other. You'll have to go back and forth between them a few times to really get a proper looking (and sounding) sine wave. Another thing you might try for the sine adjustments is to put the TH-101 in LFO mode, and apply the sine output to another VCO. You can adjust for the smoothest sounding vibrato for the shape, and listen for equal positive and negative modulation to get the offset. Agreed, you'll be SO much happier with an analog o-scope
Joined: Feb 27, 2008 Posts: 156 Location: Roma, Italy - London, UK
Audio files: 15
Posted: Fri Jan 22, 2010 8:44 am Post subject:
wow thanks guys! it feels a bit like those movies where a member of the public suddenly has to take control over an airplane cockpit and the good guys in flight control guide him through the rescue process
I finally managed to get my hands on my analog oscilloscope again.
I can confirm that the triangle wave is calibrated properly, however no joy from the sine still (sorry for the bad pict)
One thing to notice is that adjusting the waveshape trimmer doesn't bring much change and the saw output is basically mute
any advice to where to look for issues?
thanks again
aero
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Aerograma, did you follow the build notes? remember that there, is indicated how to place some components
aerogramma wrote:
however no joy from the sine still
R41 should flat the sine, and R50 place its offset to 0.
Check all the values of the resistors involved, and check if Q4 and Q5 are 2N3904 and are correct placed.
Quote:
the saw output is basically mute
Check in the build notes if Q6 is corrected placed.
Joined: Feb 27, 2008 Posts: 156 Location: Roma, Italy - London, UK
Audio files: 15
Posted: Sat Jan 23, 2010 11:53 am Post subject:
Hello Sound,
thanks for pointing it out.
I have followed the build notes but looking at Q6 now, I might have mistaken pin2 with pin3 on the MPF 102... will investigate further
Yes, double check that Q6 as that is critical to get the Saw working.
It looks like both the offset and shape trims are off, so I would probably return the Sine trimmers to their mid points and start over. If they're 10-turn, rotate them until they 'click' at the end stop and then rotate then back 5 full turns. Double check the part number and see whether they're 10, 15 or 25-turn. The 'click' is very quiet, so you'll need to be listening carefully (you can also usually feel the click in the screwdriver adjusting the trimmer). I've attached a copy of the TH-101 Build Notes, so anyone out there can look them over.
Also, don't forget that you need to jumper a wave into the PWM comparator. There's no built in connection, so you can choose either the tri, sine, or saw as the PWM input. Hang in there, you're making progress!
Joined: Feb 27, 2008 Posts: 156 Location: Roma, Italy - London, UK
Audio files: 15
Posted: Wed Jan 27, 2010 3:31 am Post subject:
gettiing there...
First of all thanks again to Sound and Tim for the invaluable assistance
the MPF was mounted correctly, however I found a large problem on the resistor front all the 2.2K were infact 2.2M!
A mouser a glitch in the order? Or my fault (also likely)... but nevertheless I proceed desoldering and substituting (giving my eyesight out to science and synth DIY in the process).
So now I have a Sinewave that looks ok, but to my ears it sounds like there are still a few armonics that perhaps shouldn't be there (see attached mp3), what do you think?
The same extra stuff goes on the other waves too (Saw is also back!)... I might have done some damage to a couple of the resistor seating and might have to do a bit of point to point soldering.
Right now I'm looking suspiciously at R23, R32 and at R69 that goes to P1, but I haven't figured out where P1 is on the board yet.
Anyway it has been a bit of a struggle but I learnt a lot !
thanks!
aero
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Posted: Wed Jan 27, 2010 7:08 am Post subject:
Re: gettiing there...
aerogramma wrote:
So now I have a Sinewave that looks ok, but to my ears it sounds like there are still a few armonics that perhaps shouldn't be there (see attached mp3), what do you think?
Try to adjust the sine wave in a lower frequency, say 60hz, then adjust there by ear to more clean sound. if you have acceptable clean sound there you will have more clean sine in upper frequencies.
Remember that the offset shold be =0
I ll check this afternoon mine.
Quote:
The same extra stuff goes on the other waves too (Saw is also back!)...
Glad to hear this.
Quote:
Right now I'm looking suspiciously at R23, R32 and at R69 that goes to P1, but I haven't figured out where P1 is on the board yet.
I dont understand. There is something not working properly?
Quote:
Anyway it has been a bit of a struggle but I learnt a lot !
In my opinion this is the process where you can learn more.
Anyway if you want to learn more about this circuit, I recommend read the book "Making Music with the 566" by Thomas Henry, work on which Tim based this oscillator design.
In other words, most people think they know what a sine wave should look like, but in fact your ears do a better job of finding the best approximation. I usually just adjust the trimmers until I hear something relatively free of harmonics. That'll usually get you down to 3% distortion or less.
Joined: Feb 27, 2008 Posts: 156 Location: Roma, Italy - London, UK
Audio files: 15
Posted: Sun Jan 31, 2010 1:20 am Post subject:
Thomas_Henry wrote:
Trust your ears before your eyes.
In other words, most people think they know what a sine wave should look like, but in fact your ears do a better job of finding the best approximation. I usually just adjust the trimmers until I hear something relatively free of harmonics. That'll usually get you down to 3% distortion or less.
Thomas Henry
thanks for the advice Thomas, I will do that.
My understanding of synth electronics is poor to say the least, my ears however have received much more training and the usually work quite all right.
By the way even with the extra harmonics your/tim design on the TH101 sounds fantastic, already thinking of building another one
Joined: Feb 27, 2008 Posts: 156 Location: Roma, Italy - London, UK
Audio files: 15
Posted: Sun Jan 31, 2010 1:26 am Post subject:
Re: gettiing there...
[quote="Sound"]
aerogramma wrote:
Quote:
Right now I'm looking suspiciously at R23, R32 and at R69 that goes to P1, but I haven't figured out where P1 is on the board yet.
I dont understand. There is something not working properly?
.
Thanks for the precious advice Sound will try to get my head around TH cookbook soon.
The resistors I quoted might have a damaged soldering pad (my fault) , so I'll have to double check with a tester to see if they're actually properly connected
Joined: Feb 27, 2008 Posts: 156 Location: Roma, Italy - London, UK
Audio files: 15
Posted: Tue Feb 16, 2010 2:30 am Post subject:
Hello again everyone,
after a final round of debugging I got to a result that sounds so good and unique that decided to stop there.
It's possibly still not the purest sinewave I could get out from this VCO but the sample I've attached here is a testament to how good and full of character this design sounds.
It's recorded with no efx of sort - passed through my neve solid state self built clone, piloted by Expert Sleepers' Silent Way in Logic and recorded on a RME Fireface 400
thanks again to all of you that helped me out completing this project
Posted: Tue Feb 16, 2010 1:09 pm Post subject:
TH 101 calibration
Hey Aero,
Congrats on getting your TH-101 up and running. Even if the sine isn't perfect, if you like the sound then that's what really matters. I like mine too, and think they have a very nice character to them. Have fun with it.
Joined: Nov 18, 2006 Posts: 236 Location: San Francisco, CA bay area
Audio files: 13
Posted: Sat Feb 20, 2010 10:51 am Post subject:
I would like to get some of these pcb's, and I have sent Tim an email, but I haven't head from him. I'm wondering if he is not receiving my emails? Tim could you contact me please?
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TH 101 calibration
