Request for resitor info

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Request for resitor info

Post by Guest »

Hi can you tell me which resistors control the following

Saw wave shape
Resonance max
decay vca
decay vcf
release vca
release vcf
attack vca
attack vcf

I want to some mods of the fine box!!

THANKS
:P

PS I am beginner in electronics so some of the above may be dumb questions!!!

Guest
 

Post by Guest »

also accent vcf amount and vca amount plz :wink:

Jonnay
 
Posts: 142
Joined: Thu Jun 02, 2005 12:28 pm

Post by Jonnay »

The schematic is your friend!

R45, R34, R35 and R36 all have SOMETHING to do with the saw wave. What exactly I don't know. But you can find that out by following the signal path from the waveform switch.

Edit: Actually that is the square wave. Duh. I had a hard time tracing the lines through the schematic. Do yourself a favour, and get the demo/educational use of eagle to view it. Looking at the schematic, it seems to me that the saw wave is always generated, and is somehow turned into the square wave by the circuit with Q8, R45, R34-36, C10 and C11. But then, I could be dead wrong about that.

TM3 is resonance max. I believe.

As for the envelope section, I am very very confused by it, so I cannot tell you what is what. I think that the VCA envelope is in the VCA section, and the VCF envelope is in the ENV section of the schematic.

If I understand everything correctly, the accent doesn't actually control the cutoff of the VCF, but rather the resonance. The 'accent envelope' is generated and controlled by D24, R46 and C13. Perhaps by changing the value of R46, you could alter the amount of resonance per accented note. I think that also by changing the value of R46, you would decrease or increase the time to make C13 charge up, thus changing the shape of this 'accent envelope', making it more saw like, or rounded, depending. For playing with this part of the circuit, you should really read http://www.geuggis.com/tb-303/art06.htm

The 4066 controls the accent (IC12A IC12B), so by looking at its signal path, you might be able to get a firmer understanding of where the attack and release section is. When voltage comes off of Q35, this is a signal that a note is to be accented, and 'A' and 'B' on IC12A and IC12B are connected. This bypasses the normal decay and gives it a standard shortened decay.

By looking at all that, you can probably isolate the part of the envelope circuit that ISN'T affected by the accent, and that will end up being your release.

After that, it is trying to figure out which section is responsible for the attack and which is responsible for the decay. By seeing where the decay knob fits into the circuit, it might not be too much trouble.

Guest
 

Post by Guest »

Indeed the saw is clipped to form the square which is why it is a funny skewed shape :lol:

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controlvoltage
 
Posts: 242
Joined: Tue Aug 09, 2005 12:17 am

Post by controlvoltage »

Accent does a couple of odd things at once... in the Roland service manual, they referred to the accent circuit as a "gimmick," which I think is a cute way of saying that it's a very quirky/nonstandard circuit design. I just sent all those files to Danjel to host, although I think they can still be found at hyperreal.org/machines if you search for 303.

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