[sdiy] TB303 transistors

[Mark Smith]

>From the work I did on my clone, I found that the voltage rails made the biggest difference to the sound of the square. The correct 2Sk30 seems to be an improvement but the whole sound hinges around the waveform being a symmetrical square - i.e. 50/50. If the 5.33v rail is high or low this changes the mark/space ratio. The final difference is the non linearity of the 2Sk30 buffer. The high edge of the sawtooth is non linear, probably caused by the gate capacitance/input impedance/leakage? This distortion is also on the square waveform. I had reasonable success with substitude mosfets (ZVN3306) after I had captured the waveforms/voltages of an original 303.

All this is only an opinion of course :-)

mark

btw  if you look at the service manual the drawing of the square shows distincts levels and it is drawn with the distortion I have just mentioned.



-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Fierce Fish
Sent: 24 May 2005 20:51
To: xyzzy at sysabend.org
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] TB303 transistors


I'd agree that the square wave is not a technically good square wave  
but I think it sounds nicer than any square wave that I have ever  
heard.  Maybe other synth manufacturers should get theirs to be not as  
"square" LOL


On 24 May 2005, at 20:24, Tom Arnold wrote:

> On Tue, May 24, 2005 at 08:18:37PM +0100, Fierce Fish wrote:
>> Tom, in your opinion does the 3031 nail the 303 square wave? I have  
>> yet
>> to find a clone that can sound like my 303's square, most clones on  
>> the
>> market can do a very convincing distorted sawtooth acid stuff, but for
>> the more refined fluid square wave stuff they all sound way off to my
>> (not that good) ears!
>
> Tony has done an excellent job of nailing the TB3031 square wave.   
> Listen to
> samples on oakleysound.com
>
>> Anyone else have any thoughts on this, I'm starting to believe some of
>> the conspiracy theories that aliens from the future designed the 303,
>> the square wave sound is like the holy grail or something. Godammit!  
>> ;)
>
> No, the truth is the square wave on the TB303 sounds like utter crap,  
> but
> its become such the basis of a Sound we like that its now the holy  
> grail.
>
> :-)
>
> --  
>   
> ----------------------------------------------------------------------- 
> -
>  - Tom Arnold -       When I was small, I was in love,                  
>  -
>  - Sysabend   -       In love with everything.                          
>  -
>  - CareTaker  -       And now there's only you...                       
>  -
>  --------------         -- Thomas Dolby, "Cloudburst At Shingle  
> Street" -
>