power mod C7 C8

[evostars]

Hi everybody!
I was comparing the x0xb0x powersection to the original powersection of the TB303 and found 2 condensators that are bigger in the x0xb0x.

They influence the VCF , VCA and the VCO.
bigger Condensators mean stable voltage... but I guess, I dont want that!
Maybe I need the fluctuations for my analog ears

So...

C7 is 100uF 25V in the x0xb0x, but in the tb303 it's, 10uF 16V
C8 is 100uF 25V in the x0xb0x but in the tb303 it's 47uF 16V

Did anybody try bmod this before?
I'm hoping for more unstable analog sound

[guest]

interesting
let us know how it goes
im suspecting that c8 wont make much difference
i think its been tried before to investigate the warble
but didnt have much effect

c7 is likely to have more of an effect
but the zener in the x0x is way more stable
so it probably wont be bothered by any extra fluctuations

ultimately the x0x powersupply is pretty different
so it will be tough to get it mimic the 303

[evostars]

Yeah the zener. I looked into that. Thats hard to fix... Maybe make the 2200 uF smaller also...

Have there been other solutions for the zener?

[evostars]

by the way, its not a zener, its a schottky 6,4V

[evostars]

vishay has one. TZX6V2E (6.4V schottky)
but to get it... is a different story.

at least, d44 d45 d46 and d47 could be removed, and replaced with wire..

[guest]

its a 6.4v zener
with .005%/C temperature coefficient

youd have to put the rest of the resistors in
to get it to work
probably not worth it

i think the most important difference
between the x0x and 303 powersupply
is the switch supply on the 303
it produced a much lower voltage of around 15v
with a higher output impedance

[evostars]

its a 6.4v zener
with .005%/C temperature coefficient

youd have to put the rest of the resistors in
to get it to work
probably not worth it

i think the most important difference
between the x0x and 303 powersupply
is the switch supply on the 303
it produced a much lower voltage of around 15v
with a higher output impedance

I found a 6.2 V zener wich should work in combi with the resistors.
Shouldn't be to hard.

What do you mean with the switch supply?

[guest]

the x0x powersupply is linear
it just rectifies the incoming AC
and then sends it to the opamp for regulation

the 303 on the other hand
takes in a lower voltage
and then steps it up to 15v or so
using a transformer and an oscillator circuit

[evostars]

the x0x powersupply is linear
it just rectifies the incoming AC
and then sends it to the opamp for regulation

the 303 on the other hand
takes in a lower voltage
and then steps it up to 15v or so
using a transformer and an oscillator circuit

Ah ok. Yes i saw the big differences.

I dont understand why the x0xb0x has this stable supply thats so different than the 303...

Anyway, i havent build it yet, so i like to look for mods before i have to di the work twice...

[evostars]

I cant find information on modding the power supply, hasn't anybody tried it? Makes me motivated to score a zener and try it out myself.

I did find some info, but not enough...
Guess i also need to lower the dc psupply of the opamp itself...

[antto]

did you check the x0x wiki?
there was something about lowering the value of the first few resistors (which are in the power supply)
other than that, i don't know..

[evostars]

did you check the x0x wiki?
there was something about lowering the value of the first few resistors (which are in the power supply)
other than that, i don't know..

Yes, checked. That should lower the ps to the opamp

[evostars]

I think I'm going to replace IC22 for a 6.4V zener (or a voltage near that).
Together with a resistor between pin 6 and 7 of IC23, and a trace cut, and some wires, and reduce C8 to 47uF.
The PS will be more like the TR303.
I could use the 2K trimpot, and change R4 according, to get 5.333V

A 6.4V schottky would even be better (less noise I guess, maybe put in a 0,1uF bypass cap over the zener) but its harder to buy...

I think I'm gonna try this.
If anybody got comments, please post!

edit: forgot C7... also change it to 10uF/16V

[antto]

it would a good idea (if it's not too late) to record a pattern before the modification, and the re-record the same pattern after the modification
this way we can see/hear what exactly happened

[evostars]

it would a good idea (if it's not too late) to record a pattern before the modification, and the re-record the same pattern after the modification
this way we can see/hear what exactly happened

Yes, that is a good plan.
A bit more work though.

Haven't started building yet

I think ill use 2 zeners in series that ad up to 6.3V