filter cutoff mods

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CoolColJ
 
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filter cutoff mods

Post by CoolColJ »

Ok there is a mod to extend the cutoff lower range
-
Your friends 303 could have had the cutoff mod done, here's how - remove R47
(10k) and replace with a wire link, adjust the trimpot (TM3 IIRC but check)
in your x0x to taste, you can get the widest range of frequencies I think
with the trimpot fully cw, but you may find it goes too low so adjust to
taste. This will extend the range of the cutoff considerably in the lower
region without affecting the top range and is probably one of the best mods
IMHO. If you don't like it it's pretty simple to revert back - just put the
resistor back and alter the trimpot.

is there a mod to extend the top end range of the cutoff?

Jonnay
 
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Post by Jonnay »

In a nutshell.. the trim potentiometer in the filter section.

CoolColJ
 
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Post by CoolColJ »

just an update on this mod by the guy making mine - and some comments on the other mods I have for your interest

with the original jumper method described above the cutoff knob gets too sensitive
Found the perfect value for the cutoff range mod- it's 4.7k. Goes down almost to inaudibility. Top end is not affected by this mod- I've got the trimmer wide open for the most top end cutoff, but getting it into ultrasonic territory must be done with the env knob along with the cutoff. The env mod that lets you go down to zero envelope isn't all that useful because of that since with the env all the way down the cutoff knob is so limited. Tweakability is improved times a billion with that 4.7k resistor in there instead of the jumper. In fact you ought to post that mod update on the forum and tell whoever came up with it- remember though, the 4.7k resistor is in parallel with what's in there already, not replacing it. That particular mod also affects the env range, so I maay put the unused switch on it. Since as we talked about before that one changes the way the filter tuning works, with the mod off the cutoff still has it's upper limit, but loses a lot of lower cutoff, so lemme fiddle with it some more and get the clips up, and you can decide if it's worth screwing with.

I'm no longer disappointed with the mods now that that one is under control. The b0x is sounding and playing great. Oh, last thing- the env range mod with the switch is awesome- at first I had my doubts but it's almost a necessity now!
Jonnay you may want to put that in your wiki :)


here are the mods I ahve going into it - couldn't get the bass boost one done, due to space and risks involved - best to get that done from the start. BTW he said he didn't notice much of a difference with the power supply mod :?:


2) power supply warble mod on adjustable trimmer that can be turned from the outside, range from 110 to 220

3) audio input for the filter with switch for turning VCO off

4) on and off power switch at back

5) Env Mod - so it can be set to fully off. Put on a jumper


8) VCF cutoff frequency range extension mod - as above


9) Increase env mod range - with a switch to turn it on and off

taken from here under the env mod amount section.
http://wiki.jonnay.net/x0x/envelopemods

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controlvoltage
 
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Post by controlvoltage »

Thanks for the extra info! :)

I don't get this bit though:
couldn't get the bass boost one done, due to space and risks involved
what risks? It's changing two capacitors for slightly bigger-value capacitors. It's totally easy. In fact the ceramic caps I used are smaller than the original (polystyrene?) caps. But hey, it's a small thing that could in fact be added at any later time with minimal hassle...

Jonnay
 
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Post by Jonnay »

Jonnay you may want to put that in your wiki Smile
Have you ever seen the movie Desperado? There is this great part, where Butcho (the antagonist) is telling his evil henchmen that they need to go find this strange "man with the guitar". He says to his henchmen, "Take my car, thats what I got eet for!"

That being said, I'll post it to the wiki, but suffice to say, anyone else can do it. That is why it is a wiki afterall...

CoolColJ
 
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Post by CoolColJ »

controlvoltage wrote:Thanks for the extra info! :)

I don't get this bit though:
couldn't get the bass boost one done, due to space and risks involved
what risks? It's changing two capacitors for slightly bigger-value capacitors. It's totally easy. In fact the ceramic caps I used are smaller than the original (polystyrene?) caps. But hey, it's a small thing that could in fact be added at any later time with minimal hassle...
well he said access to the caps was tight, so risky to do soldering etc

CoolColJ
 
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Post by CoolColJ »

Jonnay wrote:
Jonnay you may want to put that in your wiki Smile
Have you ever seen the movie Desperado? There is this great part, where Butcho (the antagonist) is telling his evil henchmen that they need to go find this strange "man with the guitar". He says to his henchmen, "Take my car, thats what I got eet for!"

That being said, I'll post it to the wiki, but suffice to say, anyone else can do it. That is why it is a wiki afterall...
I don't know much about wiki, too new for me :o

CoolColJ
 
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Post by CoolColJ »

Mp3 showing the mods in action - with commentary

http://www.soundclick.com/util/download ... 5D31C69E-6

sounds so good even when played over midi!

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subatomic
 
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Post by subatomic »

CoolColJ wrote:Mp3 showing the mods in action - with commentary
http://www.soundclick.com/util/download ... 5D31C69E-6
sounds so good even when played over midi!
Interesting. So how many of these mods are stock ones from the mods page or the wiki?
How many have changes from the stock ones, and
will you submit your changes to us so future people can use what you've learned?

Do you have a list of all the mods done to your b0x? (I didn't feel like writing them down from the mp3, and in case there's more I figured I'd ask).
These "instructional" mp3s are kind of cool, would be neat if someone could archive them off somewhere for x0x/303 community... (does the wiki have a file drop?)

CoolColJ
 
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Post by CoolColJ »

subatomic wrote: Interesting. So how many of these mods are stock ones from the mods page or the wiki?
How many have changes from the stock ones, and
will you submit your changes to us so future people can use what you've learned?

Do you have a list of all the mods done to your b0x? (I didn't feel like writing them down from the mp3, and in case there's more I figured I'd ask).
These "instructional" mp3s are kind of cool, would be neat if someone could archive them off somewhere for x0x/303 community... (does the wiki have a file drop?)
All of em are stock ones and from the wiki, except the cutoff range extension mod using the jumper as described above. prtobably in the wiki now :)
But as you can read above, it worked better with a resistor in there in parallel with the existing one rather than jumpering the whole thing. That's what the audio clip was describing in the latter half

I think I have a list of mods listed in this thread :)
But here is the full thing I had done as far as the sonic side of things

1) high beta transitors etc

2) power supply warble mod on adjustable trimmer that can be turned from the outside

3) audio input for the filter with switch for turning VCO off - clips to come of this, you really need to switch the VCO off

4) Env Mod - so it can be set to fully off. Put on a jumper so it's active all the time


5) VCF cutoff frequency range extension mod - as above

6) Increase env mod range, increasing the range by 3 times - with a switch to turn it on and off

taken from here under the env mod amount section.
http://wiki.jonnay.net/x0x/envelopemods


Just wish I could have had the bass boost mod done right off the bat at the start :(

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subatomic
 
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Post by subatomic »

I think I have a list of mods listed in this thread
Thanks for listing the complete list again... So tell us how you did the adjustable PS trimmer adjustable from the outside? What part did you use? I've been thinking I'd like to mount the resonance trimmer as well as that PS one from the outside, but haven't found a trimmer yet that seems to have a thumb piece as well as panel mount... I can also think of a few other reasons for trimpots I'd like to mount to the back as well... I'm thinking something like the typical thumb pot, like what the juno106 has for tuning, and I've seen for contrast adjustment on LCDs before as well..

Also... how do you like your VCF input (the VCO audio bypass)? Sounds cool.... I'd love to hear a demo of it...

briar_electrics
 

Post by briar_electrics »

subatomic wrote:
I think I have a list of mods listed in this thread
Thanks for listing the complete list again... So tell us how you did the adjustable PS trimmer adjustable from the outside?


Also... how do you like your VCF input (the VCO audio bypass)? Sounds cool.... I'd love to hear a demo of it...
I used a 100 ohm trimpot in series with the 100 ohm resistor so it's adjustable from no mod to the recommended 200 ohms. The difference is apparent, but I don't care for it a whole lot. There is a small hole drilled for the trimmer next to the power switch, but it's kind of hanging in there loose at the moment until all the mods are totally for sure 100% completely done and working. At that point I'll superglue the switches and trimmer, then hot glue for extra hold and of course insulation/protection.

The VCF input is ok. Having a switch to cut off the oscillator is necessary. When you plug something in, the osc drops in volume and becomes muffled. I cut the trace and threw in a switch- works great. With a midi sequencer you could do all kinds of intricate patterns. It's especially good if you drop the resonance, up the cutoff and use it as a tremolo/auto mute. The clicking in the VCA or wherever the hell it comes from kind of ruins the mod unless you've got a good pop/click filter or put it on top of a loud beat. C'est la x0x.

And regarding the "bass boost." It IS too damn crowded to fit an additional 2 capacitors in there- the idea was to have it on a switch. What the hell is wrong with using EQ? If this mod is indeed lowering the cutoff of the fabled "high pass" filter within the box, then the extremely bassy low resonance notes are going to be even bassier and the proportion of lots of bass to a lot less bass as you crank the res knob will be maintained. That dispairity remains unchanged and there is no benefit or evening out of the bass by changing those capacitors. If I'm wrong then tell me cause I don't want to be an idiot- and maybe I'll reconsider doing the mod.

As for the 4.7k resistor instead of the jumper on that cutoff range mod- it works great. But don't forget, that 4.7k resistor is in parallel with the existing resistor, not replacing it. You could replace the resistor completely if the proper value was calculated. But it's easier to just tack it in on the solder side of the PCB.

Jonnay
 
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Post by Jonnay »

I'm not an electronics engineer but...

I think C20 and C21 along with R121, R122, R124 and C37 make a passive RC filter network.

R124 and C37 make a low pass filter.
C21, R121 and R124 make a high pass filter along with
C20, R122 and R124 make another high pass filter.

One thing to keep in mind: It is far easier to subtract it from your mixing desk using EQ, then to try and add it again later. In fact on the Devilfish site, Robin Whittle suggests doing just that.

greg
 

Post by greg »

also,
why not just solder the extra caps to the solder side of the board? there's inches and inches of space on that side.

i probably won't do it, i like the way it sounds now. but it does sound dead easy to toss in there.

briar_electrics
 

Post by briar_electrics »

I don't want to do it because I'm hard headed. But I'm going to do it. Why not! The fabled filter exists, it's easier to take bass out than to put it back, and Col is excited about it. I'm curious to see what it does anyhow. More clips to come, including the VCF input and an unmodded bass extravaganza. Then in a few days I'll do a modded bass and we can compare.

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