CMOS Aliaser's frequency pot question

[gigimarga]

Hello,

I've just finished an CMOS Aliaser using the layout from here (thx a lot John!): http://www.diystompboxes.com/smfforum/index.php?topic=54135.0

It sounds fabulous, i didn't find a stompboxes to like so much from the Maestro FSH

The only little problem is that when i turn the Frequency pot to the minimum it stops sounding and it restart to work only after i turn the pot over the half.

On John's layout the value of the Frequency pot is not mentioned, but I found the schematic (thx Miguel!) http://www.dedalofx.com.ar/bioroids/external/nyquist_aliaser.jpg and there it is 50K.
Or maybe i need to increase R10 from 1K?

Thx a lot all!

[bioroids]

Wow I don't remember much how this circuit works

But yes, I would try higher values for R10. How low is the frequency when it stops oscillating?

Regards!

Miguel

[gigimarga]

Thx a lot bioroids!

Until now i found only 3-4 stompboxes with which it was "love at first sight"...and the CMOS Aliaser is the first in the top...i start to test it at 1:30 AM and i've gone to bed at 3:00 !!!

When the guitar is not plugged in it self-oscillates, but after i plugged the jack in the input it was ok.
The value of the pot where it oscillates is something at 20-25K...but i observed that the touch of the pot wires with my fingers have a big influence.

Thx a lot again!

[gigimarga]

 

[bioroids]

But you got oscillation only in the 20-25k range? That doesn't sound too good, you should have a wide frequency range of oscillation.

4016's tend to be very picky, maybe you can try a different one if everything is double checked and appears to be OK

If it oscillates when no guitar is plugged in you should wire the switch so the input of the effect is grounded on bypass.

Regards!

Miguel

[Fuzz Aldryn]

Hi,

this is gonna be my first post here! So first thank you all!:) Build this liitle gadget yesterday. Got the same Problem as mentioned above. Swept the freq pot from 22k to 100K, but none of them worked on the full spectrum. Also got a problem with bleeding through oscillation. Pure coincidence in this case? I used two CD4016BE as it was recommended. Would be very nice if we could cure the problem, because despite that it's a nice little gadget.
Thx!!!

With regards!
Helge

[gigimarga]

I used a HEF or HCF, not a CD

[gigimarga]

But you got oscillation only in the 20-25k range?

No, i got oscillation over the 20-25K until 50K

[Fuzz Aldryn]

I used a HEF or HCF, not a CD

My first glance was a bit to fast. Overlooking it quickly I have used one HCF4016BE manufactored by ST an one CD4016BE by ... hmmm might be Fairchild - don't know exactly. So you think that may cause the problem I've got with that circuit? Thought only the BE was of importance.
Thx!

Regards!
Helge

[bioroids]

I'm not quite sure if BE suffix is of importance. When I built it I used several CD4016 and CD4066, the 4066 were useless if I recall correctly, and there was variation in respect to bleeding with different CD4016's. I didn't try it with HCF's, there's a possibility they may be causing the issues.

I don't think enough people have built this to extrapolate a definite version of the 4016 that works perfect, you should keep trying with different chips (I assume you used sockets - that's the way to go when abusing CMOS chips for things they weren't intended for  )

How wide is the frequency range you get on the "usable" part of the pot? If its wide enough you can then just substitute a higher value for R10 and be done. If not, the we should keep troubleshooting.

I'm glad you find the effect in itself interesting!

Regards

Miguel

[Fuzz Aldryn]

Hi,

I thought the BE (which stands for "buffered" like UBE for "unbuffered"?) was of importance as the building instruction recall for it (to be exactly the CD4016BE is mentioned) and as in the other thread was reported that the CN version doesn't work.
Of course I used sockets - as this is mostly a clever idea and sometimes the point where the fun starts.
So you would say I should try another CD4016BE? As I remember my local store did carry varius types of 4016, but unsorted in one box and only a few BE (I hope so).
Atm I got a 22K lin pot wired to the circuit an the usable pot range starts at measured 10,5K to its full resistance. As I already mentionted I also tried a 100K pot (did tapered it with 47K in parallel in lack of an unused 50K pot) whre th usable pot range started an 3:00 pm.
Thx!

Regards
Helge

Edit: Ah wait! You were asking me about the frequency! As far as I can judge by listening to this example http://www.mrdwab.com/john/AliaserCMOSfreakout.mp3 I don't get that wide sweep -  no that high and not that low; stucks somewhere in the middle.

[Fuzz Aldryn]

Just wanted to say that it doesn't work with the two CD4016BE i got now in it either.

[gigimarga]

I remeasured the pot very carefully and it has the range from 0 to 37K...so it don't oscillates between 38K and 47K!
I replaced it with a 100K pot tapered with a 62K resistor (to obtain something near 38K) and now it works very well.
Another problem is that it has a strong oscillation (or maybe the carrier frequency)...and i have no ideea what to do!

[gigimarga]

The whizzing sound is still here...what can i do?

[bioroids]

That really sucks... all I can say is it should work ok with barely no whizzing. Are you sure there are no mistakes either in the pcb or the components?

[gigimarga]

That really sucks... all I can say is it should work ok with barely no whizzing. Are you sure there are no mistakes either in the pcb or the components?

Yes...i'm sure that there are no mistakes...maybe the HCF/HFE could be the problem, but i have no luck to find a CD here

[gigimarga]

 

[gigimarga]

A little cap from output (or input) to ground could solve the problem?

[gigimarga]

 

[bioroids]

I still think you should try with the CD4016 (several of them if possible), The cap from input to output, I don't know if that could help (don't think so), but in any case it was not necessary in the other builds.

Regards

Miguel