Klon centaur clone

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ward

Well-known member
Joined
Jun 4, 2004
Messages
348
Location
Belgium
I know this is not a stompbox forum but it's the forum I trust the most.
I'm making a clone for someone,
http://www.sabrotone.com/?p=729

But for the moment  it makes a weird tremolo like sound, the distortion it produces is sweet, the pots act normal. 
I'm suspecting this has to do with the power supply design?
Anybody here got any experience with this charge pump ?

Thanks,
Ward
 
stompboxes are cool

do you get the same voltage readings as the chart in the linked website ? what are you powering the circuit with ?

if the voltages are ok you should try using an oscilloscope and trace the circuit to find where the problem originates

if you don't have a scope you could try with a simple audio probe connected to an amplifier

in my point of view veroboard are just crap, it's very easy to make mistakes

given the popularity of klon klones i am pretty sure you can find a ready made pcb which would certainly make things easier
 
Thanks Beatnik,

I took your advice, made a little pcb and started fresh.
It's working now but without input it oscillates like crazy. :eek:

The dc voltages are like on the site I linked.
And if I solder a 100nF from signal to ground on input and output it's gone but that doesnt feel like the right solution ?
And if thats ok with the guitar impedance ??  For the moment I'm checking with an iphone oscillator...
I'll check tomorrow with guitar and amp.
 
I might help to know what layout you're working from, but here goes:

The input impedance is 1M. The gain is very high in this pedal, so it's perfectly possible for it to oscillate when all the knobs are cranked. Many builds will oscillate with all the knobs cranked even with a guitar plugged in.

100nF is a drastic solution. It's a 2800Hz cut, which is right in the good stuff of a guitar signal.

I would sooner use shielded wire on the input and output. Putting a capacitor on the output indicates to me that your input is picking up some in-phase feedback from the output, and shielded wire is the first and best solution. If that doesn't work, there are some other hoops you can jump through before resorting to a capacitor on the output. Check your switch wiring, because some switching schemes will put in and out wires in close proximity. I designed a project one time that ended up needing a relay switching system to avoid feedback.*

Other possible problems: I had one build (of a different pedal) that was picky about its op amps. Try a different FET-input op amp, see if that fixes it.

The Klone is also occasionally picky about layouts.

(Actually, I should say ... the way I designed it, and the circuitboard layout I made, and the prototypes I built for the guy didn't have any feedback problems with any switching solution, but he insisted on removing a single inexpensive part that otherwise made no difference and spent $500 to have another layout made for his trouble and spent an extra $8 per build to use relays.)
 
I just tested with guitar and amp, ....
The squeel is there, even with the guitar plugged in.
I did change the opamps to ne5532 just to check, it didn't make any difference.

This is the layout I used,
http://effectslayouts.blogspot.be/2016/01/klon-centaur.html?m=1
This is my reference schematic,
https://aionelectronics.com/wp-content/uploads/2013/11/klon-centaur-schematic.png

And I didn't use any switching scheme.  The pedal is to be controlled with a switcher.  So the output comes directly  from the wiper of the volume pot.

Big chance is that my homemade pcb has a shorted trace or I put in a wrong component value.
Is there a way to narrow it down where the oscillation starts?
If I pull out IC1 the oscillation is still there,  only a lot smaller.

The oscillation is a tone of around 4KHz.
::)Could it be I'm hearing half the switching frequency of the ICL7660SCPA ?
 
ward said:
I found it,
The 7660 was misbehaving, I replaced it and away goes the whine....

Nice.

Try also the freestompboxes forum, lots of help and info there on that circuit. Its the right place to go for stompboc builders
 
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