KLON clone, even with Gain knob at 10 it never breaks up. Why?

[half_smith]

Hi all, I've been tinkering with my Klon (built from kit from GGG)

It works. I mostly love the sound shaping I get from it.
I've tried a dozen different diodes, changed some resistors and capacitors and tried a 4558 in place of IC1 (TL072)
Still works fine. I use it stacked with a TS808 and I love the "transparent" girthy boost.

But, no matter how high I crank the Gain knob it never breaks up. Why?

thanks for suggestions!

[GibsonGM]

Hi Half,

Can you get us voltages on the opamp pins, by any chance? 

I'm wondering if maybe a resistor value is wrong / swapped in the feedback loop of the 1st opamp? Only one of a few possible reasons why...

[half_smith]

Hi GibsonGM, thanks for the reply

Here are my voltages right now.

I was having a low reading on IC1p3, around 1.3v (should be +/-3.7v)
So I took a stab in the dark and lowered R2 to 51k (from 1M) and the voltage on IC1p3 went up to 4v
I know this is messing with my input impedance...
but this did not effect the sound, clearly there is something else wrong.

[idy]

You didn't need to change the R from 1M to 51k, yes it is lowering impedance, but the reason you were seeing low volts on pin 3 and not on 1 or 2 is that the meter was loading the + input. You will almost always notice that when measuring Voltages on opamps.
If diodes are not clipping (and you are using the magic Ge ones?) you need to confirm that there is continuity (they are connected) one one end to R13 and C10, and the other sides go to ground. If they are there and you turn up the gain, they will clip.

[half_smith]

Idy, thanks, my cheap DMM probably screws with me a lot, I hadn't thought of that.
Anyway, I socketed the 1M so I can put it back.

I have continuity between R13, C10, GND and I just don't know man.

I'm starting to wonder if my Dual Gang Gain pot is possibly out of spec. I didn't check it and now it's buried in a nest of wires and jacks.

I'm going to go through it with an Audio Probe. The Klon circuit has multiple paths through that the audio can take, I think something is bad and the diodes aren't even seeing the audio and yet the summing OpAmp and tone circuit work so there's still a little goodness happening, but it's not what it should be.

[antonis]

I have continuity between R13, C10, GND and I just don't know man.

Set your DMM to "diode testing" mode and place RED probe to point A and BLACK probe to point B..
You should read 200 - 400mV..
Then reverse probes and you should take the same measurement as before..



P.S.
IMPORTANT..!!
Point B should NOT be considered the D2/D3 junction pad but some ground point far away from diodes legs..
(just to be sure each diode is effectivelly connected to GND..)

[half_smith]

Hi Antonis, thanks for the tip!
My crappy DMM with questionable battery reads 200 across the diodes in both directions.
I hear (audio probe) the signal at the base of the Diodes, and it gets marginally stronger there as I increase the Gain knob, but I assume it is too weak to really drive the diodes.

I have just gone through and checked connections, continuity, values, orientations, etc.
All seems correct but for some reason, there is never "clipping" just a punch and boost when I dime the Gain knob. I'm baffled.

1 thing is, the GGG Wiring diagram, when I follow it exactly the GAIN pot ends up backwards (less gain as I turn it clockwise).
I've tried switching the 1,3 pins of the Gain pot and the pedal sounds the same - but with the knob action correct.
makes me wonder if I am reading the diagram wrong and have the Gain pot wired wrong?

another thing, the GGG Schematic vs other "Klon" schems I've seen has C9, C10 as Electrolytic with polarity both facing in toward the Diodes, whereas other Schematics online show these Caps as non-polar.
Any thoughts there?

Thanks gang!

[idy]

Easy question first; the two caps are only 1uf, so they are available as film which are always non-polarized. So that savers a worry if you use them. There are also NP electrolytic, loved by audiophiles, and those are fine. If you go with the polarized cap there you *must* observe the polarity. There will be positive DC voltage on the "outside" end of each and a path to ground through the diodes on the "inside" ends, no DC there.

Now about this no clipping business: What kind of guitar/pick up? Have you tried a booster between guitar and Klon to see if you can drive it to clip?

About the gain pot: that is a dual pot, right? One side turns down the clean buffered full range signal while the other side is turning up the gain on the mid-rangey clipped signal....

[half_smith]

Have you tried a booster between guitar and Klon to see if you can drive it to clip?

I've found that if I send a hotter signal into the pedal I do get some noticeable tastey clipping, but only with the Gain nob maxxed and only a small amount of breakup.

Maybe it's a matter of my input signal strength / Impedance? (Please help! I still black out and wake up half naked with a stick of butter in my mouth whenever I try to understand Impedance)
I could put a booster before the Klon on my board, but I really want to get to the bottom of this and understand why it's not cranking when I crank it.

About the gain pot: that is a dual pot, right? One side turns down the clean buffered full range signal while the other side is turning up the gain on the mid-rangey clipped signal....

Yes it's a B100k Dual Gang
I'm struggling to understand how the two pots are functioning in tandem, but I think what you said is correct.

[Clayton Custom Cabs]

Hi New to this forum, but I have now built no less than 6 Klon Klones - 2 of which are from the same kit supplier as you are using. My first build was a nightmare, I mis-read and mixed up 4k7 and 47 resistors (I now measure them before installing them) I also put one of the electrolytics in backwards and I installed the diodes backwards first time around.

I got really good at desoldering on the first build, I would check my wiring on the dual gang pots and the leads to the pcb...in addition to polarity of caps and diodes.

Good luck!

[half_smith]

Hey, just a quick question, because mine is the only Klon I've played.

Is the blazing crunch I've seen on YouTube demos of Klons actually just from hitting the front of the amp harder?
Is it never going to get "breakup" "clipping" on its own (like a Tubescreamer definitely will)?

I'm probably just going to try building a new one from scratch, something isn't working right on this one, but I've gone over almost every single joint, part, trace, anon.

The Dual Gang pot is messing with me, but I don't know what else to try?

[idy]

Yes the Klon is not designed to giver creamy satisfying sustain like a Tube Screamer by itself, and people (like me) who aren't using it the way the designer intended are often dissapointed.
A single wrong value for a R could change the gain, especially R10, R11, R12.

Your readings on the diodes (200mV or .2V) imply you are using Ge like the schematic. But...you never finished Antonis' suggestion: Confirm that one end of the diodes really goes to ground, and that the other end goes to R13 and C10.

[half_smith]

thanks Idy, yes I did what Antonis suggested, the Diodes are GNDed to the enclosure.

It's so weird because I can hear the signal reach the diodes, it gets a bit louder there when i crank the Gain knob,
but it's like the overall level goes down when I max the Gain knob. Something in the Op Amp Gain Stage is just missing.

A single wrong value for a R could change the gain, especially R10, R11, R12.

well, I've tried changing all of those around. R10 down to 1K, R11 jumpered, R12 up to 510k, no difference.

I have built a MXR Dist+ and TS808, (and the Antonis General Purpose Stereo Amplifier  ) and I've seen Op Amps and feedback loops w/ soft clipping diodes before, this is just messed up somehow.

[half_smith]

curiously, I tried lifting a leg on R7, R15, R17, R18 completely taking the FeedForward networks out of the equation, and I get a lot more Diode action.

This confirms my gut feeling that the whole circuit is working but the balance of signals on the 3 different routes to the Summing Op Amp is off.

Can anyone use this information to give me a direction to pursue further?

[antonis]

Can't recall the occasions I've noticed that most of Klon Centaur issues are settled by just adding a cap somewhere between R12/C8 junction and R10/GAIN pot one..
(just to roll-off IC1b DC gain to unity..)

[half_smith]

interesting, so even though I'm trying to get more drive into the Diodes, you are suggesting bringing down the gain on IC1b ... not intuitive

Can you throw out a few values for me to try?

Thanks so much!

[antonis]

Not exactly..

I suggest to bring down DC gain, only..
(no DC path for R12/R11/R10/POT wiper voltage divider..)

But let's focus on your previous post..
Try to "isolate" one network at a time..

[half_smith]

thanks again Antonis

I dug deeper into the forum and found this comment you made on another thread:

That's because there is DC flowing through Gain pot (RV-GAIN_a)..
Its wiper is wired to +4.5V point, which point goes to DC ground via R30..
DC voltage gain is higher than unity, due to abscence of DC blocking capacitor inside NFB loop, so there is DC flowing from pin 7 through R12, R11, R10, pot lower lug,wiper and R30 to GND..

A cap between pot lower lug & R10 should make Gain setting more quite and smooth..
(don't try it on pot wiper 'cause you'll "break" pin 5 bias..)

I understand now what you mean about DC to unity, in other words get rid of DC.
I'll try a 2.2uf cap at R10 and see from there...

[half_smith]

I tried putting a 10uf cap (smallest I have over 2.2) on R10 or R15 or R17, I don't know what I was supposed to see. Still have 4.5v coming from the Gain Pot (why does that pot get loaded with 4.5v on both pots? Seems a mess.

Can you tell me where I should be seeing 0V DC by adding a cap?

I started to narrow down that C11 was leading DC, but I changed it out and still have VB+ on the "inside"
I was thinking I would have to put a cap on each route from the Gain Pot (R15, R17, R18), but there's already C4, C6, C11, and C12, are they not accomplishing the decoupling? Would I need to put a >2.2uf Cap on each route?

[antonis]

Can you tell me where I should be seeing 0V DC by adding a cap?

I think I confused you a bit..

We want to have DC unity gain, meaning not amplified DC on op-amp output..
(we would want to see 0 VDC in case of bi-polar supply where non-inverting input is biased at GND (0 VDC)