Aion Refractor (Klon Centaur Klone) Unique Issue?

[uviteru]

Hey guys, so I built the Klon Klone using the Aion Refractor PCB. It was a pretty straight forward build, and it worked first time I plugged it in. Sounds great! HOWEVER.... there is a strange thing happening when I push the gain and volume up above 3 o'clock. It's hard to describe and hard to capture on a cell phone recording, but when I slam a chord with it cranked up that high, the sound kind of drops out for like a quarter of a second and them comes back (almost like a revers gated effect). Most of the time it is fine, and it seems to happen more when I'm playing from silence.

These are the voltages on the ICs. Notice that the 18v supply is low... not sure what would cause that... bad IC? Also don't know if that could be the cause of the strange behavior?

IC1: pins 1,2,3 & 5,6,7 4.65v, pin8 9v, pin4 0v
IC2: pins 1,2,3 & 5,6,7 4.65v, pin8 16.7v, pin4 -9.3v
IC3: pin1 9.3v, pin2 4.8v, pin3 0v, pin4 -4.3, pin5 -9.3v, pin8 9v
Positive side of D4 is only reading 16.7v instead of the 18 that is indicated in the schematic

Any ideas???

[midwayfair]

It's polite to link to the build doc for the specific project you're building.

https://www.dropbox.com/s/4xhwadzx2rxbm8z/aion-refractor-centaur-documentation-v2.pdf

Your "18V" supply is just fine. If you want slightly higher voltage, you can use 1N5817 instead of the 1N400x used in the schematic in the charge pump section. They will drop half as much voltage across them and you will end up with about one more volt. You can never get exactly double voltage -- there's always some loss.

There are some instances where this effect can create enough gain to oscillate the chip, but I've never heard of it happening without lifting the diodes. I really doubt that's what's happening here.

>happening when I push the gain and volume up above 3 o'clock.

Does this happen when it's the GAIN only and the volume is low, or does it have to be both the gain AND volume turned up that high? Does it happen at all with just the volume turned all the way up (and maybe the tone knob)?

[uviteru]

Oops sorry about that.

I think the clipping happens when both knobs are up regardless of the tone, but I will check again when I get home tonight.

[uviteru]

Ok, I tested it and with the gain high and volume lowish, it does it, but with gain low and volume high, it doesn't. Tone doesn't seem to matter. So it seems like it is around the gain adjustment.

Any ideas from that?

[uviteru]

*bump*

Does anyone have any thoughts on what could be causing this? The link for the documentation is the same as was posted above: https://www.dropbox.com/s/4xhwadzx2rxbm8z/aion-refractor-centaur-documentation-v2.pdf?dl=1


And I have a picture of my build here:  http://imgur.com/a/OnfAR



I've triple-checked the circuit and I don't see anything that obviously wrong... it sounds great, I just get that weird behavior when the gain is cranked.

[EBK]

From the Madbeans Kingslayer docs (also a centaur clone):

The Kingslayer is what I call a good "two up, one down" design. IOW, the best settings tend to happen when
two controls are turned up and one down. For example, volume and gain up with tone floating between 10ock
and 2ock. Or, volume and tone up with gain pretty far down (this is the boost setting). What it does not do is let
you max everything out...unless you like lots of nasty feedback. This is a consequence of the design (true for
every klone I've built...not just the Kingslayer and Sunking). You have lots of boost, gain and treble available,
but pick two because all three just don't work that well together.

Maybe that helps.  I've also ordered a Refractor board, but I don't have it yet, and it will be a while before I get a chance to build it, but I will eventually report back with my notes if you don't somehow notice anything wrong with your build and fix it in the meantime.

[uviteru]

From the Madbeans Kingslayer docs (also a centaur clone):

The Kingslayer is what I call a good "two up, one down" design. IOW, the best settings tend to happen when
two controls are turned up and one down. For example, volume and gain up with tone floating between 10ock
and 2ock. Or, volume and tone up with gain pretty far down (this is the boost setting). What it does not do is let
you max everything out...unless you like lots of nasty feedback. This is a consequence of the design (true for
every klone I've built...not just the Kingslayer and Sunking). You have lots of boost, gain and treble available,
but pick two because all three just don't work that well together.

Maybe that helps.  I've also ordered a Refractor board, but I don't have it yet, and it will be a while before I get a chance to build it, but I will eventually report back with my notes if you don't somehow notice anything wrong with your build and fix it in the meantime.

I see... so you're saying that its possibly normal operation. That's interesting, I hadn't heard that before. Let me know how yours turns out! Thanks for the advice.

[EBK]

Minor update: I received my Refractor board today. Man, Kevin designs beautiful boards!    I'll probably start soldering resistors right away, but I don't have all the other parts on hand, so like I said, it will take a while before I can compare notes, but I'm eagerly looking forward to it.

Minor update to minor update: Ordered everything I need to populate the board from Smallbear (well, they were out of 10kB PCB mounted pots, but I can manage).

[cnspedalbuilder]

I built this and like the pedal very much. I've not noticed the gain issue. For me, though, the problem is that the pedal will not do a clean boost. If the gain is low, the overall volume drops even if volume is set high. This is not unlike other overdrives, but from what I understand, the Klon should work as a clean boost.

I'll mess with the gain settings and see if I can replicate your problem.

[EBK]

I'm building this one more carefully than I usually do.  I'm testing each part before it gets soldered in place.  Hopefully, that will give a decent benchmark to debug yours with.  That said, I am planning some part substitutions suggested by the aion docs:
C1.  390nF
C14.  8.2nF
IC1.  JRC4558D
IC2.  NE5532
D1, D2.  BAT41
D3, D4.  1N4001 (figured I'd at least mention this sub for the sake of completeness)
VOL.  10kA
I will socket IC1, IC2, D1, D2, and C14.  And, I will take voltage measurements with TL072s in place initially.  I also have some other miscellaneous Schottky and Ge diodes laying around that I can test out.

[midwayfair]

from what I understand, the Klon should work as a clean boost.

The clean is 1x gain from the input buffer, and then the gain from the tone control stages, which is a ~20x low pass filter (around 400Hz) from the third op amp stage and a tilt treble control with IIRC about 10x gain. So yes, it should work as a boost and if yours is at unity when you're at 0 gain you've done something wrong.

[EBK]

Christmas Eve deliveries from Smallbear and Mammoth!  My build starts in earnest soon now.   

[armillary]

I built the Aion Refractor, but I haven't played with it much. I will try what you describe in the next couple days and report.

The temporary disappearing output that you describe reminds me of at least one tube amp project I have worked on that did that when it was overdriven. So I will ask, are you using a tube amp? Have you overdriven it with other pedals, and if so, does it behave OK?     

[uviteru]

I built the Aion Refractor, but I haven't played with it much. I will try what you describe in the next couple days and report.

The temporary disappearing output that you describe reminds me of at least one tube amp project I have worked on that did that when it was overdriven. So I will ask, are you using a tube amp? Have you overdriven it with other pedals, and if so, does it behave OK?   

I am playing through a tube amp, but other pedals I have don't do it. The disappearing output also happens when I play through my headphone amp, which is solid state.

[armillary]

OK, thanks. Just wanted to rule that out.

[armillary]

Today I broke out the Aion Refractor I built a year or two ago. Testing with a Champ-style tube amp, I couldn't find a combination of Vol and Gain settings that would cause a brief dropping of output. Then I looked at your build picture link above and opened mine up and was struck by the difference between your Refractor board and mine. They are both black epoxy, but the layout is very different, including the location of the ICs and diodes. Mine says Aion Refractor and 2014 on the back of the board. Is your board dated?     

[EBK]

Today I broke out the Aion Refractor I built a year or two ago. Testing with a Champ-style tube amp, I couldn't find a combination of Vol and Gain settings that would cause a brief dropping of output. Then I looked at your build picture link above and opened mine up and was struck by the difference between your Refractor board and mine. They are both black epoxy, but the layout is very different, including the location of the ICs and diodes. Mine says Aion Refractor and 2014 on the back of the board. Is your board dated?     

My board (one week old) is the same as uviteru's.  It's version 2.

[armillary]

Thanks EBK!

uviteru, just my two cents, I'd suggest reflowing all solder joints except the ICs and diodes and test again to see if there's any improvement. I believe ICs and diodes are more sensitive to soldering heat than other components, so reflowing the other components first makes sense to me. For the same reason, I think using sockets for ICs and diodes is a good investment, as sockets make replacing and substituting components a breeze compared to desoldering/resoldering. Finally , I'm a big fan of using flux remover on a q-tip to clean up all traces of flux around op amps.   

[EBK]

I've finished soldering my Refractor, with the part substitutions I mentioned previously (turns out my inventory of TL072s has been depleted, so I can't report on using those  ).  Works perfectly, as far as I can tell.  I do not get reverse gating at high gain, but there is some sort of very noticeable compression artifact when gain is maxed, which I suspect is from the diodes. 

The clean is 1x gain from the input buffer, and then the gain from the tone control stages, which is a ~20x low pass filter (around 400Hz) from the third op amp stage and a tilt treble control with IIRC about 10x gain. So yes, it should work as a boost and if yours is at unity when you're at 0 gain you've done something wrong.

I get clean boost just fine with gain control at 0 (approximate unity with gain 0 and volume/tone at 1 o'clock). 
You can tell me I've done something wrong if you'd like. 

The amount of available treble boost is insane, especially with a Strat.  I may tweak things a bit more to let some more bass through.

[EBK]

As a wild guess at what could go wrong while building one of these, I'd suggest maybe a dead spot in one half of the dual gang pot could be the culprit.  The gain control trades clean for saturated over its travel, so in the event of a dead spot, the affected component would drop out or operate in an unexpected manner.