AionFX Aphelion: Tone switch not working

[velonut]

Hey folks!

Just finished a build of the updated version of the AionFX Aphelion. It's working...but not the Tone switch, which was the Treble switch in the Legacy version I believe. I've switched out the capacitors and even socketed some of them for switching them out in order to tweak the tone of each setting a bit. Nada. No change in tone whatsoever. No idea why...especially when everything else works.

Can provide pics of the board if needed.

[eh la bas ma]

check this thread around reply 4 and later around reply #24 :

https://www.diystompboxes.com/smfforum/index.php?topic=125888.msg1201522#msg1201522

I did the changes suggested by iainpunk and I do have 3 different tones now: normal, fat and "tight" (less bass freq).

It's about the comp switch,though. The treble switch is very subtle, i think i hear more changes with the treble switch now that I did the mod on the comp switch.

and welcome 

Edit : Oups, I just looked at the schems and there isn't a comp switch. Is that your version ?

https://aionfx.com/app/files/docs/aphelion_documentation.pdf

[velonut]

Thanks for the reply! Mucho appreciated! 

I did check out that thread and did actually try some of those mods by comparing the legacy circuit to the new one. No change at all...even with some of the more extreme capacitor changes.

Gotta be some oddity to it that I'm missing. I'm thinking that either a capacitor in the tone stage isn't being grounded properly, which might explain why the switch doesn't work. Or it could be the switch itself. However, I did test the switch and it appears to be working...but then again, working doesn't always mean "working".

[eh la bas ma]

You never know...maybe some good pics of both sides of your circuit, and one with everything in the enclosure, might do some good. In case someone can spot something suspicious.

[velonut]

Good point. Will break it out and take pics.

[velonut]

Alright, so here's some pics of the boards themselves. Did an inspection and I can't find anything really wrong with them. Solder points look clean and everything. Just odd.

Now, as for the point about the tone switch settings being super subtle...I can't buy that to a point. Really should be able to hear at least a bit of a difference when switching...I don't even get any of that. It's like the capacitors and/or switch are totally being bypassed. Really weird. Could be a bad switch...but I tested the continuity of both the input and ground and it seems to check out.

[eh la bas ma]

"Note that the input treble-cut capacitor works in conjunction with the impedance of what comes before, so it’ll have a much different effect if the pedal is getting its signal directly from a guitar or if it’s coming from the low-impedance output of an earlier pedal."

I assume you took this into consideration ?

treble switch caps are c2 and c3, the switch allows to select between c2 and c3 I suppose . Which caps are socketed on your build ? looks like c2 isn't. If you increase the treble-cut cap's value, you decrease the treble.

I'm not sure that there is an audible change between 1n and 2.2n.
Try to leave one empty, they are treble-cut caps so without it there should be more treble, more high frequencies.



Reflowing a bit the switch's pads can't hurt, in case there is a bad contact there. Suck out with your desoldering pump and put some fresh solder on these pads.

I broke a switch once (by heat) : I could feel the difference when i was using it, it didn't click very well, the lever didn't move correctly. Inside there's a little piece of metal in balance, making connections between poles (imagine a skateboard  , if your foot pushes on the nose, the tail goes upward).  You should be able to feel it if the switch is bad. It's quite easy to repair.

[eh la bas ma]

red : never seen this technique before, what happened, looks like it's been sawed or filed ? it's kind of beautiful but highly uncommon, i'd say. Surprising even.

green : usual soldering, looks perfect.

I wonder if you are an artist with the soldering iron, or if you improvised this leg-sawing technique ? From what I can understand, there is a slight risk of bad contact when we cut the legs of components, most cautious builders manage to cut the legs before soldering (I don't do it), so there is no risk of bad contact at all.

I guess I would reflow everything looking suspicious. Take out the Ic so it doesn't overheat, and just apply some heat on all sawed pads so that it looks like the green ones (or you did many circuits this way and it's even better, I'm not sure, never seen this before).

[velonut]

Yeah, I need to work on my technique a bit. I tend to oversolder a bit and end up trimming a bit too close. If I back off a bit, that problem won't happen. Thanks for the tips!

Gonna reflow the points and socket a few more capacitors that are part of the tone control so I can swap them out easier. Two of them are already socketed so just need to do two others and go from there.

I did verify with a signal tracer that the capacitors for the tone control are working though. When the switch is in the center, both C2 and C3 work. Switching up or down turns one or the other off so this appears to be the correct functionality. Guess I just need to play with the values a bit to see what works.

[velonut]

Ok, so I socketed all four of the capacitors that effect the tone switch and updated the values based on the recommendations in that other thread. No change. Tests with the signal tracer do seem to indicate that the capacitors are working so I'm at a loss as to why it doesn't work. If the tone switch results in a "subtle" change then it's stupid subtle, as in undetectable.

One last little wrinkle that may explain things. That first capacitor in the circuit, C1. In the legacy version, it has a value of 1nF, whereas the new version is set to 47pF. Could that be the problem? My understanding is that this capacitor acts as a high-pass filter to prevent radio interference. Could that be what's messing with the impedance?

Gonna try socketing C1 and play with it to see what impact it has on things.

[velonut]

Ok, last post for a bit and then I'll shut up.

Socketed C1 and tried out different caps. 47pF is the default for the new one. Tried 1nF...no change. Tried no cap at all...no change. Only thing I noticed is that, yes, no cap at all does tend to introduce more radio interference so having the recommended 47pF is indeed a good thing.

I also double-checked the rest of the caps with everything assembled within the enclosure to rule out any grounding issue. All caps appear to be accepting signal at each connection. Also tested the switch and all the correct caps appear to be disabled with the up and down settings. Signal is coming through and, based on the signal tracer, the caps do appear to be working in terms of a change to tone.

So...yeah...the pedal works, which is good. I just hoped that the tone switch would work so that I could get a few extra tones out of it. Not a total loss...just a bit disappointing and concerning. Weird circuit! 

[PRR]

Let's get the plan in the thread:


Now: What are you driving "In" with? A super-hot guitar pickup? Or another pedal full of buffering chips?

The cap is directly connected to the input. If the source is "strong", in the sense of plenty of current, then it will fill-up that cap and deliver the highs anyway.

You may want to try a 47k resistor between IN and the cap-network.

[velonut]

Good tips, PRR! I did try running the pedal first in the chain and changed amps.

I have two guitars: a 7-string Ibanez and a Gretsch, both with passive pickups. Now, the Ibanez does have pretty hot pickups so I eliminated that one. The Gretsch does have dual humbuckers but I wouldn't describe them as super hot.

For testing, I rolled back the volume on the Gretsch and tried both pickups individually. I noticed a slight change in tone when changing the Tone switch so, yeah, I suppose it's stupid sensitive to impedance...even more sensitive than my Germanium fuzzes.

I doubt I'll spend much more time on it. The pedal does work. Plus, it's a rather simple circuit really. The introduction of a Treble/Tone switch, while cool in theory, just doesn't work all that well with this circuit. I think the only way to make it work would be to put it in it's own stage and update it so that the capacitors will work even after a buffer. Just way, way too sensitive as it is.

I'm thinking about switching gears and building a clone of the EQD White Light, which is based on the MXR Distortion+ / DOD 250 as well but adds a Weight control and Compression switch to give more control over the tone. Will be interesting to compare this one with the Aphelion, even without the Tone switch.

[eh la bas ma]

Just to make sure, in order to get as much as possible from your aphelion, you should send an email to aion fx with a link to this thread.

Ask him about your tone switch and give a description of the gear you are using with the aphelion.

I'm sure he will give you all the answers.

[velonut]

Good idea! Will do that now.

[aion]

The idea was to switch between Dist+ (1n) and 250 (no cap). For the 250 mode I left a 47pf in there for RF suppression, pretty common practice without impacting audible frequencies. Then since the switch had 3 positions I added an in-between mode with 470pf.

If it doesn't do much in your rig, it's likely because those treble frequencies are all rolled off already so there's nothing to cut, so if it sounds good as-is then best to just ignore the switch if it's not needed.

If it has too much treble then you can increase one of the capacitors to have a "more cut" option. The gray DOD 250 actually uses a 2n2 cap here, so you might swap out the 470pf capacitor for a 2n2 and see if it makes a difference.

It's simple, perhaps overly so, but anything more complex and it's not a Dist+ anymore. The OD-855 is basically a Dist+ with a true tone control.

[velonut]

Ah, I see. That's a great explanation. Thx man! 👍😁