AionFX L5 Preamp hates Chorus pedals. Rate LFO is audible and annoying

Forum dedicated to helping people debug and troubleshoot non-functional pedals or builds. Please use an clear and informative title, indicating circuit and basic problem. Don't forget to mark the issue as fixed if this is the case.
Post Reply
User avatar
Bobb_Lobblaw
Information
Posts: 4
Joined: 11 Jul 2022, 16:01

Post by Bobb_Lobblaw »

Hello all,
Here's an odd one. I recently built the AIONFX L5 https://aionfx.com/app/files/docs/l5_pr ... tation.pdf preamp pedal, which I'm using as a preamp into my pedalboard, then into a Seymour Duncan Powerstage 170 and finally a 16-ohm speaker/cab.
Sounds great...quite loud, especially channel 2.
But here's the thing.
It plays well with all my other pedals save one category.
When I kick on a chorus pedal...any chorus pedal, I can hear the Rate LFO.

Current Signal Chain--Guitar-EQD Swiss Things In--(Loop 1) Fuzz--OD--L5 Preamp--Return (Loop 2) Skyscape--Phaser--Reverb/Delay--Delay--Return--SwissThings Out--SD170--Cab

I have three chorus pedals: EQD Sea Machine, DeadAstronautFX Skyscape https://deadastronaut.wixsite.com/effec ... -x-fuzz-ii, and an Aalberg Audio KOR (short-lived boutique brand), and I hear the LFO at different volumes and pitches with all three. If I put a pedal with a volume knob before the chorus (in this case, Fairfield Circuitry Shallow Water which is kind of a chorus pedal) in Loop 2, the LFO volume goes down, but I can still hear it...mocking me.
I've never seen/heard of this phenomenon before, and I have no idea what the issue could be.
With the Skyscape, the LFO is very loud, but if I turn the TIME knob to just under noon, it goes away until I turn the pedal off and on again or move the knob. On all the other pedals, it's pretty faint but annoyingly noticeable and consistent.
What the hell, man?
No combination of knob twiddling or toggle toggling on the L5 seems to make a difference. Low channel volume, high Master volume, bright switch, Hi/Lo input, none of it changes anything. I haven't calibrated the L5's "distortion" or "compression" trimmers yet, but they seem to have no effect on the phenomena either. I've tried it on my main pedalboard and my aux board (no Swiss Things, a standard direct signal chain into a cab simulator into my audio interface)...same thing happens. Is the L5's 9 volts of alternating current just pushing everything after it too hard?

Here's another oddity. If I place the L5 last in the signal chain, directly in front of the SD170, and crank the Vol. on the SD170 to noon-ish, it immediately overclocks and cuts the signal...
I am legit stumped, don't even know where to start. Should I just build a noise gate pedal and keep it movin'?
So, thanks for any and all suggestions on what it could be and/or how to fix it.

User avatar
luix
Information
Posts: 49
Joined: 17 Mar 2009, 01:56
Has thanked: 3 times
Been thanked: 22 times

Post by luix »

To avoid this problem I usually supply the ticking oscillator with a capacitance multiplier filter, I don't know if this is a viable solution for your pedals.

The kind of rectifier used in Aion preamp is the worst solution to power an fx, it's the same used in the tube driver and have the same noise problem, also LM7x15 regulator have poor noise rejection, you could try LM317/337.

Can you change the transformer to a center tap and the power supply to full bridge?

Otherwise you can use a laptop SMPS supplying 19VDC (choose one with more than 20kHz switching frequency) and an inverting buck regulator to get the negative voltage (also with working frequency >20kHz), current consuption is sufficiently high to mantain the regulator in continous mode.
you can find some of my creation on instagram @ luixanalogdevices

User avatar
Frank_NH
Solder Soldier
Information
Posts: 246
Joined: 12 Jun 2013, 14:18
Has thanked: 114 times
Been thanked: 152 times

Post by Frank_NH »

I have built the Aion L5 preamp and use it regularly. I typically place modulation pedals after the preamp and have not noticed any noise issues at all. The pedals I have used include the Visual Sound liquid chorus, MXR phaser and micro flanger, and a homemade vibrato pedal. I also checked to see if the power supply placement (9V AC wall wart) made any difference and it didn’t. I also checked to see if using my chorus before and it didn’t.

By the way, Aion now has a PCB for the L5 overdrive channel only which uses a new circuit to obtain +/-15V from a 9V DC power source. I’m building this project now and can report back how it compares. The only bummer is that the overdrive PCB does not include the multifilter, which I like to have on to add presence to the tone. May have to build the multifilter circuit as a separate effect on vero! :D

User avatar
plush
Cap Cooler
Information
Posts: 641
Joined: 08 Dec 2015, 09:29
Location: Moscow, Evil Russia
Has thanked: 36 times
Been thanked: 172 times

Post by plush »

I don't think there's an issues with L5 in particular. It has plenty of gain and most of the noise will eventually get amplified.
Some (if not the most) analog-ish (and some digital too) choruses bleed lfo into the signal line, this gets amplified and becomes more pronounced. IMO, you should put your modulation after L5. If you want to use your modulation before the preamp, you'll either need to place a gate between mod and preamp or find a better modulation.

Bobb_Lobblaw wrote: 12 Jan 2023, 20:35 If I place the L5 last in the signal chain, directly in front of the SD170, and crank the Vol. on the SD170 to noon-ish, it immediately overclocks and cuts the signal...
IMO, L5, when cranked, provides so much signal amplitude, that it either triggers SD170 input stage protection or makes it push the output so much, that it makes it's OC protection trigger.
It will push a tube amp into overdrive, but not the SD1700.

User avatar
Frank_NH
Solder Soldier
Information
Posts: 246
Joined: 12 Jun 2013, 14:18
Has thanked: 114 times
Been thanked: 152 times

Post by Frank_NH »

[/quote]
IMO, L5, when cranked, provides so much signal amplitude, that it either triggers SD170 input stage protection or makes it push the output so much, that it makes it's OC protection trigger.
It will push a tube amp into overdrive, but not the SD170.
[/quote]

I think this is the issue. The L5 preamp from Aion is authentic in that it produces a large amplitude output signal which is appropriate for the 100W solid state power amp design of the L5. However, its output is probably exceeding the input sensitivity of the SD170. I would simply adjust the Master output pot of the L5 pedal to provide just enough output without the power amp clipping. My guess is that the knob will be well under 50%. Of course, you can also try a tube power amp like the Mooer Tube Engine - hey, tube power amp clipping is a thing... :D

Post Reply