Aion Andromeda - works but small issues

[stevengkeezer]

I recently built an Aion Andromeda odr-1 clone and it's functioning well, delivering great sound. However, I encountered two minor issues that have been bothering me.

Firstly, I don't hear any increase in volume when I turn the volume knob past 12 o'clock. I'm unsure if there is a limit to how much volume the device can produce, but it's not a big problem since the volume at 12 o'clock is sufficient. I'm not sure if this is a design feature or if I made an error during the build.

Secondly, when I turn the gain knob on and off, it produces a popping sound. Additionally, there are some noises that resemble those from a dirty pot when I turn the gain knob from 0 to 12 o'clock. However, the behavior smoothens out above 12 o'clock. I tried using contact cleaner to clean the pot and touched up the solder points on the pot, but the issue remained unresolved.

I don't really mess with the gain knob when I am recording so I can live with it, just wanted to see if anyone smarter than me had any insight into possible causes.

[idy]

Did you use an "a" (audio or log) taper pot for the Volume? If you used a "b" or linear it would feel like that.

[stevengkeezer]

Well you are dead on about that. I have the bass and volume pots swapped. Going to change them and see if it might resolve the drive knob issues. Unlikely but lets pray.

[ElectricDruid]

For the Level and Bass controls, one pot is a "C", a Rev-Log, and the other is "A", a Log/Audio pot, so they'll behave quite differently. Swapping them into their right positions should improve the control feel a lot.

The Drive knob issue is likely unrelated. Scratchy pot noises are often caused by there being a DC voltage across the pot. Given the circuit, that *shouldn't* happen, but if there's a fault somewhere, it might. You could check for shorts on C4 and C5 as a starter.
You could also post the voltages on the pot and around that IC1A op-amp and we'll take a look and see if we can see what's going on.

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

[stevengkeezer]

I swapped the pots and it fixed the issue. Thank you all for the help.


C4 to ground didn't register continuity
C5 to ground didn't register continuity
From pin to pin on C4 & C5 both have continuity
Ground to all legs of the pot: 4.44
Each leg to other leg of the pot (i'm assuming this is what you meant by across the pot): 0
Ground to each leg of IC1:


Please let me know if I measured this right or what I might be missing. I am still learning.

[idy]

Good work. Those voltages are golden, that is what you *usually* will be looking for on *most* dual opamp circuits you will encounter. Gnd on pin 4, supply on pin 8, and midvoltage on the other 6 pins.

[ElectricDruid]

+1 what idy said. Those voltages look fine.

If you look at the schematic, you'll see that the drive pot is wired between pins 1 and 2 of that op-amp (it has R6 in series with it too). Since both pins 1 and 2 have the same voltage, there's no DC across the pot, so we can rule that out as the source of any crackles.