SOLVED Compressor indicator LED noisy turn on…

[LukeFRC]

Right, so this might be a common problem but it’s impossible to google…

I built Aions trace of the L4 preamp https://aionfx.com/app/files/docs/l4_bass_preamp_documentation.pdf
It has a LED indicator that the limiter circuit is limiting. It switches on a bit late (ie well into limiting) but most problematic every time it turns on it causes noise in the audio.

Before I dive in- I’ve heard this is a common issue with compressor indicator LED - either I’ve messed up something or wrong LED - but I’m looked and can’t find anything!

Yep, not the “is the pedal on LED” nor thr “optical LED - LDR compressor” just an indicator - which is why it’s such a pain to google.

Anyone point me in the right direction?

 

[LukeFRC]

Screen grab here

 

[LukeFRC]

Oh and you don’t notice it into an amp - but into PA and IEM very noticeable.

Btw link to other threads in similar circuits solving similar LED switch on noise good, I know it’s a common thing, and even commercial pedals display it sometimes

 

[LukeFRC]

Hmmm

 

[Gordo]

Crickets huh??? I'm really not much help here except that I had the same issue with the earlier AC powered Lab circuit and it was a power issue with mine. The compressor would kick in with a thump and a lot of distortion.

On my Lab bass build I haven't noticed any issues either thru an amp, thru a PA or thru my audio interface at the computer.

The usual: check your parts and reflow solder joints...blah, blah. I'd take a close look at the values on R76/77/78 and if it's doable maybe try swapping out Q7?

 

[LukeFRC]

Oddly on the original schematic R77 and that connection to -VA doesn’t seem to be there.

 

[LukeFRC]

Removing Q7 turned the light off but if anything made the noise louder…

 

[LukeFRC]

Oh FFS

Took all the transistors out, Musikding kit sent me sockets - I’m not convinced by sockets…
Then noticed one of the ICs wasn’t sat neatly in its socket - pushed that in and it was fine.
Stupid me

 

[Nic]

At least you found out before breaking that Aion bord in pieces...

 

[LukeFRC]

At least you found out before breaking that Aion bord in pieces...

I hear that’s the done thing around here!

It’s a well designed board/kit, and the breakout board in this case is a fairly clever way to fit the power regulator in. If I was being critical- the way the pedal goes
Preamp (a/b) -> distortion -> master vol -> limiter - to my mind is calling for an effects loop between master volume and limiter - but there’s no/little space for a footswitch!

 

[Nic]

I hear that’s the done thing around here!

It’s a well designed board/kit, and the breakout board in this case is a fairly clever way to fit the power regulator in. If I was being critical- the way the pedal goes
Preamp (a/b) -> distortion -> master vol -> limiter - to my mind is calling for an effects loop between master volume and limiter - but there’s no/little space for a footswitch!

Yep, that's crowded in there. I've just finished populating the resistors on mine. Really excited to get this thing finished, but don't have a lot of spare time.

 

[LukeFRC]

Slow and steady











And resist the urge to snap it in half!

 

[darwin999]

General advice on LED popping noise from AMZ FX:

AMZ - LED Popping

How to stop the pops in audio from LED current surges when switched.

www.muzique.com