First Build - Aion Aurora 125B

I’ve got a very bad case of G.A.S. that is causing me to build my dream rig. I used to have a Keeley C4 and really liked it, so Aurora seemed a natural choice. The 125B version is a PCB that’s based off the available LM13700 chip.

I’ve never soldered a PCB before but have decent experience with a soldering iron, so I think I’ll be OK. I’m tired of being afraid to work on PCBs. I already have dual channel, high gain tube preamp so no need for drive pedal otherwise I’d start there.

I like that this kit recommends metal film resistors which are used in higher quality audio products. I don’t know what other components (caps) make sense to change, but if there are suggestions I’m all for them as I’m a bit of a tone snob.

The intended use is to go after pre-amp and any drive pedals. This allows the volume knob to control gain/drive but keeps overall volume about the same. Turning off the compressor gives additional ‘boost’ if needed. Clean tone is very important to me, FWIW.

https://aionelectronics.com/project/...na-compressor/

Just make sure you have an appropriate soldering iron and 1mm resin core solder and you should be fine. I always inspect each join under magnification immediately after soldering, which can help catch issues early.

Metal film resistors are so cheap these days, so I don't use anything else.

For capacitors, this is an interesting but somewhat technical overview of capacitors in audio circuits. For my own circuits, I am guilty of using whatever I have on hand, which is mostly multilayer monolithic ceramics for smaller values, and polarised electrolytics for higher. I am getting good results, but I also don't have particularly fussy ears.

I also like putting a dynacomp/ross style compressor after dirt pedals. Oddly though, I put the Orange Squeezer in front because I liked the sound more that way. But the Orange Squeezer adds more colour and is not an always-on pedal, while I never turn the dynacomp compression running after off. They do a different job.

Given that I have never paid a lot of attention to capacitor types before, I was interested to read

Monolithic (High-k) Ceramic: Designed as bypass capacitors, these are physically small, and have excellent HF performance. Stability is suspect, and they are not recommended for use in the audio path. Must not be used in filters because of thermal instability.

on the ESP Sound pages.

Apart from larger electrolytics, these are the caps I have used in all recent builds, including in filters. If I start getting issues I will have one more place to look.

Great info, thanks Dan. I don't know enough about the circuit to make too many judgement calls. However, being this is a reputable circuit designer and he's used different materials for different applications (some but not all ceramic, some plastic, and the first cap is specifically said to be OK for audio, etc) I will assume whatever is specified is adequate.

So much easier that way :)

Good stuff mate. It would be interesting to hear the old and new versions side by side.

Sent from my SM-G960F using Tapatalk

Everything's on order! I ordered basically the recommended list. Reverse audio taper, right-angle PCB mount pots are very difficult to find. Small Bear has them but are closed, so I ended up ordering normal PCB mount pots (not right angle) and will just make an adapter or solder wire to them or something.

I chose 150pF for C1 instead of 220pF since that's what's in the Keeley comp.

I also added 5 Tantalum resistors to the order, as my very dear friend Mr. Woltz, with his magnificent taste in electrolytically-induced capacitance tonality, seems to like them (they're recommended in the Aurora 1 instructions, but interestingly not mentioned in Aurora 2, though used in at least 1 build log).

Hopefully I will learn a little something about electronic circuits besides just learning to solder a PCB. But if I don't, that's OK too - especially if I end up with a decent compressor pedal I built myself! :)

C1 looks like a DC smoothing capacitor (helping filter noise and ripples from the DC power), so you likely won't hear a difference. But sticking to the Keeley mods is a safe choice.

Maybe the Kale-yeah Compressor? lol

Attachment 35098

I love the graphic. Will you be screen printing? Or a colour decal? Or the radical step of hand painting direct to the enclosure?

I should build or buy a screen. Black decals are quite limiting.

I was thinking I could make a stencil and spray it - at least for the text. I could do the veggies by hand. Not sure if I would paint the eyes or stick on real googly eyes :)