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.

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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 :)

Googly eyes would be cool, but maybe also prone to falling off.

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Originally Posted by jugglindan

Googly eyes would be cool, but maybe also prone to falling off.

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Maybe not if 2 part epoxy was used to adhere instead of ca glue?

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Yeah I was thinking some kind of epoxy. Only if I can find a nice heavy made googly eye, haha. Maybe the epoxy would stick over the paint/finish. But it’s just an idea at this point. The pedal needs to work before I paint the box!

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Originally Posted by Joe Garfield

The pedal needs to work before I paint the box!

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Not around here! But having the enclosure for my Phase 45 ready is good motivation for getting the circuit to sound like a phaser instead of a vibe.

Good point :) Although the priority of painting the box will depend on everything else that's going on. If I don't get either of my electric guitar kits in the next 2 weeks then it's very likely I'll paint the box. But I'm really itching to check out my new Effectrode tube preamp and Two Notes CAB emulator! So one of the electric kits will get priority when it comes. Until then there's some crazy acoustic guitar on my bench =)

You do have a lot of projects in the pipeline.

Attachment 35205Attachment 35206Attachment 35207

All this stuff for 1 little pedal, and I’m still waiting for more parts! Lol. It looks like a nice little board. It’s heavy! And I found proper right angle pots at the tube store, so I feel better about that.

That was quick. Much quicker than for mine to arrive here in Aus. I'm already thinking about ordering another couple PCBs from them for future builds.

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Yeah shipping within the USA (including Hawaii, the 50th state) is relatively unaffected. I’m not making anymore international purchases (besides the second custom guitar I just ordered from Adam ;). )

I still need the 6 (chips?) that should be arriving tomorrow from Mojotone.

I hope the build goes well. And I am a little envious since I am still waiting on a bunch of op amps and other parts. It's been ages ...

It’s going on 7 weeks for my initial PSH-1 order from Adam, if that makes you feel any better :)

Thanks, I”m looking forward to getting started on this one. I don’t feel to anxious about soldering to the board, so I guess that’s good!

Do I need to solder both sides of the board?

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Originally Posted by Joe Garfield

It’s going on 7 weeks for my initial PSH-1 order from Adam, if that makes you feel any better :)

Thanks, I”m looking forward to getting started on this one. I don’t feel to anxious about soldering to the board, so I guess that’s good!

Do I need to solder both sides of the board?

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Yes the pots, led, switch and footswitch are soldered to one side. Caps, resistors etc the other side. Doubt you'll have any issue following the build guide. I found Aion's instructions to be very clear.

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Oh, thanks - so each component is only soldered at one side, right? That's what I mean - I know there are things like multi-layer boards that need solder on both sides for some components. I don't see anything in the instructions about this - there really aren't any instructions although there are some 'general build notes' in the documentation for the older Aurora.

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Originally Posted by Joe Garfield

Oh, thanks - so each component is only soldered at one side, right? That's what I mean - I know there are things like multi-layer boards that need solder on both sides for some components. I don't see anything in the instructions about this - there really aren't any instructions although there are some 'general build notes' in the documentation for the older Aurora.

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Oh right. Yes each component is only soldered on one side. Have a look at some of the pcb soldering videos on YouTube. It'll give you an idea of how to approach it. You may want to get something to clean the residual flux off the pcb as well after you've finished soldering.

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In general, you insert all components from the front of the board and solder at the back. On your board, the front is the side with all the component names screen-printed onto it (R10, C3, IC1 etc). But because your board is tinned through the holes, you will see solder flow right through the hole so it can look like the component was soldered from both sides. Here's a blurry (sorry!) photo of my Julius Squeezer board. On the germanium diode (top left) the effect of solder flowing through from the back is quite visible.
Attachment 35212

A good trick is to put a bit of tape (masking, electrical, doesn't matter) on the components after inserting them in the board so they stay put when you flip the board to solder. Although you can do multiple components at once this way, I prefer the slow and steady method of soldering 1 component at a time. Double check the component value, bend leads to right length, insert, double check placement, tape, flip, solder, inspect solder joins with magnified desk lamp. Then rinse and repeat. I also like to work from smaller components to larger, so the larger ones don't get in the way when inserting the smaller. So typically, resistors, diodes, small caps, sockets (ICs, transistors), large caps, and then pots and off-board wiring.

These are all just my preferences, but I find being systematic helps prevent errors.

Thanks guys! I think I saw Woltz's board with the solder wicking through so that's why I was asking.

I really really want to build this pedal.........:eek:

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Originally Posted by Andy40

I really really want to build this pedal.........:eek:

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Which one haha? The Aurora or the Julius?

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Originally Posted by Woltz

That was quick. Much quicker than for mine to arrive here in Aus. I'm already thinking about ordering another couple PCBs from them for future builds.

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Yeah I was looking at their ross compressor but was unsure about shipping times. I might wait until international shipping gets a bit better.


and yeah the Aurora

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Originally Posted by Andy40

Yeah I was looking at their ross compressor but was unsure about shipping times. I might wait until international shipping gets a bit better.


and yeah the Aurora

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If there are enough people on the forum that are here in Aus I was actually wondering about us doing a forum order to minimise shipping costs. Shipping time was around 4 weeks for mine.

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Originally Posted by Woltz

Which one haha? The Aurora or the Julius?

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The Julius is very nice. Not a transparent compressor, it adds it's own juicy flavour to the tone. Right now, the julius into the Barber CDD at low gain is my favourite clean tone. So sweet, with just the tiniest hint of breakup when you push it hard. Very responsive to guitar volume as well (this into a finely tuned Blues Jr patch on my THR).

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Originally Posted by Woltz

If there are enough people on the forum that are here in Aus I was actually wondering about us doing a forum order to minimise shipping costs. Shipping time was around 4 weeks for mine.

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I would be interested in that, but we would have to make sure that local shipping to split the order doesn't erode the savings. For those in Canberra we could probably arrange something.