Aion Tube Screamer build

[AnalogPackrat]

An old friend who is now a veterinarian helped me out in a time of need. He plays guitar, so rather than sending him some generic thank you gift, I offered to build him a pedal of his choice. After some discussion about options he decided on a Tube Screamer. I gave him several options from kit build to full DIY and he chose the Aion Stratus kit. It includes bass cap switching and clipping switching.

Started building over the weekend. Nice kit with quality finished enclosure, all parts, and good instructions. It uses three PCBs--the main board with all controls mounted on it, a small board with footswitch and LED, and a board with the top-mounted jacks and 9V input.
Here it is after I've soldered most of the resistors. The kit included some very thin light red resistors. I replaced all but two with standard 1/4w 1% metal film or 5% carbon film when I didn't have the value needed. Used two of the included resistors because I had no 510k in my stash.



Kit includes Wima box caps, alpha pots, a machined pin socket, and a new JRC4558.




My first mod was to increase the lowest "bass" switch cap to 470n to cover the full guitar spectrum (including possible 7-string as my friend is a metalhead).



The boards are connected by ribbon cables with snap connectors on one end. The included 9V batter jack is poor. I'll be removing that as my friend won't be using batteries.



I didn't like the limited clipping options included, so I tacked on an umbilical to allow for easy auditioning of various options (the base TS-9 will be one).



That's a Fuzz Face on the upper part of the breadboard. Need to finish that some decade. I'm also comparing other 4558s (mostly TI of various vintage).



In TS-9 mode it sounds pretty close to my very early (1980) unit. Having different bass caps is cool. One of the first clipping options is crap, so more experimenting today.


Had to put some green somewhere! Knobs are upgraded, too. The kit included black plastic with silver top inserts.

Hope to button this up in the next few days. I bought myself an Aion BD2 kit, so maybe I'll get on that or my Fuzz Face next.

 

[fallout]

Kits have come a long way. My intro to diy was when Geofex kits shipped with only an instruction sheet a few transistors and an iron-on toner transfer kit to etch your own PCBs! haha

 

[AnalogPackrat]

Kits have come a long way. My intro to diy was when Geofex kits shipped with only an instruction sheet a few transistors and an iron-on toner transfer kit to etch your own PCBs! haha

Yeah, I usually buy a bare PCB or if the circuit is simple, build it on perfboard. This is my first full pedal kit. Nice, but it really limits some mods with the board-mounted controls, etc.

 

[Mworthin]

BTW, the photo isn't clear, but those red resistors look like PRP resistors which are usually sold in 0.1-1% tolerances...you may not want to throw them away...

 

[AnalogPackrat]

BTW, the photo isn't clear,

My "new" phone takes worse pictures than it's 6 year predecessor, especially macro stuff.

but those red resistors look like PRP resistors which are usually sold in 0.1-1% tolerances...you may not want to throw them away...

I'm a packrat. I don't throw anything away. The unused parts all were added to my hoard.

These aren't like the 0.1% and better precision resistors I have from a reputable source (some red, some black). They're smaller than any other 1/4w 1% I've seen. No tolerance marking, only a "D" on the opposite side from the value. All measured fine, but I prefer to use a known type, especially since I'm giving this away.

Top is a 0.1% known precision part, bottom a mystery part. I'm guessing it's some kind of 1/8w from who knows where.

 

[AnalogPackrat]

After a couple of hours messing with different diode options I've settled on:

I back to back single 1N456 Si (Vf 0.75V)
II back to back 3mm bright red LED (Vf 1.89V)
III single 1N751 Si (Vf 0.78V) and two 1N914 in series (Vf 0.73V each) for an asymmetrical option

I also put the included JRC4558 in instead of one of my 93 date code TI units. Mode I now sounds very close to my vintage TS-9. I tried several other asymmetrical options with 1N60 & LED, 1N270 & LED, BA148 & LED, and a couple of others. All sounded fizzy/spitty at lower gains and when notes faded out. Maybe the asymmetry was too extreme (I was trying to keep the relative volume levels from being too extremely different).

 

[fazer]

I was trying to keep the relative volume levels from being too extremely different

The moment you add distortion sustain there is this fight for dynamics and volume. When you bypass the pedal the volume feels like it jumps between settings of the 2 choices. It sometimes easier when your playing in a band with other musicians and all you really need is a volume boost for solos.