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The Mighty 250!

Project: Aphelion (250/Distortion+)

Build description

This build is based on the 1977 gray DOD 250. It uses the LM741 op amp. As with my Aion Boss OD-1 build, this one went smoothly, except that I installed the 4.7 uf electrolytic cap in C5 incorrectly and it didn’t work at first. Once I got it oriented correctly, it fired up perfectly. Be mindful that there are three solder pads for C5 and you need to make sure you use the correct ones and have the polarity right if using an electrolytic cap there. The three toggle switches are board-mounted while the pots are off board. I used a BB-sized enclosure so that I could include a battery and have the ¼ inch jacks and DC jack all mounted on the back.

The clipping switch toggles from stock to a Bluesbreaker stacked diode configuration with the diodes lifted in the center. Stock has more gain and less volume while the stacked arrangement is the opposite. So far, I prefer stock, but like that I have the extra option. The softness trimmer is awesome for fine tuning purposes since this circuit can get pretty bright with the gain knob at or near maximum. I’m still experimenting with the comp and treble switches. They do give you some different tones and textures.

Even without the added toggle switches, this is still a very versatile circuit, especially given it only has two controls. It can be used as a booster all the way up to heavy Randy Rhodes style distortion. That said, why not build it with the switches? The pads are already included on the PCB. Thanks to Kevin for the very well documented and easy to follow project instructions.

Robert Jackson

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‘Cause of Randy Rhoads!

Project: Aphelion (250/Distortion+)
Variant: Distortion+

Build description

I tried this Aion Electronics MXR Distortion+ build with a vintage Motorola LM741 and then with a Burr-Brown OP275, which seemed a little more harmonically rich and lively, but wasn’t really all that much different than the LM741 to my ears.

Someone recommended that I try an OPA2134. Well, that really woke things up. First off, the output has to be double what it was previously. This board lets you switch between two diode arrays. I have one set up like the original pedals were and then the other one is set up for asymmetric clipping with two diodes on one side and one on the other. With the 741 and the 275 the asymmetric clipper only hit unity gain with the volume pretty much all the way up. Not anymore! Now unity gain is where you see it in the photo. Not even 12 o’clock. This thing has an insane amount of gain now and it’s really clean. Not noisy at all. The 741 and 275 were about the same; they weren’t terribly noisy, but there was a little noise there. To get to that same amount of noise now I’m at least doubling the output volume.

So yeah, it’s loud, but it’s also much more alive and harmonically rich. Maybe because the circuit is being hit by more voltage. I don’t know exactly, but it’s a whole different beastie now. Still kind of a one-trick pony, although now it can behave like a clean booster if I back off the Gain because there’s so much Volume on tap. I’d have to say that one trick is kind of cool.

BTW, someone mentioned to me that the OPA2134 is an expensive op-amp. They’re currently $3.30 each at Mouser if you buy ten. So WAY more expensive than something like the Tube Screamer’s JRC4558, which is like 30 cents or so. Still, it’s not a break-the-bank kind of thing for a pedal you plan to use a lot. Or even a little.

Modifications or part substitutions

OPA2134 op-amp and alternate asymmetric clipping array.


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Project: Aphelion (250/Distortion+)
Variant: YJM308

Build description

I currently own 2 original YJM308 overdrives. I have since replaced both of the PCBs with a General Guitar Gadget for the “Grey ’77” variant & a Griffin Effects PCB for the MXR variant & populated both boards premium parts.

This is my first foray into the YJM308 variant using AION Electronics’ “Aphelion” project PCB. Their PCBs are compact, has extremely well-thought of features, very easy to populate, fun & exciting to build. My build includes all the three (3) AION mods + the Softness trimmer. I used metal film resistors, Panasonic brand for both the film & solid polymer caps. The only ceramic cap is the 25pF one which I ‘scavenged’ from my original YJM308. I will be changing this particular cap with a same value CDE dipped mica cap as soon as my order for this rare part arrives. I have observed that mica caps does wonders to tones in FX pedal circuits. I use ‘em a lot wherever it’s applicable.

Lastly, I installed Small Bear’s light plate. It makes your pedal look very cool!

OpAmps tested: KA4558 & OPA2134 & I finally decided to install the OPA2134. This OpAmp does wonders to your pedal’s sound quality too.

Equipment used: Marshall JVM 205H head / Marshall 1960A cab / 1997 Fender Strat Ultra & 1988 Fender HM Strat both with Seymour Duncan “Everything Axe” pickup set / ESP JH-600 with 2 EMG humbuckers. Only Aphelion is connected.

Test results: A killer sound for both rhythm & lead parts. The Comp & Treble mods enable subtle changes & the Softness trim is a big plus to the overall pedal circuit. As usual, the 4-diode/2-red LED mod help make the distortion very variable not to mention the toggle switch’s center-off position which in turn lift the diodes and enable a creamy-type desirable distortion with a louder volume, to boot.

Kudos to Kevin & AION Electronics for raising the bar of the effects pedals!

Thanks for reading! Aphelion builders…..we wanna hear from you!