AionFX Stratus: One of these is not like the other

[jeffwhitfield]

So I built an AionFX Stratus a few months or so ago. Basically wanted to get a solid clone of a TS-808 Tube Screamer. Decided to revisit it to see if I could get one that's closer to the original spec. Plus, with the extra sets of diodes via the Clip switch, I figured I'd play around with it and see if there are any interesting combinations. These are just personal builds so no fancy enclosures...just a bunch of Sharpies and some clear coat.

First thing I wanted to do was stick with what I thought was stock components. Basically, RC4558 op-amp, 2SC1815 transistors, and MA150 diodes. The RC4558 and MA150 components weren't a problem...but the 2SC1815 transistors were. Those didn't work at all. I ordered some 2N5088's, which were used in my first Stratus. But on a whim, I looked in my spare parts box and found a set of BC108C's which I understand are compatible with the 2N5088. They work like a charm! More on that later.

Next, I wanted to try out some different diode combinations. Specifically, I wanted to try a Nanolog N2 device...which I couldn't get to work at all. Will mess with that later. In the meantime, I tried a few other things. D9E Germaniums didn't work very well...like no clipping at all. A BAT41 works too well...way too compressed.

The weird one was a set of NTE555A diodes I had sitting around. These are actually VHF band switch diode. Seems that they're very, very close to the same specs as the MA150. Switching between the two I honestly can't tell much of a difference. Very, very subtle difference. MA150 might be slightly smoother with less attack. Upside of this is that if I decided to build more of these I could Duse the NTE555A as a cheaper replacement to the NOS MA150 diodes.

For now, I'm sticking with both the MA150 and NTE555A diodes so I can continue evaluating them.

Now, how does the new one sound? Compared to all the other Tube Screamer clones I've built, this one is perhaps the most different of all of them. Along with the original Stratus I built, I also built an Actual Overdrive Jr. (KHDK Ghoul Jr) and a Bootleg Overdrive (JHS Moonshine v2). The main common component among all of them is the 2N3904 transistors used for the input and output stages, which is similar to the 2N5088 I used on the original Stratus. By comparison to the Stratus I build using the BC108C's, these all sound more on the fizzy side with a slight bit of fuzz. Not bad per se...but not quite as good as the new Stratus. Something about the BC108C's adds a bit of sparkle to the sound. With lower bits of drive, the sound is smoother. Crank up the drive and you get a more crunchier sound. The difference is quite stark. I'm almost tempted to get an authentic Tube Screamer so I can do an A/B test.

Now, I won't be able to confirm this till I get a set of 2N5088's to test with. All the main components are socketed so no problem there. Will report more later.

 

[cooder]

Great builds. The SC1815 has a different pinout (E-C-B) that's I guess why it didn't work? Check pinouts with google and a bit of leg twisting and it might work then. 2n5088 pinout is E-B-C.

 

[Harry Klippton]

I like your paint jobs

 

[jeffwhitfield]

Great builds. The SC1815 has a different pinout (E-C-B) that's I guess why it didn't work? Check pinouts with google and a bit of leg twisting and it might work then. 2n5088 pinout is E-B-C.

Doh! Can't believe I missed that! AionFX even provides and extra E pin too. Once I added a socket for it and threw in the SC1815 it worked.

 

[jeffwhitfield]

Alright, so quick update on the build of this one. Thanks to a tip @cooder I got the SC1815 working.

I also got the Nanolog N2 device working too. If anyone is messing with these, keep in mind that it doesn't need a loop to work. For a two-diode config, just keep one diode spot open and add the Nanolog to the other. For a four-diode config like this one, keep one part of the loop completely open so that it doesn't form a complete circuit loop. For the other, jumper one diode slot and add the Nanolog to the other. Works like a charm!

In terms of sound, it seems the SC1815 doesn't rally sound any different to the 2N5088 of the first Stratus pedal. They're virtually identical. If there's a difference it's super, super subtle. What's more, with that transistor, the MA150's don't even sound that different compared to the 1N914 diodes. So it appears that all the substitutes used in various Tube Screamer type builds are pretty much on the money. No real need for any NOS stuff it would seem.

What does make a difference though is the transistor choice. The BC108C's do indeed make a huge difference. With the BC108, the sound is less compressed with less gain. It also seems a bit more transparent. Makes sense when you consider that the BC108 is used in a lot of overdrives that promote a more transparent sound. They're also used in fuzzes too. That said, while the sound is pretty awesome, I'm not 100% convinced it belongs in this pedal. I don't think Tube Screamers should be more transparent. So I'll likely stick with the SC1815 and experiment a bit more.

The Nanolog N2 is an interesting one. In a Tube Screamer, it gives it a less compressed, lighter clipped sound. It definitely likes more gain so using the SC1815 is certainly a better choice here. It's somewhat like a Germanium but with a little more bite. Definitely an in-betweener type thing for sure. Gives it a different character. Need to play with it some more. In fact, I'm gonna try it out in a Rat circuit later to see what that's like.

 

[fig]

Thanks for the info on the N2 Jeff. Great looking builds!

 

[jeffwhitfield]

Decided to yank the Nanolog and use it for a different build. Sticking with a full set of MA150’s which sound just fine.

 

[HamishR]

The thing I like to do with diodes in these kinda pedals is to use pairs. So instead of two opposing 1N914s I might use two pairs to reduce the compression. I prefer a punchier sound.

 

[jeffwhitfield]

The thing I like to do with diodes in these kinda pedals is to use pairs. So instead of two opposing 1N914s I might use two pairs to reduce the compression. I prefer a punchier sound.

That’s exactly what I did. It’s actually the default config. The Clip switch defaults to a set of LED diodes. Up is a single pair and down is two pairs. Ended up just using all MA150’s.