I was super excited to see AionFX recently release the Amethyst Analog Delay project, based on the Boss DM-2.
My first delay was a TC Electronic Flashback. I never really found a setting that worked for me. I also briefly used on of my earliest DIY pedals, the BYOC Classic Delay, but similarly did not find it compelling. Somewhere along the way I grabbed a used Boss DM-2w. Right when I engaged it, I said to myself, "Now that's the delay sound I've always wanted!" The DM-2w hasn't left my board since!
I always wanted to build a DIY DM-2, but until the Aion Amethyst was released, I wasn't aware of any readily-available PCBs in a 125B enclosure. The circuit is complex enough that I was afraid to design my own PCB without a reference (I didn't want to use the actual Boss DM-2w as a reference, given that all the extra circuitry to support the Custom mode, and it's all surface mount). Now that I have the Amethyst to reference, I might consider making my own PCB.
This build was a bit challenging. First, for the enclosure, I did something I've only done one other time: mandala stickers and Envirotex (epoxy resin). I previously did this in my Mach 1 (Greer Lightspeed). Credit to @DAJE for the mandala stickers idea (see his Tone Vendor mk 2), and to @SillyOctpuss for the Envirotex Build Guide! The enclosure is a matte black 125B from Tayda. My Envirotex pour was decent. Despite covering it during the 72 hours of curing, a couple tiny pieces of lint or fuzz managed to get on the top finish (though they can't be seen unless you look closely). I deliberately poured on the sides, even though the guide suggests not doing that. The sides definitely aren't nice and smooth; but you can't tell from a distance, and the main reason I'm using the Envirotex is to protect the stickers from peeling.
I let the resin cure for about three days, and was so excited - it really makes the sticker colors pop, and turns the matte enclosure finish shiny! The problem came when I drilled the epoxy. I had pre-drilled the actual aluminum enclosure before applying the stickers or resin. However, when drilling the Envirotex, it started to lift a bit for most of the holes. Fortunately, it generally lifted only a tiny bit, and that's (mostly) covered up by washers. If you look closely, you can see where the sticker and resin are a bit rough near the LED bezel, which is the only thing for which I don't have a washer. Looking at it now, I should probably try to find a black bezel to match the footswitch and knobs.
On the top of the enclosure, I got pretty bad lift-up of the stickers and Envirotex around one of the I/O jacks. I used some super glue to re-attach it to the enclosure. So far it seems to be holding, and I think it also helps that the big fat washers around the jacks help hold it down.
Despite all this, from an arm's length distance (or more realistically, the distance from my eyes to the floor!), you can't see any of these flaws, and I still think it looks great. Hopefully, for future builds, I'll figure out a way to drill the epoxy without causing any lift.
As for the actual circuit build, that presented some challenges too. The first was of my own doing: as with virtually all of my builds these days, I prefer to use a soft-touch relay bypass scheme. And my most recent builds have primarily used my CMOS hex inverter-based scheme. I have both through hole and SMD versions of this circuit and PCB. For the SMD boards, I actually had them fabricated by JCLPCB (everything except the relay, which is through hole). These are my new favorite bypass boards, because they use virtually no power and are ultra-simple (no power-hungry NE555 or microcontroller programming required). And the SMD boards are nice and compact as well.
The problem wasn't with the relay boards per se, but the fact that Aion sometimes puts actual parts of the effect circuit on the bypass board (and to be fair, there doesn't seem to be a spare mm^3 of space on the effect PCB, so I think he quite literally ran out of room). In this case, it was the input pulldown resistor, input RF filter (resistor and cap), as well as the output pulldown resistor. I hemmed and hawed over how to address this. I nearly went with the "air sculpture" approach, where I'd just have the components soldered to the relay and/or effect boards wherever I could find a spot for them (which means they'd generally be "flying" from leads). This approach makes me uncomfortable, because it seems somewhat fragile. Then I thought what would be perfect would be a little bit of vero board to go between the bypass and effect boards. I don't actually have any vero board, but then I realized, I could do the same with Aion's footswitch board! So it looks clunky, but I basically have input and output signals, plus power, going to my relay bypass board. Then I have the Aion board sitting between that and and the effect board, where the Aion bypass board is hard-wired to the "on" position.
The last problem was the most frustrating, and continues to leave me with a little uncertainty: biasing and calibration. Aion's excellent documentation covers this process, but it ideally requires an oscilloscope, which I don't have. (This build might be the one that pushes me to finally get an oscilloscope!) The clock frequency calibration is very easy, as my DMM has a frequency function. And without an oscilloscope, the clock cancellation adjustment is just "set the trimpot to the noon position". But the BBD Bias, now that one is a bear! Without an o-scope, you basically adjust it by ear, until you don't hear any distortion on the repeats. What I found was that in roughly the middle 1/3 of the trimpot sweep, I had audible distortion on the repeats, and if I adjusted the sweep out of the middle range, there was no effect sound at all! I got upset, assuming I had made a significant mistake. I had a to take a break and come back later!
Eventually I watched the video linked in Aion's documentation: How to Calibrate a BOSS DM-2 or Way Huge Aqua Puss Using an Oscilloscope. | MN3005 by The Tone Geek. The biggest takeaway from this video, for me, was that having the BBD Bias swept to either extreme would indeed cause the circuit to have no effect (basically sounds exactly like bypass mode). The video also notes that the Bias is very sensitive; he was making super minute adjustments.
So I went back and spent some more time trying to dial it in, and I eventually got it to a decent state. But I achieved that by making the slightest (and I mean absolute smallest possible) adjustments to the trimpot. I felt a mix of satisfaction and trepidation: obviously I was happy that the circuit works. But I intend to keep this pedal on my board and use it regularly. I'm not hard on my gear, but it will get moved around regularly, and used for gigs. I was concerned that it was only one little bump away from losing its calibration. I thought about putting a bit of superglue or hot-melt glue on the BBD Bias trimpot to keep it from moving; but honestly, I was afraid the weight of the glue itself would knock it out of calibration.
So the only thing I felt I could do that I could live with was to replace that single-turn trimpot with a multi-turn trimpot. Then I went back and re-calibrated it (by ear). The good news is, there's now a decent range on the trimpot where the sound is acceptable. I literally put this pedal and my Boss DM-2w (in standard mode) side by side, on the same settings, and went back and forth, until I got them to sound as close as possible. On a really hard hit and/or big hard-strummed chord, there is still a bit of distortion on the repeats whereas there appears to be none on the Boss DM-2w.
Furthermore, I'm not sure how fair of a comparison it is to use the DM-2w version as a reference. I've never actually heard the original DM-2, only the Waza version, which has two modes, "S"tandard and "C"ustom. The Standard mode is supposed to be identical to the original DM-2 (but with "all upgraded components"). I also found the knob sweeps across my Amethyst versus the DM-2w in standard mode are greater than I usually find in clones. Again, not sure if that's an effect of comparing it to the Waza, or something else.
Despite all the struggles, ultimately I'm happy with it. It looks good, and for the way I use it (generally a subtle slapback), it sounds great. It's going on the board now, in a "probationary" state - it needs some hard time "under the foot" to give me the confidence that it should stay.
Tagging @HamishR per How hard would it be to bypass the buffers in a Boss DM2-W? - this board may be the answer!
Edit: see post #9 below where I replaced the kludged bypass scheme with a custom bypass PCB that includes the needed Amethyst circuit components.
My first delay was a TC Electronic Flashback. I never really found a setting that worked for me. I also briefly used on of my earliest DIY pedals, the BYOC Classic Delay, but similarly did not find it compelling. Somewhere along the way I grabbed a used Boss DM-2w. Right when I engaged it, I said to myself, "Now that's the delay sound I've always wanted!" The DM-2w hasn't left my board since!
I always wanted to build a DIY DM-2, but until the Aion Amethyst was released, I wasn't aware of any readily-available PCBs in a 125B enclosure. The circuit is complex enough that I was afraid to design my own PCB without a reference (I didn't want to use the actual Boss DM-2w as a reference, given that all the extra circuitry to support the Custom mode, and it's all surface mount). Now that I have the Amethyst to reference, I might consider making my own PCB.
This build was a bit challenging. First, for the enclosure, I did something I've only done one other time: mandala stickers and Envirotex (epoxy resin). I previously did this in my Mach 1 (Greer Lightspeed). Credit to @DAJE for the mandala stickers idea (see his Tone Vendor mk 2), and to @SillyOctpuss for the Envirotex Build Guide! The enclosure is a matte black 125B from Tayda. My Envirotex pour was decent. Despite covering it during the 72 hours of curing, a couple tiny pieces of lint or fuzz managed to get on the top finish (though they can't be seen unless you look closely). I deliberately poured on the sides, even though the guide suggests not doing that. The sides definitely aren't nice and smooth; but you can't tell from a distance, and the main reason I'm using the Envirotex is to protect the stickers from peeling.
I let the resin cure for about three days, and was so excited - it really makes the sticker colors pop, and turns the matte enclosure finish shiny! The problem came when I drilled the epoxy. I had pre-drilled the actual aluminum enclosure before applying the stickers or resin. However, when drilling the Envirotex, it started to lift a bit for most of the holes. Fortunately, it generally lifted only a tiny bit, and that's (mostly) covered up by washers. If you look closely, you can see where the sticker and resin are a bit rough near the LED bezel, which is the only thing for which I don't have a washer. Looking at it now, I should probably try to find a black bezel to match the footswitch and knobs.
On the top of the enclosure, I got pretty bad lift-up of the stickers and Envirotex around one of the I/O jacks. I used some super glue to re-attach it to the enclosure. So far it seems to be holding, and I think it also helps that the big fat washers around the jacks help hold it down.
Despite all this, from an arm's length distance (or more realistically, the distance from my eyes to the floor!), you can't see any of these flaws, and I still think it looks great. Hopefully, for future builds, I'll figure out a way to drill the epoxy without causing any lift.
As for the actual circuit build, that presented some challenges too. The first was of my own doing: as with virtually all of my builds these days, I prefer to use a soft-touch relay bypass scheme. And my most recent builds have primarily used my CMOS hex inverter-based scheme. I have both through hole and SMD versions of this circuit and PCB. For the SMD boards, I actually had them fabricated by JCLPCB (everything except the relay, which is through hole). These are my new favorite bypass boards, because they use virtually no power and are ultra-simple (no power-hungry NE555 or microcontroller programming required). And the SMD boards are nice and compact as well.
The problem wasn't with the relay boards per se, but the fact that Aion sometimes puts actual parts of the effect circuit on the bypass board (and to be fair, there doesn't seem to be a spare mm^3 of space on the effect PCB, so I think he quite literally ran out of room). In this case, it was the input pulldown resistor, input RF filter (resistor and cap), as well as the output pulldown resistor. I hemmed and hawed over how to address this. I nearly went with the "air sculpture" approach, where I'd just have the components soldered to the relay and/or effect boards wherever I could find a spot for them (which means they'd generally be "flying" from leads). This approach makes me uncomfortable, because it seems somewhat fragile. Then I thought what would be perfect would be a little bit of vero board to go between the bypass and effect boards. I don't actually have any vero board, but then I realized, I could do the same with Aion's footswitch board! So it looks clunky, but I basically have input and output signals, plus power, going to my relay bypass board. Then I have the Aion board sitting between that and and the effect board, where the Aion bypass board is hard-wired to the "on" position.
The last problem was the most frustrating, and continues to leave me with a little uncertainty: biasing and calibration. Aion's excellent documentation covers this process, but it ideally requires an oscilloscope, which I don't have. (This build might be the one that pushes me to finally get an oscilloscope!) The clock frequency calibration is very easy, as my DMM has a frequency function. And without an oscilloscope, the clock cancellation adjustment is just "set the trimpot to the noon position". But the BBD Bias, now that one is a bear! Without an o-scope, you basically adjust it by ear, until you don't hear any distortion on the repeats. What I found was that in roughly the middle 1/3 of the trimpot sweep, I had audible distortion on the repeats, and if I adjusted the sweep out of the middle range, there was no effect sound at all! I got upset, assuming I had made a significant mistake. I had a to take a break and come back later!
Eventually I watched the video linked in Aion's documentation: How to Calibrate a BOSS DM-2 or Way Huge Aqua Puss Using an Oscilloscope. | MN3005 by The Tone Geek. The biggest takeaway from this video, for me, was that having the BBD Bias swept to either extreme would indeed cause the circuit to have no effect (basically sounds exactly like bypass mode). The video also notes that the Bias is very sensitive; he was making super minute adjustments.
So I went back and spent some more time trying to dial it in, and I eventually got it to a decent state. But I achieved that by making the slightest (and I mean absolute smallest possible) adjustments to the trimpot. I felt a mix of satisfaction and trepidation: obviously I was happy that the circuit works. But I intend to keep this pedal on my board and use it regularly. I'm not hard on my gear, but it will get moved around regularly, and used for gigs. I was concerned that it was only one little bump away from losing its calibration. I thought about putting a bit of superglue or hot-melt glue on the BBD Bias trimpot to keep it from moving; but honestly, I was afraid the weight of the glue itself would knock it out of calibration.
So the only thing I felt I could do that I could live with was to replace that single-turn trimpot with a multi-turn trimpot. Then I went back and re-calibrated it (by ear). The good news is, there's now a decent range on the trimpot where the sound is acceptable. I literally put this pedal and my Boss DM-2w (in standard mode) side by side, on the same settings, and went back and forth, until I got them to sound as close as possible. On a really hard hit and/or big hard-strummed chord, there is still a bit of distortion on the repeats whereas there appears to be none on the Boss DM-2w.
Furthermore, I'm not sure how fair of a comparison it is to use the DM-2w version as a reference. I've never actually heard the original DM-2, only the Waza version, which has two modes, "S"tandard and "C"ustom. The Standard mode is supposed to be identical to the original DM-2 (but with "all upgraded components"). I also found the knob sweeps across my Amethyst versus the DM-2w in standard mode are greater than I usually find in clones. Again, not sure if that's an effect of comparing it to the Waza, or something else.
Despite all the struggles, ultimately I'm happy with it. It looks good, and for the way I use it (generally a subtle slapback), it sounds great. It's going on the board now, in a "probationary" state - it needs some hard time "under the foot" to give me the confidence that it should stay.
Tagging @HamishR per How hard would it be to bypass the buffers in a Boss DM2-W? - this board may be the answer!
Edit: see post #9 below where I replaced the kludged bypass scheme with a custom bypass PCB that includes the needed Amethyst circuit components.
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