Alan W
Well-known member
- Build Rating
First off, another TL;DR post, which I apologize for ahead of time. Second issue is that its the second build report where I'm crazy happy with a pedal. I promise to write a more critical review soon.
I only became aware of this pedal after reading about it on this forum, (thank you, @peccary), but became instantly interested in it, since my favorite truly clean boost, the Transcendence, has no tone controls—which is one of the reasons that it is so damn transparent. Since all I really want in a tone control is some fairly mild midrange fattening or thinning out, if the Mercurial was clean enough, this seemed like the perfect companion. Once I got it working properly, it does just that. BUT— it also has a lovely sound of it's own, and also has an immediacy (in playing feel, very amp-like) that strongly reminds me of the Chop Shop I just finished last week.
I started out with it as a stock build, but with the addition of a 100nF bypass cap on each op amp, at pins 1 and 8. (See bottom of board photo below.) Very natural break-up, and a ton of fun to play. Most of the dB knob play for me is within 30 degrees to either side of noon (flat); somewhere around 1:30 the output tends to be slightly overloaded, but it is a very even harmonic type of thickening. But I did have fun, especially with my baritone, really pumping the lower frequencies; getting a bit of an old Ampeg thud out of it, that I could see being useful. I will eventually plug a bass or two through it.
Even set completely flat and with unity gain, I get a bit of distortion compared to the Transcendence, but certainly not compared to the Chop Shop, the Quantum Dynamic, my Origin Revival Custom, etc—its a clean sound, as far as pedals go. But I wanted it cleaner. My two main guitars right now both have Wilde Alnico Microcoils in them; they are very "hi-fi" pickups that have changed my playing style. So, after querying about running it at 18v, I played it last night, and it definitely did what typically happens—more headroom, less texture to the grain—but anytime I'd switch to the Transcendence, the upper overtones would just re-appear. My next try was to replace the 072s with some OPA2134s, which are my favorite op amps that are still (relatively) affordable. I think the change to the 2134s made a bigger difference than the 9 to 18 volt bump. More high end opened—almost getting to the Transcendence level. (Which also uses a 2134...)
[EDIT: Sat night! When I played through the Mercurial this evening, it started making a low level, higher pitch whine, so I shut it off. I’m thinking that the “bypass caps” that I incorrectly placed were more the cause than the 18v, but feel it important to urge caution until I see what the problem is.]
But, if my original conception was pairing the Mercurial with the Transcendence, it's with the Chop Shop that the magic really happens! Just unbelievable great, possibly the best slightly brown (in a late 50's big jazz box way) (and this sound is one of my most favorites!) sounds and feels that I've played. It's almost like some EL84s were dropped in where the 6L6es are in my amp. So—now my last thing to decide is what voltage to run the Mercurial at. If the (slight) difference is what I expect it to be, then I want to put a switch in to be able to easily choose, or possibly just add in a sag knob like the Chop Shop. As a matter of fact, I'm contemplating a dual build, with a dual gang sag that will do both—so as I add sag to the Chop Shop, the voltage on the Mercurial will automatically drop too.
BUILD REPORT:
I'll think of this as the first pedal in my "large resistor period." I placed a large end of year Mouser order, mainly getting the caps (Elnas and Nichicon Fine Golds or above) and resistors (Dale RN55s is my standard). Much to my surprise, I must've done a bad search in Mouser, and ordered all RN60 resistors. Even though they're rated at 1/8 and 1/4 watt, they look like 1/2 watt or more! I was pretty bummed at first; it was a big order. In any case, they do fit in with a bit of creativity.
Since the last bunch of pedals I've made worked right away, I've gotten a bit cavalier about using a small test rig, and just plugged it in. HUGE amount of gain, just a crazy amount! Something must be wrong. It was very easy to find, I had switched two resistors, and had a 1M (in what I am incorrectly calling the feedback loop of the op amp that sets gain) where a 10K should be—so that was a quick fix.
The mock up is what I think is very close to the final design. I was planning on a Ferrari yellow pedal, but after playing it , it needed a more vintage look; so I'm going for more of a saddle tan color. (That Tayra textured copper would look great!).
Oh!—I do like the inverted layout on this, but, following the template, I think everything is too close to the pedal top. I had to really shoehorn the barrel jack in, since there's a central pot. I like this pedal enough that I will just redrill another box for it; the rendering below has the lowered location, which looks much better to me.
I only became aware of this pedal after reading about it on this forum, (thank you, @peccary), but became instantly interested in it, since my favorite truly clean boost, the Transcendence, has no tone controls—which is one of the reasons that it is so damn transparent. Since all I really want in a tone control is some fairly mild midrange fattening or thinning out, if the Mercurial was clean enough, this seemed like the perfect companion. Once I got it working properly, it does just that. BUT— it also has a lovely sound of it's own, and also has an immediacy (in playing feel, very amp-like) that strongly reminds me of the Chop Shop I just finished last week.
I started out with it as a stock build, but with the addition of a 100nF bypass cap on each op amp, at pins 1 and 8. (See bottom of board photo below.) Very natural break-up, and a ton of fun to play. Most of the dB knob play for me is within 30 degrees to either side of noon (flat); somewhere around 1:30 the output tends to be slightly overloaded, but it is a very even harmonic type of thickening. But I did have fun, especially with my baritone, really pumping the lower frequencies; getting a bit of an old Ampeg thud out of it, that I could see being useful. I will eventually plug a bass or two through it.
Even set completely flat and with unity gain, I get a bit of distortion compared to the Transcendence, but certainly not compared to the Chop Shop, the Quantum Dynamic, my Origin Revival Custom, etc—its a clean sound, as far as pedals go. But I wanted it cleaner. My two main guitars right now both have Wilde Alnico Microcoils in them; they are very "hi-fi" pickups that have changed my playing style. So, after querying about running it at 18v, I played it last night, and it definitely did what typically happens—more headroom, less texture to the grain—but anytime I'd switch to the Transcendence, the upper overtones would just re-appear. My next try was to replace the 072s with some OPA2134s, which are my favorite op amps that are still (relatively) affordable. I think the change to the 2134s made a bigger difference than the 9 to 18 volt bump. More high end opened—almost getting to the Transcendence level. (Which also uses a 2134...)
[EDIT: Sat night! When I played through the Mercurial this evening, it started making a low level, higher pitch whine, so I shut it off. I’m thinking that the “bypass caps” that I incorrectly placed were more the cause than the 18v, but feel it important to urge caution until I see what the problem is.]
But, if my original conception was pairing the Mercurial with the Transcendence, it's with the Chop Shop that the magic really happens! Just unbelievable great, possibly the best slightly brown (in a late 50's big jazz box way) (and this sound is one of my most favorites!) sounds and feels that I've played. It's almost like some EL84s were dropped in where the 6L6es are in my amp. So—now my last thing to decide is what voltage to run the Mercurial at. If the (slight) difference is what I expect it to be, then I want to put a switch in to be able to easily choose, or possibly just add in a sag knob like the Chop Shop. As a matter of fact, I'm contemplating a dual build, with a dual gang sag that will do both—so as I add sag to the Chop Shop, the voltage on the Mercurial will automatically drop too.
BUILD REPORT:
I'll think of this as the first pedal in my "large resistor period." I placed a large end of year Mouser order, mainly getting the caps (Elnas and Nichicon Fine Golds or above) and resistors (Dale RN55s is my standard). Much to my surprise, I must've done a bad search in Mouser, and ordered all RN60 resistors. Even though they're rated at 1/8 and 1/4 watt, they look like 1/2 watt or more! I was pretty bummed at first; it was a big order. In any case, they do fit in with a bit of creativity.
Since the last bunch of pedals I've made worked right away, I've gotten a bit cavalier about using a small test rig, and just plugged it in. HUGE amount of gain, just a crazy amount! Something must be wrong. It was very easy to find, I had switched two resistors, and had a 1M (in what I am incorrectly calling the feedback loop of the op amp that sets gain) where a 10K should be—so that was a quick fix.
The mock up is what I think is very close to the final design. I was planning on a Ferrari yellow pedal, but after playing it , it needed a more vintage look; so I'm going for more of a saddle tan color. (That Tayra textured copper would look great!).
Oh!—I do like the inverted layout on this, but, following the template, I think everything is too close to the pedal top. I had to really shoehorn the barrel jack in, since there's a central pot. I like this pedal enough that I will just redrill another box for it; the rendering below has the lowered location, which looks much better to me.
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