DEMO GCI MT-2 (Boss Metal Zone)

[owlexifry]

first of all, many thanks and kudos to @zeropluszero for taking the hit and getting GCI boards into australia then sending me an MT-2 pcb



when i breadboarded the MT-2 last year, i didn’t think i was actually going to build one (any time soon), so unfortunately i didn’t make a lot of decisions/notes, except i did learn that red LED hard clipping sounds bad and doesn’t cut enough volume for the following EQ section, so i at least knew i wasn’t going to do that.

so when it came time to build, i thought heck maybe it’ll sound good with Ge diode hard clipping? (logic being, i enjoy Ge hard clipping in some things...)
so i put in a pair of 1N277s & a pair of NOS Philips 4148s (0.68mV).

also, i gotta say, i was pretty stoked when i saw Tayda release the metallic black option. i wish the other metallic options were satin/matte like this. so much nicer than gloss.



since i was going to have toggle options (on/off/on), i thought i may as well try the suggested soft clipping option, and tbh i never actually tried it on the breadboard cos i thought it’d be a waste of time (and sadly, it is).

Ge diode hard clipping wasn’t bad, it had a nice ‘vintage’ (smoother) response, but i wasn’t all that keen on it, so i replaced them with a pair of 1S2473 diodes (0.65mV) that initially bought to breadboard with DS-1 builds, but never really did.

to my surprise i actually really liked and preferred the sound and response of these 1S2473 diodes.
i was kinda shocked that i could hear such a difference from the 4148s, and then almost fell into rabbit hole to try some other diodes (including some 1SS168s measuring at 0.80mV) but i snapped out of it and moved on and im glad that i did.



playing against a genuine MT-2 it’s pretty close and sounds great as any MT-2 should, but i’ll have to say in this circuit, the choice of hard clipping diode imo has quite an influence on the distortion / response, and while i am satisfied, i wish i had investigated this more closely when i breadboarded it.

demo is hard clipping nos philips 4148s.
(soft clipping off)

there are dozens of us that have been calling for a pedalpcb MT-2 production, and after building this GCI version, i only yearn for this even more.

here's why:
- pcb layout tedious to populate, it’s all over the place
- thru-holes are huge lmao, so much solder (that’s my bad though but still)
- the drill layout fucked me over, had to bend pot legs. tedious.
- per boss, C10 should be 47p (it’s 100p in the build doc & schematic). i forgot to check this and then fixed it later whilst being indecisive and changing clipping diodes.
- soft clipping in the feedback loop is a useless toggle option and it sounds bad.

 

[OD is Glorious]

Aggressive!

 

[zeropluszero]

Oh you're welcome, I consider it payment for how much info I've gotten reading your build logs.

I wish I built mine without the toggles too but I already had to order a second enclosure after I had Tayda drill the holes too high the first time, so I think a third enclosure would be excessive.
It does really sound amazing and quiet for so much gain.

 

[owlexifry]

had to order a second enclosure after I had Tayda drill the holes too high the first time

was it tayda’s error? or is it the drill template that was off?
cos i had similar issue, i just used the paper template and hand drill like i always do and all the pots ended up too high and i had to bend everything. was a bastard to fit lol.

ended up using shielded wiring on the input, cos with all of that, the input jack tip sits uncomfortably close to IC3.

 

[zeropluszero]

Nah it was my measuring, my input jack actually pushed the chip out of place, and it was the same template for the HM2...that was an expensive and time consuming screw up.

 

[owlexifry]

my input jack actually pushed the chip out of place

crikey. that’s a bit rude

 

[HamishR]

I have never used a drill template - most of the time I'm using a different sized enclosure so I just measure where things are on the PCB and transfer that to the enclosure. Some white masking tape makes marking where holes go on the enclosure and a drill press with a home-made timber fence makes drilling accurate. I even have a piece of wood cut at exactly 25.4mm wide so can use that between the fence and enclosure to drill the next row down of holes without moving the fence.

BTW Owlexfry I wouldn't trust a skinny piece of shielded wire like that on my input. I'd want it twice as thick as that little fella. Apart from that really nice work!

 

[Erik S]

i just used the paper template and hand drill like i always do and all the pots ended up too high and i had to bend everything.

The paper template in the build doc is definitely off.

I was annoyed at Kurt when I built my first one and the toggle location was wrong.

Drilling my second one wrong is kinda on me though.

 

[szukalski]

I guess you'll be needing one in 125B format as well.

 

[owlexifry]

I guess you'll be needing one in 125B format as well.

View attachment 122745

heck yes!