Got my MKI working on a breadboard. Now what?

[G.G.]

I got my MKI set up on the breadboard (first breadboard project BTW) and it sounds quite good. So I took my components from the breadboard and soldered them in to a vero board based on an existing layout, but it just doesn't sound the same. It still sounds good overall but there's a bunch of really high frequency sizzle and hash. I can adjust the Q2 bias to kind of gate out the sizzle but it's still very present over sustained notes and adjusting bias to eliminate it completely makes the sound kind of lifeless. The breadboard build doesn't have any sizzle at all from what I can tell, but it's very present in the vero build.

It's possible (probable, actually) that I put components in the wrong places in the layout I used. I've gone over my parts values and the layout many, many times; and the MKI is a pretty simple circuit, and it all appears to be right. AFAIK the layout is good, it looks correct to me.

Maybe I should make my own perf layout? What's the best strategy for making sure what I have on the breadboard is replicated on my circuit board? My capacity for self sabotage is very high.

 

[andare]

Did you use the same exact components? The MKI is a finicky circuit and small value variations due to tolerance may change the sound a bit if the circuit was barely stable before.

Anyway if you use a verified layout and you build it correctly it should sound the same.

I stay away from stripboard. Too much margin for error. I use point to point or eyelet boards now and it's much easier to build simple circuits.

Sucks if you've already blown the transistors but it's worth breadboarding another one. This time try to leave the circuit 100% stock and only change transistors until it sounds good. I've tried tweaking resistors and simulating leakage and it's not the same.

I do recommend using a log pot for Attack, however, because it makes the whole sweep of the knob useable.

 

[G.G.]

I forgot to mention: after fiddling with the vero build a bit I took it back to the breadboard. Fortunately the transistors are fine and it sounds like it did on the previous breadboard arrangement. So I'll probably try making a perf layout. Hopefully sticking to the schematic and breadboard arrangement will keep everything in order.

 

[andare]

I forgot to mention: after fiddling with the vero build a bit I took it back to the breadboard. Fortunately the transistors are fine and it sounds like it did on the previous breadboard arrangement. So I'll probably try making a perf layout. Hopefully sticking to the schematic and breadboard arrangement will keep everything in order.

I highly recommend trying an eyelet or turret board. The former is easier to solder to.

This blog helped me a ton with the MKI

TONE BENDER MKI: Component Values Table

TONE BENDER MKI Component Values Table

vero-p2p.blogspot.com

Btw the one I built works intermittently. Today was a good day, sometimes it just crackles.
And the one I have on a breadboard only oscillates now. Haha.

 

[G.G.]

Yes! That's the blog I've been looking at, it's been incredibly helpful to have the schematic and component table. I've been going with his Castledine values for the most part, and subbed in a 500k trim pot for R3. Also a 1.8M for R9 to get a little more output volume. My breadboard setup sounds pretty good, not quite the same as the Castledine demo vid he posted on the blog, but quite good for a "generic" set of transistors. Very pleased with the breadboard sound, now to get it into an enclosure.....

 

[G.G.]

First layout EVAR! unverified!

 

[G.G.]

Verified, baby!! I noticed that the vero layout I had used before was doing the offboard ground connections differently, so maybe that was the issue. Anyway, works great, no noise other than the regular MKI stuff!

 

[G.G.]

If I was doing this again I would flip the 10n so the Input pad could go down by the Ground pad. Also, my sockets are straight in line so the trace routing through Q1 was kind of a problem. I could have maybe compacted it a bit more but I used a large axial 25u cap that took up a 9x4 space, but it all still fits in a 1590b with enough room for the power inverter daughter board.

 

[G.G.]

I made a new layout that puts all the pads except the -9v on the bottom row and turned the transistor orientations to allow more space if you have long leads you want to bend. Verified!!

 

[G.G.]

I'm planning to do a proper build report, but thought I would put these here to kind of bookend this thread. The silver MKI is built to standard specs and the gold is Castledine specs. There was MKI pain but they sound great.

 

[andare]

I'm planning to do a proper build report, but thought I would put these here to kind of bookend this thread. The silver MKI is built to standard specs and the gold is Castledine specs. There was MKI pain but they sound great.

Really nice work. What voltage inverter board is that?

 

[G.G.]

It's a Madbean Road Rage 2019 version