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Shetland Klony, AKA Dwarvish Centaur, and some 1590A tips for larger boards

Started by midwayfair, September 28, 2012, 03:05:39 AM

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Well, I had to do something special, since it wasn't the first in the world, right? This is, so far as I know, the first 1590A Klone with buffered bypass. Edit: I looked at Saxoftenest's trailblazer build, and his was indeed buffered bypass. I'm not sure how I missed that.

This is part build report and part tutorial. The actual build report is at the bottom. I wasn't really sure which forum to put it in, so if one of the mods thinks it's more appropriate for the member tutorials, please move it there.

This is one of Jimmybjj's prototype Apis boards. This is NOT the final layout for the group buy. That will be getting verified separately. He said it was okay to post a build report, so I figured I'd use the opportunity to head off some of the potential issues people might experience fitting a particularly large layout in a 1590A. I've done a few layouts that go almost to the switch (and are therefore bigger than any of Brian's boards thus far), and these are the best tips I've got.

-) Absolutely, positively, rock it before you box it. Make dead certain you're happy with it and don't want to make any mods, because getting it out and back in again is extra hard.

A) The first major step is properly routing your bypass wiring. You need all the vertical space you can get, so don't plan on having any wires between the board and the jacks. Route them all underneath and completely out of the way to the side of the switch -- try to avoid having them come back up in front of the switch. You'll need to turn the "In" jack sideways, the way Brian shows the output jack. I usually have room to turn it either way, but I chose to flip it toward the switch because this puts the proper lug to solder to on top. Solder to it before screwing it down. You don't want to try to fit your soldering iron between the switch and the jack. You'll melt something if you try. I've tried. And I've melted things! :)

Needless to say, careful drilling with the recommended low-profile jacks from Smallbear is a must. This is one case where I think builders in the U.S. have an advantage because I'm not sure if there's another source for that type of jack. If you use the other kind (that Mouser sells), you'll lose 2-3mm of veritcal space and you'll have to get creative with the lugs. I can't say for certain that it'll fit.

Here's a picture of the true bypass wiring:

In this picture, the blue wire is to the output jack. The orange wire is the input jack. The black wire is the LED anode. The white wire is ground --- ground everything with this wire and you won't have to use a second board ground wire. I also ground my enclosure by running a small wire from the ground lugs of the switch to the enclosure and putting a glob of solder there. You can also solder a wire to a steel washer and place the washer between the jack and the enclosure ... but that requires a special washer.

B) Your next step is going to be wiring the DC jack and seating the pots. Do the DC jack first.  Then tackle the pots. This is a serious, major pain with large boards and more than a couple pots in such a small enclosure, because you can't leave the wires too long or they won't fit in the cavity, and you can't really see what you're doing when you screw the pots in, and you can't just move the board out of the way or get in through a different angle. The dual gang on the klone makes it even tougher because it's such a large mass of wires.

I put a screwdriver or tiny piece of perf between the side of the enclosure and the pot when I'm screwing them in so that they don't ground out on the enclosure and so I don't have to stick a finger in the cavity to hold them in place. Then I just fish out the perf with my needlenose pliers.

Here's a picture of the upper cavity with the pots screwed in and the DC jack wired:

And here's a picture showing the 0 space between the board and switch and the very good reason we were so careful with out bypass wiring:

The board is not connected to the switch, but solder two wires and it can be rocked at this point. I did so just to test it once more. Then I disassembled the true bypass wiring, so I could do buffered bypass.

C) True bypass Klone converted to buffered bypass in 10 easy steps.


That's right, kiddies, it's not going to look super pretty when you do this. I don't think it's very messy looking -- hell, I've had worse looking builds with true bypass wiring and no off-board components -- but it won't be manicured like the shot above.

Switch - DPDT (or two rows of 3PDT, feel free to make use of the extra lugs for convenience)
1  4
2  5
3  6

5: Output jack
2: Ground
3: LED cathode

1) Wire the input jack to the board input. Mine would have looked better if I hadn't decided to make this buffered bypass AFTER the board was populated.

2) Solder one lead each of a 100K and 560R to the negative side of a 4.7uF cap. I used a tantalum because it's smaller and I like them. You could probably use a normal sized electrolytic, but make sure it'll lie sideways somewhere first. I had to use a 562R because Mouser was out of 560R. :)

3) Solder the positive side of the 4.7uF cap to pin 1 of IC1. You can also solder it to one side of the 1.5K that's also tied to pin 1 (and leave the resistor sticking up slightly to make soldering easy) if you'd prefer not to risk frying your chip. Me, I like to live on the wild side, so I soldered it right to the chip. It's a good idea to put some leftover wire poly on the lead of the cap to keep it from shorting something.

4) Solder the 560R to 4 and the 100K to 2 (ground).

5) Wire a 68K between 4 and 5 and another 68K between 5 and 6.

6) Wire a 100K between 5 and 2 (ground).

7) Solder a wire to any part at the junction of D1/D2/R12/C11. I picked R12 because it was convenient. This is the green wire in my build. Again, if you plan ahead, you can leave one side of the resistor standing up to make it easier to solder to. We've established how I roll.

8) Wire the green wire to 1.

9) Wire the board output to 5.

10) Wire ground to 2.

Some final notes about my build:
-Diodes are D9E. I didn't feel like measuring and just stuck something in there I knew I liked. I did fiddle a bit, but the gain in this version was a little higher and I was getting some op amp distortion on higher gain settings even with BAT41s. I had originally planned to use OA126s again, because I was building it the same as the My Little Klony. Oh well. It still sounds good, and I've liked these diodes in everything.

-82nF (bass cap) is reduced to 68K, and 3n9 (tone cap) is reduced to 3n3. These two changes are the same I did in the My Little Klony to get a little more treble. I realize one of the things some people complain about is that the Klones don't have "as much lower mids," but I think the stock values can sound like mud in a clean amp that hasn't had its bass flub out. I think it sounds more like a classic OD. Or maybe it just fits better with the rhythm side on my amp this way.

-Mostly box caps because I'm tired of using expensive discontinued panasonic caps in these things. Tants because they're cooler. Or at least more yellow.

-The Kingslayer is still better, but this is fun if you want a 1590A challenge.

Here's a picture of the final result with the obligatory cute artwork::

tl;dr: I'm glad my Scottish friend didn't get impaled by that rino at the Baltimore Zoo, because he made a great model for the centaur art.


I'm glad this thread exists, and I don't even have any interest in building a Klon!

Jon, you are rad. (Also, A+ pun.)


Sent via soup cans and string.


How on earth do you do this?  I once won a competition at primary (elementary) school for how many objects you could fit in a matchbox.  I'm glad I didn't go to school with you!  :D


Quote from: Guybrush on September 28, 2012, 10:01:22 AM
How on earth do you do this?

Man, it's old hat by now!

Quote from: Om_Audio on September 28, 2012, 09:44:03 AM
Why buffered bypass?

Because it was funny.

Turns out I was wrong, anyway. I just looked at saxoftenest's build again and his was indeed buffered bypass. Oh well. I'll edit my other posts to give due credit.