Lowell's Crackatwoa Build Log

larcenasb · 10097

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Offline larcenasb

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Reply #30 on: October 07, 2022, 05:31:19 AM
Thanks for the quick reply, Paul. So, to make sure I understand, regardless of which power switch pin I solder "L" from the IEC socket to, will the "on" side of the switch always be on, or will choosing the wrong pin switch which side is "on"?

Lowell B.


Offline Paul Birkeland

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Reply #31 on: October 07, 2022, 05:40:22 AM
When you turn the switch on, that connects the two lugs on the power switch together.  Just hook one wire to each lug and it will work as intended.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline larcenasb

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Reply #32 on: October 07, 2022, 05:47:46 AM
...that connects the two lugs on the power switch together.

Ah, okay, perfect bit of info I needed. Thanks again and have a nice day, Paul. :)

Lowell B.


Offline larcenasb

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Reply #33 on: October 08, 2022, 04:53:18 PM
I have some extra time this weekend. Still waiting for the bell cap's paint to dry, but there's no harm in me soldering up the input wires to the bal and vol pots, right? And perhaps the Speedball boards?

Lowell B.


Offline Paul Birkeland

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Reply #34 on: October 08, 2022, 05:02:35 PM
You can definitely build the boards and run the CAT5 from the jacks to the selector switch. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline larcenasb

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Reply #35 on: October 08, 2022, 05:06:00 PM
Awesome, thanks, Paul! I'm off!! I'll try and take it slow though and make sure the mechanical connections and soldering are on point. Have a great rest of your weekend. :)

Lowell B.


Offline larcenasb

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Reply #36 on: October 09, 2022, 05:05:33 PM
Finished soldering the input wires. I have lots of Mogami and Canare bulk wire, but when I closely examined the Cat 5 cable, I didn't want to replace it! I love its high-quality construction with the blue foil layer and pure copper conductors. And how resourceful to use a network spec cable for an audio amp! I love that, a very Seattle mindset with the repurposing. It also seems like such a flex, the C2a saying to my modded-out Crack, "Use whatever audio-grade or boutique cable you want, you know I'll still sound better." In fact, this whole process building the C2a is kind of weaning me off the desire for boutique parts, and assuring me to trust—as I keep reading about on these forums—the more sophisticated circuit. Another reinforcement of this was picking up the C2a's power transformer...wow is it heavy and all-business. Of course, I did get some boutique parts like the gold tube sockets, Audio Note pots, and some film caps, but that's about it—nothing over the top like with my Crack. I still don't regret that journey, but I do feel as if I'm evolving and wising up with this kit.

I'm trying my best to make good mechanical connections before soldering. In fact, it's been my mantra while doing all the wiring so far, "Make good mechanical connections! Make good mechanical connections!"

Also, I finished building the high-voltage C4S boards. Will work on the low-voltage board during the week. And then the following week, the paint should be dry so I can complete the build. Cheers!
« Last Edit: October 10, 2022, 05:09:10 AM by larcenasb »

Lowell B.


Offline larcenasb

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Reply #37 on: October 15, 2022, 05:33:26 PM
Okay, so I couldn't wait the full 14 days for the paint to dry haha, I waited 11 then decided I'd really like to enjoy the amp this weekend. I was very careful about securing the power transformer to the chassis. Like I said I would do before, I held the screw and turned the nut instead of vice versa. Worked out perfectly; no paint chipping or tearing.

The build was super relaxing and it was a lot of fun planning and carefully routing each wire, though the way I did it made me run out of wire about 4/5 of the way through the build. I used 19AWG Kimber copper wire that I had on hand for the headphone jack because of this.

I was originally going to use alligator clips for the output caps for easy rolling, but thanks to Paul (PB), I improved upon this idea. He made it clear that alligator clips aren't the most reliable and could potentially pop off. So, I went with spade connectors—they're both secure and not difficult to detach. Though, I did have to test fit the connectors and use pliers to make the tension just perfect. The cable for the output caps is from an old, standard composite video cable that would otherwise never be used. Glad I could call that benchwarmer into the game after sitting in a dark A/V box for well over a decade. Its flexibility is great for this scenario. Also, I zip-tied these cables to the chassis, so the solder joints won't get stressed when I cap roll.

What else can I say? Everything went smoothly....I took my time and tried my best. :) It passed all the resistance and voltage checks, and whoa....

Been listening for a couple hours now....the bass detail and imaging is really getting me excited! Keep in mind, I did A/B compare the Crack and C2a at Bottleheadquarters back in January of 2020. Doing so again brings back a lot of what I remember. The lower registers are more detailed and separated from the mix, and the whole sonic picture has a power and spaciousness about it, but with a sense of ease as well. Similar to what going from a 40WPC to a 120WPC amp did for my inefficient bookshelf speakers.

Tangled Up in Blue by Bob Dylan [HD track] sounds ever more atmospheric—his voice is a little more spaced forward compared to the more closed-in sound of the Crack, and the space around him can be sensed better as well. Same with Nocturn by Kate Bush [vinyl rip], the wind and swooshing sounds seem outside of my headphones. The Sextetts have really good spaciousness, but I haven't heard it anywhere near this level with other amps. And here we go....what it's all about for me, and a good reason why I wanted this amp....to get me closer to this performance....Nirvana Unplugged in NY (DTS track, DVD concert). Pat's guitar is very easy to follow compared to how it gets a bit blurred with Kurt's guitar on the Crack. And Kurt's voice in Come As You Are....man, he sounds so much better here than in the studio version....and the C2a delivers with startling clarity and serious, serious verve.... Kurt's voice grabs my soul as if it were a tangible thing. It has a grip on it and the experience is exhilarating. The C2a delivers all the rasp and all the emotion in his voice, and he's placed very precisely in the soundscape, again with the atmosphere all around him expanded beyond what I'm used to hearing and all the other instruments easy to follow in their precise locations. I'm so happy I discovered OTL amps, they really do drive my 600-ohm AKG K240 Sextetts better than any other amp type I've tried—and the Crackatwoa is a seriously deluxe OTL design. I also tried the C2a as a preamp in my downstairs speaker system with a 6.35mm-to-RCAs cable. The sound projects more into the room, dynamics are greatly improved, the tone overall is very full sounding, and voices especially sound much more full-bodied and lifelike compared to going through just my A/V receiver.

Interestingly, my AudioQuest DragonFly v1.0 is completely silent through the C2a, whereas with every other amp, the USB noise comes through at louder volumes. At max volume with no music playing, the C2a has a bottomless pit of a noise floor. So, it's a USB noise killer along with being a beautiful-sounding amplifier. I'm so, so pleased with this. Also, the Audio Note pot I have is sooooo smooth to use. People often describe weighty pots like butter, but this is more like warm Laffy Taffy haha—the resistance is truly luxurious feeling. Okay, I'm going to go keep listening till the sun rises. :)

Thank you so much, Dan, Eileen, Paul, and Paul, for everything. I'm really, really happy right now. :)
« Last Edit: October 17, 2022, 02:18:20 PM by larcenasb »

Lowell B.


Offline larcenasb

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Reply #38 on: October 15, 2022, 05:34:58 PM
Some more photos. And one to show that a 6F8G has room to spare beside a 6AS7G, in case anyone was wondering (I was....).
« Last Edit: October 17, 2022, 02:18:05 PM by larcenasb »

Lowell B.


Offline Paul Birkeland

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Reply #39 on: October 16, 2022, 05:41:10 AM
That came out great!

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline larcenasb

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Reply #40 on: October 16, 2022, 06:05:37 AM
Thanks so much, Paul! All your help on the forums is greatly appreciated. :) I'll cherish this amp for life. :)

Lowell B.


Offline Doc B.

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Reply #41 on: October 16, 2022, 06:09:33 AM
Looks great, Lowell.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline larcenasb

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Reply #42 on: October 16, 2022, 06:12:09 AM
Thank you, Dan! I really tried my best :)

Lowell B.


Offline adeep42

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Reply #43 on: October 16, 2022, 09:02:31 AM
That is just a stunning build. Your mods look just great in my mind. On a interesting note, my last build was a Moreplay for my second system. It's quite amazing and I am just delighted. A few forum members took issue with my modern silver knob choice. I love what you did.



Offline larcenasb

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Reply #44 on: October 16, 2022, 12:06:55 PM
Thank you for the kind words, adeep42 :) Took issue with a difference in taste? Psh, don't mind all that. Is it the same as the silver knob of your Crack in your profile pic? If so, I always liked those knobs. It reminds me of the vintage Yamaha receiver's rectangular silver knobs. But hey, it's yours and you're delighted, that's all that matters. Turn it up and tune out the rest. :)

Lowell B.