Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Crack-a-two-a => Topic started by: larcenasb on September 30, 2022, 07:45:54 AM
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Hello all! There isn’t an abundance of C2a builds on the forum, —not like the Crack anyway—so I thought I’d share my build process here.
I’m sure others have thought of this, but the one-sided sticky bubble wrap that the kit came with is perfect to hold and keep track of all the screws and other small bits.
Finished going through the inventory checklist, and then painted the chassis plate (Rust-Oleum Universal hammered silver) and power transformer bell cap (Rust-Oleum Custom matte emerald green). Two light coats, a medium coat, then a heavy coat. It’s been drying for four days now. My emerald green spray paint was spitting the last time I used it, and Doc’s tip in the Bottlehead YouTube tutorial about letting it sit in warm water for a while solved the problem for me. Thanks, Doc!
Glued the wood base yesterday and am about to apply the first coat of Tried & True Varnish Oil today—I really like its formula of just linseed oil and pine resin. In the YouTube tutorial, Doc said, “If you have a desire to finish the whole inside, knock yourself out!†I then thought to myself, “Alright, I will!†Haha, this is a labor of love for me and an amp I’ve wanted for a while now. So, I’m trying to—forgive the old phrase—leave no stone unturned, and make this as nice a finished product as I can.
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Those colors should work really well together.
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Thanks, Paul! Yeah, I was going to spray-paint the bell cap black, but then thought, "Eh, why not give it a little more pop?" I already had the green paint anyway.
Alright, just applied the first coat of the varnish oil. Will wait 1 hour, as the instructions indicate, then will wipe/buff dry. Then after 24 hours, I'll lightly burnish with 0000 steel wool before the next coat. I plan on doing four coats, so not rushing the build process at all.
Also designed some simple badges that will go on the rear of each of my respective amps.
Lastly, I'll share this for fun....got some tomatoes outside and just put in the fire-roasted veggies for my Navy bean soup! Gotta let it slow-cook for a while now. Have a great weekend all, will update this as I move along….the build, not the soup. :)
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Very nice job on the finishes.
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Thanks, Doc! I owe it to your YouTube tutorials, really appreciate you making them.
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Just got a message that my custom control overlay is finished! A photo was sent too. Should arrive by the time I'm done with the wood base.
I measured the C2a chassis plate and designed a simple overlay in MS Paint, then found someone on Etsy to laser-cut it out of acrylic. The seller/craftsperson first had to make a computer model/proof with all the correct measurements. This was good as my Paint version was done by eye so is imperfect with regard to proportion and centering. I was thrilled to hear that the text would be done by engraving and then filled with a powder coat, so I shouldn't have to worry about it fading. And the price was $25 for everything, which was definitely less than I was expecting. The first overlay made had an imperfection on the top of the "volume" tab, so the seller made another and is giving me both. I can easily sand that imperfection and the rest of the tabs to make them uniform, and it'll be nice to have a backup.
But yeah, it's really cool to see the idea I had in my head realized. I wanted it to look a little 1930s, so the Art Deco font called "DK Otago" helped a lot with that.
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A nice surprise, the custom control overlay came in today! Was expecting Monday.
I'm very happy with how it turned out. The glossy acrylic gives off some dreamy reflections! It is 1/8" thick, so the stock volume pots would've been too short. I did measure the Audio Note pots and stock selector switch, they're all just long enough. Whew! If they weren't, it'd be no problem sanding down the bottom of the control overlay.
Also, I really like using heavy-duty toggle switches, but needed to find a way to cleanly install it. The cutout for the stock rocker switch is wide enough for the toggle switch to mount securely, but the corners of the cutout are visible. I wanted to use some thick plastic as a rectangular washer to cover it up. So, I cut a piece from an old Blockbuster DVD case that wasn't being used. The case is still usable, just a small amount was cut off it. Then drilled it and cut it to size with some heavy-duty scissors. Things are coming along nicely. :)
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Finished installing the components last night and am ready to solder! Just waiting on the wood base's last coat of varnish to cure. Will work on the soldering little by little each evening.
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Always nice to see someone going the extra mile on the finish and some customization. Your solution for the power switch works well with the control overlay. Keep the pics coming as you bring it to life.
Karl
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The control overlay looks good (as does the soup!). Volume up to 11 is a nice touch - "it's one more, innit?"
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Thanks Karl, and will do, more pics coming :)
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Thank pboser, I love Spinal Tap(!) but I got the idea for the Crackatwoa from Bourney's recent build. A really well-done, recent custom build on the forum here. Cheers!
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So, I had a bit of a blunder.... just noticed it this morning. When I tightened the screws of the transformer bell cap last night, the paint tore away a bit. Maybe I tightened too much?
I could spot/dab some paint, but I want to do this right. I'll take out the power supply, strip the paint, and re-do it. Then when I screw on the bell cap again, instead of holding each nut and turning the corresponding screw....I'll hold each screw, and turn the corresponding nuts. Hope it'll go well. If any tearing occurs again, it should be more minimal and I could then do the spot/dab painting with a toothpick.
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I've been in the same boat before. Some of these paints take a week or two to fully harden. It's something you cant rush.
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Take each screw out carefully one at a time, then put a copper washer under each one and put it back.
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Hi Natural Sound, yeah, I was wondering how many other builds this has happened to. I did let the paint dry for a week and the can says it fully dries in 24 hrs....so I think it was just the heavy torque.
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Hi Paul! Yeah, that's definitely the smart approach, and one I'd do on other builds. But as I said before, I've wanted the Crackatwoa for a while and have spent a lot of time imagining how I'd go about the build. I want it to be as nice as I can make it. I can fix this with just a little more time and effort. :) Plus, I've never stripped paint before with mineral spirits (like in that American Restoration show), so it was a good learning experience.
All done, will let dry for two days just to be safe (can says fully dry in 24 hrs), then will tighten the screws carefully--turning the nuts, not the screws.
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All done, will let dry for two days weeks just to be safe (can says fully dry in 24 hrs), then will tighten the screws carefully--turning the nuts, not the screws.
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Alright, this will test my patience haha. But I've waited so long for this amp, I can wait a little longer. :) Two weeks, will do. Will keep busy with classes till then.
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Thanks for always being so present on these forums and helping us out, Paul. I really appreciate that. Quite rare really.
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I'm not patient enough to use that stuff, and that's part of the reason I learned to powder coat ;)
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Washering the bell can look pretty good IMO. I swapped the steel machine screws for brass ones on my Cracks, S3X, and Moreplay. I like the contrast it provides and it matches up with the RCA's. I think it would look great with the gold accents on your amp.
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Paul, hopefully I'll get there one day! Would love to learn how to powder coat. I can just imagine, I bet you have an awesome workshop. :)
And Mucker, yeah, the washers will be a backup plan for me if the paint still tears. Either that or spot/dab painting. The brass would look nice for my build, but I really like the gold tube sockets stealing the limelight! :)
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Right on. You're amp is killer as is!
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Thanks Mucker, really excited to complete it!
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This build is looking very nice.
I really like that Art Deco font and era-appropriate heavy toggle switch. Nice touch.
My rule about paint drying is that if you can still smell it, even a little, then it is not fully dry.
Looking forward to seeing the finished product.
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Thanks Bourney! Means a lot coming from you, as your build is one of my favorite Bottlehead builds I've seen, and an inspiration for me to build mine. :)
And yes, I'll be sure to wait for the paint to fully dry. Will keep busy and distracted till then. Cheers!
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Only been three days waiting for the bell cap's paint to dry....eleven more days to go lol. I quickly realized I'm not strong enough to cold turkey the Crackatwoa build process, I needed a little taste...
Good there were a lot of minor things to work on:
First, I worked out the wiring for the output caps. Since mine have radial leads, not the default axial, I needed to route one lead to the other side. I soldered an extra wire for each cap, covered the joints with heatshrink, then hot glued the wires where the velcro straps will be, so the joints won't get stressed. The caps are still to this day 91% off on Parts Connexion (https://www.partsconnexion.com/ASC-81958.html), so only cost about $5 a piece—for that price, any quirks are worth dealing with. Also, 60uF is more than sufficient for my 600-ohm AKG K240 Sextetts.
Next, the Audio Note pots don't have a stopping pin (or orientation pin?), so the pots under the chassis could potentially rotate over time and perhaps ruin the wiring or solder joints. To make sure that isn't an issue, I fabricated side-mounted plates with stopping pins. I cut some hard plastic into shape (from a plastic container lid....it's really stiff) with my heavy-duty scissors and attached one to each pot with industrial-grade double-sided Gorilla Tape. It works very well!
Lastly, I got my solid aluminum control knobs in the mail today, but the selector switch's shaft is a little too thick for them, so I had to drill one knob's hole to make it ever-so-slightly wider. Worked out perfectly. I'll save the photos of the knobs on top for when the amp is complete hehe.
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Also, I was looking at the wiring of the Crackatwoa and noticed the wiring from the IEC socket to the power switch is different than on the Crack (please see photo). Why is this so? And does anyone know how I would solder the IEC socket to the toggle power switch on the Crackatwoa? L on the IEC would go to which power switch pin? Thanks so much for any help.
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You can use whichever power switch pin you like, as they both kind of do the same thing, just be sure the wire going to the power transformer comes off the lug that you don't use to connect to the IEC module.
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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"?
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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.
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...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. :)
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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?
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You can definitely build the boards and run the CAT5 from the jacks to the selector switch.
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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. :)
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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!
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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. :)
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Some more photos. And one to show that a 6F8G has room to spare beside a 6AS7G, in case anyone was wondering (I was....).
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That came out great!
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Thanks so much, Paul! All your help on the forums is greatly appreciated. :) I'll cherish this amp for life. :)
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Looks great, Lowell.
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Thank you, Dan! I really tried my best :)
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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.
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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. :)
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Lowell - well done inside and out. Thanks for including all the pics. I hadn't noticed the kind of 'deco' font before, nice choice. Enjoy the tunes!
Karl
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Thank you, Karl! Will do, seriously loving the sound from my C2a :) BTW, it's really cool you have Fonken speakers! I remember looking at their website way back and admiring the innovative cabinets. Must be killer with the SEX amp. Hope you're enjoying them! Cheers! :)