Crack;Bottlehead OTL
Apr 23, 2017 at 6:10 PM Post #8,536 of 11,049

Paladin79

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Yeah just was working too late and too tired. Stupid of me just was having fun. No biggy though it will be fixed in short order and then the Speedball. The other Crack is wired a bit differently the transformer must be different. Well back at the task at hand thanks for the support.

Yeah I have the older version also. Neither have the speedball yet but I want to test one against the other as I build the modified one, I will add it to one and make sure i like it before putting it in the second.
 
I have some plans for the vent opening on mine, one would be a rotating finned disk that moved with increased heat but finding something the perfect size is not easy and i do not want to run the risk of it making noise. That is only my second choice, my first choice has no moving parts but would look cool.
 
Apr 23, 2017 at 10:32 PM Post #8,537 of 11,049

MIKELAP

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  For me getting those copper/aluminum plate are easy finding the time to work on the amp is more difficult,busy at work plus family so yeah this will take some time.Luckily i have the CRACK to enjoy!

I have been pretty busy so I am rushing through the electronics a bit but cutting the copper was my biggest holdup. I need to get the cabinets before I proceed. 
 
You may have been the one who asked me what kind of copper I got. I know nothing about copper and even less about how to cut it well lol. The square opening for my transformer is a bit crooked but luckily there is some wiggle room there and it is covered well by the part.

When cutting copper you need to use somekind of oil based coolant mixture to prevent from sticking and jamming and altogether  will make a nicer cut .
 
Apr 24, 2017 at 7:04 AM Post #8,538 of 11,049

Paladin79

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I appreciate the info, one of my employees mentioned that. I will look into it before I take on the second set of plates. I figured with the round holes and drill press it would get pretty messy but that is part of it I suppose. I did stop several times to let the metal cool. Anything that conducts electricity well also conducts heat well.
 
Apr 24, 2017 at 11:14 PM Post #8,539 of 11,049

Timoteo80

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I'm loving this thread...very interesting & seeing the different aesthetic styles is cool too. Having already built my own Crack I can understand & appreciate some of the comments made. Thx guys for documenting your diy projects here. It's one of the few things I like to check out on my phone periodically. This patined copper is out there bud rad! (Yeah I said rad...)
 
Apr 25, 2017 at 4:01 AM Post #8,540 of 11,049

Paladin79

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Thanks for the kind words. It will be a week or so before I will have done more work on this. I need to get busy on the matching headphones and headphone stand but I doubt they belong in this thread. Maybe just one photo when all parts are done. Heck my wife was impressed with the looks of the amp so far and she has little interest in the hobby otherwise lol.


This is fun to play around with so before I am done I may build several of these amps. My son is more interested in a Mainline so I will probably grab a couple of those and do mods as well.

Tom
 
Apr 25, 2017 at 11:07 AM Post #8,542 of 11,049

Paladin79

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  Matching headphones and stands do belong in this thread. So does a matching Mainline! Keep us updated!


Thanks Tom, I always feel like I am talking to myself when I see your name. My first name is Tom and my last name begins with S. That is my handle on several of the book groups with which I associate.
 
Anyway right now I am in pursuit of a box full of brass pressure gauges I heard about. Such things as watch mechanisms and gears also lend themselves to steampunk. I love learning new things so now I am working on my copper cutting skills.
 
Apr 26, 2017 at 9:37 PM Post #8,543 of 11,049

wolfmath

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I just finished building my Crack and it sounds awesome with my HD 650's! I'll be attaching the Speedball soon, but I think I'll wait on that.

One issue that I've noticed is that the volume is very unbalanced at low levels. Does anybody else have that problem, or is that just my unit? I'm guessing the problem lies with the potentiometer...
 
Apr 27, 2017 at 7:40 AM Post #8,544 of 11,049

Tom-s

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Finally found my way around the new website. But hate it much and probably can't find this again thread after this reply.

Anyways, it's a normal thing with the stock volume pot. To get more out of it, look up the FAQ #3 mod on the Bottlehead forum.
 
Apr 27, 2017 at 10:18 AM Post #8,545 of 11,049

Paladin79

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I might be wrong on this but I measured one of the stock pots the other day and it did not measure like an audio taper (logarithmic taper) pot to me, more like a linear taper, it is one of the first things I replaced on the amp I am currently building. I could not find many markings on it to determine who made it but I will have others on both of my Crack builds soon.
 
Apr 27, 2017 at 11:56 AM Post #8,546 of 11,049

silvrr

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Has anyone seen any good instructions of the FAQ #3 mod for the resistors on the input or for the choke on the power supply circuit? Pretty sure I understand them, however, wouldn't mind having a go-by or something to reference off of.
 
Apr 27, 2017 at 2:08 PM Post #8,547 of 11,049

Tom-s

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The FAQ #3 instructions:
Disconnect the white wire at the pot that originated at the left RCA jack. Install a 75K resistor between this wire and where it connected on the pot.
Repeat this step for the red wire coming from the right RCA jack.
Attach and solder one 33K resistor between each outer pair of lugs on each level of the volume pot.
Resistor wattage is unimportant, 1/10 Watt or greater will work nicely.

For the Choke, remove powersupply resistor (either one is fine, but most remove the first), and replace with the choke. It's not directional.

Don't have any pictures for you as i build in the FAQ on a VALAB pot (not the stock) and used a pair of chokes vs only one in my PS.
 
Apr 27, 2017 at 8:16 PM Post #8,548 of 11,049

Timoteo80

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Congrats on your Crack. I agree with waiting on the SB upgrade. I did the same thing. In fact I've had my Crack on daily listening & STILL have not added the SB. In fact it's been sitting on the shelf waiting to be installed for a few months. I MIGHT start assembling it tonight if I find some time. The wife is in the garden, so I have the house to myself, kinda nice lol.

The stock Crack is so pleasing with my HD600s that I've just been loving it as is. Hoping I hear a pleasing improvement with the SB. Some claim to like the Crack without. We'll see what side of the fence I'm on soon.
 
Apr 27, 2017 at 8:17 PM Post #8,549 of 11,049

Timoteo80

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Oh and I too have some slight channel imbalance on the Crack's pot but it's very minor & only at the lowest of volumes. You may want to consider upgrading your volume pot if it's as bad as you mentioned. Good luck bro!!

*Digging the look of the new site*
 
Apr 27, 2017 at 10:15 PM Post #8,550 of 11,049

LikeABell

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Thanks for the kind words. It will be a week or so before I will have done more work on this. I need to get busy on the matching headphones and headphone stand but I doubt they belong in this thread. Maybe just one photo when all parts are done. Heck my wife was impressed with the looks of the amp so far and she has little interest in the hobby otherwise lol.


This is fun to play around with so before I am done I may build several of these amps. My son is more interested in a Mainline so I will probably grab a couple of those and do mods as well.

Tom
You're in luck! The Mainline is on sale right now.
 

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