Bottlehead Crack

I finally build my basic crack. Speedball and choke still to install, but I'm just going to enjoy the basic crack for a while.

I upgraded all the wire to solid core silver, and put in a stepped attenuator. Doc says I should also replace the long black wire to the headphone jack with silver, which I will do when install the speedball.

External case is black lacquer. It came out OK, but I need to sand it down and do it again for that piano finish.

The silver wire is sleeved in cotton, then I used clear heat shrink.

Just thought I would share.

 

Here's the Crack with two more "signal path" wires converted to silver, and the choke installed. It's sounding nice!

 

What is that giant pot?

 

Looks more like a stepper to me?

Edit: Yes, he even says so a couple of posts above

God damn @AllanMarcus that's oddly lovely. There's a tiny bit of me that'd love to pick up a pre-built and tweaked Crack, with the speedball, choke, and maybe fancy caps in key places when the owner gets tired of it- skipping the nervosa and tweaking stages blatantly. I know that's cheating, but you see people selling them off occasionally when they've outgrown them and run out of tweaks to make.

I really don't need one, but there's a bit of me who'd love to have it just for the flavour and satisfaction of such a lovely one-off unit that reeks more of the shed than the factory. Is that weird?

Does braiding the wires out to the line outs like that adversely affect the capacitance? Could you hear any effect on the highs?

 

Thanks. It's really fun to build.

The braiding, from what I understand, is for EMI/RFI rejection. Since the wires from the line in to the attenuator go right by the transformer, they have to either be shielded or braided.

I have a mainline on order, so once I build that and live with both for a while, I will likely sell the crack for cost and shipping.

 

Ah, that does make some sort of sense, at least. Thanks!

 

FWIW, twisting (like your green heater wiring) is better for EMI/RFI rejection. Braiding is not quite as good, but retains more flexibility (ie: for headphone cables).

 

I made it as far as choke, bias pots for e80cc, film bypass caps in critical spots. At this point I'm hesitant to install the speedball as I've achieved a sound I enjoy that differs from other tube and hybrid amps in my lab. I'm inclined to keep it that way. The sound is addictive for my preferences.

 

I got to the same point (more or less) and had the same dilemma. I stopped there too, but the SB package gives me angry looks once in a while, and makes me wonder. *Sigh*

What tubes @atomicbob?

 

I too am in the boat of stock tube upgrades. I was thinking of the Tung Sol 6080 and the Siemens 12au7. I figure the tube upgrade is the best bang for the buck (about a hundred of them). I will install the speedball. The marketing says:

"Things get tighter and quicker, bass and midrange get cleaner and more dynamic sounding, and the background gets more quiet"

cleaner, tighter and more dynamic mid and bass would be great.

I should be able to recoup the investment if I opt to sell the crack if I prefer the mainline (on order).

At any rate, would love to get opinions on which tube combinations you are using now and would recommend. I know that's not an open ended question but many will see it as one. Would be great if folks stay focused

 

Same boat. Have the SB upgrade and a custom PCB from a head-fier that allows selection of bias resistors for various tubes with SB upgrade sitting in the lab in a drawer somewhere.

I have plenty of 6AS7, 6080, 12AU7 etc. But the ones that have caught my ear are:
WE421A (unobtainum)
GEC A1834 / 6AS7g brown base (also unobtainum)
Philips JAN 6080WC (a colleague found several of these for $5 tube in a local surplus selloff)
This last one is what I am listening most with at the moment.

Also helped that I installed the bias pots to allow use of e80cc. Currently using a Tungsram e80cc.

Exactly. If this was my one and only amp then I'd probably consider more seriously the SB upgrade. However that will narrow the difference in sound signature from other tube amps in my lab.

 

Pictures of my current BH Crack build state:




Note I am using 820 uF Rubycon output caps bypassed with film caps. Do not do this unless you are prepared to power on and off amp with headphone disconnected or risk damaging your headphone. This improves bass response but at the expense of substantial DC transients at power on/off. I am not responsible for anyone damaging their headphones if they do this.

 

Hi everyone, i'm newbie here and would like to know you guys opinion.
My HD6XX should be arrived in August, and with the hype of Bottlehead, i'm looking to build the Crack for myself.
But this is the first time i got a audiophile headphone, and while i honestly think i need a stepup in sound quality from my previous cans (specifically V-Moda M100), there's something i want to ask:

1. Would getting a tube amp from the beginning a good idea?
2. What DAC should i pair with the Crack? I heard good thing about the Modi Multibit, but i think it'd be great to start with an solid state Amp+DAC which have fixed DAC output that gonna pair great with the Crack. (a lot of people recommend the Audio-GD R2R-11 as a good amp and ladder DAC out, but i don't know if they gonna do well with the Crack)

 

Just my 2 cents. I had a really bad experience with audio gd products quality control. Really cannot recommend their products to anyone that are not a masochist. Nevertheless, some of their products seems very good for the price.

 

I know folks here not really fond of their product.
Again i'm looking for a good for Amp+DAC that have decent power output, with good DAC line out that pair great with the Crack. Haven't seen anything under $400 tick as much boxes as R2R11, so... any other recommendation?

 

Great to hear that Modi Multibit pair well with Crack. Thanks for the response!

 

I see you added some adjustment pots. What are those for? Bias adjustment? Channel balance?

 

@atomicbob the trimmer resistor is a brilliant idea.I suggest changing your rectifier bridge diodes to the cree schottky . They made a difference for me. I have extras of the diodes and the board from partsconnexion, will send them to you.

 

Bias adjustment for driver tube (two pots for dual triode). Allows me to accommodate both e80cc and 12au7 with more precise adjustment than fixed resistors.