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May 24, 2019, 12:20:22 pm

Author Topic: Crack-a-two-a completed!  (Read 1105 times)

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Offline ALL212

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Crack-a-two-a completed!
« on: January 23, 2018, 01:56:50 pm »
Yep - got it all in there.  No issues with resistance or voltage tests.  Worked fine on first try!

3rd pic are the cousins.  And there is a Mainline hiding off to the right out of picture.

Figured out what to use to cover up the balance control cutout - last pic.

« Last Edit: January 24, 2018, 02:48:10 am by ALL212 »
Aaron Luebke

Offline mcandmar

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Re: Crack-a-two-a completed!
« Reply #1 on: January 24, 2018, 01:51:58 am »
You got the whole family at this stage.  Would be interested to hear your opinions on it vs the other amps.
M.McCandless

Offline ALL212

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Re: Crack-a-two-a completed!
« Reply #2 on: January 24, 2018, 02:47:30 am »
I intend to do just that!  And I'll write up what I did with this one.  It was a long day at work yesterday...
Aaron Luebke

Offline Paul Birkeland

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Re: Crack-a-two-a completed!
« Reply #3 on: January 24, 2018, 04:13:20 am »
That's a good call on using the badge to cover the balance pot hole!
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline denti alligator

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Re: Crack-a-two-a completed!
« Reply #4 on: January 24, 2018, 04:39:53 am »
Any reason you left off the balance pot?
- Sam

Rega P3-24 (w/AT 150MLX) w/Groovetracer upgrades / C4S Seduction / FLAC -->J.River -->DSD256 -->Gustard X20 / Stereomour II / Klipsch Forte II w/Crites upgrades / C4S S.E.X. 2.0 +Nickel MQ Iron / Speedball Crack / Sennheiser HD600 w/Cardas cable

Wish list: Eros / Crackatwo / Tode

Offline ALL212

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Re: Crack-a-two-a completed!
« Reply #5 on: January 24, 2018, 04:47:56 am »
Balance pot gone missing...

From what I understood that was put in to compensate for low volume balance issues with the stock pot.  I used a Goldpoint volume pot that is a stepped attenuator like the TwoQuiet stepped attenuator and is very balanced at all positions.  The TwoQuiet kit also removes the balance pot.

The stock goldpoint uses surface mount resistors and some don't like that sound.  I just can't bring myself to buy the blank and solder in 48 resistors...  Call it lazy if you'd like! 

The TwoQuiet is a better option but I had the goldpoint left over and it's a 100k so it was an easy decision. 
Aaron Luebke

Offline ALL212

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Re: Crack-a-two-a completed!
« Reply #6 on: January 24, 2018, 05:47:59 am »
Changes from Stock - done at my own risk for reasons that could be vague or completely without reason.  Some of this was done in an attempt to equalize this build with the modifications I've done on the Crack to make a comparison fairer.  Some of this was done because I already had the part.

Please reread - "done at my own risk".  I'm not recommending modifications to ANY Bottlehead kit without approval from BH staff.  This is kit number...10 or 11 or 12...so I've got a few under my belt.

Cree diodes - fairly inexpensive and done on the Crack.  I used the mounting holes of the terminal strips replaced with nylon standoffs and then added a standoff to the center vent slot.  The nuts are on the board side and the board fits between nut and base - no holes drilled.  I think I stole this idea from someone's Crack build.  Holds it in very well.

I don't like sandcast resistors - it's just a "thing" with me - but the ones in this kit fit perfectly and I could not get anything else to physically fit that well.  I really like how those go in.

Cap #1 replaced - I had this monster Jensen with mount so I crammed it in.  Tipped with a 1uf film cap - just because.

Wiring - ya, I like that cloth wrapped (has a rubber interior so it's not just cloth protecting those) look when I can use it.  It's a slightly larger diameter solid core so it can't be used everywhere.  Other wire is 20 Ga. Stranded, Silver Plated, Aerospace Grade, PTFE from TubeDepot.  It's probably a bit larger than the stock wire but I only had a challenge with it when I needed three wires in a single terminal hole.

Upgraded caps on the two outboard boards.  Completely unnecessary but I was placing an order anyway...

Upgraded caps on the center board.  From what I understand they can have a small effect on the sound and my very favorite economical cap are Sonicaps.  Necessary.... ?

Wiring from inputs to selector to volume and then to headphone jack (can't be seen) is Mogami and all the same wire in spite of color.  The color helps me with the wiring at the selector.  It's shielded and the shields are all connected and grounded.  W2534 has shield + 4 conductors.  I used another version of this at the headphone jack - it has 2 conductors and shield (W2549?). These two Mogami wires have blue and white conductors - have a MM on hand to figure out what goes where.  You might notice small red bands on wire pairs - this tells me those are the right side.

Selector switch and Volume:  Yup...I took out the balance pot.  I had the volume laying around doing nothing from a prior experiment and it happens to be a 100k.  I lucked out.  Selector is Goldpoint. 

The big blue babies...I like the sound signature of ClarityCaps.  I'd forgotten how big these were...  They fit, barely.  Once installed don't plan on getting to the terminal strips behind them without dropping the circuit boards to do so.  Or uninstall the caps.

Top side - power switch.  It's just a Cherry Switch with writing on it - nothing complicated or needed.  I like it.

Headphone jack is just the black version of the one that comes in the kit.  It was already in house. 

Bottlehead badge fits quite well over the unused balance pot hole.

Knobs come from Goldpoint.  I like the smooth ones for volume and the knurled for selector.

RCA's - I put "different" ones in.  Whether better or not would be questionable.

My brother is building a custom base for it.  Not sure which wood he's working with, probably oak.

IERC covers - in house, they work.  I am using one of those graphite 6080WC's and everything gets warm.  I think those are indirectly heated and really warm up the place.  The IERC over the 12AU7 isn't the right size but I'm not sure if I have the smaller version.

I put the HD650's on last night and was just sucked into the sound.  Crystal clear...this thing is going to rival the Mainline I think...!

I'm hoping to run up all four of the headphone amps I have from BH and compare them.

Thank you Bottlehead - another great kit!


Aaron Luebke

Offline JamieMcC

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Re: Crack-a-two-a completed!
« Reply #7 on: January 24, 2018, 09:09:06 pm »
Nice work  :)
Shoot for the moon if you miss you will still be amongst the stars!

Offline itsikhefez

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Re: Crack-a-two-a completed!
« Reply #8 on: February 04, 2019, 08:33:29 am »
Sorry for resurecting this but was curious if you have any thoughts on the Crack-a-two-a vs. Mainline for HD650.
I just finished the Mainline for the HD800S but actually finding using it more with the HD650.
Was curious how the Crack-a-two-a stacks up?

Offline ALL212

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Re: Crack-a-two-a completed!
« Reply #9 on: February 07, 2019, 07:49:40 am »
This is obviously a personal opinion:

Each iteration of the BH headphone amp adds a bit of something - more refinement - at each step.  I think that the headphones used on these should be of similar quality.  So from my perspective the HD650 is a Crack/Cracka2a match and the HD800 is a Mainline match.  Having said that I think that either headphone will sound wonderful with either amp.  I'm just not sure you'll realize the potential of the pairings.

And I'm not sure what it is but those HD650's have magic in them.  I'm not surprised that you're wearing the 650's over the 800's.  I've got both also and do find myself wearing the 800's more but I like to run the 650's also.
Aaron Luebke

Offline itsikhefez

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Re: Crack-a-two-a completed!
« Reply #10 on: February 14, 2019, 07:50:00 pm »
Thanks for your perspective!  I listen to all sorts of rock music and I think the 650's simply make it sound more pleasing for longer periods. The occasional classical sounds in a different league on the 800S.
I've always liked to tone of the HD650, but was missing some of the technicalities other headphones have. The Mainline injected more bass quantity and refinement, and is more holographic, so now there isn't much I'm missing with the HD650.