My Crack . . .

[Raksasa]

Just got a new case made for my Crack with Speedball upgrade.
Made by a friend of mine in Western Australia, who also builds guitar speaker cabinets, amplifier headshells & slab Australian wood tables.

It is made from 15,000 year old New Zealand Kauri wood offcuts, so it had to be butted the way it is due to available sizes of the offcuts.
Still looks great though:

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi204.photobucket.com%2Falbums%2Fbb272%2Fraksasajohn%2FaaaaPro%2FPhotos%2FHi%2520Fi%2FBottleheadCrackinKauribox001.jpg&hash=03421e4061a65eca998a08a1bd2fbe3a7217a1e6)


Here's a photo of an ancient Kauri guitar speaker cab he built for another mate of mine:

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi7.photobucket.com%2Falbums%2Fy299%2FGooma1%2FAncientkauriHomepage.jpg&hash=cf49fd9403d000daad9c030691439292c0c8434b)


Also a question:

Is the 12BH7 driver tube a direct drop in ?


Cheers all,

John from Oz.

[ironbut]

Wow, that is some beautiful wood!
I'm glad to see some of the Crack amps finding their way around the globe.

[Raksasa]

Thanks ironbut.
My mate had the wood carbon dated in NZ. Came from a swamp. Actually measured 10 - 18,000 years old.
But I split the difference, sorta.

Here's a Youtube link if you're interested in knowing more re this wood:


PS

I found a post here re 12BH7 is direct drop in for Crack.

Cheers,

John T

[Grainger49]

Beautiful wood!  

There is a thread that lists tubes that drop in and work here:

http://www.bottlehead.com/smf/index.php/topic,663.0.html

The 12BH7 is mentioned in the thread but not listed in the original post.  It is not a direct substitute for the 12AU7, but seems to work in the Crack.  There are several Bottleheads using it.

[Raksasa]

Thanks Grainger,

John T

[Grainger49]

Thanks Grainger,

John T

Now I know who else is up at 5:00 EDT, guys in Australia.

[ironbut]

Very cool video Raksasa!
It's interesting that even though the wood wasn't that far below the surface, that gigantic log was still in great condition.
It kinda reminds me of some wood that we use here in the US that was already cut into large rough pieces and were lost when ships from the mills were sunk during storms on the Great Lakes. The depths of those lakes are just above freezing so the wood is perfectly preserved but aged without any degradation from the air or microbes.
The pressure also kept the wood from gassing out. The result is wood with an amazing amount of grain contrast.
It also smells great but is a bitch to cut!

[Raksasa]

Yeah Steve, interesting resource harvesting old wood.

My mate Brad said this about working with the ancient Kauri:

  .  .  .  it`s a really interesting wood to work with, clogs up sandpaper easily and is very prone to tearout, it`s even tested the spiral head machines here,
but i think the challenges of working with it will be hopefully worth the effort.

Here's a shot of a big offcut offa one of the big slabs he got from NZ:

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi7.photobucket.com%2Falbums%2Fy299%2FGooma1%2FAncientKauri2.jpg&hash=bd35a47b158a92c2f0a539ea7b8350754544fc72)

John

[Raksasa]

Question re pot & caps.

I have a Speedball upgraded Crack.

Is it worth upgrading the pot ? If so, does anyone know a worthwhile upgrade (pot or attenuator) that will drop right in ?
Or at most need a mounting hole ream etc ? It looks a bit squeezy to me with Speedball in there.

Also, with the Speedball added, are the coupling caps still worth upgrading ? Say to AXON polyprops ?
Are 0.1 bypasses of better quality film types worth doing, once say, AXONS are in ?

All advice gratefully received,

Cheers,

John

[Grainger49]

I don't have a Crack (can't believe I typed that!) or a manual so I don't know the value of the volume pot.  I have a favorite cheapie.  I am a known cheapie. 

Radio Shack sells a stereo audio taper 100k ohm volume pot for about $3.  It is made by Alps, a highly regarded pot manufacturer.  Some say it doesn't track well at the lowest volume settings.  I haven't found that to be a problem and I have used many upgrading tube equipment, in passive preamps and in scratch built pieces.  There are a lot of options and they can cost up to hundreds of dollars.  Many are under a hundred dollars so it isn't awful.

Getting to the real answer, yes the pot is in the audio path and it can make a difference.

[HF9]

IIRC it's a 100K pot.

Here's a few options that I think should fit without issue and their appx. costs:

Alps Blue Velvet Stereo Pot: $12

TKD Conductive Plastic Stereo Pot: $75

DACT CT2 Stereo Stepped Attenuator $150

[ironbut]

I have a 100k TKD conductive plastic pot in mine. It installed it before I upgraded to the Speedball so I can't really say if it's a marked improvement over the stock one now. It does have a slightly different taper from most pots so it seems like the volume increases sooner than a normal taper does.
That said, I do like how well balanced the channels are even at very low volume settings. When I listen to my Audio Technica AD2000 headphones (which are very efficient), I don't notice any balance issues at super low settings.
Overall, I can't say that changing the pot is a must. I think the cheaper ones won't last as long but once they get noisy, you can always replace it then.

[Beefy]

It does have a slightly different taper from most pots so it seems like the volume increases sooner than a normal taper does.

Depends which model of the pot you get. They have a popular 'A' model available for the CP2500, which they refer to as an audio taper, and it does get a few extra dB of volume in the early part of the rotation. But I bought a 2CP2511 from Parts Connexion for my impending Crack build, and it has a regular log taper. It is indicated by the lack of an 'A' in the part number on the back of the pot.

Datasheet here for more info: http://www.tkd-corp.com/02_products/pdf/p06_cp-2500.pdf

[Raksasa]

Thanks all for the info. Sorry for the late response as have been in house hunting mode for last 2 months.

Decided to get the TKD Beefy recommended.

Really don't need any taper that increases the way volume comes in, as have been using an old CBS 7236 (computer rated 5998)
with an old CBS 12BH7A and find that I don't have much room to move before it gets too loud. Heaps of grunt.
Using Beyer DT880/600 Manufakturs.

In the middle of house buying and moving again, so won't get it all in till later in 2011, after I get a workspace set up.
Also have some 90uf AXONS and nice Mundorfs for bypasses for the couplers.

Also quickly tried an old Sylvania 12AU7A with one of those Russian Winged C 6H13C (6AS7G equivalent).
Will run in further as that combo sounded nice as well, plenty of grunt too.

All the best for the Holidays,

John T
Australia.

[coca]

One of the best sounding pots I know of, is a military carbon pot made by P.E.C.. It is made about 120 miles from me in Toronto Canada I believe. However it will have to be
purchased from the states, as no one around these parts sell them, as so it seems. This pot is very high quality, will come in both single and double channel.

Bernie.