Crack;Bottlehead OTL

[CAPT Deadpool]

Glad you figured it out. Would p**s me off if It happened to me. THAnks for posting the problem you probably won’t be the only one

 

[Th3Drizzl3]

i just used a wet stone and flattened the wings out really nice where the screws go ill report back. its nice and smooth though now.

edit. not perfect yet but a LOT better. i can move it still but it takes a bit more force to move it around now. it doesnt just rattle around im going to take a tad bit more off and test again

 

[Th3Drizzl3]

@Paladin79 where did you find the ceramic socket you used? if you would share id like to get a few. the one they included is very meh imo

 

[Paladin79]

It’s been a while but I found them on ebay

 

[Th3Drizzl3]

ill look again i searched for them but nothing came up that would fit. thanks!

i took a tiny bit more off the ring and its nearly polished on the bottom of the wings now lol. im also going to add a couple delrin flat washers under the screw heads there on top because it did kink the thin metal a bit where the screws were tightened.

 

[Th3Drizzl3]

ahhhh perfect now. nice and snug now i cant even move it at all. so if anyone has this issue take the mounting ring and gently file down the bottom side of the wings a bit and its perfect.

edit again found a couple that would fit. hopefully they are a bit nicer then this one. i found a few brass retaining rings also im going to test out.

 

[atomicbob]

atomicbob's nuclear crack system:

My crack is non-speedball, has power supply choke mod, re-biased for Tunsram e80cc driver, and larger than normal output capacitors, which requires care during power up (headphones disconnected until warmed up.)
HD800 J-mod headphones (originally modified by mikoss.)


Here is a hot-rod analogy to what this system is like:

 

[chuckwheat]

It has been a while since I've touched my beloved bottlehead crack amp. I'm looking to get back to regular music sessions, but I think my crack needs some help. It's the stock crack with speedball, and I've replaced the smaller tube with a new Mullard 12au7 ecc82. I'm experiencing consistent ringing and humming noises in the left channel. When I press or wiggle the big power tube, I can get it to go away for a short time. This was always the case after I assembled it almost 2 years ago, but I'd love to solve it once and for all. Does anyone have any tips on what I can do? Thanks fellas

 

[hawkwindx]

It has been a while since I've touched my beloved bottlehead crack amp. I'm looking to get back to regular music sessions, but I think my crack needs some help. It's the stock crack with speedball, and I've replaced the smaller tube with a new Mullard 12au7 ecc82. I'm experiencing consistent ringing and humming noises in the left channel. When I press or wiggle the big power tube, I can get it to go away for a short time. This was always the case after I assembled it almost 2 years ago, but I'd love to solve it once and for all. Does anyone have any tips on what I can do? Thanks fellas

I had a tube that would cause some ringing. I switched to a different tube, and no ringing. So in your case, maybe it's the tube.

 

[AthenaZephyrian]

atomicbob's nuclear crack system:



My crack is non-speedball, has power supply choke mod, re-biased for Tunsram e80cc driver, and larger than normal output capacitors, which requires care during power up (headphones disconnected until warmed up.)
HD800 J-mod headphones (originally modified by mikoss.)


Here is a hot-rod analogy to what this system is like:

Good for rock?

 

[AthenaZephyrian]

It has been a while since I've touched my beloved bottlehead crack amp. I'm looking to get back to regular music sessions, but I think my crack needs some help. It's the stock crack with speedball, and I've replaced the smaller tube with a new Mullard 12au7 ecc82. I'm experiencing consistent ringing and humming noises in the left channel. When I press or wiggle the big power tube, I can get it to go away for a short time. This was always the case after I assembled it almost 2 years ago, but I'd love to solve it once and for all. Does anyone have any tips on what I can do? Thanks fellas

I got a vintage 12aT7 I pulled out of an old philco radio. No idea if it works, but I can do a multimeter test sometime next week, and if nothing seems amiss, I'm happy to post it to you if you cover S&H.

 

[JamieMcC]

so heres a question before i finalize this thing the 9 pin front socket is your a bit loose under the mounting ring? i have it as tight as it will go and the 9 pin really moves around a good amount in the hole like if i shake the plate the 9 pin rattles? the other socket is nice and snug without being to tight. im torn on the top plate finish still.

i have not fully snapped in the switch or the wall sockets yet so i can easily get them out. im thinking a orange or titanium chrome vinyl over the top or polishing it or an actual hammer type finish (you can achieve this in the aluminum but it takes a long time and is super tedious i have a friend who is a blacksmith who showed me this type of finish before) or leave it bare just because i like the look. hmmmmmmmmm. lol i was going to just anodize it at first but now im undecided haha

i do have a custom real carbon fiber top plate being made for the second kit i have here that should be interesting. ill have to run a ground for everything since the top will not be metal though

Carbon fibre conducts electricity you should be able to ground your carbon plate the same as the stock alloy one however the type of resin used and method used in forming the carbon sheet material will have an impact on how conductive the carbon ends up.

Its easy enough to test conductivity with a multi meter on the underside of the carbon plate before you start. Where the ground connections are made it would be advisable to locally sand the carbon to remove any surface resin to expose the actual carbon fibres for better conductivity. Similar to how you would remove paint or anodized finish to expose the metal.

Couple of pics that show the 12au7 mounted on the top and from below with a carbon top plate in case its any help. Its pretty easy to mount both ways and see for yourself.

Went with from underneath myself.

 

[Tom-s]

It has been a while since I've touched my beloved bottlehead crack amp. I'm looking to get back to regular music sessions, but I think my crack needs some help. It's the stock crack with speedball, and I've replaced the smaller tube with a new Mullard 12au7 ecc82. I'm experiencing consistent ringing and humming noises in the left channel. When I press or wiggle the big power tube, I can get it to go away for a short time. This was always the case after I assembled it almost 2 years ago, but I'd love to solve it once and for all. Does anyone have any tips on what I can do? Thanks fellas

Sounds like a problem with the powertube. Replace it with another and test again.
Bottle shaped or larger glass envelope powertubes are more suspectable for microphonics in my experience.

If in EU, i have enough spares.

I got a vintage 12aT7 I pulled out of an old philco radio. No idea if it works

Even if it works (and they will when good); PB on Bottlehead forum strongly recommended me once not to use them.
As these would severely impact the operating points of Crack's powertube in a negative way.

 

[Paladin79]

A friend from here gave me a couple very nice old 6SN7's to try my crack in place of the 12AU7. The change is shocking and very good. I am running a Schiit Gungnir Dac into a Freya pre-amp with four of Tung Sol 6SN7's in it. The tube sound is crisp and accurate but has the warmth I seek.

 

[buke9]

You find the Tung Sol 6SN7’s to be a bit warm on the Freya? I have been seeking that myself .