Bottlehead Crack

Little help here? I see a buck listed on their website. Which one is right for me? Also how do I go about installing this? Just follow the steps from the manual at the part about the stock pot and just switching it for the new one?

http://www.alps.com/prod/info/E/HTML/Potentiometer/RotaryPotentiometers/RK271/RK271_list.html

 

Sorry to double post but could I maybe turn the volume up on the Crack then turn my volume down on the windows mixer? I read somewhere that I shouldn't do this so I have curious to hear what you guys have to say.

 

I bought my Bottlehead Crack with Speedball pre-assembled off of ebay. So I am going from things that I have read. I have no experience building/working on one.

One of those things I have read about often is that the stock pot often does not track well at the lower settings of the volume control.

I don't think the Speedball will help with this. Mine came with a TKD pot which tracks perfectly but costs $99.

I think that I would go with @Hands Alps RK27 suggestion. I googled those and see that they are much more reasonably priced.

The only other thing that comes to mind, is if you have a way to turn down the volume going into your Crack. If you do that you could get your volume control to a higher level for the same volume level where it should be more linear in it's tracking.

 

I am typing more slowly than you.

I am guessing that turning the volume down on the windows mixer would not give the best sound.

But it would not hurt to try it. It may show whether or not if it really is your volume control/pot (at low settings) that is causing the imbalance problem.

 

Turning down the volume and turning up the crack doesn't change the situation any.

I can change my current tubes to the default ones to check if that is the problem. I will buy the new pot as a last resort.

 

ALPS 100K, Blue Velvet - STEREO Potentiometer ALPS-64605 has been ordered. Might as well install the Speedball after I install the new pot as well. Can't wait!

 

This is the pot you want. You will need to use a drill to enlarge the pot hole a little.

http://www.ebay.com/itm/Japan-ALPS-...AX2-Slotted-/320816794126?hash=item4ab22bca0e

I recommend the $2 for ePacket shipping

 

@Ryu Great job with your build.

I agree with the others that upgrading the pot is a nice move. You can also solve the channel imbalance issue by padding the stock pot with resistors as laid out in the Crack FAQ (No.3) http://bottlehead.com/smf/index.php?topic=4295.0 , which will help put your moderate listening volume in a more open and more reliable portion of the pot.

Actually you might want to consider doing this anyway, even if you do upgrade the pot. It just allows you more room to set an accurate volume and significantly decreases the chances of you or a friend/visitor accidentally blowing their head off. The Speedball increases the gain a little bit too.

As Hands says, lots of the Alps don't have solder-lugs with holes, so you can just wrap the ends of the wires around the pins and crimp them tightly to get a nice positive connection first before soldering. The only other thing is that I think the small guide pin on the Alps is in a slightly different position than the stock pot so you might need a small metal file to elongate the existing hole.

Good luck

 

I ordered 7119 Amperex PQ tubes. I have been reading the bottlehead tube rolling threads and this tube seems very promising.

So far I am addicted to the sound of the Crackatwoa, my T3 haven't been getting much action lately.

 

I finally got around to putting in another couple of mods into my Crack: the C-7X inductor, a 100uF panasonic film cap in place of the last cap in the power supply, and a 2.2uF wima film cap bypass on the second to last cap in the power supply (just cause I had it), all at once. Superglue is holding the smaller film cap in place, the inductor is mounted onto wood posts superglued to the chassis (so not grounded), and the big black power cap just kind of...like...sits there. It's not really mounted in at all and juset sits on the desk below the crack. It didn't fit in like I thought it would, just barely too big. It can be remedied if all the wires move to the transformer side of the terminal, but I didn't feel like doing all that tonight, so for now it's just...precariously lying there. Not gonna lie, I saw a spark fly out from under the amp the first time I fired it on. A couple little adjustments and it was fine.

These mods are in addition to dayton output film caps, a cheap chinese stepped attenuator, Tung-Sol 5998 and a vintage Sylvania 6SN7 (both balanced). Basically all popular mods except cree diodes.

Listening through modded HD650. First impressions are very very positive. Honestly? It sounds like a totally different amp... in a good way. Resolution is on a different level all around. Seriously not even a competition vs before. Notably quieter background, better speed, improved dynamics. I was listening to Mosquito Control by ISIS (not THAT ISIS...) and I think Aaron Turner's vocals were actually halfway coherent for the first time ever.

Mods still in the works: still planning on putting a 3-way gain switch on the amp (50k stepped plus 0,50K,150K for 0,-6,-12), probably pass on the cree diodes for now. I think my power supply is souped up enough as it is. after that I'm pretty much out of room. I will say, though, that all of these mods have yielded exceptional gains in sound quality. It's really stunning.

 

Hi guys,

Just got Hands' Crack arrived. I got enough tubes for a while, but been wondering whether I can upgrade this even further. More caps?

 

@WNovizar - Reading the listing it seems like he maxxed out on what you can do with the space available. The Bottlehead Crackatwoa is the same basic circuit but with a more advanced power supply showing how far you can take the concept.

You could make the filament heaters DC instead of AC powered, however that seems to be a bigger deal with directly heated tubes instead of indirectly heated like the 12AU7 and 6080. Here's some regulators you can use.

http://www.neurochrome.com/universal-filament-regulator/

 

Installed the speedball upgrade and it sounds absolutely banging. So much clarity and resolution. Everything sounds less congested now. I also installed the ALPs pot as recommended earlier in the thread. Everything is great except one problem. My volume knob is much to small for my new pot and it looks really bad. Can anyone recommend a cheap, decent looking one that fits this thing?

 

This is the knob I got. Looks great and really clarifies the sounds. I can expertly dial in the volume I desire with this knob.

https://www.amazon.com/gp/product/B00X773QEU

Takes a few weeks to arrive, but I just consider that in lue of burn in time. I never really believed knobs get better with burn in, but some do.

 

This isn't mentioned in the manual, but also make sure the knob goes up to 11.

 

As already mentioned, you're maxed with available space. Getting the choke alone to squeeze in required a bit of luck. In terms of PS noise, the choke it a huge upgrade. It's silent, you have wanky wire for signal runs, fancy ass caps and a GoldPoint SA. Roll some toobs and just enjoy it.

 

Thanks @fishski13. My local guy who also has been tinkering bottlehead stuff also said the same things. He even shocked "who the f crazy enough to fit the choke to the Crack !?!?!?!" and toss me some old NOS Chatham 6080 to tube roll.