Tube Rolling with Bottlehead Crack

The 6as7/6080 types are pretty homogeneous no matter who makes them. You have get into the 5998/421a types to get meaningful better perfromance. Go look at the prices for a 5998 OUCH!

Get this, 2x 1uF 250V 2% K71-4 Polystyrene capacitors | eBay
and tie the leads to the leads of the output caps. They should fit into the chassis but check the dimensions.

Here is a picture of two paralleled capacitors. Both of them are film caps. In your case one cap will be the Russian caps I linked and the other will be the output electrolytic cap on your headphone amp.


If you are using 300 ohm headphones your audio signal from 500 hz and above will be passing through the Russian polystyrene cap. THAT is a good thing!

 

Okay, I see, that’s good to know! - I see, you meant “from what I’ve seen you will have to have a lot of coin to get one”! You’re right!

I’ll check the dimensions for sure. So once I get those caps you linked to, I simply solder each lead to one of the leads on the current output capacitors? I’m not really replacing anything, more so adding, correct? Does polarity matter?

 

I guess my last question is what exactly you mean when you say replace the output tube cathode resistors with current sources? Is there a specific part I’m looking to replace those resistors with? I’m not even sure which ones the output cathode resistors are, I think I know...

 

I'd have to read up on tube theory as it's been a while, but I'm pretty sure the big ceramic resistors, which are removed when you install the speedball board, are the cathode resistors.

 

Yep, those cathode resistors are removed with the speedball upgrade... so I'd say the most important "upgrade" is the speedball addition. I pretty much agree about the 6080 tube, I've tried a few different brands and not much to talk about. Might be more important to have a back-up 6080 on hand which these are bargain at $2.99 for NOS and sound great.

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Okay, so then that will be taken care of with the speedball, I have it, but haven't built it yet.
So I need to parallel the capacitors with the ones linked above, replace the rectifier diodes, as well as look into upgrading the volume potentiometer.
Then I'll look into a 12AU7 replacement.
Everything checks out?!

 

Just ordered my Crack over the weekend. It’s at least a month out! Stay tuned. Can’t wait!

 

Where you able to to make the above changes? Interested in your impressions. Thinking about tinkering as well and thought of starting with these changes too.

 

How has the AN volume pot worked out for you? Thinking about swapping out the standard kit pot.

 

I don't know as I built the amp with the standard pot to make sure all was good. I then put in the C4S kit and it looked like the AN volume pot was too tall to fit.

I will say the S.E.X. sounds quite a bit better than the Crack.

 

I second the 13D5. It is the best sounding 12AU7 ever made.

 

Unfortunately no, after I did the Speedball, I was so thrilled with the sound I figured I’d just leave it for a bit, and I haven’t looked back since. I’ll get around to it, but for now, boy does it sound great!

 

The speedball is definitely a worthy addition. I'm basically the same but after awhile now I'm ready to do a few small upgrades... nothing to costly. I went ahead and ordered the Russian caps mentioned earlier so I'll give those a shot. Also the potentiometer will be upgraded with the AN piece. Neither are to costly as I don't want to over spend... really the big move will be to build a Crackatwoa but I don't see that happening any time soon even though it would be fun....

 

Is the upgrade to the Crackatwoa even a worthy step? I would imagine it would be worth it at that point to spend even more and make a bigger jump? We can’t discuss this now though, because you and I both know it will lead to bad things financially...

 

...then don't even look at the BH site and price at the moment.

The Crackatwoa is pretty substantial upgrade, especially given how much people spend on upgrading the Crack. It's shunt regulated and has a larger transformer which I think would be pretty awesome. For me personally, I don't need it but man it would be fun. I don't really need a larger headphone amp taking up more space on my desk. I guess spending even more would yield even more results but I think the Crackatwoa is a worthy upgrade form the Crack....

 

I don’t really know, so I’m sure you’re right. I think in terms of Bottlehead builds, I would be most interested to try the new speaker kit, that would be cool, as much as I loved the technique and circuitry involved with the Crack, a departure within the same confines would be most unique.