Most worthwhile upgrades for Speedballed Crack?

[Welderboy]

Hi guys,

I ordered a crack+speedball kit recently, but I know it won't ship until some weeks from now. This gives me a bit of time to gather some extra components. There's a huge amount of information on the forum, but I'm feeling a bit lost to be honest. Are there some well established upgrades and/or modifications that are considered especially worthwhile? Or should I play with rolling tubes first?

Much appreciated!

[Deke609]

I'm laughing as I start typing because I'm going to give advice that I should be following with my new Stereomour II: be patient. Let the amp burn in for a few months before considering any mods.

That said, I think there are a couple of things that are worth investing in now that you won't regret:

(1) Build equipment and supplies: A well built stock Crack will almost certainly sound better than a crappily built one that incorporates all the latest and greatist mods. If you don't already own one, I suggest getting a pretty good soldering station (e.g., Weller or Hakko) and some narrow-ended soldering tips (or just some small tips to go with the soldering iron you have). The typical tips that look like large flat-head screwdrivers make soldering small leads so much more difficult than it needs to be.  I think it's also worth investing in some good solder like Cardas Quad Eutectic or Kester 24. They are so easy to work with. Will the solder make the Crack sound better? In one sense, maybe: I find it makes it easier to get a good solder joint - a bad solder joint is likely to result in impaired sound or, what is  maybe more likely, in a amp that fails the voltage checks at the end of the build.  Lastly, a pair of thin profile pliers made for electronics or jewelry making makes it easy to bend leads and crimp them around component holes before soldering.

(2) The Bottlehead Power Cord Kit: I found that it noticeably improved the sound.  And it is pretty much foolproof (but be careful with the shrink tubing).

Once the amp has been up and running for a few months, there are a ton of tweaks  and mods that you can consider. Check this forum and the Crack thread on Head-fi. For me, the best bang for my buck was the Cree Shottky diodes mod - better contrast and punch. But YMMV, and others on this forum will undoubtedly have different opinions.

cheers,

Derek

[deltaray]

Think the best advice is to stick with the stock for a while before stepping up with the speedball. As for tube rolling, it really depends on person to person, the kind of gear you are using with the crack. But if you're one who likes to tinker, try out options, this kit is plenty fun for that.

[Welderboy]

Thanks guys, sounds like a slow approach might be best here - I'm trying to teach myself more about electronics and audio, so I'll give it some time. I've got the soldering equipment covered! I'm a welder and machinist by trade, so I try not to cheap out on tools. 

I'll pick up the power cord kit next paycheck as well

[adydula]

Stick with the stock Crack for a few months.....listen to your favorite music and with your headphones....get to know the sound and enjoy.

Then and only then (IMO) get the crack upgrade and try it....by then you should have a pretty good ear as to what the speedball upgrade adds.

also by waiting for a few months you get to make sure your crack is solid and working well....many folks have minot issues that become exposed after a few weeks/months due
to a number of reasons, cold solder joints, mediocre building skills etc....

I installed the speedball after several months and I can highly recommend it, but to really appreciate it....waiting can really help you decide if you like what you here.

As far as tube rolling theres many posts in the tube recommendations thread.....for me the tubes BH ships usually are pretty good.

The mantra here is start with what you have, listen and become familiar then start playing if thats your desire and can afford to chase tubes that may or ma not
improve the base you now have.

Alex
 

[Deke609]

I've got the soldering equipment covered! I'm a welder and machinist by trade, so I try not to cheap out on tools. 

That's awesome.  You are going to have a lot of fun with BH kits. I assume that being a machinist, you can mill and bend metal, or at least have ready access to someone who can - man, I wish I had those skills.  Instead of focusing now on down-the-road upgrades and mods, you could think about how you want the Crack to look.  Maybe a different chassis that you could cut for the same layout, but made of a different metal or with a different finish? Maybe a cool looking metal base?

If you do decide to play around with creating your own chassis or base, please post pictures when you're done.  I'd love to see them.

cheers,

Derek

[Raymond P.]

Lots of good advice given, especially about giving the stock Crack some good listening time. After that, revisit the discussions on modding and they'll be much easier to understand.

[Welderboy]

Yeah, we make custom panels and enclosures from time to time in the shop, so I might build something custom eventually. For now I think I'll powdercoat the top of the plate and stain the wood, until I know how much room I need exactly with mods and all.

[HF9]

As others have said, build it stock, get a good listen, then install the speedball and you'll really appreciate the difference. Other cost effective upgrades include EAR feet ($4), an Alps Blue or PEC pot ($20-30), a Triad or Hammond choke for the power supply ($15-20), and film coupling caps ($35+). You can also experiment with o-rings for a few dollars, I tend to like one toward the bottom of the power tubes on most power amps as it seems to increase bass quantity, but play around and see what you think. Most importantly, get some tubes to roll in.

[Paul Birkeland]

A shunt regulated power supply is also a very worthwhile upgrade.

[fromnowon]

This thread got me interested in the power supply choke mod.

From what I read there are two primary ways to do it and this comment seems to be the guideline for deciding:

"There are two schools of thought:
On the one hand, the choke can pick up magnetic-field hum, typically from the nearby power transformer. So the choke should replace the FIRST resistor, allowing the later RC stage to attenuate any hum that gets into the choke.
On the other hand, the choke provides a higher impedance than a resistor, so if the last (third) capacitor is a high-audio-quality cap then you want it to isolate it as much as possible from the earlier, crappier capacitors in the power supply. So the choke should replace the LAST resistor, and be located and oriented to minimize pickup from any nearby magnetic component."

Taking a look I see that the first resistor (between 21 and 15) would be easy to access and remove.  I like that aspect.

The last resistor (between 13 and 15) . . . wow, that would be a challenge to get in there and remove that resistor.  I hate to mess with that one!

I wonder if there are any comments from others who have made the decision to use a Triad C-7X in place of the first 270 ohm 5w resistor.  Or if you replaced the last resistor, what was the best strategy to accomplish that? 

Thanks

[Julyan9]

I did the replace the one between 13-15. Just remove old solder and remove the cap(it's a cap not a resistor). I drilled holes to the backplate above the 270ohm 5w resistor to make holes for the choke. Used nylon spacers to lift the choke above the power transformer and then used the grounding wire to ground it to the grounding lug near the power switch

[ohshitgorillas]

The choke is definitely a worthwhile upgrade, as are film cap bypasses to the 220 uF power caps. I think replacing the output caps with some kind of pp film caps is also critical for getting the most out of the amp.

When I built mine, I built the stock amp, then added the speedball, then slowly added the mods over time. I would recommend installing speedball before any other mods, since speedball and most mods take up a good amount of real estate under the hood. It's easier to work around the speedball boards when installing large film caps or a choke.

I have had the choke replacing both resistors at one point, I don't think it makes a huge difference either way and I would not spend much time worrying about which. It's more important to mount the choke so that it's not picking up noise from the power transformer.

[Deke609]

A shunt regulated power supply is also a very worthwhile upgrade.

PB - how would one implement an SR mod for the Crack? If SR for the Crack isn't too complicated, it might make a nice exercise for noobs like me  to learn how SR circuits work. If it is complicated, could the Stereomour 2 SR board be modified for use in the Crack? 

The SR upgrade on my S2 was amazing - giving me lots more bass definition/punch.  One of the major driving forces behind me getting the LCD4s and the S2 was a pursuit of bass clarity and weight.  My HD6xx and Crack/Speedball pairing gave me great mids and highs, but the bass was loose and underweighted (for my tastes/ears), and playing around with caps and tube-rolling never really changed the bass that much.  With my new setup, the HD6xx and Crack don't get used - which is a shame. It'd be nice to get them back into circulation.

cheers and thanks,

Derek

[Tom-s]

For all about a shunt regulated Crack: see https://bottlehead.com/product/crack-a-two-a/