next step mods

[tweedgv]

Hi all,

I have recently finished my speedball upgrade after a few years of enjoying the crack as standard... and i've got a massive urge to keep on soldering.  So i've been reading through the forum looking for my next step and i think i'm moving towards swapping the capacitors next but the cree has me intrigued as it seems to be relatively easy and cheap.  problem is most of the links on here are old and broken, and i'm in the UK. 

Can anyone help with a local company that can supply the parts?

and feel free to give me some advice on any others mods i can attempt. 

thanks

Gav

[Tom-s]

As EU member on here you can buy from Mouser as wel as other stores. In the UK u find rapidonline that supplies a lot of parts. Hificollective is a good source for boutique parts.

Read the forums for other upgrades. Use other members Crack for inspiration.
As a wise guy on this forum once said: there not an upgrade to any powersupply that hasn't translated to better sound. Which is very true for the Crack. Other upgrades are the output coupling capacitors.
I'm a cheapskate when it comes to cap rolling and have a large supply of Russian capacitors for my amplifiers.

So keep reading and read some more on these forums and you will find every answer you are looking for.
Sometimes i find it handy to use this website via google vs via the search to get better results.

"Upgrading" parts in an amp and tube rolling has it limits. Most gains come from circuit design and Doc B repeats this in a lot of topic you find on this subject. I've gone from Crack to a completely modded Crack (overdone it a bit) to S3X to Mainline and i got confirmation that circuit design beats every parts change "upgrade" anytime.

So, while i do think Bottlehead products have room for "improvement", it is worth it, brings better sound quality and you definitely can learn a lot from upgrading your Crack:--> Don't spend to much money on upgrades/holey grail crazy tubes and start saving for the next step up!

What i would say are reasonable upgrades:
Speedball is the best.
The bridge rectifier as this gives insight in the influence of the powersupply on sound.
A choke in the powersupply for the same reason as above.
You can bypass the last powersupply cap with a film cap (another cheap one).
E80CC/12BH7 tubes with minor changes to the speedball board can be another good learning point.
Output caps with or without bypass can make a difference.


A word on tube rolling.
All tube rolling is just fun and make for another flavour in sound and i recommend trying it.
Those super expensive tubes are like boutique/expensive capacitors. They are good for the people that buy them and want to believe they sound better. For example, in my personal experience i can't recommend any super expensive tube as they don't always sound better. I don't think my ECC802S Telefunkens sound any better than the normal ones. They sound different, with more insight, soundstage and so on, but come with a different tone compared to the normal ones, which i prefer. Same goes for other computer rated/extra overbuild/super tubes. It's all personal, beauty is in the eye of the beholder.
Do not spend money on tubes. Try to bump in to them on flea markets, local second hand online pages and the like. You don't have to pay crazy prices and with luck you get any tube you wish for. It's not abnormal to find a beautifully build Mullard Blackburn driver ECC82 tube in the UK or a GEC power tube for cheap. Be patient, keep your eyes open.

Edit:" Here's the perfect example on how you overdo it: https://bottlehead.com/smf/index.php?topic=9262.0
Will update the pictures.

[ianp]

Below are some links I have saved for these mods that I intend to do at some point.

For broken links and particularly for images I quite often just do a google image search for something relevant in the threads

Bridge Rectifier
You don't really need the PCB as the circuit is as you would expect and you can replicate on prototyping board or similar.

NB There are reminders that the tabs on the top of the diodes are live and should not touch anything ever.

• PCB - https://www.partsconnexion.com/PCB-77727.html
  
• Cree Diodes https://www.mouser.co.uk/ProductDetail/Wolfspeed-Cree/CSD01060A?qs=%2Fha2pyFaduha8e7L7P6H8AQPAaWzRYR18hPNYjU5%252Bzc%3D.
  
• Wiring guide - https://cdn.head-fi.org/g/9937481_l.jpg
  

Choke

• https://www.mouser.co.uk/ProductDetail/Triad-Magnetics/C-7X?qs=sGAEpiMZZMuMS2dUaCDnDB57UyZo4e84

This replaces one of the two big white 270 Ohm 5W resistors. Most people seem to replace the one between 13L and 15L

[tweedgv]

Thanks both,

Tom… you say you have a large supply of Russian caps, how do you usually acquire these?  Can I simply look for the same spec caps and swap them around?  I have had a look at the 100uf 250v Mundorfs.  Do they justify the price? 

I’m with you about upgrading and I do have my eye on the next amp from Bottlehead so I don’t want to spend £100s that could go to the next project but spending a bit to feed my curiosity and keep my solder station active is justifiable, so I will look into the list you have given a little further, thanks.

I’m going to look into replicating the pcb (thanks ian).  The board looks quite simple but I have zero knowledge on this so will have to do some research.  I’ve looked at your parts guide and I think I’ll order the cree diodes and choke from mouser.  in fact, I've been able to source these from a uk dealer and that has cut the cost down by half.

I've been reading this forum for days now and its tying me in knots. 

[Tom-s]

I acquire them through Ebay and online stores (tubes-store.com and the like).
They are good for my Bottlehead amps, DIY amps, speakers etc etc. Whenever they fit, i use them. Never had a problem with these Russian capacitors. I mostly use the FT (teflon type for small interstage coupling. PIO for speakers and parafeed use K40y-9, K75-10, KGB. And MBGO and other bigger versions for power supplys and as output caps for the Crack.

I only have used 10uf Mundorf caps once, the Supreme Silver Gold Oil as parafeed caps for the Mainline. Way to expensive for a Crack (and don't think they come in 100uf). They sound very good but i don't recommend using them because of the pricing.
From what i've read on here the standard Mundorf caps are an excellent choice.

Good luck with your journey into sound! Enjoy!

[ianp]

I’m going to look into replicating the pcb (thanks ian).  The board looks quite simple but I have zero knowledge on this so will have to do some research. 

So, this thread prompted me to order the PCB and Cree diodes, and to break out the soldering iron. The shunt transformer will have to wait until I next order something from Mouser.

Pictures of the PCBare attached to make it easier to replicate the circuit

[L0rdGwyn]

So, this thread prompted me to order the PCB and Cree diodes, and to break out the soldering iron. The shunt transformer will have to wait until I next order something from Mouser.

Pictures of the PCBare attached to make it easier to replicate the circuit

Doc or PB, does this modification have any theoretical benefit int he Crackatwoa circuit, or does the shunt reg power supply override any perceptible performance improvement?

[Paul Birkeland]

I have an incredibly hard time discerning any difference in any circuit, though Schottky diodes are wonderful for high current low voltage supplied (DC filament supplies) where their efficiency gives high output voltage with minimal device dissipation. 

[L0rdGwyn]

I have an incredibly hard time discerning any difference in any circuit, though Schottky diodes are wonderful for high current low voltage supplied (DC filament supplies) where their efficiency gives high output voltage with minimal device dissipation.

Thanks PB, in that case I'll probably leave the diodes alone.  I've already added film output caps, upgraded the film caps on the low current C4S, and the TwoQuiet attenuator.  My understanding other component changes likely won't make any sonic difference, but I'm always looking for a good reason to fire up the ol' soldering iron

[ALL212]

confessions of a Crack addict...

I've built 3 Cracks, a Crack-a-2-a, the S.E.X. and a Mainline (and others not headphone related).  Another Crack on the way (they are just way too much fun to build!).  I've heard all three, all three were built with similar upgrades and I've listened to all three in the same rig. One of the Cracks I still have and I refer to it as the BAC (picture included).  You could do more to it but I'm not sure exactly what.

I've had a riot planning and changing and messing with these.  Next Crack will probably get different pre tubes socketed.  I like the brain exercise that goes with the changes.

But...

No matter what you do to that Crack the Crack-a-2-a will sound better.  No matter what you do to that Crack-a-2-a the Mainline will sound better.

Put down the iron, step away slowly and save for the next kit up the line if you want to push your cans to the next level.

But for cryin' out loud have some FUN!!

[L0rdGwyn]

confessions of a Crack addict...

I've built 3 Cracks, a Crack-a-2-a, the S.E.X. and a Mainline (and others not headphone related).  Another Crack on the way (they are just way too much fun to build!).  I've heard all three, all three were built with similar upgrades and I've listened to all three in the same rig. One of the Cracks I still have and I refer to it as the BAC (picture included).  You could do more to it but I'm not sure exactly what.

I've had a riot planning and changing and messing with these.  Next Crack will probably get different pre tubes socketed.  I like the brain exercise that goes with the changes.

But...

No matter what you do to that Crack the Crack-a-2-a will sound better.  No matter what you do to that Crack-a-2-a the Mainline will sound better.

Put down the iron, step away slowly and save for the next kit up the line if you want to push your cans to the next level.

But for cryin' out loud have some FUN!!

I haven't heard the Mainline, but I always thought the Crackatwoa and the Mainline were more like different flavors, the 'twoa being more warm/euphonic/tubey, the Mainline being the more neutral/transparent.  What do you think, is that accurate?

My mind has already started wandering toward the Mainline, it's only a matter of time...

[ALL212]

WOW!!!  Shiny...I like shiny...  But I don't have anywhere near the patience to get shiny.   

I think your description of the two headphone amps is very accurate.  Doc warned me or someone when doing one of the uber Cracks that it would never get to Crack-a-2-a level and he was right.  They are very similar.  Mainline is a entirely different level.

[L0rdGwyn]

WOW!!!  Shiny...I like shiny...  But I don't have anywhere near the patience to get shiny.   

I think your description of the two headphone amps is very accurate.  Doc warned me or someone when doing one of the uber Cracks that it would never get to Crack-a-2-a level and he was right.  They are very similar.  Mainline is a entirely different level.

I long to go to a meet where I could compare my Crackatwoa with other Bottlehead amps (modded Crack, Mainline, S.E.X.) along with other tube amps in general.  As far as choice of tubes go, I think I have pushed it to the limit of its performance, in addition to the component changes I've made (film caps, TwoQuiet, etc.).  Really curious how it stacks up.

I've found there are very meaningful differences when changing shunt regulator tubes.  I have compared probably around ten different types.  I started sharing my comparisons on the Crackatwoa forum, sadly no one replied, so I never finished my post  I thought people would want to know!

[Paul Birkeland]

  I started sharing my comparisons on the Crackatwoa forum, sadly no one replied, so I never finished my post  I thought people would want to know!

You never know when, where, or how a thread will suddenly come to life down the road!

[Crackawaka]

My "next step mod" is making a new case for my Crack. I just sourced some really nice black walnut and have been playing with a design in Sketchup. I've been itching to improve my routing skills and need an excuse to use a new router fence I recently purchased!