A crack across the ocean

[deltaunit]

Hi all,

Thought I would share with you the results of my first ever build:


The wood stain is still drying here but had to fire it up and have a listen, crack use is addictive!

Tube rolling already, got these three for £8.50

Have settled on a Mullard CV4003 for now



Wiring in progress:

Passing final inspection:


Even with my less than ideal headphones the results are really great, lovely rich texture, plenty of detail and clarity with lots of black inky blackness etc etc!

Building it was such a pleasure, the sense of having made something is really great - and highly addictive - thanks Bottlehead for that experience and for all the music listening pleasure to come.

Now about these upgrades...

[mrarroyo]

Very nice and clean build, enjoy it.

[John Roman]

Nice clean wiring!
John

[deltaunit]

Have made some updates recently to my beloved Crack and am soo happy with how it is sounding I thought I'd post some pics.

Hot-rodding for more clearance:



Speedball, 1000uf BHC PS Cap, Alps Blue, Mogami input cable.


 
The upgrade to the PS and Alps Blue Pot cap have made a huge increase to SQ, am literally stunned by it!

I'm having poly caps custom made by Ansar this week and am also due delivery of a Mullard E80CC. Exciting times.

Could do with a drill to get everything fitted correctly though.

http://imgur.com/a/K0xzN#CV0XL

[STURMJ]

Does the cat look more happily at you, than before?  I bet it does

[deltaunit]

After some disappointment with my recent tube purchase my custom made 100uf 160v poly caps from Ansar were delivered today.



Hehe



They're quite short and sweet! And there's a definite level of improvement across the board straight away. Very happy with the service from Ansar, custom made caps at a very competitive price.



And there's still plenty of room in there for the next upgrade

More..

[deltaunit]

Another couple of updates are in:



Two more big caps in, 470uf BHC electrolytics (RS branded this time - bad RS, bad!) and the Triad CX-7, (free shipping from the US via RS - good RS, good!).

I had thought I would be past the point of gaining clear and obvious improvements to the SQ but surprisingly each one of the bigger caps revealed a tiny bit more background detail in playback.

I did speak with an electrical engineer (not an audio guy) prior to fitting the choke and as a result wasn't really expecting any improvement. I was told that the choke wouldn't block noise (as it is a single piece of wire unlike a transformer) but would act on current like a capacitor does on voltage. As I have the speedball already fitted I didn't really think it would therefore do very much. However I think there was a slight improvement and I'm not sure why - maybe it gives the speedball an easier time, maybe it does block some noise from the rectifiers *- maybe it doesn't add noise of its own like a resistor. It was less obvious than the PS upgrades and more along the lines of a difficult to articulate improvement in overall feeling. I suspect it might be a better improvement if the speedball upgrade seems pricey for some.

The final upgrade I tried I actually removed from the above photo, I had added a 10uf AmpOhm film bypass cap (LCR branded - bad RS, bad!) to the PS, but the change to the presentation was so startling I very quickly removed it! Maybe I didn't get a good ground connection to the tag board, maybe it was positioned badly or it really needs a lot of burning in but the result wasn't what I had expected. I'm quite used to listening to low level tape hiss in recordings (and the different levels of tape hiss in multitrack recordings being mixed up and down) and the bypass cap really reduced this source detail. It gave a far quieter result but seemed to give it a funny presentation, natural sounding but perhaps a bit overly soft with less edge. Creamy is a useless word to use but all I can think of as a description!

I will try this upgrade again at a later date and see if burning in alters it but it is making me consider planned bypass upgrade on the signal side. So I could be done!!

More photos

[Grainger49]

Wow, I like a lot of big capacitors!

There are a number of engineers here and they would also suggest more power supply capacitance and a choke in the power supply filter.  As a matter of fact a choke presents a blocking impedance to incoming high frequency noise.  I'm surprised an EE didn't know that.  Chokes also resist surges in current, is considered an upgrade in power supplies and there is a coil (choke) in classic ignition systems (because they resist changes in current). 

I would try breaking in the 10uF AmpOhm caps and try the bypass again after 100-200 hours of break in.

[deltaunit]

Thanks for the addition info and clarification, very little is clear to me in electronics at this stage so I appreciate every nugget of info I get

I suspect after a hard day and at the end of a long night he could have perhaps been thinking about it rejecting audible noise, I probably wasn't being exactly clear with my questioning either - thinking back there was lots of room for confusion on both parts. From what I've understood about noise previously is that the fewer non-audible frequencies you present to the amplifier the better or the more resources it can use to work on the audible range.  If right, then the benefit is almost like a consequence of rather than direct result of the noise rejection.

There's plenty of space for me to get confused discussing that there

It's odd that the film caps in the signal path worked so well for me straight away. I will persevere!

[deltaunit]

I've put the film bypass cap back in and it's sounding absolutely great now. I really should have given it more than a few minutes the other day - the dynamics are back, the gloop is gone and *everything* is sounding better than ever after only an hour. I wonder if it was because of the position (directly above the IEC socket) the dodgy solder to top of tag board or it just needed a few more minutes to start working.

Either way my first impressions seem to have been way off.

Which means I might not be done after all!

[TonyMc]

Deltaunit.
I wanted to say thanks for the great pics and play-by-play in this thread.
It's builds like this, HF9, and a few others I have seen that got me into looking at the crack.
I am sure the stock unit sounds wonderful, but the tweaking and upgrading is what really peaked my interest.
I'm looking forward to this build and future upgrades.

[Lee Hankins]

Deltaunit, a great looking and neatly organized built.  Since you seem to want to max your Crack here are a few suggestions.

5998 or 2399 tube, the 2399 is just Chatham's in house number for the 5998.

Tung-sol round plate 6SN7GT tube, I use mine with an adapter.  I rolled a lot of 9 pin tubes through my Crack but just kept going back to the 6SN7 round plate tube.

Goldpoint or Khozmo Acoustic attenuator; I have found that an attenuator is a big improvement over the Alps pot, even a PEC pot IMHO is better sounding than the alps.  I really like the Khozmo because it has 48 steps and only has two resistors in the signal path, the Goldpoint is a 24 step series attenuator, Goldpoint claims that the type of resistor that they use does not reduce the sound quality when used in series.  Since these two attenuators use the same type of resistors the only reason that the Khozmo sounds better (IMHO) should be the lower number of resistors in the signal path.  Both are wonderful sounding, much better than the Alps or PEC.  The biggest sound improvement to any piece of equipment I have found is better tubes and a better pot or attenuator, wire would be next but wire does not have as big an improvement as tubes and attenuator.

Better SOLID Copper or Silver wire from the inputs to the volume control.  I personally to not like stranded wire in the signal path, and do not like tin coated copper at all, silver coating is just OK.  In the signal path any coated wire does not sound as good as a non coated wire.  If I want the best possible sound I use a flat silver/gold wire.  Since the Crack has a very short signal path, using extremely expensive wire doesn't hurt the pocket book that much.

All of these opinions are not based on facts, just the imagination of an old man through years of rolling tubes and changing out parts.

[TonyMc]

Goldpoint or Khozmo Acoustic attenuator;

I've seen the Goldpoint, but not the Khozmo. Wow. It is a little work of art in and of itself.

[deltaunit]

Thanks for the kind words and advice, it's nice to hear some feedback. HF9's Crack has been a huge inspiration of course and so thanks have to go to him really.

I finally tracked down a perfect quiet Mullard E80CC and I'm perfectly happy with where mine is now, I use it for at least a couple of hours each day and am constantly amazed by it - bliss. It's very hard to imagine there is a significant upgrade left in it tbh the quality seems so high, although that does always seem to be the case.  

Quite early on it became the best piece of equipment in my system(s) and so in recent weeks I've been looking to upgrade and build up elsewhere, I fear it is going to be difficult reference to live up to though. I do plan on adding a few tiny little bits to the side of a couple of orders I'll be placing in the next few weeks though so stay tuned!

[jrihs]

Hi There!
I was hoping to find out what the big cap in the back was and how you managed to mount?
Cheers!