[JamieMcC]

   
Jamie - are these the ones that you have to cover with some sort of heatshrink because the outside is conductive?  You guys are seriously tempting me to give the ole crack a little update!

 
Hi skeptic I did originally cover mine with a precautionary covering of clear heat shrink prior to fitting. However after taking one apart they look to be very well insulated both in the ends and body from the metal shell with a generous wrapping of teflon after the actual foil part ends. I suspect the heat shrink is actually not required. Interestingly the internal leads that connect to the steel pins for hooking up look to be made of silver wire!
 
I have made some woody versions but have yet to try them

 

 

 

 

[skeptic]

Thanks for the further info Jamie! I couldn't resist and ordered up a pair. Really looking forward to hearing them!

 

[JamieMcC]

Thanks for the further info Jamie! I couldn't resist and ordered up a pair. Really looking forward to hearing them!

 
You will be pleased to know they take a lot less time to burn in than those RTI teflons!

 

[skeptic]

Good to know! I think the RTIs are still evolving but I am loving the sound regardless. If these imbue a little of the same teflon goodness in the crack, I'll be thrilled!

 

[larcenasb]

A question of concern: I was told that 470uF output caps were too much for the application of the Crack.
No disrespect to the others, but in my experience, I find the sound of my Roe 470uF 160V caps to be SO MUCH BETTER than the stock 100uF Epcos caps -- I'm unwilling to compromise. The Epcos sounds thin in the mids and a bit strained, lacking power reserves; I'm constantly trying to adjust the volume to find satisfaction. The Roes sound powerful even at low volumes, and have fleshy, natural mids. Bass also is much more potent.
 
This also enlightened me about the dependency of "the whole" in regards to tube performance. With the Epcos, my Mullard 12AU7 [k61 date code] sounds weak and thin; my Ken-Rad VT-231 (w/ an adapter) sounds more natural and powerful, but still not quite right for me. With the Roe caps, my Mullard sounds lush, beautiful and powerful (perfect for me); my Ken-Rad sounds mechanical in the mids but super powerful in the bass.
 
'crappyjones123' shared similar sentiments: "also, installed sprague 470uf 200v electrolytic caps for output caps. bass is nicer. but overall tone has gotten bloomier."
The bloom is very welcome in my AKG K612s which can be a tad clinical sounding.
 
I've used the Roe 470uF caps for months before I was told I shouldn't. So, in my experience, they were never troublesome.
 
However, I do want a safe and stable amp for years to come. So... what exactly are the negative effects of using 470uF output caps in the Crack? What is cause for concern? And is there any alteration I can make to allow the use of the 470uF caps?
 
Thanks so much.
 
(image missing)
-larcenasb(image missing) 

 

[JamieMcC]

I am wondering if the cause for concern was if using the 470uf value in the power supply rather than as output/coupling caps and I remember seeing something this about it being related to the transformer? The more common route with regards to the 100uf electrolytic output capacitors appears to be replacing them with a film equivalent.

 

[Doc B.]

Who said it was bad to use them?

 

[larcenasb]

Thanks JamieMcC. Yeah, what intrigues me is how many testimonies I've read, ppl claim they may be able to tell a difference with the 100uF film caps, or they think there might be a small difference for the better. Conversely, as I said in the post above, the 470uF cap is no small difference.
 
However, it was clear to the others that the caps were used as the outputs, not in the power supply.
 
Can anyone explain this? What's the problem?

 

[larcenasb]

Hi Doc!
 
I think ppl were hinting at it being bad but I don't understand; why? Can you then verify that it is indeed okay to use the 470uF output caps?
 
Remember too that my AKG K612s are 120ohms, so I'm trying to tailor the amp better toward them.
 
Thanks.

 

[GrindingThud]

It's not bad.... Bigger lowers the frequency cutoff:
http://www.sengpielaudio.com/calculator-RCpad.htm
Rule of thumb is 10:1 keeps the phase even (set the cap for ~2Hz). 470uf is close enough, many manufactures use that value.

 

[JamieMcC]

  Thanks JamieMcC. Yeah, what intrigues me is how many testimonies I've read, ppl claim they may be able to tell a difference with the 100uF film caps, or they think there might be a small difference for the better. Conversely, as I said in the post above, the 470uF cap is no small difference.
 
However, it was clear to the others that the caps were used as the outputs, not in the power supply.
 
Can anyone explain this? What's the problem?

 
Differences in perception are I would think very much source tube and phone dependent some tubes and phone combinations just don't have the ability to be resolving enough for the differences in component swapping to become noticeable. I bet you could get a couple of dozen Crack users together and the odds would be pretty good they would all be using different combinations of tubes, phones, caps, attenuators. Listening with say the DT 770 to a stock crack is a very different experience to listening to tricked out Crack with a flagship headphone there is no comparison. As much as I like my HD650 they can not hold a candle to the T1's when it comes to resolving such details.

Having tried a number of combinations of film output caps of varying values the lowest was 47uf and highest has been 210uf some configurations are clearly personally preferable to me than others. My own personal preference funnily enough are not audio rated caps. Generally I find the differences between capacitors extremely difficult to make out if your listening to fast of busy music. As I listen to mostly acoustic and vocally led music myself the differences in textures and tone I find to be more noticeable with acapella recordings. 
 
Most probably one of the Cracks greatest strengths is its adaptability to suit the personal tastes of who ever is listening and that's what really matters what works for you..  
 
There was a brief discussion on one of the BHF threads recently about substituting the 220uf caps in the power supply with much larger ones and may have got my wires crossed.

 

[JamieMcC]

It's not bad.... Bigger lowers the frequency cutoff:
http://www.sengpielaudio.com/calculator-RCpad.htm
Rule of thumb is 10:1 keeps the phase even (set the cap for ~2Hz). 470uf is close enough, many manufactures use that value.

 
There is a chart around which combines the cut off with the impedance of the phones being used, I read it as the higher the impedance of phones used the lower the uf value required for the same frequency cut off.
 
Edit

 

[larcenasb]

Thank you GrindingThud & JamieMcC. I feel much more at ease now happy listeninggggggg!

 

[Jimmy24]

How does the Bottlehead Crack + Speedball compare in sound with the O2 + ODAC? I'm about to upgrade my amp/dac for my Senn HD 650's but I was wondering for those of you that have heard both amp/dac combos, I'd like to know if it's worth the upgrade? Thanks!

 

[skeptic]

How does the Bottlehead Crack + Speedball compare in sound with the O2 + ODAC? I'm about to upgrade my amp/dac for my Senn HD 650's but I was wondering for those of you that have heard both amp/dac combos, I'd like to know if it's worth the upgrade? Thanks!

The crack with speedball will be a big change and a major improvement in listening enjoyment with hd650s if your ears are anything like mine. I actually like my agdr boosted o2 quite well with alpha dogs and other fostex t50rp variants. It is also pretty good with dt880s since they have kind of a diffuse presentation and the o2 helps to focus them and give them a nice impactful, albeit slightly lean sound. But hd650s are already very coherent sounding headphones as far as instrument separation, and the o2 just makes them sound compressed and rather unremarkable in comparison. Timbre also takes a big hit.

Plug into a crack and you will immediately understand the hype. It is just an excellent pairing that brings out the 650s soundstage, yields rich full lifelike timbre, and draws you right into the music. It is not a slow tubey sound like the woo otls. It is a punchy, dynamic involving match which will also hit harder and provide more substance in the bass than your o2, although at the cost of some bass tightness (which you will not miss in the least on balance). Building the kit and getting to participate in the extended bottlehead community is also extremely rewarding and is a big part of what has kept me interested and active on headfi for all these years. Plus, as Doc always says, it really does sound better when you build it yourself.