[larcenasb]

Some impressions on the Bottlehead Crack:
 
http://www.head-fi.org/forum/thread/556480/an-audio-odyssey-ending-w-akg-k601-bottlehead-crack-impressions
 
It may sound like I am not completely for the Crack's sound. But once you read my impressions, I think you will understand my position. So let me just say here, I really am happy w/ the Crack and have no plans to upgrade. I love the Crack's simplicity of design but, more importantly, it reveals to me the magic of my music and that helps keep me sane on a daily basis.

 

[LoweArt]

Quote:

Curiously that is the first time I've heard of a faulty electrolytic cap straight out of the box except for the rare case where it was damaged in shipping. Did it look dented or otherwise damaged? If so, we will adjust the packaging to avoid that in the future. Glad you got the puzzle solved, good work!

It took me a little while to actually find the problem as there was no visible external signs of damage to the capacitor and it was the 1st time that I have ever come across something
like that and I've been a DIY and kit builder for a while. It turned out that the negative axial lead on the cap was moving around inside the body of the cap, never seen that before !

 

[larcenasb]

Has anyone experimented modifying the Bottlehead Crack w/ an external power supply. I'd like to enjoy music at lower levels w/ full, full, full impact. Any advice on this?
 
http://www.amazon.com/review/R9ACSP38KYZ2D/ref=cm_cr_dp_cmt?ie=UTF8&ASIN=B001P6FO5E&nodeID=172282&tag=&linkCode=#wasThisHelpful
 
...the link above gave me the idea. If one can add a PSU like that to a dac, is it possible to do w/ the Crack?

 

[williaty]

Quote:

Has anyone experimented modifying the Bottlehead Crack w/ an external power supply. I'd like to enjoy music at lower levels w/ full, full, full impact. Any advice on this?
 
http://www.amazon.com/review/R9ACSP38KYZ2D/ref=cm_cr_dp_cmt?ie=UTF8&ASIN=B001P6FO5E&nodeID=172282&tag=&linkCode=#wasThisHelpful
 
...the link above gave me the idea. If one can add a PSU like that to a dac, is it possible to do w/ the Crack?

While in theory, something like that would be possible, in practice, it's just not reasonable to do. First, many of the things inside the Crack take SUBSTANTIALLY different voltages. The power supply built into it takes care of this. It's not set up to be fed from a single DC voltage level at all. Second, the power supply in Bottlehead kits is almost always VERY good. They don't screw around with that kind of stuff. So finding a power supply that's actually better than the one you build is going to be a hard (though possible) task.
 
The most common way of improving the power supply, if you really feel you have to, is to move the power circuit from the main kit into its own enclosure to facilitate the use of chokes, bigger caps, etc. However, to do this, you're on your own and better have a very good understanding of electrical engineering and how the Crack's circuits operate.
 
If you want to substantially improve the Crack, just add the Speedball. My Crack and Speedball are still in the mail, but the Speedball is the same basic kind of circuit as the Anticipation in the original Foreplay 1 and 2. Having built that myself, the circuit upgrade WORKS.
 
 

 

[Armaegis]

Um... not really. You wouldn't use an external power supply with the Crack unless you're doing some very heavy duty modding. You could use a power conditioner though.
 
In that link, the user replaced a wallwart (which I'm guessing was a simple AC->DC converter) with a higher quality AC->DC converter. The Crack doesn't have a wallwart, and instead feeds AC directly into it's own custom made transformer. You gotta have some pretty good DIY chops if you're going to replace their transformer with something else.

 

[larcenasb]

Thanks Williaty & Armaegis -- I am grateful for your responses.
 
Yes, I just didn't have an understanding of why that wouldn't work.
 
I have a new idea though! What are the possibilities of using two Cracks in a balanced mode? First getting Moon-Audio's balanced XLR cable upgrade, and then buying two XLR female to 1/4 male adapters (pictures below). What do you guys think would be the resulting sound of doing that? More power? Thank you very much for your time.
 
 


 

 

[BmWr75]

The Crack amp is OTL, which does not work well with low impedance cans like your AKGs.

 

[Doc B.]

 
Quote:

Has anyone experimented modifying the Bottlehead Crack w/ an external power supply. I'd like to enjoy music at lower levels w/ full, full, full impact. Any advice on this?
 
http://www.amazon.com/review/R9ACSP38KYZ2D/ref=cm_cr_dp_cmt?ie=UTF8&ASIN=B001P6FO5E&nodeID=172282&tag=&linkCode=#wasThisHelpful
 
...the link above gave me the idea. If one can add a PSU like that to a dac, is it possible to do w/ the Crack?

The poster suggesting that the 62 ohm headphones you are using might not be the best match probably has the most plausible explanation, since the Crack is designed to run headphones over 120 ohms impedance and specifically to be optimal with those in the 300 to 600 ohm range. It could also be that the output level of your source is a bit low with respect to the gain structure of the Crack. The stock power supply is actually overkill, we use the same setup in an amp that puts out 2 watts per channel. We are working on a new kit called Smack that will have transformer output with taps at 16/32/64/128 ohms and the ability to be wired for balanced output at at least one of those impedances. It should prove to be more appropriate for lower impedance headphones that the Crack amp was not designed to use, like the K701. At this point your best bet might be to replace the 6080 with a 5998 which will lower the output impedance to around 70 ohms.

 

[Armaegis]

Quote:

I have a new idea though! What are the possibilities of using two Cracks in a balanced mode? First getting Moon-Audio's balanced XLR cable upgrade, and then buying two XLR female to 1/4 male adapters (pictures below). What do you guys think would be the resulting sound of doing that? More power? Thank you very much for your time.
 
 
 
 

Should be doable. I've been wanting to try that myself actually.
 

 

[larcenasb]

I'm sorry, I only posted the picture of the K701 'cause that's the only one moon-audio had w/ the balanced cabling. I have the K601, 120 ohms. I am in fact using a Tung-Sol 5998 tube, is that not the ideal match for my headphones? Should I use a 6AS7/6080? Thanks so much for your time.

 

[Beefy]

Frankly, the whole amp isn't the best match for your headphones, even with the 5998. Your damping factor is only just above 1, which isn't enough to grab the driver by the cojones.
 
Some people are happy with the Crack on lower impedance phones like the K601, but the higher the better IMHO.
 
Quote:

I'm sorry, I only posted the picture of the K701 'cause that's the only one moon-audio had w/ the balanced cabling. I have the K601, 120 ohms. I am in fact using a Tung-Sol 5998 tube, is that not the ideal match for my headphones? Should I use a 6AS7/6080? Thanks so much for your time.

 

[Doc B.]

5998 will be the best choice. When you say you want low levels with full impact I must admit that I was a bit confused. I wasn't really clear if you meant the amp isn't playing loud enough (low levels) or if you meant the headphones are lacking low frequency punch. Presumably you mean the latter. I have found the K601s and K701s kinda bass light in general, and I'm not sure I have much to offer in terms of improving that beyond installing the Speedball upgrade if you have not already done so. It does tighten up the bass over the stock configuration.

 

[larcenasb]

Ha! I'm sorry, I really should be more clear! I'm actually very happy w/ the bass performance through the Crack. I meant at low volume levels, I would love to be able to hear the same impact as with higher volume levels -- would it still be called "headroom" like w/ speakers? I'm thinking of getting Beyerdynamic DT 880s 600 ohms; would the higher impedance yield the powerful sound @ any volume level that I'm looking for? Thanks so much Doc for being so responsive.

 

[Doc B.]

I think maybe we are talking about the overall dynamic range. To put it a bit converse to the way you are stating it, the quiet parts aren't quiet enough for you when you have the volume turned up to where you like the transient peaks. For what it's worth I haven't heard a complaint about the Crack being compressed sounding. The only real complaints have been about flabby bass when using the Crack with low impedance headphones, and that is certainly logical given the nature of the circuit. That said, headphones all behave a little differently and I haven't logged much time with the AKGs so I can't speak very intelligently about that exact setup. My SWAG is this could be a case of compression from the source rather than compression at the headphone amp or headphones. Before you change headphones you might experiment with different music and, if possible, different front end gear and see if the problem changes character at all.

 

[tdogzthmn]

 
Quote:

Ha! I'm sorry, I really should be more clear! I'm actually very happy w/ the bass performance through the Crack. I meant at low volume levels, I would love to be able to hear the same impact as with higher volume levels -- would it still be called "headroom" like w/ speakers? I'm thinking of getting Beyerdynamic DT 880s 600 ohms; would the higher impedance yield the powerful sound @ any volume level that I'm looking for? Thanks so much Doc for being so responsive.

 
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I own a K500 (120ohm) and a HD600 (300ohm)  and my crack is running a 5998 with speedball.  Listening between these two cans , I can definitely hear more control and precision with the HD600.  I can also say that you will get "more" sound at lower volumes with higher impedance cans.  I always have to turn the volume up a good amount when switching from the HD600 to the K500.  Hope my experiences can help with your decision.
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