Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Crack-a-two-a => Topic started by: Doc B. on August 04, 2015, 09:41:58 AM
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We've been discussing for some time what we would do to improve the Crack circuit if we had more real estate and a little bit bigger budget. PB has been building and testing various ideas over the past few years and this summer we decided it was time to pick the best bits from those experiments and combine them with some other tricks we have developed for other kits along the way.
One big consideration was that this kit was to fit between the Crack and the Mainline in terms of price. We wanted to keep the price below $700. Yes, the S.E.X. kit fits in that price range, but there seems to be a devout following of high impedance headphone specific OTL amps that we wanted to address, and thus this alternative offering. With that in mind we decided that the biggest benefits would be from a more sophisticated power supply and the ability to upgrade to our very special stepped attenuator as used in BeePre (and in a slightly different form in Mainline). We also know that our customers like to have multiple switched inputs, so we include three.
And so Crack-a-two-a is a premium version of the direct coupled Crack circuit, with the C4S active loads of the Speedball incorporated and also shunt voltage regulation in the form of two 6AQ5 tubes along with a bigger power transformer. There are three pairs of RCA input jacks and a volume and balance control. The standard potentiometer controlled volume/balance setup will be upgrade-able to a coarse and fine stepped attenuator very similar to the BeeQuiet attenuator used in the BeePre preamp and a similar style used in our most premium Mainline headphone amp. Like Crack this amp is intended to be used with high impedance headphones (200 ohms or higher) like Sennheiser HD600/650/800, Beyerdynamic 250 and 600 ohms headphones, etc.
The chassis is twice as big as the Crack chassis and along with fitting in the extra inputs, shunt regs and attenuator components there is plenty of space for those humongous output coupling caps everyone wants to add to their build.
Crack-a-two-a sonics? Compared to the Crack the shunt regulation gives a slightly more quiet background and a sense of better bandwidth and control. The balance control allows one to compensate for the tolerance variations in the volume pot that create imbalance at low volume settings in some Crack builds. Upgrading to the stepped attenuator is as big an improvement in the OTL circuit as we have found it to be in all of our other circuits that incorporate it - the presentation is more resolved and more natural, particularly vocals.
This kit doesn't replace Crack in the lineup. Crack is just too great a value for the dollar to let it go. The intent here is to offer a higher level of performance potential than one could ever squeeze into the Crack chassis or price point, while keeping well below the cost of the more premium Mainline kit. With this in mind the introductory price will be $599 with the stock volume and balance pot configuration. The attenuator upgrade will come out in the future and will be priced similar to those offered for our other kits. Life is not interesting without many choices, and this is another really interesting one.
Here's a link to the new web page in our online store:
http://bottlehead.com/product/crack-a-two-a/ (http://bottlehead.com/product/crack-a-two-a/)
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Ooo....I want this. I have a feeling this will be my next kit.
Great looking kit. I love the symmetry of the layout.
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It is beautiful!
Bottlehead envy...
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It is beautiful!
Bottlehead envy...
As in, your Bottlehead's bigger than mine?
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Dear Doc,
Thank you so much for your "guidance" and recommendation. I'm very excited about the Crack-a-two-a. I think the Crack-a-two-a really "fits" the gap between the Crack and the Mainline perfectly.
But for those who already had highly-modded Crack (premium tubes, big capacitors, nice stepped attenuator, good RCA jacks and many other upgrades) which cost them nearly as much as a Mainline does, how would you recommend them? Get a Crack-a-two-a or go ahead and get a Mainline?
One minor thing that makes me a bit confused, if the price for a Crack-a-two-a is ~$600 and the Crack-a-two-a is highly upgradeable , then I'm afraid the cost for a modded Crack-a-two-a can be over the cost for a Mainline.
Otherwise, great idea, Doc! I'm eagerly looking forward to hearing more news about this upcoming Crack soon!
Best regards,
Kratos.
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I'm not sure highly upgrade-able is my wording or even my implication. The Crack-a-two-a will be $699 after the intro pricing. With the attenuator upgrade it will still be under $1000. That is the only upgrade I have mentioned, all the other cool stuff like the shunt regs and multiple inputs is already in the kit. And that $1000 price with the upgrade is well under the price of the Mainline with its more expensive tubes, output transformers that allow it to run headphones of any impedance, and switchable balanced/single ended output.
As to other mods we have no control over what people might decide to mod their Crack kits with, including spending lots of money modding it with expensive caps or wire or fuses. Builders will do that same kind of stuff to any kit, so I think our consideration of the cost of mods beyond those that we we offer is rather irrelevant. Our focus is to make different kits with different levels of circuit sophistication. Throwing boutique parts at something will not make the circuit better than a more sophisticated one. A stock Mainline will still be a more refined design than a Crack with $300 Teflon caps, silver wire, a Gold point attenuator and a filter choke.
In terms of what to buy, I think one should buy what one can afford. That is precisely why we are trying to place a kit between the Crack and the Mainline. If you can afford Mainline, it's the best. If buying it is an unreasonable stretch on the budget, Crack-a-two-a will be next best. If that isn't affordable Crack has a zillion raves all over the internet. There's also a chance someone else will say this is all wrong. To each his own.
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....aaand ordered! Can't wait. :)
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Woo Hoo! Thank you Stan and Nick for getting this baby rolling!
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Thanks! Looking forward to a new project!
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Just as I was considering building my Crack into a Mainline sized enclosure this comes along...
Any chance we can get some shots of the underside?
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We're waiting for the output caps that we will supply with the kit, as right now we have some different ones under there. Once those are in I will take a photo of the underside.
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will the heater be hefty enough to roll in some 5 amp tubes?
michael
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If history is a reliable indicator this will be another legend. Congrats and keep up the great work. For the modders it's a bigger case, for the budget-minded it's already beefed-up, and for everyone else it's a BH amp. 'nuff said.
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will the heater be hefty enough to roll in some 5 amp tubes?
michael
Nope.
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Dang you Doc!!
Just after building the crack which I really, really LIKE....OMG!
Well now I know what I want for Christmas!!!
Alex
(Big Smile!)
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I should also mention that all pre-orders will ship with old stock European 12AU7's.
-PB
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Is there a 240v version cos i cant seem to find that option which the crack has?
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Is there a 240v version cos i cant seem to find that option which the crack has?
I expect it uses the new universal power transformer (as used in the Seductor), which offers all voltages.
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Yes, the power transformer is a universal one.
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Thats awesome ... recently just completed modding my crack and this popped up .... feeling really in a dilemma to whether i should give this a pass and get the mainline which i'm close to buying already .... really love how it looks with the additional 2 shunt voltage regulator tubes. It is for sure looking really sexy if you ask me. Argh!!!! so confused right now. What would you recommend ?
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As I mentioned when asked this recently, if budget allows Mainline is our best amp. If the budget is not quite there and you are interested in an amp specifically for high impedance headphones Crack-a-two-a is a less expensive alternative that is a step up from the Crack kit.
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Hey Doc,
How would this compare to the SEX Amp as a headphone amp (usually w/ Sennheiser HD-600's)?
thanks,
David
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I'd put the Crack-a-two-a a bit ahead of the S.E.X. for HD 600s. The S.E.X. is great with them too, but the shunt regulation in Ca2a really does a nice thing for vocals.
On the other hand S.E.X. will also work great with Audezes and other lower impedance planars and dynamics as well as efficient and near field speakers.
Depends a bit upon how you weigh versatility vs. performance for a specific application.
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Will we be able to modify this to accept a 6SN7 like the Crack?
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Will we be able to modify this to accept a 6SN7 like the Crack?
Yes, you'll still need to punch out the hole in the chassis (the bigger of the 2 punches available at your local hardware store ought to work), but there is actually a bit more room for everything, so the octal socket should be easier to install.
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Hi Doc,
I just sold my highly-modded Crack yesterday and is planning to get another amp soon. My budget is somewhere ~$1000, but I can wait and save a bit more to get a Mainline.
I'm using a HD650 and HD800 and frankly, I don't plan to buy ANY other headphone (I've heard as well as owned various premium headphones and now I've settled to the Senns).
Between the Crack-a-two-a and the Mainline, what would you recommend me for using JUST for my Senns (i.e. HD650, HD800)? I don't plan to use my next amp to drive other headphones.
Best regards,
Kratos.
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As I mentioned when asked this recently, if budget allows Mainline is our best amp. If the budget is not quite there and you are interested in an amp specifically for high impedance headphones Crack-a-two-a is a less expensive alternative that is a step up from the Crack kit.
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As I mentioned when asked this recently, if budget allows Mainline is our best amp. If the budget is not quite there and you are interested in an amp specifically for high impedance headphones Crack-a-two-a is a less expensive alternative that is a step up from the Crack kit.
Thanks for the clear answer. I guess I'm gonna save for a while and get a Mainline soon!
Cheers.
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Dang. I sat on selling my modded Crack too long. ::)
But thanks for finally offering a solution to the Cracks power supply. It's been the weak point of the Crack for a while now, there's only so much you can do with the stock Crack power supply on the AC and DC sides.... in the space provided.
Nice looking amp. I think it will look even better with an ST bottle on there!
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hello all
I'm interested in the new amp and have couple questions ... and sorry i don't know much about this stuff !, I have a crack amp with hd600 connected to my high end PC with a creative ZxR soundcard and really like it :) and was think of rebuilding it soon but may change my mind
Does having the exrta 2 tubes 6AQ5 affect the tube rolling on the new crack? .. will it be the same any different, I liked the way the 5998 changed the sound and wish to use these.
with changing the tubes on the normal crack really changed the sound for me, / i was thinking with these other new tubes the crack tube rolling may be different , sorry I don't know alot with this stuff guys.
Also can you change the 6AQ5 for different types and makes? , will this change the sound as well?
one of the biggest things I'm concerned about is interference noise pickup from computers and stuff? does the extra tubes effect the amp near computers ? My crack about 1 foot away from my computer but its dead silent, I can turn the amp up near full wack with no music and only then only hear a little noise (the last 1 cm of volume travel and thats blown up headphones loud and no hearing! shes perfect ....shes quiet as a mouse with good tubes)
so I'm worried about this with new amps near my pc I read valve amps can pick up noise , more chance of this happening with new amp design? :-*
also does the new amp have loads power like the normal crack
is the bass any different. I'd plug in a 5998 and work ok
I listen to my music loud and hope it has lotsof big power and can go loud
Guys does the mainline amp have bigger bass fatter bass with hd600 than the old crack speedball and 5998 tube // using high impedance headphones ?
When I installed the 5998 on my crack speedball I got a bigger sound better bass and it was less harsh with my hd600s smother sound darker sound I think you call it..
sounds awesome with my italo disco 8) 8) it thumps
Im not really interested in analyzing my music I like a rhythmic musical tubey sound, warm detailed
How does the new amps volume control and balance work ...... is it like a normal amplifiers left and right balance .... does the upgrade change this? / course and fine I dont understand it anyone have a link to explain how it works ? i will look up later but its late tonight sleep soon
I've read a little about stepped attenuator but still dont understand it ..... difference with a shunt course fine , I may build my own stepped attenuator one day for my crack but have to learn it carbon film resistors and things
I have no problems with my cracks channel balance though still use the standard pot :P
I was even thinking of buying one but with the money I could be put towards this new amp plus I always wished i painted my top plate and was think of adding a choke soon never got round to that, and fancy building an amp again as I enjoyed building the crack
finally does the upgrade part the stepped attenuator come with a black top plate like the mainline? with writing dials,
if so will it look like the mainline design or like beequiet and others , the mainlines top plate looks nice
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Does having the exrta 2 tubes 6AQ5 affect the tube rolling on the new crack? .. will it be the same any different, I liked the way the 5998 changed the sound and wish to use these.
The 6AQ5 is audible, though significantly less so than the 6080 and 12AU7.
one of the biggest things I'm concerned about is interference noise pickup from computers and stuff? does the extra tubes effect the amp near computers ?
There is additional shielding employed, which should improve this over the normal Crack.
also does the new amp have loads power like the normal crack
is the bass any different. I'd plug in a 5998 and work ok
Power output will be identical, but with the regulated power supply, bass definition is significantly improved.
Guys does the mainline amp have bigger bass fatter bass with hd600 than the old crack speedball and 5998 tube // using high impedance headphones ?
I would not say that the Mainline has fatter bass. It is very resolved, with very tight, well defined bass.
How does the new amps volume control and balance work ...... is it like a normal amplifiers left and right balance .... does the upgrade change this? / course and fine I dont understand it anyone have a link to explain how it works ? i will look up later but its late tonight sleep soon
Yes, the stock amplifier has a level control, and a balance control that function in the familiar fashion. The upgrade has two level controls. One has larger steps in attenuation and the other has smaller steps of attenuation. The two together give many steps of attenuation all with perfect channel balance.
finally does the upgrade part the stepped attenuator come with a black top plate like the mainline? with writing dials,
if so will it look like the mainline design or like beequiet and others , the mainlines top plate looks nice
The upgrade will come with the black plate as found on the BeeQuiet, which makes the operation of the attenuator more intuitive. The Mainline's plate was allowed to be much larger because it is installed during the initial build, which allows it to sit under the headphone jacks. Doing this as an upgrade would require removing components that could otherwise be left alone.
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thank you
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I wonder if there are some more pictures of the new Crack? E.g. the underside of it ;D
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Hey Doc,
I ordered one of these and have been waiting for a while, on your site it says that they will ship late september. Any word on this?
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Josh is home working on
finishing the manual today. Other than that, we [probably] have all the bits and pieces here that we need to get these rolling.
Edited to fix possible factual errors.
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I wonder if there are some more pictures of the new Crack? E.g. the underside of it ;D
Surely someone will find a film cap that won't fit, but we left tons of space!
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Bigger Caps? Are you kidding me? With all that space and the Seattle real estate market, I'll sub-let!
Beautiful layout - love the symmetry!
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Very nice. All sort of room for activities under there.
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Nice looking layout, the main current reg PCB has me curious with all the film caps hanging off it, it looks more like a mainline regulator than a speedball. What are they for? ....figured i would be first to ask, because you just know people are going to wonder if gigantic films will do anything there :)
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Nice looking layout, the main current reg PCB has me curious with all the film caps hanging off it, it looks more like a mainline regulator than a speedball. What are they for? ....figured i would be first to ask, because you just know people are going to wonder if gigantic films will do anything there :)
Yeah, that's certainly a fair question. The large PC boards with big heatsinks are the high current C4S loads. One half of each loads each cathode of the 6080, then the other half is the C4S between the raw and regulated B+ supplies.
The center PC board has the C4S load for the driver tube, and the remaining components for the high voltage shunt regulator. There's a little RC filter at the output to provide some impedance compensation at high frequencies. You sure could mess around with different caps in that position, as they ought to be audible. There is also a 2.2uF cap on each channel that feeds any residual noise on the regulated B+ back into the regulator to make things just that much quieter. I don't believe I would spend much time or money messing around with that cap.
-PB
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Thanks for the explanation. My first thought was that you are a sucker for punishment with all those PCB's to trouble shoot :)
One thing i am not keen on is shield drain wires for the input wiring crossing the output cap leads, i can see people accidentally shorting those out.
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Hi some sweet parts it the kit - good stuff. I'm interested to know why the seemingly fancy hv reg cap Cc? Low value would short hf noise but wouldnt any old cap do?
Second cap -the radial cap 100uF - why the choice and what exactly is a radial cap?
Thanks
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Hi some sweet parts it the kit - good stuff. I'm interested to know why the seemingly fancy hv reg cap Cc? Low value would short hf noise but wouldnt any old cap do?
This does indeed short HF noise to ground, which improves the stability of the TL431 regulator. That film and foil (fancy!) capacitor does a nice job of handling HF noise.
Second cap -the radial cap 100uF - why the choice and what exactly is a radial cap?
I've seen a lot of our Crack customers struggle with how to fit a pair of 100uF coupling caps inside the Crack, so I took great pains with the Crackatwoa to ensure that there were two vast regions on the chassis in which one could install a large variety of 100uF capacitors. To really be helpful in achieving that goal, we added anchors to the chassis that are bolted to the plate so that the weight of those large film caps can be supported by the chassis plate instead of terminal strips.
The 100uF radial (radial has the leads poking the same ends) capacitors are intended to have dimensions that are somewhat similar to a film capacitor, so that swapping caps is quite easy.
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Axial is a cap with a wire poking out of each end (the axes of the cylinder). Radial is like most of our lytic caps, with the wires both at one end of the cylinder so they can be bent (radially) to an attaching point.
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So I own and love my Crack w/Speedball. I think it is amazing with Sennheiser HD600s. What would I notice moving to the Crack -A -Two-A? Also adding the HD800s to the collection.
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Sorry Bob, I just found this. The Cracka2a has a blacker background and a sense of better frequency extension than Crack. I think it is a significant upgrade in terms of resolution. We did an interesting listening session Friday. We had Mainline and a Cracka2a, and a pair of stock HD800s and my Anax modded HD800s. While the Mainline sounded better on my modded 800s and that would be my choice for critical listening, we tended to prefer the Cracka2a when listening with the stock 800s. It didn't have quite the resolution of Mainline, but its more mid and lower mid-centric sound worked well with the brighter stock 800s for casual listening.
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Surely someone will find a film cap that won't fit, but we left tons of space!
Duelund.