I really want a Crack but the import costs plus the lack of free time to build it means I would end up having a bunch of money in boxes for a long time.
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Oh man, been tempted to see what the hype is about. Like others have said though, would probably stay in the box for a long time till I got around to it. Plus, I’ve never soldered in my life which makes me that much more hesitant
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I prefer to think that this hobby is more rewarding when we pursue experiences. Like going to meets and canjams, meeting the people behind the gear, learning about how the gear works, etc.
The crack is still one of my favorite amps because of the experience I had building it and the information I learned doing so.
I know there are plenty of people on the forum who have built a Crack and started off with no background in diy or soldering too; many of whom would be more than happy to help, including myself. Don’t let it be a barrier. 
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Hear hear!
(I refreshed my nearly non-existent solder skills with a $10 learn to solder kit for Amazon prior to successful making my crack tubes glow purty. The kits’s manual and forum make it a very achievable project for a first timer )
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Thanks. I appreciate the encouragement. I’ll read back and see what people mention but any suggestions for an iron or other required tools. I remember some mention of Hakka?(or something like that) in a thread. Also, is the power cord upgrade worth getting?
Think I might give it a whirl
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The hakko is sweet (and overkill, I like tools…. a lot). Make sure to use the pull down to other buying choices and get it from Ness. They are an authorized distributer and you will not get a cheap knock off.
I did the power cord. I wouldn’t again. In general I don’t believe in cord magic though.
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Here are some of the items I bought when I decided to build my Crack:
Soldering iron:
Helping hands:
Solder sucker and copper wick:
Workspace mat (this item has actually been really useful):
Solder: (You don’t need a full pound of this stuff, but you’ll probably never run out if that’s what you get.)
Heat clips:. (useful to keep components from melting, like wire sleeving)
Multimeter (with alligator clips, so handy):
Or
Pliers:
And that’s pretty much everything you need. Nothing there is super high-end, but it all works.
If you don’t mind spending a little more, these items will probably last longer and maybe be better quality…
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The cool thing about having all of those tools available, you can easily make your own headphone and interconnect cables.
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Awesome, thanks for taking the time putting that together. True about cables,too…I have been thinking about trying it. I use 3 meter HP cables, be nice to make my own.
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I haven’t gotten around to trying a tube amp, but I’ve always planned to eventually. The sale has me thinking the time might be now. I’ve heard great things about the Crack here from members I trust and building it would be part of the fun. However the only high impedance headphones I own are the Beyerdynamic DT 880 and the Hifiman HE6se. I’m kinda meh about the DT 880 and I’ve read that planar are not a good match. My daily are the Focal Clear.
Is this a good choice for a first time OTL buyer to try with the Clear? Or should I start with something like a Schiit Lyr or Vali first?
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Get an HD-6XX or HD-600 for OTL. Clear is very low impedance for OTL – bass will bloat.
Lyr and Vali are tube hybrids and work with most headphones.
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I didn’t find the HD-6XX I tried to be comfortable enough for a typical listening session. I guess I’ll put the money somewhere else for the time being.
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The Lyr and Vali will be fine with the Clear. They use solid state parts for amplification and tubes for ‘tube character.’ I use a Lyr 3 with my Clear.
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Sale is live…. Count was 37 left when I ordered mine. (They only have 50 available on sale)
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I thought long and hard, and then caved in and ordered one too. I’ve completed harder projects from scratch in the past, and projects without any instruction manual at all. Plus, the Crack is a de facto benchmark OTL headphone amp.
Thanks @mfadio for the sale offer – see the ‘building it yourself is more rewarding’ comments from @ProfFalkin, plus similar past comments from @TylersEclectic and others. I’ll likely spend more time on wood and metal finishing than on the functional wiring. I’ll probably add a hidden mechanism to keep the top fixed in place too.
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MODERATOR: Please move to a tube/Crack thread.
My Crack is still in the mail, so I’ve been researching build and setup options. I expect to spend up to a month or two on the build before using it (wood finishing can be painfully slow with dry times).
Stream of consciousness here:
One of the Crack’s standard tubes is a 12AU7. These are “a dime a dozen” and I have about a dozen that I bought for a prior amp. With that amp, the most obvious changes were associated with the metal mass inside the tube. They come in “short plate” and “long plate” versions. The short ones were routinely brighter while the long ones were bassy. The factory tube and my first aftermarket tube were both short plate, so there wasn’t much change and I wasn’t impressed. I restarted tube rolling later with different internal designs.
Beyond tone, some tubes are very resonant/harmonic/fuzzy while others are cleaner. This property varies even within specimens of the same model/brand. Some vintage tubes sound like cr*p too. Worn out, flat, and lifeless, with weird whines and artifacts. YMMV, but don’t be shocked in the vintage market. Don’t trust “New Old Stock” or NOS marketing either, as sellers sometimes don’t understand that Not Used By Me <> New. The inventory of old tubes is dwindling too.
I’ve never owned or rolled a Crack, so…we’ll see… [Insert body anatomy jokes HERE.]
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(@Audiophool replying in the crack thread)
Both the power and driver tubes in the crack can have a large impact on the sound. Synergy between the two tubes is a big factor, which is part of what makes tube rolling such a rabbit hole (and oh so much fun!). Some people swear that one power tube is the best and stick with it. Personally I find half the fun in trying new combinations and finding one that makes your ears smile. Here’s been my experience with ~2 years of tube rolling in the crack:
Power tubes
The crack’s power tube options are fairly limited and straightforward. If you want to go straight to the “best”, the top tubes to have in your stable would be:
- Bendix 6080WB (Sometimes branded Tung-Sol and Chatham)
- Chatham 6AS7G (Sometimes branded Tung-Sol)
- Tung-Sol 5998 (similar to Western Electric 421a, which is said to be slightly better but nearly unobtainable)
- GEC 6080
- Mullard 6080
- GEC 6AS7G (Pretty much unobtainable unless you are willing to spend almost the cost of the amp for a single tube)
And that’s about it. For value-oriented options, the RCA 6AS7G and russian Svetlana 6n13s have good reputations for readily available/cheap options for improving on the air & dynamics of the stock 6080 tubes (I haven’t spent much time with these myself). I’ve tried other 6080 tubes like RCA, Sylvania, etc and they are enjoyable with the right synergy, although are definitely not in the same league as the list above. The Bendix 6080WB and Chatham 6AS7G get about 90% of play time for me and my tastes.
Driver tubes
This is where the rabbit hole gets exponentially deeper. There are several routes you can go, all of which are valid and have their pros/cons:
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12au7 (Stock tube)
Many, many options. You can spend serious $$ on rare collector items i.e. Brimar CV4034, rare Mullard tubes, etc or get pretty good sound out of more budget oriented options. I’ve heard the RCA clear top as a good choice here (have not tried). I have a dozen or so of these and can personally recommend the Sylvania 5814a and Brimar 13d5 for sub $100 tubes. The best sounding tubes I have are also the most expensive (Brimar CV4034 and Amperex 7316 long plate foil d-getter) and are at the top of the tube food chain for holographic staging, detail and timbre.
https://tubemaze.info/ and Brent Jesse’s 12au7 guide are good resources for learning about “house sounds” and impressions. I know @Wes_S has a lot of experience with 12au7. -
6sn7
Another dual-triode tube in a larger envelope. The 6sn7 territory has been well explored for many years in the audio world and there are endless threads and debates on which are the best. Many people swear they are superior sounding to the 12au7, but many others say the opposite (looking at you @Wes_S
). Some common recommendations are Tung-Sol BGRP, Ken-Rad VT-231, Melz 1578, RCA, etc… Personally I have not explored this route as I went with the next family of tubes… -
6j5 (6j5g/6c5/6c5g/L63)
These are single triode tubes so each tube is electricallly 1/2 of a 6sn7. The main downside is you need a fairly larger adapter tower (Deyan on head-fi makes the best) to run 2x 6j5 style tubes in the 12au7 socket. Getting more popular, but still relatively cheap and readily available. Folks I trust that have done back-to-back comparisons with their 6sn7 counterparts say they sound superior (i.e. 2x Tung-Sol 6J5G sounds similar to a Tung-Sol 6SN7 BGRP but with better instrument separation for half the price). The wild-guess theory is that having the two triodes in separate envelopes provides some kind of benefit… but who knows. I have had good experience with many pairs of relatively inexpensive tubes here that sound as good as (or better than) the top 12au7 I have: Tung-Sol 6J5G, Brimar 6C5G & 6J5G, GEC L63 (also Marconi, Osram), Fivre 6C5G, Ken-Rad 6J5G are among the best… That being said, there are some VERY inexpensive tubes, such as the ugly $5 metal jacket RCA or Ken-Rad 6J5/6C5 tube that sound 90-95% as good. I have some rusty pairs that I got for $10 shipped that sound glorious. There are also glass “GT” shape tubes that can usually be had for cheaper than their ST counter parts and from my experience sound the same.
My recommendation for which route you choose to go down depends on your existing gear/tube collection, willingness to run adapters, and plans for the future. For example, the Pendant can run 12au7 tubes. Many amps run 6sn7. The next custom OTL I am getting will run 2x 6J5 natively, so this route made the most sense to me. Hope this helps!
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@Audiophool Just a couple of things to add to @raindownthunda’s excellent reply…
I don’t have a Crack, so I can only talk about 12au7 tubes in general, since I use them in my Pendant and Nautilus, and have learned a lot from @Wes_S and other forum experts.
If you want some bedtime reading, here’s 158 pages of Crack tube rolling advice. I believe the guy who runs Tube Maze is a regular contributor in that thread.
I’d recommend getting some cheap tubes to start with, until you figure out the sound profile you like. You can come back here with what you like about the tube, what you want more of (e.g. more bass) and what you want less of (e.g. less bright), and then people can give you recommendations on what else to try. Once you’ve narrowed down what your preferred sound profile is, you can choose to pay the big bucks, or not.
Since we all have different sonic preferences, statements like “this tube is great” are not very helpful, but if you have a baseline, and can understand how another tube can boost or reduce certain frequencies relative to that, that’s far more helpful. I happen to like fairly neutral 12au7’s with some extra warmth in the mids, so I’ve gravitated towards the TOTL Amperex and Brimar tubes that @raindownthunda mentioned.
When I started out, my favorite $20 12au7 was the yellow label Baldwin, made by Raytheon, which has the warmth that I like (and you may hate LOL). There is also a green label Baldwin 12au7, made by Sylvania, which loses the warmth, and made my tube amp sound like solid state. I found Mullard to have wonderful warm mids and bass, but the highs were too rolled off for me, and at the other end of the spectrum, I found that Mazda was a little too bright for my taste. But my bright might be your neutral.
You might find this chart helpful.
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From my experience with 6SN7 in the Crack, I thought there were just a few things I think should be mentioned.
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They sound close enough that I disagree that one sounds better than the other. Subjectively, a specific 12au7 might sound better than a specific 6sn7 for your subjective preferences, or vice versa, but I doubt enough subjective testing has been done with the hundreds of tubes available in each type to say with 100% subjective certainty that one is subjectively better than another. Subjectively. (Did I mention it’s subjective?)
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I haven’t dug into the facts on this, but I believe some issues have arisen from running the 6SN7 on a Crack without the speedball. Something about the wire wound resistors? Dunno.
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There are some amazingly bad adapters for sale out there. Incorrect pin outs, bridged pins due to sloppy soldering, sockets that crack or split, etc. Be careful.
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It’s my opinion that all of the highly recommended NOS 6sn7 tubes are gone. Finding any that are verifiably NEW old stock just doesn’t happen anymore. It may test new, but it doesn’t mean it is new. NOS also seems to be a term that ebay sellers use indiscriminately and falsely. Anyway, my point is that the 6sn7 market is a price-inflated minefield I’d rather not hazard navigating.
So, basically, I’d argue the 6SN7 juice isn’t worth the squeeze. Probably the same with the 6J5 + wonky adapter stuff too, but I haven’t tried them myself.
I figured I’d mention that I’ve been using this input tube in mine for quite a while now and it’s pretty stinking good. (They might be running out of these - they were $85 nos when I got my mine.)
As far as power tubes go, I forget which specific one I have in there now (I’m not at home), but the best one for my setup was not a super rare and expensive tube. Focus on power tubes last, imo. I think the input tube matters more for setting the overall flavor of sound. They do work together as a team here, so as mentioned, a synergistic pairing helps but can be dialed in after the input tube is chosen.
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Wow, thanks everyone for all the information and advice. Quite a wealth of knowledge here. I’ve bookmarked and I’m sure I will be referencing this many times in the future. I really appreciate everyone taking the time to post.
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