Listen for yourself. I’ve been sorely disappointed by some high-profile vintage tubes. Mine were either seriously worn or I heard them differently than others. Vintage involves a lot of unknowns and variability, and the supply has been picked over for a long time. You are in competition with the electric guitar amplifier and speaker markets – both of which tend to use a lot more tubes per amp than headphone amps. The nice thing about the Crack is that you only need singles rather than matched pairs. Singles are much easier to find and often cheaper too, while matched pairs may not actually ‘match.’
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Thanks for the link. I don’t own the Bottlehead Crack but I do run one of the listed under “sort-of-drop-in” which is the 12BH7A. Mine is an RCA 12BH7A variant that sounds quiet syrupy. I did not enjoy it at all at first when I only owned cheaper headphones. However, after acquiring better headphones (my ZMF Aeolus) I finally appreciate what this tube can do. It has risen to the top as one of my favorites along with a few other 12AU7 tubes. So, perhaps one might look into what upgrades are necessary to allow 12BH7A to play in their Bottlehead Crack in order to open up possibilities of other families of tubes.
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Clear Top tube arrived about an hour ago. Oh, yeah this is much better!
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Nice to hear! The RCA clear top is hard to beat for the value. The crack responds very well to tube rolling as you’re noticing and can transform from super warm / gooey sound to fairly tight and detailed (tho not to the level of SS) with the right tubes. I definitely would not make a final determination on how the amp sounds based on stock tubes and encourage at least a few different quality power / driver tubes to get a sense of how each tube influences the sound. Synergy between power and driver tubes is a big thing. Sometimes a driver tube will sound fantastic with one power tube, but meh with another (and vice versa).
Some good lower cost power tubes that would probably be an upgrade over stock are the Chatham/Tung-Sol 6AS7G or Chatham/Tung-Sol 6080(WA) - don’t pay more than $50 for either. Tung-Sol 5998 have some of the best clarity but are also skyrocketing in price/scarcity, but worth trying if you can find a single for ~$100. GEC 6080 is another great tube and while expensive NOS, you can get some great prices on used tubes that still sound great if you’re patient.
If you’re open to more adapters, I’m a huge fan of the 6J5/6C5/L63 single triode families running as pairs for driver replacements. A pair of 6J5 is electrically equivalent to a single 6SN7 so I do believe you need speedball (disclaimer)… They’ve gotten more expensive but still a fair bit cheaper for NOS than top-tier 6SN7 and 12AU7.
These GEC L63 are top notch for clarity and detail. Available NOS here: L63 CV1067 GEC KB/Z NOS VALVE TUBE - Langrex
The Brimar 6J5G (also NOS available through Langrex) are a great alternative with a little more warmth but still great detail.
Have fun!
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I seriously don’t understand how the 6XX has soundstage now.
The Clear Top tube basically solved all my problems with the Crack. Combined with the Custom Cans mod (with the “m” foam), this now sounds better (to my tastes at least) than cans and rigs I’ve heard that cost thousands of dollars. Holy shit.
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Welcome to synergy and harmonic distortion. I always have trouble justifying my later purchases after revisiting the HD600.
Sound is not a very complex physical or biological process (e.g., versus vision). We’ve been able to record and reproduce high quality sound since ~1930 to ~1960 so it’s quite mature technology.
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I’ve tried lots of tubes in my BHCs, and for me (who likes the cleaner side of tube sound - the E80CC (w/ Speedball only after a resistor value change)
Generic is quite right about HD/synergy. My favorite SS amps dating back to the 1980’s are those of Nelson Pass who has more HD in his amps than the .000001 jobs. So I like my tubes or tube hybrids on the “clean” side , or my SS on the tubey side.
The thing is, recording techniques are not perfect and fail to pick up many aspects of music (talking live unamplified in great halls), so the idea of say the ASR/stats uber alles crowd that wants the Harmon curve and .00000 distortion (funny how everything outside of FR is given short shrift) can’t give you the best approximation of the performance, and some judicious use of HD does help. Too much smudges the picture too much.
Wow. Read through the whole of this thread. I imported a Crack to the UK I think in 2019? Very bad timing with no sale on and a strong $ so it worked out very expensive. I’ll do a post later on the actual crack but reading through a couple of quick relies (although a bit late for the posters now I guess.
I got a stock GE 6080 and 12AU7. Was nice but not thrilling. I did buy the Svetlana 6H5C/6N13S Coke Bottles from a Ukrainian seller but before they arrived I lucked out on a pair of TS5998 so I never listened to the 6H5C until today. I also compared the stock 6080 as well.
Those 6H5C are quite impressive seeing as the TS5998 is silly price these days selling often in the £200+ mark while the 6H5C is in the £20-£30 range. Leaps ahead of the stock GE6080.
On the input side of things I pair my 5998s with cheap Mazda (Foreign) ECC82. You won’;t find any “grail” posts about them but I love the combination 
On the speedball front I miss the non speedball sound but I still have the speedball setup in there. A mix of laziness and wondering if my memory was longing for something that I would end up wanting to go speedball again Reading a post above about being overwhelmed by the syrupy goodness after long listens does ring a bell with me, however after going speedball I tend not to be drawn to listen anywhere near as much. I will compile something up on my build later. I went mad on the Mods and it was something else entirely a month after I built the stock version.
Shhh, it was my first electrical build. I was excited. I got carried away
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