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Crack;Bottlehead OTL

Discussion in 'Headphone Amps (full-size)' started by ironbut, Mar 9, 2010.
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  1. gwompki
    Thanks! I will definitely be taking a look at the Briwax approach.
  2. Paladin79
    I may try it out on my next Crack build. I ended up getting one cabinet a little darker than I liked. I will be using a similar design but I want the patinated copper to jump out more on my next build. I have more of this quartered oak and do not want it to go to waste.

    so IMG_1942.JPG
    swmtnbiker likes this.
  3. Voyst
    Hello everyone,

    I have a very newbee question:
    Which of the two tubes has the most influence on the sound signature ? The input (12AU7) or output (6080) tube ?

    I ask that because i have several input and output tubes, and was wondering on which position i should roll first (in order to change only one factor at a time).

    Of my understanding so far, it is the output tube which has the most influence. So I should roll between my 6080s and choose my favourite, and then roll 12AU7s and choose the best combo with my favourite 6080, right ?

    Thank you very much in advance !
  4. attmci
    Most of the people agree that the driver tube has more influence on a crack.
  5. Paladin79
    IMG_2296 (1).JPG Agreed.

    I did a lot of side by side listening and testing, switching back and forth between two stock cracks. It made the most sense to me to do it that way and I did it over a period of time so I could give each combination a good listen but it is not for everyone. I was also fortunate to allow others to listen and give me their feedback but in the end I arrived at tubes that I love but I am doubtful my final selections would match those of other enthusiasts. I strive for a balance between subjective and objective.:)

    You will also find that when buying new or used old stock, the sound and quality can vary between specific brands and builds depending on condition and prior usage. In dealing with old tubes you will find yourself needing to clean the tube pins to insure good contact. There are new, new old stock (if you can believe the seller), and used tubes. Keep your original tubes handy and go back to them when in doubt, they may well be better than some you find on the used market.

    Just remember you cannot improve sound, you can only hope to maintain it and not diminish it.

    Above is the start of my latest build. Try as I might I still like the looks of 1/8 inch copper and quartered one inch oak. This is the challenging part of a build for me and I have some new Alps pots I fell in love with on another build that I cannot wait to use. I may try for a brushed copper look but if that does not work out, a patina will hide most any imperfection.
    Last edited: Nov 26, 2017
  6. attmci
    Tom, you forgot a very important thing here:

    Cryo-treated tubes have “tighter focus from top to bottom”, “more holographic 3D soundstage”, “more subtle inner resolution extracted from recordings”, “tighter bass”, “increased dynamic range”, “faster transient response”.
    Discussed here:
  7. Paladin79
    Tempus sure does fugit, is it April 1 already?

    I have seen that article but it is best I do not say much here. I am not supposed to disparage against any product or products, I just tend to wince each time I hear Cryo this or that.

    I will say I own many Mullard tubes and they are one of my first choices for drivers.
    Last edited: Nov 26, 2017
  8. DavidA
    Which tube makes the most difference is also dependent on the headphone you will be using since the power tube influences the output impedance which will affect some headphones more than others while other headphones will be more sensitive to driver tube changes is what I've noticed so far. @Paladin79 has a great suggestion of just using the stock tubes to start so you get familiar with how they sound with your headphones. I've also noticed that how a tube sounds is affected by the speedball, I've removed my speedball since I like the sound without it with the set of tubes that I like most.
  9. Maxhawk
    The way I've heard it explained is that the input tube makes a big difference because it's the gain stage. The output tube will make a bigger difference as you lower the impedance of the load.
  10. attmci
    Tube rolling won't change your amp from a $400 equipment to a $1000 one. :)
  11. DavidA
    I never said it did but its a persons opinion that tubes can change a $400 amp to a $1000 amp and I think there are some who would say the proper tubes/caps/etc can make the BH Crack compete with some $1000 amps but its a personal preference / opinion to me.
    Paladin79 likes this.
  12. JamieMcC
    Dont chase expensive input tubes do this simple inexpensive mod ($5) and you can run both 12au7 or e80cc at optimal voltages as specified by the PB the Cracks designer at the flick of a switch. Once you have tried E80cc you might never buy another12au7 again.

    Last edited: Nov 27, 2017
  13. Paladin79
    In my limited experience working with the Crack amps, I have found performance and appearance to be factors in adding value to the basic Crack amp. I have mostly built the amps for family and friends but I have had several requests to build them for folks who have seen my work. One way of measuring what something is worth is what an individual is willing to pay and while I am not in the amp building business the offers have been fairly high for amps I may build. That being said, there was a fairly nice one on Ebay for about $900 that I kept seeing for a long time. I have been offered more but I do believe that hearing the amps makes a big difference in the selling process.

    I do not have the speedball in my steampunk styled Crack amp, I have heard them side by side and while the speedball does remove some of the background noise I am happy with the amp as it sits. I may add it to my next build but not in its current form, I want to build my own pc board on which to mount the parts but that is just me. It should not change the performance any.
    DavidA likes this.
  14. bloodhawk
    Weird question, but do you know if it is possible to swap out the transformer in the Crack 1.0 with one that is compatible with (and can be rewired) 120V and 240V? Its almost impossible to get a hold of an original Bottlehead universal transformer, since they are custom wound for them. Plus i can make my own face plate to accommodate the size / shape differences.
  15. Paladin79
    I believe the newer transformers are 120v and 240v capable and Bottlehead may well sell you one. They are having a sale on some product so this would certainly be a time to check. If they will sell you one, they should fit without modification but you would have to get the 1.1 build info that covers the transformer wiring. Doc Bottlehead is on here on occasion and I am sure he can easily answer this for you or just go to the website and look under their spare part section.
    bloodhawk likes this.
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